}
@TechReport{Dartmouth:TR2000-362,
author = "Chris Bailey-Kellogg and John J. Kelley and Clifford
Stein and Bruce Randall Donald",
title = "{Reducing Mass Degeneracy in SAR by MS by Stable
Isotopic Labeling}",
institution = "Dartmouth College, Computer Science",
address = "Hanover, NH",
number = "TR2000-362",
year = "2000",
month = feb,
URL = "http://www.cs.dartmouth.edu/reports/TR2000-362.ps.Z",
comment = "This report supercedes TR99-359.
To appear in the 8th International
Conference on Intelligent Systems for Molecular
Biology, (August 20-23, 2000) La Jolla, CA
(Accepted; in press).",
abstract = "Mass spectrometry (MS) promises to be an invaluable
tool for functional genomics, by supporting low-cost,
high-throughput experiments. However, large-scale MS
faces the potential problem of mass degeneracy --
indistinguishable masses for multiple biopolymer
fragments (e.g. from a limited proteolytic digest).
This paper studies the tasks of planning and
interpreting MS experiments that use selective isotopic
labeling, thereby substantially reducing potential mass
degeneracy. Our algorithms support an
experimental-computational protocol called
Structure-Activity Relation by Mass Spectrometry (SAR
by MS), for elucidating the function of protein-DNA and
protein-protein complexes. SAR by MS enzymatically
cleaves a crosslinked complex and analyzes the
resulting mass spectrum for mass peaks of hypothesized
fragments. Depending on binding mode, some cleavage
sites will be shielded; the absence of anticipated
peaks implicates corresponding fragments as either part
of the interaction region or inaccessible due to
conformational change upon binding. Thus different mass
spectra provide evidence for different
structure-activity relations. We address combinatorial
and algorithmic questions in the areas of data analysis
(constraining binding mode based on mass signature) and
experiment planning (determining an isotopic labeling
strategy to reduce mass degeneracy and aid data
analysis). We explore the computational complexity of
these problems, obtaining upper and lower bounds. We
report experimental results from implementations of our
algorithms.",
}
@TechReport{Dartmouth:TR2000-363,
author = "Jon Howell and David Kotz",
title = "{A Formal Semantics for SPKI}",
institution = "Dartmouth College, Computer Science",
address = "Hanover, NH",
number = "TR2000-363",
year = "2000",
month = mar,
comment = "This TR supercedes TR1999-361. This technical report
is an extended version of a paper submitted to ESORICS
2000. For more information, see the project
web page.",
abstract = "We extend the logic and semantics of authorization due
to Abadi, Lampson, et al. to support restricted
delegation. Our formal model provides a simple
interpretation for the variety of constructs in the
Simple Public Key Infrastructure (SPKI), and lends
intuition about possible extensions. We discuss both
extensions that our semantics supports and extensions
that it cautions against.",
}
@TechReport{Dartmouth:TR2000-364,
author = "Jon Howell and Keith Kotay",
title = "{Landmarks for absolute localization}",
institution = "Dartmouth College, Computer Science",
address = "Hanover, NH",
number = "TR2000-364",
year = "2000",
month = mar,
URL = "http://www.cs.dartmouth.edu/reports/TR2000-364.ps.Z",
comment = "This document describes work done in the Dartmouth
Robotics Laboratory in April of 1997 and August of
1999. It was previously ``published'' as a web page,
but we thought it would make sense to document it more
permanently.",
abstract = "For certain experiments in mobile robotics, it is
convenient to eliminate positional estimation error in
the interest of analyzing other parts of the
experiment. We designed and implemented a simple,
accurate scheme for encoding and recovering absolute
position information. The encoding is a two-dimensional
image printed on the plane of the floor, and the
absolute position information is recovered using a
downward-looking video camera mounted on a mobile
robot.",
}
@TechReport{Dartmouth:TR2000-365,
author = "Robert S. Gray and David Kotz and George Cybenko and
Daniela Rus",
title = "{Mobile Agents: Motivations and State-of-the-Art
Systems}",
institution = "Dartmouth College, Computer Science",
address = "Hanover, NH",
number = "TR2000-365",
year = "2000",
month = apr,
URL = "http://www.cs.dartmouth.edu/reports/TR2000-365.ps.Z",
comment = "This technical report will appear as a chapter in
Jeffrey M. Bradshaw, editor, Handbook of Agent
Technology, AAAI/MIT Press, 2000. In Press.",
abstract = "A mobile agent is an executing program that can
migrate, at times of its own choosing, from machine to
machine in a heterogeneous network. On each machine,
the agent interacts with stationary service agents and
other resources to accomplish its task. In this
chapter, we first make the case for mobile agents,
discussing six strengths of mobile agents and the
applications that benefit from these strengths.
Although none of these strengths are unique to mobile
agents, no competing technique shares all six. In other
words, a mobile-agent system provides a single general
framework in which a wide range of distributed
applications can be implemented efficiently and easily.
We then present a representative cross-section of
current mobile-agent systems.",
}
@TechReport{Dartmouth:TR2000-366,
author = "David Kotz and Guofei Jiang and Robert S. Gray and
George Cybenko and Ronald A. Peterson",
title = "{Performance Analysis of Mobile Agents for Filtering
Data Streams on Wireless Networks}",
institution = "Dartmouth College, Computer Science",
address = "Hanover, NH",
number = "TR2000-366",
year = "2000",
month = may,
URL = "http://www.cs.dartmouth.edu/reports/TR2000-366.ps.Z",
comment = "In August 2000 a revised version appeared in the
International Workshop on Modeling and Simulation of
Wireless and Mobile Systems (MSWiM 2000). In October
2000 a further revised version appeared as Dartmouth
Technical Report TR2000-377, and was submitted to the
journal Mobile Networks and Applications (ACM MONET).",
abstract = "Wireless networks are an ideal environment for mobile
agents, because their mobility allows them to move
across an unreliable link to reside on a wired host,
next to or closer to the resources they need to use.
Furthermore, client-specific data transformations can
be moved across the wireless link, and run on a wired
gateway server, with the goal of reducing bandwidth
demands. In this paper we examine the tradeoffs faced
when deciding whether to use mobile agents to support a
data-filtering application, in which numerous wireless
clients filter information from a large data stream
arriving across the wired network. We develop an
analytical model and use parameters from our own
experiments to explore the model's implications.",
}
@TechReport{Dartmouth:TR2000-367,
author = "Cliff Stein and David P. Wagner",
title = "{Approximation Algorithms for the Minimum Bends
Traveling Salesman Problem}",
institution = "Dartmouth College, Computer Science",
address = "Hanover, NH",
number = "TR2000-367",
year = "2000",
month = apr,
URL = "http://www.cs.dartmouth.edu/reports/TR2000-367.ps.Z",
comment = "Submitted to FOCS 2000.",
abstract = "The problem of traversing a set of points in the order
that minimizes the total distance traveled (traveling
salesman problem) is one of the most famous and
well-studied problems in combinatorial optimization. It
has many applications, and has been a testbed for many
of the must useful ideas in algorithm design and
analysis. The usual metric, minimizing the total
distance traveled, is an important one, but many other
metrics are of interest. In this paper, we introduce
the metric of minimizing the number of turns in the
tour, given that the input points are in the Euclidean
plane. To our knowledge this metric has not been
studied previously. It is motivated by applications in
robotics and in the movement of other heavy machinery:
for many such devices turning is an expensive
operation. We give approximation algorithms for several
variants of the traveling salesman problem for which
the metric is to minimize the number of turns. We call
this the minimum bends traveling salesman problem. For
the case of an arbitrary set of $n$ points in the
Euclidean plane, we give an O(lg z)-approximation
algorithm, where z is the maximum number of collinear
points. In the worst case z can be as big as n, but z
will often be much smaller. For the case when the lines
are restricted to being either horizontal or vertical,
we give a 2-approximation algorithm. If we have the
further restriction that no two points are allowed to
have the same x- or y-coordinate, we give an algorithm
that finds a tour which makes at most two turns more
than the optimal tour. Thus we have an approximation
algorithm with an additive, rather than a
multiplicative error bound. Beyond the additive error
bound, our algorithm for this problem introduces
several interesting algorithmic techniques for
decomposing sets of points in the Euclidean plane that
we believe to be of independent interest.",
}
@TechReport{Dartmouth:TR2000-368,
author = "Eric Michael Greenberg",
title = "{A Simulation of Auroral Absorption}",
institution = "Dartmouth College, Computer Science",
address = "Hanover, NH",
number = "TR2000-368",
year = "2000",
month = may,
URL = "http://www.cs.dartmouth.edu/reports/TR2000-368.pdf",
comment = "Advisor: Dan Rockmore",
abstract = "HF radio transmissions propagate long distances by
reflecting off the ionosphere. At high latitudes radio
propagation is strongly affected by the northern lights
(aurora borealis), which causes ionization at low
altitudes and hence the absorption of radio waves.
Models of this process are still in a primitive state.
A simulation of radio wave propagation was created in
order to test Foppiano and Bradley's empirical model of
auroral absorption. The simulation attempts to predict
the net absorption of signals at a receiver by
simulating a large number of transmitters, even though
the exact sources of the signals are unknown. Although
the simulation takes into account auroral and
nonauroral absorption as well as other sources of path
loss, the analysis focuses on the nighttime aurora. An
intelligent search algorithm is used in order to
efficiently adjust the model to best fit the data. The
output of the simulation is qualitatively and
quantitatively compared to signal levels observed with
HF radio receivers located in northern Canada. The
analysis allows us to develop alternative models of
auroral absorption which account for the level of
geomagnetic activity, and these are compared to the
standard Foppiano and Bradley model.",
}
@TechReport{Dartmouth:TR2000-369,
author = "Karolyn A. Abram",
title = "{Registration of Images with Dissimilar Contrast using
a Hybrid Method Employing Correlation and Mutual
Information}",
institution = "Dartmouth College, Computer Science",
address = "Hanover, NH",
number = "TR2000-369",
year = "2000",
month = jun,
URL = "http://www.cs.dartmouth.edu/reports/TR2000-369.ps.Z",
comment = "Undergraduate Honors Thesis Advisor: Daniel N.
Rockmore",
abstract = "The problem of fitting one image into another is
commonly called {"}registration.{"} Finding the best
possible translation and rotation necessary to align
two images is one approach to solving this problem.
Registration is a crucial component of many remote
sensing and medical image interpretation applications.
Image alignment techniques aid in volumetric
estimations of complicated structures and allow
radiologists to accurately identify changes between
sequential images. Radiologists require image alignment
capabilities to correct for patient motion and/or
content displacement between images. Numerous image
registration techniques exist for correcting the
alignment problems mentioned above. Unfortunately, most
of these techniques, such as Correlation, fail to find
a good alignment when dealing with images that differ
in contrast. The Mutual Information method is able to
align images independently of contrast, but it is
computationally intensive. We explore a hybrid
technique that utilizes both Correlation and Mutual
Information. The Hybrid technique hopes to gain greater
contrast independence than Correlation alone while
achieving a lower running time than a pure Mutual
Information technique.",
}
@TechReport{Dartmouth:TR2000-370,
author = "Debbie O. Chyi",
title = "{An Infrastructure for a Mobile-Agent System that
Provides Personalized Services to Mobile Devices}",
institution = "Dartmouth College, Computer Science",
address = "Hanover, NH",
number = "TR2000-370",
year = "2000",
month = may,
URL = "http://www.cs.dartmouth.edu/reports/TR2000-370.ps.Z",
comment = "Undergraduate Honors Thesis. Advisor: David F. Kotz",
abstract = "In this paper, we present the design of a mobile-agent
system that provides a mobile user with a personalized
information retrieval service and we describe the
implementation of the infrastructure for such a system.
This {"}Personal Agent System{"} gathers information
from the Internet and uses context-aware mechanisms to
manage the information according to a mobile user's
needs and preferences. The user's schedule and location
are the context indicators in this system. These
indicators are critical in ensuring that users obtain
only the information they want, receive information in
a form that is most useful for viewing on their mobile
device, and is notified of new information in a
minimally intrusive manner. The system incorporates a
rule-based learning system to enhance the
personalization achieved by the system.",
}
@TechReport{Dartmouth:TR2000-372,
author = "John C. Artz",
title = "{Personal Radio}",
institution = "Dartmouth College, Computer Science",
address = "Hanover, NH",
number = "TR2000-372",
year = "2000",
month = jun,
URL = "http://www.cs.dartmouth.edu/reports/TR2000-372.ps.Z",
comment = "Undergraduate Honors Thesis. Advisors: David Kotz and
Daniela Rus",
abstract = "With the development of new technologies that allow
the broadcast of digital data over radio signals, there
are many possibilities for improving upon the
traditional radio station model for content delivery.
The idea of Personal Radio is a system that tailors
content to meet the needs of each individual. Using
Global Positioning System (GPS) technology to play
location specific content, the listening history to
play content an appropriate number of times, and user
feedback to learn personal preferences, the Personal
Radio provides the listener with the content that is
the most useful/interesting to them. This paper will
examine the general design of such a system and present
solutions developed in the implementation of several
pieces of the design.",
}
@TechReport{Dartmouth:TR2000-373,
author = "David B. Martin",
title = "{Depth from Flash}",
institution = "Dartmouth College, Computer Science",
address = "Hanover, NH",
number = "TR2000-373",
year = "2000",
month = jun,
URL = "http://www.cs.dartmouth.edu/reports/TR2000-373.ps.Z",
comment = "Undergraduate Honors Thesis. Advisor: Hany Farid",
abstract = "Digital camera technology has recently seen
substantial improvements in image quality while lower
prices have made it affordable to the average consumer.
Camera manufacturers, however, are not taking full
advantage of this new medium for image capture. By
filtering the already digitized image produced by these
cameras through on-board image processing algorithms we
can dramatically increase the power of digital cameras.
For example, according to experts in the photographic
industry, most people simply take bad pictures. Classic
examples of this phenomenon are photographs taken
indoors with a point-and-shoot style camera using its
built-in flash. The subjects of these photographs often
seem to have a spotlight on them, making them look
bright and washed out while the rest of the photograph
is dark and indistinct. This can primarily be accounted
for by a well known property of point light sources:
falloff in brightness is inversely proportional to the
square of the distance between the light and the object
being illuminated. A technique first introduced in the
field of computer vision has been shown to successfully
recover information about the distance between the
light source and objects in the world. We propose using
this technique, which is readily implementable in
hardware, to correct for a variety of poorly
illuminated digital images.",
}
@TechReport{Dartmouth:TR2000-375,
author = "Ezra E. K. Cooper and Robert S. Gray",
title = "{An Economic CPU-Time Market for D'Agents}",
institution = "Dartmouth College, Computer Science",
address = "Hanover, NH",
number = "TR2000-375",
year = "2000",
month = jun,
URL = "http://www.cs.dartmouth.edu/reports/TR2000-375.ps.Z",
comment = "Undergraduate honors thesis. Advisor: Bob Gray.",
abstract = "A usable and efficient resource-management system has
been created for use with D'Agents. The software
dynamically negotiates a price rate for CPU time, using
the competitive bids of mobile agents that offer
currency in return for fast computation. The system
allows mobile agents to plan their expenditures across
many hosts while minimizing the time needed for their
tasks. The ability to price CPU time opens the door for
service owners to be compensated for the computation
consumed by agents and provides an incentive for
servers to allow anonymous agents. We discuss the
theoretical background which makes a CPU market system
possible and the performance of the D'Agents market
system.",
}
@TechReport{Dartmouth:TR2000-376,
author = "Martin Mundhenk",
title = "{The complexity of planning with partially-observable
Markov decision processes}",
institution = "Dartmouth College, Computer Science",
address = "Hanover, NH",
number = "TR2000-376",
year = "2000",
month = jun,
URL = "http://www.cs.dartmouth.edu/reports/TR2000-376.ps.Z",
abstract = "This work surveys results on the complexity of
planning under uncertainty. The planning model
considered is the partially-observable Markov decision
process. The general planning problems are, given such
a process, (a) to calculate its performance under a
given control policy, (b) to find an optimal or
approximate optimal control policy, and (c) to decide
whether a good policy exists. The complexity of this
and related problems depend on a variety of factors,
including the observability of the process state, the
compactness of the process representation, the type of
policy, or even the number of actions relative to the
number of states. In most cases, the problem can be
shown to be complete for some known complexity class.
The skeleton of this survey are results from Littman,
Goldsmith and Mundhenk (Journal of Artificial
Intelligence Research 1998), Mundhenk (Mathematics of
Operations Research 2000), Mundhenk, Goldsmith, Lusena
and Allender (Journal of the ACM 2000), and Lusena,
Goldsmith and Mundhenk (University of KY CS TR). But
there are also some news.",
}
@TechReport{Dartmouth:TR2000-377,
author = "David Kotz and George Cybenko and Robert S. Gray and
Guofei Jiang and Ronald A. Peterson and Martin O.
Hofmann and Daria A. Chacon and Kenneth R. Whitebread
and James Hendler",
title = "{Performance Analysis of Mobile Agents for Filtering
Data Streams on Wireless Networks}",
institution = "Dartmouth College, Computer Science",
address = "Hanover, NH",
number = "TR2000-377",
year = "2000",
month = oct,
URL = "http://www.cs.dartmouth.edu/reports/TR2000-377.ps.Z",
comment = "Updated version of TR2000-366. To appear, after
revisions, in the journal Mobile Networks and
Applications (ACM MONET).",
abstract = "Wireless networks are an ideal environment for mobile
agents, since their mobility allows them to move across
an unreliable link to reside on a wired host, next to
or closer to the resources that they need to use.
Furthermore, client-specific data transformations can
be moved across the wireless link and run on a wired
gateway server, reducing bandwidth demands. In this
paper we examine the tradeoffs faced when deciding
whether to use mobile agents in a data-filtering
application where numerous wireless clients filter
information from a large data stream arriving across
the wired network. We develop an analytical model and
use parameters from filtering experiments conducted
during a U.S. Navy Fleet Battle Experiment (FBE) to
explore the model's implications.",
}
@TechReport{Dartmouth:TR2000-378,
author = "Jon Howell",
title = "{Naming and sharing resources across administrative
boundaries (Volume I)}",
institution = "Dartmouth College, Computer Science",
address = "Hanover, NH",
number = "TR2000-378",
year = "2000",
month = may,
URL = "http://www.cs.dartmouth.edu/reports/TR2000-378.ps.Z",
comment = "This technical report represents Volume One of the
dissertation. Volume One (187 pages) is the heart of
the dissertation. Volume Two (237 pages) contains a
software manual introduced with illustrated code
fragments, plus plots of the raw data used for the
experimental results presented in Volume One. That
material is optional; I recommend that the interested
reader begin with just Volume One. Volume II is
available as TR2000-379. Please note that a list of
errata is available as TR2000-380.",
abstract = "I tackle the problem of naming and sharing resources
across administrative boundaries. Conventional systems
manifest the hierarchy of typical administrative
structure in the structure of their own mechanism.
While natural for communication that follows
hierarchical patterns, such systems interfere with
naming and sharing that cross administrative
boundaries, and therefore cause headaches for both
users and administrators. I propose to organize
resource naming and security, not around administrative
domains, but around the sharing patterns of users. The
dissertation is organized into four main parts. First,
I discuss the challenges and tradeoffs involved in
naming resources and consider a variety of existing
approaches to naming. Second, I consider the
architectural requirements for user-centric sharing. I
evaluate existing systems with respect to these
requirements. Third, to support the sharing
architecture, I develop a formal logic of sharing that
captures the notion of restricted delegation.
Restricted delegation ensures that users can use the
same mechanisms to share resources consistently,
regardless of the origin of the resource, or with whom
the user wishes to share the resource next. A formal
semantics gives unambiguous meaning to the logic. I
apply the formalism to the Simple Public Key
Infrastructure and discuss how the formalism either
supports or discourages potential extensions to such a
system. Finally, I use the formalism to drive a
user-centric sharing implementation for distributed
systems. I show how this implementation enables
end-to-end authorization, a feature that makes
heterogeneous distributed systems more secure and
easier to audit. Conventionally, gateway services that
bridge administrative domains, add abstraction, or
translate protocols typically impede the flow of
authorization information from client to server. In
contrast, end-to-end authorization enables us to build
gateway services that preserve authorization
information, hence we reduce the size of the trusted
computing base and enable more effective auditing. I
demonstrate my implementation and show how it enables
end-to-end authorization across various boundaries. I
measure my implementation and argue that its
performance tracks that of similar authorization
mechanisms without end-to-end structure. I conclude
that my user-centric philosophy of naming and sharing
benefits both users and administrators.",
}
@TechReport{Dartmouth:TR2000-379,
author = "Jon Howell",
title = "{Naming and sharing resources across administrative
boundaries (Volume II)}",
institution = "Dartmouth College, Computer Science",
address = "Hanover, NH",
number = "TR2000-379",
year = "2000",
month = may,
URL = "http://www.cs.dartmouth.edu/reports/TR2000-379.ps.Z",
comment = "This technical report represents Volume Two of the
dissertation. Volume One (187 pages) is the heart of
the dissertation. Volume Two (237 pages) contains a
software manual introduced with illustrated code
fragments, plus plots of the raw data used for the
experimental results presented in Volume One. That
material is optional; I recommend that the interested
reader begin with just Volume One. Volume I is
available as TR2000-378. Please note that a list of
errata is available as TR2000-380.",
abstract = "I tackle the problem of naming and sharing resources
across administrative boundaries. Conventional systems
manifest the hierarchy of typical administrative
structure in the structure of their own mechanism.
While natural for communication that follows
hierarchical patterns, such systems interfere with
naming and sharing that cross administrative
boundaries, and therefore cause headaches for both
users and administrators. I propose to organize
resource naming and security, not around administrative
domains, but around the sharing patterns of users. The
dissertation is organized into four main parts. First,
I discuss the challenges and tradeoffs involved in
naming resources and consider a variety of existing
approaches to naming. Second, I consider the
architectural requirements for user-centric sharing. I
evaluate existing systems with respect to these
requirements. Third, to support the sharing
architecture, I develop a formal logic of sharing that
captures the notion of restricted delegation.
Restricted delegation ensures that users can use the
same mechanisms to share resources consistently,
regardless of the origin of the resource, or with whom
the user wishes to share the resource next. A formal
semantics gives unambiguous meaning to the logic. I
apply the formalism to the Simple Public Key
Infrastructure and discuss how the formalism either
supports or discourages potential extensions to such a
system. Finally, I use the formalism to drive a
user-centric sharing implementation for distributed
systems. I show how this implementation enables
end-to-end authorization, a feature that makes
heterogeneous distributed systems more secure and
easier to audit. Conventionally, gateway services that
bridge administrative domains, add abstraction, or
translate protocols typically impede the flow of
authorization information from client to server. In
contrast, end-to-end authorization enables us to build
gateway services that preserve authorization
information, hence we reduce the size of the trusted
computing base and enable more effective auditing. I
demonstrate my implementation and show how it enables
end-to-end authorization across various boundaries. I
measure my implementation and argue that its
performance tracks that of similar authorization
mechanisms without end-to-end structure. I conclude
that my user-centric philosophy of naming and sharing
benefits both users and administrators.",
}
@TechReport{Dartmouth:TR2000-380,
author = "Jon Howell",
title = "{Naming and sharing resources across administrative
boundaries (errata)}",
institution = "Dartmouth College, Computer Science",
address = "Hanover, NH",
number = "TR2000-380",
year = "2000",
month = may,
URL = "http://www.cs.dartmouth.edu/reports/TR2000-380.ps.Z",
comment = "This technical report contains errata for the
dissertation. Volume One (187 pages) is the heart of
the dissertation. Volume Two (237 pages) contains a
software manual introduced with illustrated code
fragments, plus plots of the raw data used for the
experimental results presented in Volume One. That
material is optional; I recommend that the interested
reader begin with just Volume One. Volume I is
available as TR2000-378. Volume II is available as
TR2000-379.",
abstract = "I tackle the problem of naming and sharing resources
across administrative boundaries. Conventional systems
manifest the hierarchy of typical administrative
structure in the structure of their own mechanism.
While natural for communication that follows
hierarchical patterns, such systems interfere with
naming and sharing that cross administrative
boundaries, and therefore cause headaches for both
users and administrators. I propose to organize
resource naming and security, not around administrative
domains, but around the sharing patterns of users. The
dissertation is organized into four main parts. First,
I discuss the challenges and tradeoffs involved in
naming resources and consider a variety of existing
approaches to naming. Second, I consider the
architectural requirements for user-centric sharing. I
evaluate existing systems with respect to these
requirements. Third, to support the sharing
architecture, I develop a formal logic of sharing that
captures the notion of restricted delegation.
Restricted delegation ensures that users can use the
same mechanisms to share resources consistently,
regardless of the origin of the resource, or with whom
the user wishes to share the resource next. A formal
semantics gives unambiguous meaning to the logic. I
apply the formalism to the Simple Public Key
Infrastructure and discuss how the formalism either
supports or discourages potential extensions to such a
system. Finally, I use the formalism to drive a
user-centric sharing implementation for distributed
systems. I show how this implementation enables
end-to-end authorization, a feature that makes
heterogeneous distributed systems more secure and
easier to audit. Conventionally, gateway services that
bridge administrative domains, add abstraction, or
translate protocols typically impede the flow of
authorization information from client to server. In
contrast, end-to-end authorization enables us to build
gateway services that preserve authorization
information, hence we reduce the size of the trusted
computing base and enable more effective auditing. I
demonstrate my implementation and show how it enables
end-to-end authorization across various boundaries. I
measure my implementation and argue that its
performance tracks that of similar authorization
mechanisms without end-to-end structure. I conclude
that my user-centric philosophy of naming and sharing
benefits both users and administrators.",
}
@TechReport{Dartmouth:TR2000-381,
author = "Guanling Chen and David Kotz",
title = "{A Survey of Context-Aware Mobile Computing
Research}",
institution = "Dartmouth College, Computer Science",
address = "Hanover, NH",
number = "TR2000-381",
year = "2000",
month = nov,
URL = "http://www.cs.dartmouth.edu/reports/TR2000-381.ps.Z",
abstract = "Context-aware computing is a mobile computing paradigm
in which applications can discover and take advantage
of contextual information (such as user location, time
of day, nearby people and devices, and user activity).
Since it was proposed about a decade ago, many
researchers have studied this topic and built several
context-aware applications to demonstrate the
usefulness of this new technology. Context-aware
applications (or the system infrastructure to support
them), however, have never been widely available to
everyday users. In this survey of research on
context-aware systems and applications, we looked in
depth at the types of context used and models of
context information, at systems that support collecting
and disseminating context, and at applications that
adapt to the changing context. Through this survey, it
is clear that context-aware research is an old but rich
area for research. The difficulties and possible
solutions we outline serve as guidance for researchers
hoping to make context-aware computing a reality.",
}
@TechReport{Dartmouth:TR2000-382,
author = "Javed A. Aslam and Mark Montague",
title = "{Bayes Optimal Metasearch: A Probabilistic Model for
Combining the Results of Multiple Retrieval Systems}",
institution = "Dartmouth College, Computer Science",
address = "Hanover, NH",
number = "TR2000-382",
year = "2000",
month = dec,
URL = "http://www.cs.dartmouth.edu/reports/TR2000-382.ps.Z",
comment = "Preliminary version appeared in SIGIR 2000.",
abstract = "We introduce a new, probabilistic model for combining
the outputs of an arbitrary number of query retrieval
systems. By gathering simple statistics on the average
performance of a given set of query retrieval systems,
we construct a Bayes optimal mechanism for combining
the outputs of these systems. Our construction yields a
metasearch strategy whose empirical performance nearly
always exceeds the performance of any of the
constituent systems. Our construction is also robust in
the sense that if ``good'' and ``bad'' systems are
combined, the performance of the composite is still on
par with, or exceeds, that of the best constituent
system. Finally, our model and theory provide
theoretical and empirical avenues for the improvement
of this metasearch strategy.",
}
@TechReport{Dartmouth:TR2000-383,
author = "Hany Farid",
title = "{Reconstructing Ancient Egyptian Tombs}",
institution = "Dartmouth College, Computer Science",
address = "Hanover, NH",
number = "TR2000-383",
year = "2000",
month = dec,
URL = "http://www.cs.dartmouth.edu/reports/TR2000-383.ps.Z",
abstract = "From the pyramids of Giza to the tombs of Thebes
(modern Luxor), ancient Egypt's glorious history has
produced remarkable architecture. Sadly, the nearly
four million yearly tourists have taken a heavy toll on
many of these ancient structures. Of particular concern
are many of the tombs located opposite to Luxor on the
western bank of the Nile. Digital reconstruction of
these tombs has the potential to help document and
preserve these important historical structures.
Photographing and reconstruction of these tombs poses
new and unique problems that this paper begins to
address. Techniques for removing image distortions,
recovering 3-D shape, and correcting for lighting
imbalances are discussed. A complete reconstruction of
the tomb of Sennedjem is shown.",
}
@TechReport{Dartmouth:TR2001-384,
author = "Chris Bailey-Kellogg and Naren Ramakrishnan",
title = "{Ambiguity-Directed Sampling for Qualitative Analysis
of Sparse Data from Spatially-Distributed Physical
Systems}",
institution = "Dartmouth College, Computer Science",
address = "Hanover, NH",
number = "TR2001-384",
year = "2001",
month = jan,
URL = "http://www.cs.dartmouth.edu/reports/TR2001-384.ps.Z",
abstract = "A number of important scientific and engineering
applications, such as fluid dynamics simulation and
aircraft design, require analysis of
spatially-distributed data from expensive experiments
and complex simulations. In such data-scarce
applications, it is advantageous to use models of given
sparse data to identify promising regions for
additional data collection. This paper presents a
principled mechanism for applying domain-specific
knowledge to design focused sampling strategies. In
particular, our approach uses ambiguities identified in
a multi-level qualitative analysis of sparse data to
guide iterative data collection. Two case studies
demonstrate that this approach leads to highly
effective sampling decisions that are also explainable
in terms of problem structures and domain knowledge.",
}
@TechReport{Dartmouth:TR2001-385,
author = "Xiaowen Liu and David M. Nicol and King Tan",
title = "{Lock-free Scheduling of Logical Processes in Parallel
Simulation}",
institution = "Dartmouth College, Computer Science",
address = "Hanover, NH",
number = "TR2001-385",
year = "2001",
month = jan,
URL = "http://www.cs.dartmouth.edu/reports/TR2001-385.ps.Z",
comment = "A revision of this report appears on PADS 2001.",
abstract = "With fixed lookahead information in a simulation
model, the overhead of asynchronous conservative
parallel simulation lies in the mechanism used for
propagating time updates in order for logical processes
to safely advance their local simulation clocks.
Studies have shown that a good scheduling algorithm
should preferentially schedule processes containing
events on the critical path. This paper introduces a
lock-free algorithm for scheduling logical processes in
conservative parallel discrete-event simulation on
shared-memory multiprocessor machines. The algorithm
uses fetch\&add operations that help avoid
inefficiencies associated with using locks. The
lock-free algorithm is robust. Experiments show that,
compared with the scheduling algorithm using locks, the
lock-free algorithm exhibits better performance when
the number of logical processes assigned to each
processor is small or when the workload becomes
significant. In models with large number of logical
processes, our algorithm shows only modest increase in
execution time due to the overhead in the algorithm for
extra bookkeeping.",
}
@TechReport{Dartmouth:TR2001-386,
author = "Robert S. Gray and David Kotz and Ronald A. Peterson
and Peter Gerken and Martin Hofmann and Daria Chacon
and Greg Hill and Niranjan Suri",
title = "{Mobile-Agent versus Client/Server Performance:
Scalability in an Information-Retrieval Task}",
institution = "Dartmouth College, Computer Science",
address = "Hanover, NH",
number = "TR2001-386",
year = "2001",
month = jan,
URL = "http://www.cs.dartmouth.edu/reports/TR2001-386.ps.Z",
comment = "Revised version appeared in Mobile Agents 2001. See here.",
abstract = "Mobile agents are programs that can jump from host to
host in the network, at times and to places of their
own choosing. Many groups have developed mobile-agent
software platforms, and several mobile-agent
applications. Experiments show that mobile agents can,
among other things, lead to faster applications,
reduced bandwidth demands, or less dependence on a
reliable network connection. There are few if any
studies of the scalability of mobile-agent servers,
particularly as the number of clients grows. We present
some recent performance and scalability experiments
that compare three mobile-agent platforms with each
other and with a traditional client/server approach.
The experiments show that mobile agents often
outperform client/server solutions, but also
demonstrate the deep interaction between environmental
and application parameters. The three mobile-agent
platforms have similar behavior but their absolute
performance varies with underlying implementation
choices.",
}
@TechReport{Dartmouth:TR2001-388,
author = "Michael F. Ringenburg",
title = "{Applying the Vector Radix Method to Multidimensional,
Multiprocessor, Out-of-Core Fast Fourier Transforms}",
institution = "Dartmouth College, Computer Science",
address = "Hanover, NH",
number = "TR2001-388",
year = "2001",
month = mar,
URL = "http://www.cs.dartmouth.edu/reports/TR2001-388.ps.Z",
comment = "Masters Thesis. Advisor: Tom Cormen.",
abstract = "We describe an efficient algorithm for calculating
Fast Fourier Transforms on matrices of arbitrarily high
dimension using the vector-radix method when the
problem size is out-of-core (i.e., when the size of the
data set is larger than the total available memory of
the system). The algorithm takes advantage of multiple
processors when they are present, but it is also
efficient on single-processor systems. Our work is an
extension of work done by Lauren Baptist in [Bapt99],
which applied the vector-radix method to 2-dimensional
out-of-core matrices. To determine the effectiveness of
the algorithm, we present empirical results as well as
an analysis of the I/O, communication, and
computational complexity. We perform the empirical
tests on a DEC 2100 server and on a cluster of
Pentium-based Linux workstations. We compare our
results with the traditional dimensional method of
calculating multidimensional FFTs, and show that as the
number of dimensions increases, the vector-radix-based
algorithm becomes increasingly effective relative to
the dimensional method. In order to calculate the
complexity of the algorithm, it was necessary to
develop a method for analyzing the interprocessor
communication costs of the BMMC data-permutation
algorithm (presented in [CSW98]) used by our FFT
algorithms. We present this analysis method and show
how it was derived.",
}
@TechReport{Dartmouth:TR2001-389,
author = "Thomas B. Stephens",
title = "{Improving a Brokering System for Linking Distributed
Simulations}",
institution = "Dartmouth College, Computer Science",
address = "Hanover, NH",
number = "TR2001-389",
year = "2001",
month = jun,
URL = "http://www.cs.dartmouth.edu/reports/TR2001-389.ps.Z",
comment = "Senior Honors Thesis. Advisor: Linda F. Wilson.",
abstract = "The Agent Based Environment for Linking Simulations
(ABELS) is a software framework designed to provide
disparate simulations with dynamically updated data
sources. It allows simulations and other agents to join
a {"}cloud{"} of interacting producers and consumers of
data. Once they have joined the cloud, they can publish
services to other members and use methods published by
others. This paper presents the initial design of a set
of matchmaking components for the ABELS framework.
These components dictate how services describe their
abilities and requirements to ABELS. Furthermore, they
help ABELS successfully match data producing services
to the requests of data consuming clients. We begin by
describing a system for a data producing service to
describe itself to the ABELS cloud, as well as a
corresponding system for a data consumer to describe
its needs. We then describe in detail the three
components that make up the ABELS matchmaking system:
the match ranker, which ranks a data producer's ability
to fill the request of a data consumer; the thesaurus,
which helps the match ranker recognize closely related
terms; and the unit database, which allows participants
in the ABELS system to translate between related data
units. We also discuss how these basic components can
be built upon and improved in future versions of the
ABELS framework.",
}
@TechReport{Dartmouth:TR2001-390,
author = "G. Ayorkor Mills-Tettey",
title = "{Mobile Voice Over IP (MVOIP): An Application-level
Protocol}",
institution = "Dartmouth College, Computer Science",
address = "Hanover, NH",
number = "TR2001-390",
year = "2001",
month = jun,
URL = "http://www.cs.dartmouth.edu/reports/TR2001-390.ps.Z",
comment = "Senior Honors Thesis. Advisor: David Kotz.",
abstract = "Current Voice over Internet Protocol (VOIP) protocols
require participating hosts to have fixed IP addresses
for the duration of a VOIP call. When using a
wireless-enabled host, such as a tablet computer on an
802.11 wireless network, it is possible for a
participant in a VOIP call to roam around the network,
moving from one subnet to another and needing to change
IP addresses. This address change creates the need for
mobility support in VOIP applications. We present the
design of Mobile Voice over IP (MVOIP), an
application-level protocol that enables such mobility
in a VOIP application based on the ITU H.323 protocol
stack. An MVOIP application uses hints from the
surrounding network to determine that it has switched
subnets. It then initiates a hand-off procedure that
comprises pausing its current calls, obtaining a valid
IP address for the current subnet, and reconnecting to
the remote party with whom it was in a call. Testing
the system shows that on a Windows 2000 platform there
is a perceivable delay in the hand-off process, most of
which is spent in the Windows API for obtaining DHCP
addresses. Despite this bottleneck, MVOIP works well on
a wireless network.",
}
@TechReport{Dartmouth:TR2001-391,
author = "Ammar Khalid",
title = "{A Directory Infrastructure to Support Mobile
Services}",
institution = "Dartmouth College, Computer Science",
address = "Hanover, NH",
number = "TR2001-391",
year = "2001",
month = jun,
URL = "http://www.cs.dartmouth.edu/reports/TR2001-391.ps.Z",
comment = "Senior Honors Thesis. Advisor: David Kotz.",
abstract = "Traditional Voice-over-IP applications such as
Microsoft NetMeeting assume that the user is on a
machine with a fixed IP address. If, however, the user
connects to the Internet, via a wireless network, on a
handheld device, his IP address frequently changes as
he moves from one subnet to another. In such a
situation, we need a service that can be queried for
the most current IP address of a person whom we wish to
contact. In this project, we design and implement such
a directory service. The service authenticates all
callers and callees, is robust against most host
failure, and scales to several thousand registered
users.",
}
@TechReport{Dartmouth:TR2001-392,
author = "Arun Mathias",
title = "{SmartReminder: A Case Study on Context-Sensitive
Applications}",
institution = "Dartmouth College, Computer Science",
address = "Hanover, NH",
number = "TR2001-392",
year = "2001",
month = jun,
URL = "http://www.cs.dartmouth.edu/reports/TR2001-392.ps.Z",
comment = "Senior Honors Thesis. Advisor: David Kotz.",
abstract = "Designing context-sensitive applications is
challenging. We design and implement SmartReminder to
explore designing context-sensitive applications and to
demonstrate how the SOLAR system can be used in
developing such applications. SmartReminder is an
application that reminds the user based on contextual
information. Current appointment-reminder applications
remind the user about their appointments at an
arbitrarily specified time. For instance, they might
remind the user ten minutes before each appointment.
SmartReminder, on the other hand, uses contextual
information, like location, to better estimate the
appropriate reminder time for each appointment. It
reminds the user based on where they are, where they
need to be, and how long it will take them to get
there. This paper presents SmartReminder as an
illustration of how context-sensitive applications can
be designed using the SOLAR system for dissemination of
contextual information.",
}
@TechReport{Dartmouth:TR2001-393,
author = "Pablo Stern",
title = "{Measuring early usage of Dartmouth's wireless
network}",
institution = "Dartmouth College, Computer Science",
address = "Hanover, NH",
number = "TR2001-393",
year = "2001",
month = jun,
URL = "http://www.cs.dartmouth.edu/reports/TR2001-393.ps.Z",
comment = "Senior Honors Thesis. Advisor: David Kotz.",
abstract = "In Spring 2001, Dartmouth College installed a
campus-wide 802.11b wireless network. To understand how
that network is used, we examined the usage
characteristics of the network over a five-week period.
We monitored access points to determine user behavior,
and user and network traffic characteristics. Because
our study coincided with the deployment of the access
points, our analysis captures the growth of a wireless
network. The results of this study help understand the
behavior of mobile users and provide a reference to
network engineers wishing to deploy and expand similar
wireless networks.",
}
@TechReport{Dartmouth:TR2001-394,
author = "David D. Latham",
title = "{An Empirical Study of Training and Testing Error in
Boosting}",
institution = "Dartmouth College, Computer Science",
address = "Hanover, NH",
number = "TR2001-394",
year = "2001",
month = jun,
URL = "http://www.cs.dartmouth.edu/reports/TR2001-394.ps.Z",
comment = "Senior Honors Thesis. Advisor: Jay Aslam.",
abstract = "Bounds have been proven for both training and testing
error for the boosting algorithm AdaBoost, but in
practice neither seem to produce a particularly tight
bound. In this paper we share some observations of
these bounds from empirical results, and then explore
some properties of the algorithm with an eye towards
finding an improved bound for the performance of
AdaBoost. Based on our empirical evidence, the error of
a hypothesis which labels examples probabilistically
based upon the confidence of the vote of the weak
hypotheses forms a tighter bound for the training
error.",
}
@TechReport{Dartmouth:TR2001-395,
author = "Tiffany M. Wong",
title = "{An Implementation of Object-Oriented Program
Transformation for Thought-Guided Debugging }",
institution = "Dartmouth College, Computer Science",
address = "Hanover, NH",
number = "TR2001-395",
year = "2001",
month = jun,
URL = "http://www.cs.dartmouth.edu/reports/TR2001-395.ps.Z",
comment = "Senior Honors Thesis. Advisor: Tom Cormen",
abstract = "This paper presents our design and implementation of
program transformation for C++ that will be used in the
context of a thought-guided debugging system. The
program uses a lexical analyzer written in Flex and a
grammar written in Bison that work in conjunction to
scan the inputted C++ code for function definitions and
class definitions. The code is then transformed to
produce trace information for each defined function,
while the original functionality of the code is left
untouched. We also implement two additional data
structures that are used for information storage during
the course of the program.",
}
@TechReport{Dartmouth:TR2001-396,
author = "Tiffany M. Wong",
title = "{Implementing a Database Information System for an
Electronic Baseball Scorecard }",
institution = "Dartmouth College, Computer Science",
address = "Hanover, NH",
number = "TR2001-396",
year = "2001",
month = jun,
URL = "http://www.cs.dartmouth.edu/reports/TR2001-396.ps.Z",
comment = "Senior Honors Thesis. Advisor: Tom Cormen",
abstract = "We present our design and implementation of a database
system of information storage and retrieval for an
electronic baseball scorecard. The program uses the
relational MySQL database to hold information and a Tcl
API to handle interactions between the database and the
user interface code. This paper discusses the inner
workings of how information storage was broken down
inside the database, how queries were internally
constructed in accordance with the user's input, and
how statistics for players and teams were calculated
and returned to the user. Finally, we discuss some
limitations attached to our current implementation of
the program and propose improvements that can be made
in future versions.",
}
@TechReport{Dartmouth:TR2001-397,
author = "Guanling Chen and David Kotz",
title = "{Supporting Adaptive Ubiquitous Applications with the
SOLAR System}",
institution = "Dartmouth College, Computer Science",
address = "Hanover, NH",
number = "TR2001-397",
year = "2001",
month = may,
URL = "http://www.cs.dartmouth.edu/reports/TR2001-397.ps.Z",
abstract = "As we embed more computers into our daily environment,
ubiquitous computing promises to make them less
noticeable and help to prevent information overload. We
see, however, few ubiquitous applications that are able
to adapt to the dynamics of user, physical, and
computational context. We believe that there are two
challenges causing this lack of ubiquitous
applications: there is no flexible and scalable way to
support information collection and dissemination in a
ubiquitous and mobile environment, and there is no
general approach to building adaptive applications
given heterogeneous contextual information. We propose
a system infrastructure, Solar, to meet these
challenges. Solar uses a subscription-based operator
graph abstraction and allows dynamic composition of
stackable operators to manage ubiquitous information
sources. After developing a set of diverse adaptive
applications, we expect to identify fundamental
techniques for context-aware adaptation. Our
expectation is that Solar's end-to-end support for
information collection, dissemination, and utilization
will make it easy to build adaptive applications for a
ubiquitous mobile environment with many users and
devices.",
}
@TechReport{Dartmouth:TR2001-398,
author = "David Marmaros",
title = "{A System for Audio Personalization with Applications
on Wireless Devices}",
institution = "Dartmouth College, Computer Science",
address = "Hanover, NH",
number = "TR2001-398",
year = "2001",
month = jun,
URL = "http://www.cs.dartmouth.edu/reports/TR2001-398.pdf",
comment = "Senior Honors Thesis. Advisors: David Kotz and Daniela
Rus.",
abstract = "We present and analyze a system for dynamically
tailoring discrete audio content for numerous users
based on aggregate data and intuitive feedback
mechanisms. The framework for this system utilizes a
flexible client-server architecture to facilitate audio
dissemination, with particular attention to
distribution over wireless networks. We discuss the
requirements and specifications of such a system. We
further analyze the algorithms and protocols required
for its operation. Finally, we outline and provide data
from a demonstration of this application.",
}
@TechReport{Dartmouth:TR2001-399,
author = "Shan Jiang",
title = "{WebALPS Implementation and Performance Analysis:
Using Trusted Co-servers to Enhance Privacy and
Security of Web Interactions}",
institution = "Dartmouth College, Computer Science",
address = "Hanover, NH",
number = "TR2001-399",
year = "2001",
month = jun,
URL = "http://www.cs.dartmouth.edu/reports/TR2001-399.ps.Z",
comment = "Master's thesis.",
abstract = "The client-server model of the Web poses a fundamental
trust issue: clients are forced to trust in secrecy and
correctness of computation occurring at a remote server
of unknown credibility. The current solution for this
problem is to use a PKI (Public Key Infrastructure)
system and SSL (Secure Sockets Layer) digital
certificates to prove the claimed identity of a server
and establish an authenticated, encrypted channel
between the client and this server. However, this
approach does not address the security risks posed by
potential malicious server operators or any third
parties who may penetrate the server sites. The WebALPS
(Web Applications with Lots of Privacy and Security)
approach is proposed to address these weaknesses by
moving sensitive computations at server side into
trusted co-servers running inside high-assurance secure
coprocessors. In this report, we examine the
foundations of the credibility of WebALPS co-servers.
Then we will describe our work of designing and
building a prototype WebALPS co-server, which is
integrated into the widely-deployed, commercial-grade
Apache server. We will also present the performance
test results of our system which support the argument
that WebALPS approach provides a systematic and
practical way to address the remote trust issue.",
}
@TechReport{Dartmouth:TR2001-400,
author = "Alex Iliev",
title = "{An Armored Data Vault}",
institution = "Dartmouth College, Computer Science",
address = "Hanover, NH",
number = "TR2001-400",
year = "2001",
month = may,
URL = "http://www.cs.dartmouth.edu/reports/TR2001-400.pdf",
comment = "Senior Honors Thesis. Advisor: Sean Smith.",
abstract = "We consider the problem of secure long-term archiving
of network traffic, an instance of the problem of
storing data securely. We approach the problem using
secure hardware, which enables the enforcement of
flexible access policy. The policy cannot be
circumvented by anyone, even insiders, and so we are
assured that access to the data is as originally
intended. The policy can be expressed as any feasible
computation, as it will be checked inside the secure
hardware without possibility of interference. We
discuss our design of a device to perform such network
data archiving and have implemented a prototpe device.
We discuss other possible application areas of the
design.",
}
@TechReport{Dartmouth:TR2001-401,
author = "Sean W. Smith",
title = "{Outbound Authentication for Programmable Secure
Coprocessors}",
institution = "Dartmouth College, Computer Science",
address = "Hanover, NH",
number = "TR2001-401",
year = "2001",
month = mar,
URL = "http://www.cs.dartmouth.edu/reports/TR2001-401.ps.Z",
abstract = "A programmable secure coprocessor platform can help
solve many security problems in distributed computing.
These solutions usually require that coprocessor
applications be able to participate as full-fledged
parties in distributed cryptographic protocols. Thus,
to fully enable these solutions, a generic platform
must not only provide programmability, maintenance, and
configuration in the hostile field---it must also
provide outbound authentication for the entities that
result. A particular application on a particular
untampered device must be able to prove who it is to a
party on the other side of the Internet. To be
effective, a secure outbound authentication service
must closely mesh with the overall security
architecture. Our initial architecture only sketched a
rough design for this service, and did not complete it.
This paper presents our research and development
experience in refining and implementing this design, to
provide PKI-based outbound authentication for the IBM
4758 Model 2 secure coprocessor platform.",
}
@TechReport{Dartmouth:TR2001-402,
author = "Jeremy T. Fineman",
title = "{Optimizing the Dimensional Method for Performing
Multidimensional, Multiprocessor, Out-of-Core FFTs}",
institution = "Dartmouth College, Computer Science",
address = "Hanover, NH",
number = "TR2001-402",
year = "2001",
month = jun,
URL = "http://www.cs.dartmouth.edu/reports/TR2001-402.ps.Z",
comment = "Senior Honors Thesis. Advisor: Tom Cormen.",
abstract = "We present an improved version of the Dimensional
Method for computing multidimensional Fast Fourier
Transforms (FFTs) on a multiprocessor system when the
data consist of too many records to fit into memory.
Data are spread across parallel disks and processed in
sections. We use the Parallel Disk Model for analysis.
The simple Dimensional Method performs the
1-dimensional FFTs for each dimension in term. Between
each dimension, an out-of-core permutation is used to
rearrange the data to contiguous locations. The
improved Dimensional Method processes multiple
dimensions at a time. We show that determining an
optimal sequence and groupings of dimensions is
NP-complete. We then analyze the effects of two
modifications to the Dimensional Method independently:
processing multiple dimensions at one time, and
processing single dimensions in a different order.
Finally, we show a lower bound on the I/O complexity of
the Dimensional Method and present an algorithm that is
approximately asymptotically optimal.",
}
@TechReport{Dartmouth:TR2001-403,
author = "Aidan S. Marcuss",
title = "{EcomRISK.org : A site to classify and organize the
risks of performing business on the Internet}",
institution = "Dartmouth College, Computer Science",
address = "Hanover, NH",
number = "TR2001-403",
year = "2001",
month = jun,
URL = "http://www.cs.dartmouth.edu/reports/TR2001-403.ps.Z",
comment = "Senior Honors Thesis. Advisor: Fillia Makedon.",
abstract = "As the use of the Internet and other computer networks
to transact business grows, there is an ever increasing
need for those taking part in those transactions to
understand the risks of doing so. While there are many
web sites that have created valuable databases of
specific vulnerabilities for certain types of hardware
and software, there is a lack of focus on attempting to
analyze the interaction of businesses, their systems,
computer networks, and their customers and the risks
that are created by either intended or unattended
interactions. EcomRISK.org is a web site that presents
a clear taxonomy to classify these risks and provides
other features to aid in the general discussion of
e-commerce risk. The site, and the taxonomy at the
center of it, creates a database of these incidents so
they can be clearly searched. This paper discusses the
creation of EcomRISK.org, from vision to birth.",
}
@TechReport{Dartmouth:TR2001-404,
author = "Eric Kidd",
title = "{Efficient Compression of Generic Function Dispatch
Tables}",
institution = "Dartmouth College, Computer Science",
address = "Hanover, NH",
number = "TR2001-404",
year = "2001",
month = jun,
URL = "http://www.cs.dartmouth.edu/reports/TR2001-404.ps.Z",
comment = "Senior Honors Thesis. Advisor: Chris Hawblitzel.",
abstract = "A generic function is similar to an overloaded
operator, but provides a way to select an appropriate
behavior at run-time instead of compile-time. Dujardin
and colleagues have proposed an algorithm for building
and compressing generic function dispatch tables. We
present several modifications to their algorithm,
including an improvement to Pseudo-Closest-Poles and
two new algorithms for compressing pole tables. The two
new compression algorithms are simple and fast, and one
produces smaller output than the original.",
}
@TechReport{Dartmouth:TR2001-405,
author = "Mehmet Iyigun",
title = "{DaSSFNet: An Extension to DaSSF for High-Performance
Network Modeling}",
institution = "Dartmouth College, Computer Science",
address = "Hanover, NH",
number = "TR2001-405",
year = "2001",
month = jun,
URL = "http://www.cs.dartmouth.edu/reports/TR2001-405.ps.Z",
comment = "Senior Honors Thesis. Advisor: David M. Nicol",
abstract = "Scalable Simulation Framework (SSF) is a
discrete-event simulation framework providing a unified
programming interface geared towards network
simulation. Dartmouth SSF (DaSSF) is a C++
implementation of SSF, designed for simulating very
large-scale multi-protocol communication networks. As
of the latest release, DaSSF lacks many features
present in SSF and this prevents it from achieving
mainstream use. To alleviate this shortcoming we
designed and implemented DaSSFNet which extends DaSSF
to the levels of functionality found in SSF. In this
paper, we show that DaSSFNet and SSFNet are identical
in operation given the same input. We also show that
DaSSFNet is about twice as fast and has one third the
memory consumption of SSFNet when simulating identical
networks. Therefore, we argue, that the DaSSF
simulation package with DaSSFNet now offers a viable
alternative to SSF in high-performance network
simulation.",
}
@TechReport{Dartmouth:TR2001-406,
author = "Jeremy I. Robin",
title = "{Fastab: Solving the Pitch to Notation Problem}",
institution = "Dartmouth College, Computer Science",
address = "Hanover, NH",
number = "TR2001-406",
year = "2001",
month = may,
URL = "http://www.cs.dartmouth.edu/reports/TR2001-406.ps.Z",
comment = "Senior Honors Thesis. Advisor: Scot Drysdale",
abstract = "I have always been frustrated with the length of time
necessary to notate a piece of music. Computers have
simplified so many other aspects of our lives, it seems
that they should be able to simplify this task as well.
In fact, there are already two distinct ways that
engineers have attempted to attack this problem. The
first analyzes the waveform generated by microphone
input and relies on Fourier Analysis and other similar
methods. The other examines the analog signal generated
by a electric guitar-like pickup placed beneath the
strings. The method used by Fastab relies much less on
the musical properties of an instrument. Instead,
Fastab records where and when the fingers and pick
contact the instrument using digital electronics and
microprocessor technology. Fastab provides a solution
to the pitch to notation problem which is cheaper and
more accurate than any other device available today.",
}
@TechReport{Dartmouth:TR2001-407,
author = "Michael G. Khankin",
title = "{TCP/IP Implementation within the Dartmouth Scalable
Simulation Framework}",
institution = "Dartmouth College, Computer Science",
address = "Hanover, NH",
number = "TR2001-407",
year = "2001",
month = jun,
URL = "http://www.cs.dartmouth.edu/reports/TR2001-407.ps.Z",
comment = "Senior Honors Thesis. Advisor: David M. Nicol",
abstract = "This paper discusses TCP/IP networking, and in
particular, the DaSSF implementation of TCP/IP. The
paper reviews the protocols, outlines the
implementation design, and demonstrates some tests. In
addition, some performance and memory usage analysis is
performed. We find DaSSF TCP/IP to be a viable option
to the existing SSF. DaSSF TCP/IP is faster and uses
less memory so we can simulate larger, more complex,
models.",
}
@TechReport{Dartmouth:TR2001-408,
author = "Jonathan L. Bredin",
title = "{Market-based Control of Mobile-agent Systems}",
institution = "Dartmouth College, Computer Science",
address = "Hanover, NH",
number = "TR2001-408",
year = "2001",
month = jun,
URL = "http://www.cs.dartmouth.edu/reports/TR2001-408.ps.Z",
comment = "A Ph.D thesis from the Department of Computer Science,
Dartmouth College.",
abstract = "Modern distributed systems scatter sensors, storage,
and computation throughout the environment. Ideally
these devices communicate and share resources, but
there is seldom motivation for a device's owner to
yield control to another user. We establish markets for
computational resources to motivate principals to share
resources with arbitrary users, to enforce priority in
distributed systems, to provide flexible and rational
limitations on the potential of an application, and to
provide a lightweight structure to balance the workload
over time and between devices. As proof of concept, we
implement a structure software agents can use to
discover and negotiate access to networked resources.
The structure separates discovery, authentication, and
consumption enforcement as separate orthogonal issues
to give system designers flexibility. Mobile agents
represent informational and computational flow. We
develop mechanisms that distributively allocate
computation among mobile agents in two settings. The
first models a situation where users collectively own
networked computing resources and require priority
enforcement. We extend the allocation mechanism to
allow resource reservation to mitigate utility
volatility. The second, more general model relaxes the
ownership assumption. We apply our computational market
to an open setting where a principal's chief concern is
revenue maximization. Our simulations compare the
performance of market-based allocation policies to
traditional policies and relate the cost of ownership
and consumption separation. We observe that our markets
effectively prioritize applications' performance, can
operate under uncertainty and network delay, provide
metrics to balance network load, and allow measurement
of market-participation risk versus reservation-based
computation. In addition to allocation problems, we
investigate resource selection to optimize execution
time. The problem is NP-complete if the costs and
latencies are constant. Both metrics' dependence on the
chosen set complicates matters. We study how a greedy
approach, a novel heuristic, and a
shortest-constrained-path strategy perform in
mobile-agent applications. Market-based
computational-resource allocation fertilizes
applications where previously there was a dearth of
motive for or means of cooperation. The rationale
behind mobile-agent performance optimization is also
useful for resource allocation in general distributed
systems where an application has a sequence of
dependent tasks or when data collection is expensive.",
}
@TechReport{Dartmouth:TR2001-409,
author = "Yougu Yuan and Eileen Zishuang Ye and Sean W. Smith",
title = "{Web Spoofing 2001}",
institution = "Dartmouth College, Computer Science",
address = "Hanover, NH",
number = "TR2001-409",
year = "2001",
month = jul,
URL = "http://www.cs.dartmouth.edu/reports/TR2001-409.ps.Z",
abstract = "The Web is currently the pre-eminent medium for
electronic service delivery to remote users. As a
consequence, authentication of servers is more
important than ever. Even sophisticated users base
their decision whether or not to trust a site on
browser cues---such as location bar information, SSL
icons, SSL warnings, certificate information, response
time, etc. In their seminal work on web spoofing,
Felten et al showed how a malicious server could forge
some of these cues---but using approaches that are no
longer reproducible. However, subsequent evolution of
Web tools has not only patched security holes---it has
also added new technology to make pages more
interactive and vivid. In this paper, we explore the
feasibility of web spoofing using this new
technology---and we show how, in many cases, every one
of the above cues can be forged. In particular, we show
how a malicious server can forge all the SSL
information a client sees---thus providing a cautionary
tale about the security of one of the most common
applications of PKI. We stress that these techniques
have been implemented, and are available for public
demonstration.",
}
@TechReport{Dartmouth:TR2001-410,
author = "Shan Jiang and Sean Smith and Kazuhiro Minami",
title = "{Securing Web Servers against Insider Attack}",
institution = "Dartmouth College, Computer Science",
address = "Hanover, NH",
number = "TR2001-410",
year = "2001",
month = jul,
URL = "http://www.cs.dartmouth.edu/reports/TR2001-410.ps.Z",
abstract = "Too often, ``security of Web transactions'' reduces to
``encryption of the channel''---and neglects to address
what happens at the server on the other end. This
oversight forces clients to trust the good intentions
and competence of the server operator---but gives
clients no basis for that trust. Furthermore, despite
academic and industrial research in secure
coprocessing, many in the computer science community
still regard ``secure hardware'' as a synonym for
``cryptographic accelerator.' This oversight neglects
the real potential of COTS secure coprocessing
technology to establish trusted islands of computation
in hostile environments---such as at web servers with
risk of insider attack. In this paper, we apply secure
coprocessing and cryptography to solve this real
problem in Web technology. We present a vision: using
secure coprocessors to establish trusted co-servers at
Web servers and moving sensitive computations inside
these co-servers. We present a prototype implementation
of this vision that scales to realistic workloads.
Finally, we validate this approach by building a simple
E-voting application on top of our prototype. From our
experience, we conclude that this approach provides a
practical and effective way to enhance the security of
Web servers against insider attack.",
}
@TechReport{Dartmouth:TR2001-411,
author = "Arne Grimstrup and Robert S. Gray and David Kotz and
Thomas Cowin and Greg Hill and Niranjan Suri and Daria
Chacon and Martin Hofmann",
title = "{Write Once, Move Anywhere: Toward Dynamic
Interoperability of Mobile Agent Systems}",
institution = "Dartmouth College, Computer Science",
address = "Hanover, NH",
number = "TR2001-411",
year = "2001",
month = jul,
URL = "http://www.cs.dartmouth.edu/reports/TR2001-411.ps.Z",
comment = "Revised July 25, 2001.",
abstract = "Mobile agents are an increasingly popular paradigm,
and in recent years there has been a proliferation of
mobile-agent systems. These systems are, however,
largely incompatible with each other. In particular,
agents cannot migrate to a host that runs a different
mobile-agent system. Prior approaches to
interoperability have tried to force agents to use a
common API, and so far none have succeeded. Our goal,
summarized in the catch phrase ``Write Once, Move
Anywhere,'' led to our efforts to develop mechanisms
that support dynamic runtime interoperability of
mobile-agent systems. This paper describes the Grid
Mobile-Agent System, which allows agents to migrate to
different mobile-agent systems.",
}
@TechReport{Dartmouth:TR2001-412,
author = "Hany Farid",
title = "{Detecting Steganographic Messages in Digital
Images}",
institution = "Dartmouth College, Computer Science",
address = "Hanover, NH",
number = "TR2001-412",
year = "2001",
month = sep,
URL = "http://www.cs.dartmouth.edu/reports/TR2001-412.ps.Z",
abstract = "Techniques and applications for information hiding
have become increasingly more sophisticated and
widespread. With high-resolution digital images as
carriers, detecting the presence of hidden messages has
also become considerably more difficult. It is
sometimes possible, nevertheless, to detect (but not
necessarily decipher) the presence of embedded
messages. The basic approach taken here works by
finding predictable higher-order statistics of
``natural'' images within a multi-scale decomposition,
and then showing that embedded messages alter these
statistics.",
}
@TechReport{Dartmouth:TR2001-413,
author = "Senthil Periaswamy and Hany Farid",
title = "{Differential Elastic Image Registration}",
institution = "Dartmouth College, Computer Science",
address = "Hanover, NH",
number = "TR2001-413",
year = "2001",
month = sep,
URL = "http://www.cs.dartmouth.edu/reports/TR2001-413.ps.Z",
abstract = "We have applied techniques from differential motion
estimation to the problem of automatic elastic
registration of medical images. This method models the
mapping between images as a locally affine but globally
smooth warp. The mapping also explicitly accounts for
variations in image intensities. This approach is
simple and highly effective across a broad range of
medical images. We show the efficacy of this approach
on several synthetic and clinical images.",
}
@TechReport{Dartmouth:TR2002-414,
author = "Valentino Crespi and George Cybenko and Massimo
Santini and Daniela Rus",
title = "{Decentralized Control for Coordinated flow of
Multi-Agent Systems}",
institution = "Dartmouth College, Computer Science",
address = "Hanover, NH",
number = "TR2002-414",
year = "2002",
month = jan,
URL = "http://www.cs.dartmouth.edu/reports/TR2002-414.ps.Z",
abstract = "This paper describes a distributed algorithm for
coordinating the flow of a mass of vehicles approaching
a highway exit or a tollbooth. We provide the problem
formulation, a general methodology for distributed
control and an instantiation of this methodology to the
coordinated flow problem. We analyze our algorithm and
provide experimental data.",
}
@TechReport{Dartmouth:TR2002-415,
author = "David Kotz and Robert S. Gray and Daniela Rus",
title = "{Future Directions for Mobile-Agent Research}",
institution = "Dartmouth College, Computer Science",
address = "Hanover, NH",
number = "TR2002-415",
year = "2002",
month = jan,
URL = "http://www.cs.dartmouth.edu/reports/TR2002-415.ps.Z",
abstract = "During a discussion in September 2000 the authors
examined the future of research on mobile agents and
mobile code. (A mobile agent is a running program that
can move from host to host in network at times and to
places of its own choosing.) In this paper we summarize
and reflect on that discussion. It became clear that
the field should shift its emphasis toward mobile code,
in all its forms, rather than to continue its narrow
focus on mobile agents. Furthermore, we encourage the
development of modular components, so that application
designers may take advantage of code mobility without
needing to rewrite their application to fit in a
monolithic mobile-agent system. There are many
potential applications that may productively use mobile
code, but there is no ``killer application'' for mobile
agents. Finally, we note that although security is an
important and challenging problem, there are many
applications and environments with security
requirements well within the capability of existing
mobile-code and mobile-agent frameworks.",
}
@TechReport{Dartmouth:TR2002-416,
author = "John C. Marchesini and Sean W. Smith",
title = "{Virtual Hierarchies - An Architecture for Building
and Maintaining Efficient and Resilient Trust
Chains.}",
institution = "Dartmouth College, Computer Science",
address = "Hanover, NH",
number = "TR2002-416",
year = "2002",
month = feb,
URL = "http://www.cs.dartmouth.edu/reports/TR2002-416.ps.Z",
abstract = "In Public Key Infrastructure (PKI), the simple,
monopolistic CA model works fine until we consider the
real world. Then, issues such as scalability and
mutually suspicious organizations create the need for a
multiplicity of CAs, which immediately introduces the
problem of how to organize them to balance resilience
to compromise against efficiency of path discovery.
However, security has given us tools such as secure
coprocessing, secret splitting, secret sharing, and
threshold cryptography for securely carrying out
computations among multiple trust domains; distributed
computing has given us peer-to-peer networking, for
creating self-organizing distributed systems. In this
paper, we use these latter tools to address the former
problem by overlaying a virtual hierarchy on a mesh
architecture of peer CAs, and achieving both resilience
and efficiency.",
}
@TechReport{Dartmouth:TR2002-417,
author = "Eileen Ye and Yougu Yuan and Sean Smith",
title = "{Web Spoofing Revisited: SSL and Beyond}",
institution = "Dartmouth College, Computer Science",
address = "Hanover, NH",
number = "TR2002-417",
year = "2002",
month = feb,
URL = "http://www.cs.dartmouth.edu/reports/TR2002-417.ps.Z",
comment = "This TR supercedes TR2001-409.",
abstract = "Can users believe what their browsers tell them? Even
sophisticated Web users decide whether or not to trust
a server based on browser cues such as location bar
information, SSL icons, SSL warnings, certificate
information, and response time. In their seminal work
on Web spoofing, Felten et al showed how, in 1996, a
malicious server could forge some of these cues.
However, this work used genuine SSL sessions, and Web
technology has evolved much since 1996. The Web has
since become the pre-eminent medium for electronic
service delivery to remote users, and the security of
many commerce, government, and academic network
applications critically rests on the assumption that
users can authenticate the servers with which they
interact. This situation raises the question: is the
browser-user communication model today secure enough to
warrant this assumption? In this paper, we answer this
question by systematically showing how a malicious
server can forge every one of the above cues. Our work
extends the prior results by examining contemporary
browsers, and by forging all of the SSL information a
client sees, including the very existence of an SSL
session (thus providing a cautionary tale about the
security of one of the most common applications of
PKI). We have made these techniques available for
public demonstration, because anything less than
working code would not convincingly answer the
question. We also discuss implications and potential
countermeasures, both short-term and long-term.",
}
@TechReport{Dartmouth:TR2002-418,
author = "Eileen Ye and Sean Smith",
title = "{Trusted Paths for Browsers: An Open-Source Solution
to Web Spoofing}",
institution = "Dartmouth College, Computer Science",
address = "Hanover, NH",
number = "TR2002-418",
year = "2002",
month = feb,
URL = "http://www.cs.dartmouth.edu/reports/TR2002-418.ps.Z",
abstract = "The security of the vast majority of ``secure'' Web
services rests on SSL server PKI. However, this PKI
doesn't work if the the adversary can trick the browser
into appearing to tell the user the wrong thing about
the certificates and cryptography. The seminal web
spoofing work of Felten et al demonstrated the
potential, in 1996, for malicious servers to
impersonate honest servers. Our recent follow-up work
explicitly shows how malicious servers can still do
this---and can also forge the existence of an SSL
session and the contents of the alleged server
certificate. This paper reports the results of our work
to systematically defend against Web spoofing, by
creating a trusted path from the browser to the user.
Starting with the Mozilla source, we have implemented
techniques that protect a wide variety of browser-user
communications, that require little participation by
the user and minimal disruption of the displayed server
content. We have prepared shell scripts that install
these modifications on the Mozilla source, to enable
others to replicate this work. In on-going work, we are
cleaning up and fine-tuning our code. In future work,
we hope to examine more deeply the role of user
interfaces in enabling users to make effective trust
judgments.",
}
@TechReport{Dartmouth:TR2002-419,
author = "Dennis M. Healy and Daniel N. Rockmore and Peter J.
Kostelec and Sean S. B. Moore",
title = "{FFTs for the 2-Sphere - Improvements and
Variations}",
institution = "Dartmouth College, Computer Science",
address = "Hanover, NH",
number = "TR2002-419",
year = "2002",
month = mar,
URL = "http://www.cs.dartmouth.edu/reports/TR2002-419.ps.Z",
comment = "Preliminary versions of some of these results have
appeared in the Dartmouth College Department of
Computer Science Technical Report PCS-TR94-222 and ``An
FFT for the 2-sphere and Applications'', Proc. of
ICASSP-96, Volume 3, pp. 1323--1326.",
abstract = "Earlier work by Driscoll and Healy has produced an
efficient algorithm for computing the Fourier transform
of band-limited functions on the 2-sphere. In this
paper we present a reformulation and variation of the
original algorithm which results in a greatly improved
inverse transform, and consequent improved convolution
algorithm for such functions. All require at most
$O(N\log^2 N)$ operations where $N$ is the number of
sample points. We also address implementation
considerations and give heuristics for allowing
reliable and computationally efficient floating point
implementations of slightly modified algorithms. These
claims are supported by extensive numerical experiments
from our implementation in C on DEC, HP, SGI and Linux
Pentium platforms. These results indicate that
variations of the algorithm are both reliable and
efficient for a large range of useful problem sizes.
Performance appears to be architecture-dependent. The
paper concludes with a brief discussion of a few
potential applications.",
}
@TechReport{Dartmouth:TR2002-420,
author = "Guanling Chen and David Kotz",
title = "{Context Aggregation and Dissemination in Ubiquitous
Computing Systems}",
institution = "Dartmouth College, Computer Science",
address = "Hanover, NH",
number = "TR2002-420",
year = "2002",
month = feb,
URL = "http://www.cs.dartmouth.edu/reports/TR2002-420.ps.Z",
comment = "To appear in WMCSA 2002.",
abstract = "Many ``ubiquitous computing'' applications need a
constant flow of information about their environment to
be able to adapt to their changing context. To support
these ``context-aware'' applications we propose a
graph-based abstraction for collecting, aggregating,
and disseminating context information. The abstraction
models context information as events, produced by
sources and flowing through a directed acyclic graph of
event-processing operators and delivered to subscribing
applications. Applications describe their desired event
stream as a tree of operators that aggregate low-level
context information published by existing sources into
the high-level context information needed by the
application. The operator graph is thus the dynamic
combination of all applications' subscription trees. In
this paper, we motivate and describe our graph
abstraction, and discuss a variety of critical design
issues. We also sketch our Solar system, an
implementation that represents one point in the design
space for our graph abstraction.",
}
@TechReport{Dartmouth:TR2002-421,
author = "Guanling Chen and David Kotz",
title = "{Solar: A pervasive-computing infrastructure for
context-aware mobile applications}",
institution = "Dartmouth College, Computer Science",
address = "Hanover, NH",
number = "TR2002-421",
year = "2002",
month = feb,
URL = "http://www.cs.dartmouth.edu/reports/TR2002-421.ps.Z",
abstract = "Emerging pervasive computing technologies transform
the way we live and work by embedding computation in
our surrounding environment. To avoid increasing
complexity, and allow the user to concentrate on her
tasks, applications must automatically adapt to their
changing \emph{context}, the physical and computational
environment in which they run. To support these
``context-aware'' applications we propose a graph-based
abstraction for collecting, aggregating, and
disseminating context information. The abstraction
models context information as \emph{events}, which are
produced by \emph{sources}, flow through a directed
acyclic graph of event-processing \emph{operators}, and
are delivered to subscribing applications. Applications
describe their desired event stream as a tree of
operators that aggregate low-level context information
published by existing sources into the high-level
context information needed by the application. The
\emph{operator graph\/} is thus the dynamic combination
of all applications' subscription trees. In this paper,
we motivate our graph abstraction by discussing several
applications under development, sketch the architecture
of our system (``Solar'') that implements our
abstraction, report some early experimental results
from the prototype, and outline issues for future
research.",
}
@TechReport{Dartmouth:TR2002-422,
author = "Kazuhiro Minami and David Kotz",
title = "{Controlling access to pervasive information in the
``Solar'' system}",
institution = "Dartmouth College, Computer Science",
address = "Hanover, NH",
number = "TR2002-422",
year = "2002",
month = feb,
URL = "http://www.cs.dartmouth.edu/reports/TR2002-422.ps.Z",
abstract = "Pervasive-computing infrastructures necessarily
collect a lot of context information to disseminate to
their context-aware applications. Due to the personal
or proprietary nature of much of this context
information, however, the infrastructure must limit
access to context information to authorized persons. In
this paper we propose a new access-control mechanism
for event-based context-distribution infrastructures.
The core of our approach is based on a conservative
information-flow model of access control, but users may
express discretionary relaxation of the resulting
access-control list (ACL) by specifying relaxation
functions. This combination of automatic ACL derivation
and user-specified ACL relaxation allows access control
to be determined and enforced in a decentralized,
distributed system with no central administrator or
central policy maker. It also allows users to express
their personal balance between functionality and
privacy. Finally, our infrastructure allows
access-control policies to depend on context-sensitive
roles, allowing great flexibility. We describe our
approach in terms of a specific context-dissemination
framework, the Solar system, although the same
principles would apply to systems with similar
properties.",
}
@TechReport{Dartmouth:TR2002-423,
author = "David Kotz and Kobby Essien",
title = "{Characterizing Usage of a Campus-wide Wireless
Network}",
institution = "Dartmouth College, Computer Science",
address = "Hanover, NH",
number = "TR2002-423",
year = "2002",
month = mar,
URL = "http://www.cs.dartmouth.edu/reports/TR2002-423.ps.Z",
comment = "A major revision of this paper appeared in Mobicom
2002. The Mobicom paper contained two erroneous
figures, however; another report, TR2002-432, is the
final corrected version.",
abstract = "Wireless local-area networks (WLANs) are increasingly
common, but little is known about how they are used. A
clear understanding of usage patterns in real WLANs is
critical information to those who develop, deploy, and
manage WLAN technology, as well as those who develop
systems and application software for wireless networks.
This paper presents results from the largest and most
comprehensive trace of network activity in a large,
production wireless LAN. For eleven weeks we traced the
activity of nearly two thousand users drawn from a
general campus population, using a campus-wide network
of 476 access points spread over 161 buildings. Our
study expands on those done by Tang and Baker, with a
significantly larger and broader population. We found
that residential traffic dominated all other traffic,
particularly in residences populated by newer students;
students are increasingly choosing a wireless laptop as
their primary computer. Although web protocols were the
single largest component of traffic volume, network
backup and file sharing contributed an unexpectedly
large amount to the traffic. Although there was some
roaming within a network session, we were surprised by
the number of situations in which cards roamed
excessively, unable to settle on one access point.
Cross-subnet roams were an especial problem, because
they broke IP connections, indicating the need for
solutions that avoid or accommodate such roams.",
}
@TechReport{Dartmouth:TR2002-424,
author = "Mark H. Montague",
title = "{Metasearch: Data Fusion for Document Retrieval}",
institution = "Dartmouth College, Computer Science",
address = "Hanover, NH",
number = "TR2002-424",
year = "2002",
month = may,
URL = "http://www.cs.dartmouth.edu/reports/TR2002-424.ps.Z",
comment = "Ph.D dissertation.",
abstract = "The metasearch problem is to optimally merge the
ranked lists output by an arbitrary number of search
systems into one ranked list. In this work: (1) We show
that metasearch improves upon not just the raw
performance of the input search engines, but also upon
the consistency of the input search engines from query
to query. (2) We experimentally prove that simply
weighting input systems by their average performance
can dramatically improve fusion results. (3) We show
that score normalization is an important component of a
metasearch engine, and that dependence upon statistical
outliers appears to be the problem with the standard
technique. (4) We propose a Bayesian model for
metasearch that outperforms the best input system on
average and has performance competetive with standard
techniques. (5) We introduce the use of Social Choice
Theory to the metasearch problem, modeling metasearch
as a democratic election. We adapt a positional voting
algorithm, the Borda Count, to create a metasearch
algorithm, acheiving reasonable performance. (6) We
propose a metasearch model adapted from a majoritarian
voting procedure, the Condorcet algorithm. The
resulting algorithm is the best performing algorithm in
a number of situations. (7) We propose three upper
bounds for the problem, each bounding a different class
of algorithms. We present experimental results for each
algorithm using two types of experiments on each of
four data sets.",
}
@TechReport{Dartmouth:TR2002-425,
author = "Marco A. Barreno",
title = "{The Future of Cryptography Under Quantum Computers}",
institution = "Dartmouth College, Computer Science",
address = "Hanover, NH",
number = "TR2002-425",
year = "2002",
month = jul,
URL = "http://www.cs.dartmouth.edu/reports/TR2002-425.ps.Z",
comment = "This paper was written as a senior honors thesis with
advisor Sean W. Smith.",
abstract = "Cryptography is an ancient art that has passed through
many paradigms, from simple letter substitutions to
polyalphabetic substitutions to rotor machines to
digital encryption to public-key cryptosystems. With
the possible advent of quantum computers and the
strange behaviors they exhibit, a new paradigm shift in
cryptography may be on the horizon. Quantum computers
could hold the potential to render most modern
encryption useless against a quantum-enabled adversary.
The aim of this thesis is to characterize this
convergence of cryptography and quantum computation. We
provide definitions for cryptographic primitives that
frame them in general terms with respect to complexity.
We explore the various possible relationships between
BQP, the primary quantum complexity class, and more
familiar classes, and we analyze the possible
implications for cryptography.",
}
@TechReport{Dartmouth:TR2002-426,
author = "Christopher P. Masone",
title = "{Role Definition Language (RDL): A Language to
Describe Context-Aware Roles}",
institution = "Dartmouth College, Computer Science",
address = "Hanover, NH",
number = "TR2002-426",
year = "2002",
month = may,
URL = "http://www.cs.dartmouth.edu/reports/TR2002-426.ps.Z",
comment = "Senior Honors Thesis. Advisor: David Kotz.",
abstract = "As wireless networks become more prevalent, a widening
array of computational resources becomes available to
the mobile user. Since not all users should have
unrestricted access to these resources, a method of
access control must be devised. In a context-aware
environment, context information can be used to
supplement more conventional password-based access
control systems. We believe the best way to achieve
this is through the use of Context-Aware Role-Based
Access Control, a model in which permissions are
assigned to entities called roles, each principal is a
member of one or more roles, and a role's membership is
determined using context information. We designed and
implemented RDL (Role-Definition Language), a simple,
expressive and somewhat extensible programming language
to facilitate the description of roles in terms of
context information.",
}
@TechReport{Dartmouth:TR2002-427,
author = "A. Abram White",
title = "{Performance and Interoperability In Solar}",
institution = "Dartmouth College, Computer Science",
address = "Hanover, NH",
number = "TR2002-427",
year = "2002",
month = jun,
URL = "http://www.cs.dartmouth.edu/reports/TR2002-427.ps.Z",
comment = "Senior Honors Thesis. Advisor: David Kotz. See also
TR2002-429.",
abstract = "Ubiquitous computing promises to integrate computers
into our physical environment, surrounding us with
applications that are able to adapt to our dynamics.
Solar is a software infrastructure designed to deliver
contextual information to these applications. To serve
the large number and wide variety of context-aware
devices envisioned by ubiquitous computing, Solar must
exhibit both high performance and the ability to
interoperate with many computing platforms. We created
a testing framework to measure the performance of
distributed systems such as Solar, as well as a
pluggable data-transfer mechanism to support the
dissemination of information to heterogeneous
applications. This paper explores the testing framework
developed, analyzes its findings concerning the
performance of the current Solar prototype, presents
several optimizations to Solar and their effects, and
finally discusses the design of the pluggable
data-transfer mechanism.",
}
@TechReport{Dartmouth:TR2002-428,
author = "Sebastien M. Lahaie",
title = "{Information-theoretic Bounds on the Training and
Testing Error of Boosting}",
institution = "Dartmouth College, Computer Science",
address = "Hanover, NH",
number = "TR2002-428",
year = "2002",
month = may,
URL = "http://www.cs.dartmouth.edu/reports/TR2002-428.ps.Z",
abstract = "Boosting is a means of using weak learners as
subroutines to produce a strong learner with markedly
better accuracy. Recent results showing the connection
between logistic regression and boosting provide the
foundation for an information-theoretic analysis of
boosting. We describe the analogy between boosting and
gambling, which allows us to derive a new upper bound
on training error. This upper bound explicitly
describes the effect of noisy data on training error.
We also use information-theoretic techniques to derive
an alternative upper-bound on testing error which is
independent of the size of the weak-learner space.",
}
@TechReport{Dartmouth:TR2002-429,
author = "A. Abram White",
title = "{XSLT and XQuery as Operator Languages}",
institution = "Dartmouth College, Computer Science",
address = "Hanover, NH",
number = "TR2002-429",
year = "2002",
month = jun,
URL = "http://www.cs.dartmouth.edu/reports/TR2002-429.ps.Z",
comment = "See also TR2002-427.",
abstract = "Ubiquitous computing promises to integrate computers
into our physical environment, surrounding us with
applications that are able to adapt to our dynamics.
Solar is a software infrastructure designed to deliver
contextual information to these applications. Solar
represents context data as events, and uses small
programs called operators to filter, merge, aggregate,
or transform event streams. This paper explores the
possibility of using XSLT and XQuery to build
language-neutral Solar operators.",
}
@TechReport{Dartmouth:TR2002-430,
author = "Eileen Zishuang Ye",
title = "{Building Trusted Paths for Web Browsers}",
institution = "Dartmouth College, Computer Science",
address = "Hanover, NH",
number = "TR2002-430",
year = "2002",
month = may,
URL = "http://www.cs.dartmouth.edu/reports/TR2002-430.ps.Z",
abstract = "The communication between the Web browser and the
human user is one component of the server-client
channel. It is not the user but the browser that
receives all server information and establishes the
secure connection. The browser's user interface
signals, such as SSL lock, https protocol header et
al., indicate whether the browser-server communication
at the current moment is secure. Those user interface
signals indicating the security status of browser
should be clearly and correctly understood by the user.
A survey of modern Web browsers shows the information
provided by current browsers is insufficient for users
to make trust judgment. Our Web spoofing work further
proved that the browser status information is not
reliable either. We discuss the criteria for and how to
build the trusted paths between a browser and a human
user. We present an open source implementation of one
of the designs--synchronized random dynamic (SRD)
boundary, based on Modified Mozilla source code,
together with its usability study results.",
}
@TechReport{Dartmouth:TR2002-431,
author = "Kobby Essien",
title = "{Analysis of Protein Sequences Using Time Frequency
and Kolmogorov-Smirnov Methods}",
institution = "Dartmouth College, Computer Science",
address = "Hanover, NH",
number = "TR2002-431",
year = "2002",
month = may,
URL = "http://www.cs.dartmouth.edu/reports/TR2002-431.ps.Z",
comment = "Senior Honors Thesis. Advisor: Metin Akay.
",
abstract = "The plethora of genomic data currently available has
resulted in a search for new algorithms and analysis
techniques to interpret genomic data. In this two-fold
study we explore techniques for locating critical amino
acid residues in protein sequences and for estimating
the similarity between proteins. We demonstrate the use
of the Short-Time Fourier Transform and the Continuous
Wavelet Transform together with amino acid
hydrophobicity in locating important amino acid domains
in proteins and also show that the Kolmogorov-Smirnov
statistic can be used as a metric of protein
similarity.",
}
@TechReport{Dartmouth:TR2002-432,
author = "David Kotz and Kobby Essien",
title = "{Analysis of a Campus-wide Wireless Network}",
institution = "Dartmouth College, Computer Science",
address = "Hanover, NH",
number = "TR2002-432",
year = "2002",
month = sep,
URL = "http://www.cs.dartmouth.edu/reports/TR2002-432.ps.Z",
comment = "This paper is a revision of the MOBICOM '02 paper by
the same title. The only difference is the correction
of Figures 27-28 and the associated text. This report
supplants TR2002-423.",
abstract = "Understanding usage patterns in wireless local-area
networks (WLANs) is critical for those who develop,
deploy, and manage WLAN technology, as well as those
who develop systems and application software for
wireless networks. This paper presents results from the
largest and most comprehensive trace of network
activity in a large, production wireless LAN. For
eleven weeks we traced the activity of nearly two
thousand users drawn from a general campus population,
using a campus-wide network of 476 access points spread
over 161 buildings. Our study expands on those done by
Tang and Baker, with a significantly larger and broader
population. We found that residential traffic dominated
all other traffic, particularly in residences populated
by newer students; students are increasingly choosing a
wireless laptop as their primary computer. Although web
protocols were the single largest component of traffic
volume, network backup and file sharing contributed an
unexpectedly large amount to the traffic. Although
there was some roaming within a network session, we
were surprised by the number of situations in which
cards roamed excessively, unable to settle on one
access point. Cross-subnet roams were an especial
problem, because they broke IP connections, indicating
the need for solutions that avoid or accommodate such
roams.",
}
@TechReport{Dartmouth:TR2002-433,
author = "Ron Oldfield and David Kotz",
title = "{Using the Emulab network testbed to evaluate the
Armada I/O framework for computational grids}",
institution = "Dartmouth College, Computer Science",
address = "Hanover, NH",
number = "TR2002-433",
year = "2002",
month = sep,
URL = "http://www.cs.dartmouth.edu/reports/TR2002-433.ps.Z",
abstract = "This short report describes our experiences using the
Emulab network testbed at the University of Utah to
test performance of the Armada framework for parallel
I/O on computational grids.",
}
@TechReport{Dartmouth:TR2002-434,
author = "Ryan H. Lilien and Hany Farid and Bruce R. Donald",
title = "{Probabilistic Disease Classification of
Expression-Dependent Proteomic Data from Mass
Spectrometry of Human Serum}",
institution = "Dartmouth College, Computer Science",
address = "Hanover, NH",
number = "TR2002-434",
year = "2002",
month = oct,
URL = "http://www.cs.dartmouth.edu/reports/TR2002-434.ps.Z",
comment = "To appear in Journal of Computational Biology
(2003).",
abstract = "We have developed an algorithm called Q5 for
probabilistic classification of healthy vs. disease
whole serum samples using mass spectrometry. The
algorithm employs Principal Components Analysis (PCA)
followed by Linear Discriminant Analysis (LDA) on whole
spectrum Surface-Enhanced Laser Desorption/Ionization
Time of Flight (SELDI-TOF) Mass Spectrometry (MS) data,
and is demonstrated on four real datasets from
complete, complex SELDI spectra of human blood serum.
Q5 is a closed-form, exact solution to the problem of
classification of complete mass spectra of a complex
protein mixture. Q5 employs a novel probabilistic
classification algorithm built upon a dimension-reduced
linear discriminant analysis. Our solution is
computationally efficient; it is non-iterative and
computes the optimal linear discriminant using
closed-form equations. The optimal discriminant is
computed and verified for datasets of complete, complex
SELDI spectra of human blood serum. Replicate
experiments of different training/testing splits of
each dataset are employed to verify robustness of the
algorithm. The probabilistic classification method
achieves excellent performance. We achieve sensitivity,
specificity, and positive predictive values above 97%
on three ovarian cancer datasets and one prostate
cancer dataset. The Q5 method outperforms previous
full-spectrum complex sample spectral classification
techniques, and can provide clues as to the molecular
identities of differentially-expressed proteins and
peptides.",
}
@TechReport{Dartmouth:TR2002-435,
author = "Qun Li and Michael De Rosa and Daniela Rus",
title = "{Distributed Algorithms for Guiding Navigation across
a Sensor Network}",
institution = "Dartmouth College, Computer Science",
address = "Hanover, NH",
number = "TR2002-435",
year = "2002",
month = oct,
URL = "http://www.cs.dartmouth.edu/reports/TR2002-435.ps.Z",
abstract = "We develop distributed algorithms for
self-reconfiguring sensor networks that respond to
directing a target through a region. The sensor network
models the danger levels sensed across its area and has
the ability to adapt to changes. It represents the
dangerous areas as obstacles. A protocol that combines
the artificial potential field of the sensors with the
goal location for the moving object guides the object
incrementally across the network to the goal, while
maintaining the safest distance to the danger areas. We
report on hardware experiments using a physical sensor
network consisting of Mote sensors.",
}
@TechReport{Dartmouth:TR2002-436,
author = "Robert C. Fitch",
title = "{Heterogeneous Self-Reconfiguring Robotics}",
institution = "Dartmouth College, Computer Science",
address = "Hanover, NH",
number = "TR2002-436",
year = "2002",
month = nov,
URL = "http://www.cs.dartmouth.edu/reports/TR2002-436.ps.Z",
abstract = "Self-reconfiguring robots are modular systems that can
change shape, or {"}reconfigure,{"} to match structure
to task. They comprise many small, discrete, often
identical modules that connect together and that are
minimally actuated. Global shape transformation is
achieved by composing local motions. Systems with a
single module type, known as {"}homogeneous{"} systems,
gain fault tolerance, robustness and low production
cost from module interchangeability. However, we are
interested in {"}heterogeneous{"} systems, which
include multiple types of modules such as those with
sensors, batteries or wheels. We believe that
heterogeneous systems offer the same benefits as
homogeneous systems with the added ability to match not
only structure to task, but also capability to task.
Although significant results have been achieved in
understanding homogeneous systems, research in
heterogeneous systems is challenging as key algorithmic
issues remain unexplored. We propose in this thesis to
investigate questions in four main areas: 1) how to
classify heterogeneous systems, 2) how to develop
efficient heterogeneous reconfiguration algorithms with
desired characteristics, 3) how to characterize the
complexity of key algorithmic problems, and 4) how to
apply these heterogeneous algorithms to perform useful
new tasks in simulation and in the physical world. Our
goal is to develop an algorithmic basis for
heterogeneous systems. This has theoretical
significance in that it addresses a major open problem
in the field, and practical significance in providing
self-reconfiguring robots with increased
capabilities.",
}
@TechReport{Dartmouth:TR2002-437,
author = "Heng Huang and Chris Hawblitzel",
title = "{Proofs of Soundness and Strong Normalization for
Linear Memory Types}",
institution = "Dartmouth College, Computer Science",
address = "Hanover, NH",
number = "TR2002-437",
year = "2002",
month = nov,
URL = "http://www.cs.dartmouth.edu/reports/TR2002-437.ps.Z",
abstract = "Efficient low-level systems need more control over
memory than safe high-level languages usually provide.
As a result, run-time systems are typically written in
unsafe languages such as C. This report describes an
abstract machine designed to give type-safe code more
control over memory. It includes complete definitions
and proofs.",
}
@TechReport{Dartmouth:TR2002-438,
author = "Valentino Crespi",
title = "{Exact formulae for the Lovasz Theta Function of
sparse Circulant Graphs}",
institution = "Dartmouth College, Computer Science",
address = "Hanover, NH",
number = "TR2002-438",
year = "2002",
month = nov,
URL = "http://www.cs.dartmouth.edu/reports/TR2002-438.ps.Z",
abstract = "The Lovasz theta function has attracted a lot of
attention for its connection with diverse issues, such
as communicating without errors and computing large
cliques in graphs. Indeed this function enjoys the
remarkable property of being computable in polynomial
time, despite being sandwitched between clique and
chromatic number, two well known hard to compute
quantities. In this paper I provide a closed formula
for the Lovasz function of a specific class of sparse
circulant graphs thus generalizing Lovasz results on
cycle graphs (circulant graphs of degree 2).",
}
@TechReport{Dartmouth:TR2003-439,
author = "Chris J. Langmead and Bruce R. Donald",
title = "{3D-Structural Homology Detection via Unassigned
Residual Dipolar Couplings}",
institution = "Dartmouth College, Computer Science",
address = "Hanover, NH",
number = "TR2003-439",
year = "2003",
month = jan,
URL = "http://www.cs.dartmouth.edu/reports/TR2003-439.pdf",
comment = "A revised and expanded version of this TR will appear
as a refereed paper at the
IEEE Computer Society Bioinformatics Conference ,
Stanford, California (August, 2003),",
abstract = "Recognition of a protein's fold provides valuable
information about its function. While many
sequence-based homology prediction methods exist, an
important challenge remains: two highly dissimilar
sequences can have similar folds --- how can we detect
this rapidly, in the context of structural genomics?
High-throughput NMR experiments, coupled with novel
algorithms for data analysis, can address this
challenge. We report an automated procedure for
detecting 3D-structural homologies from sparse,
unassigned protein NMR data. Our method identifies the
3D-structural models in a protein structural database
whose geometries best fit the unassigned experimental
NMR data. It does not use sequence information and is
thus not limited by sequence homology. The method can
also be used to confirm or refute structural
predictions made by other techniques such as protein
threading or sequence homology. The algorithm runs in
O(pnk3) time, where p is the number of
proteins in the database, n is the number of residues
in the target protein, and k is the resolution of a
rotation search. The method requires only uniform
15N-labelling of the protein and processes unassigned
1H-15N residual dipolar couplings, which can be
acquired in a couple of hours. Our experiments on NMR
data from 5 different proteins demonstrate that the
method identifies closely related protein folds,
despite low-sequence homology between the target
protein and the computed model.",
}
@TechReport{Dartmouth:TR2003-440,
author = "David M. Nicol and Sean W. Smith and Meiyuan Zhao",
title = "{Efficient Security for BGP Route Announcements}",
institution = "Dartmouth College, Computer Science",
address = "Hanover, NH",
number = "TR2003-440",
year = "2003",
month = may,
URL = "http://www.cs.dartmouth.edu/reports/TR2003-440.R2.ps.Z",
comment = "Revision 2 released May 9, 2003. Original revision 1,
of February 2003, is available in pdf
or ps.Z.",
abstract = "The Border Gateway Protocol (BGP) determines how
Internet traffic is routed throughout the entire world;
malicious behavior by one or more BGP speakers could
create serious security issues. Since the protocol
depends on a speaker honestly reporting path
information sent by previous speakers and involves a
large number of independent speakers, the Secure BGP
(S-BGP) approach uses public-key cryptography to ensure
that a malicious speaker cannot fabricate this
information. However, such public-key cryptography is
expensive: S-BGP requires a digital signature operation
on each announcement sent to each peer, and a linear
(in the length of the path) number of verifications on
each receipt. We use simulation of a 110 AS system
derived from the Internet to evaluate the impact that
the processing costs of cryptography have on BGP
convergence time. We find that under heavy load the
convergence time using ordinary S-BGP is nearly twice
as large as under BGP. We examine the impact of highly
aggressive caching and pre-computation optimizations
for S-BGP, and find that convergence time is much
closer to BGP. However, these optimizations may be
unrealistic, and are certainly expensive of memory. We
consequently use the structure of BGP processing to
design optimizations that reduce cryptographic overhead
by amortizing the cost of private-key signatures over
many messages. We call this method
Signature-Amortization (S-A). We find that S-A provides
as good or better convergence times as the highly
optimized S-BGP, but without the cost and complications
of caching and pre-computation. It is possible
therefore to minimize the impact route validation has
on convergence, by being careful with signatures,
rather than consumptive of memory.",
}
@TechReport{Dartmouth:TR2003-442,
author = "Alex Iliev and Sean Smith",
title = "{Privacy-enhanced credential services}",
institution = "Dartmouth College, Computer Science",
address = "Hanover, NH",
number = "TR2003-442",
year = "2003",
month = feb,
URL = "http://www.cs.dartmouth.edu/reports/TR2003-442.ps.Z",
comment = "Submitted to the 2nd Annual PKI Research Workshop.",
abstract = "The use of credential directories in PKI and
authorization systems such as Shibboleth introduces a
new privacy risk: an insider at the directory can learn
much about otherwise protected interactions by
observing who makes queries, and what they ask for.
Recent advances in Practical Private Information
Retrieval provide promising countermeasures. In this
paper, we extend this technology to solve this new
privacy problem, and present a design and preliminary
prototype for a LDAP-based credential service that can
prevent even an insider from learning anything more
than the fact a query was made. Our preliminary
performance analysis suggests that the complete
prototype may be sufficiently robust for academic
enterprise settings.",
}
@TechReport{Dartmouth:TR2003-443,
author = "John C. Marchesini and Sean W. Smith and Meiyuan
Zhao",
title = "{Keyjacking: Risks of the Current Client-side
Infrastructure}",
institution = "Dartmouth College, Computer Science",
address = "Hanover, NH",
number = "TR2003-443",
year = "2003",
month = feb,
URL = "http://www.cs.dartmouth.edu/reports/TR2003-443.ps.Z",
abstract = "In theory, PKI can provide a flexible and strong way
to authenticate users in distributed information
systems. In practice, much is being invested in
realizing this vision via client-side SSL and
browser-based keystores. Exploring this vision, we
demonstrate that browsers will use personal
certificates to authenticate requests that the person
neither knew of nor approved (and which password-based
systems would have defeated), and we demonstrate the
easy permeability of these keystores (including new
attacks on medium and high-security IE/XP keys). We
suggest some countermeasures, but also suggest that a
fundamental rethinking of the trust, usage, and storage
model might result in a more effective PKI.",
}
@TechReport{Dartmouth:TR2003-444,
author = "Geeta Chaudhry and Thomas H. Cormen",
title = "{Stupid Columnsort Tricks}",
institution = "Dartmouth College, Computer Science",
address = "Hanover, NH",
number = "TR2003-444",
year = "2003",
month = apr,
URL = "http://www.cs.dartmouth.edu/reports/TR2003-444.ps.Z",
abstract = "Leighton's columnsort algorithm sorts on an $r \times
s$ mesh, subject to the restrictions that $s$ is a
divisor of~$r$ and that $r \geq 2s^2$ (so that the mesh
is tall and thin). We show how to mitigate both of
these restrictions. One result is that the requirement
that $s$ is a divisor of~$r$ is unnecessary; columnsort
sorts correctly whether or not $s$ divides~$r$. We
present two algorithms that, as long as $s$ is a
perfect square, relax the restriction that $r \geq
2s^2$; both reduce the exponent of~$s$ to~$3/2$. One
algorithm requires $r \geq 4s^{3/2}$ if $s$ divides~$r$
and $r \geq 6s^{3/2}$ if $s$ does not divide~$r$. The
other algorithm requires $r \geq 4^{3/2}$, and it
requires $s$ to be a divisor of~$r$. Both algorithms
have applications in increasing the maximum problem
size in out-of-core sorting programs.",
}
@TechReport{Dartmouth:TR2003-445,
author = "Geeta Chaudhry and Elizabeth A. Hamon and Thomas H.
Cormen",
title = "{Relaxing the Problem-Size Bound for Out-of-Core
Columnsort}",
institution = "Dartmouth College, Computer Science",
address = "Hanover, NH",
number = "TR2003-445",
year = "2003",
month = apr,
URL = "http://www.cs.dartmouth.edu/reports/TR2003-445.ps.Z",
abstract = "Previous implementations of out-of-core columnsort
limit the problem size to $N \leq \sqrt{(M/P)^3 / 2}$,
where $N$ is the number of records to sort, $P$ is the
number of processors, and $M$ is the total number of
records that the entire system can hold in its memory
(so that $M/P$ is the number of records that a single
processor can hold in its memory). We implemented two
variations to out-of-core columnsort that relax this
restriction. Subblock columnsort is based on an
algorithmic modification of the underlying columnsort
algorithm, and it improves the problem-size bound to $N
\leq (M/P)^{5/3} / 4^{2/3}$ but at the cost of
additional disk I/O\@. $M$-columnsort changes the
notion of the column size in columnsort, improving the
maximum problem size to $N \leq \sqrt{M^3 / 2}$ but at
the cost of additional computation and communication.
Experimental results on a Beowulf cluster show that
both subblock columnsort and $M$-columnsort run well
but that $M$-columnsort is faster. A further advantage
of $M$-columnsort is that it handles a wider range of
problem sizes than subblock columnsort.",
}
@TechReport{Dartmouth:TR2003-446,
author = "Prasad Jayanti and Srdjan Petrovic",
title = "{Efficient and Practical Constructions of LL/SC
Variables}",
institution = "Dartmouth College, Computer Science",
address = "Hanover, NH",
number = "TR2003-446",
year = "2003",
month = jun,
URL = "http://www.cs.dartmouth.edu/reports/TR2003-446.pdf",
abstract = "Over the past decade, LL/SC have emerged as the most
suitable synchronization instructions for the design of
lock-free algorithms. However, current architectures do
not support these instructions; instead, they support
either CAS or RLL/RSC (e.g. POWER4, MIPS, SPARC,
IA-64). To bridge this gap, this paper presents two
efficient wait-free algorithms for implementing 64-bit
LL/SC objects from 64-bit CAS or RLL/RSC objects. Our
first algorithm is practical: it has a small, constant
time complexity (of 4 for LL and 5 for SC) and a space
overhead of only 4 words per process. This algorithm
uses unbounded sequence numbers. For theoretical
interest, we also present a more complex bounded
algorithm that still guarantees constant time
complexity and O(1) space overhead per process. The
LL/SC primitive is free of the well-known ABA problem
that afflicts CAS. By efficiently implementing LL/SC
words from CAS words, this work presents an efficient
general solution to the ABA problem.",
}
@TechReport{Dartmouth:TR2003-448,
author = "Thomas Mueller",
title = "{Billiards Adviser as a Search in a Continuous Domain
with Significant Uncertainty}",
institution = "Dartmouth College, Computer Science",
address = "Hanover, NH",
number = "TR2003-448",
year = "2003",
month = may,
URL = "http://www.cs.dartmouth.edu/reports/TR2003-448.pdf",
comment = "Advisor: Zack Butler",
abstract = "Typical search algorithms are limited to problems in
which there is a certain number of moves for any given
state, and the effect of each move is well known. In
order to overcome this limitation, we consider the
problem of determining the optimal shot given the
positions of balls on a billiards table. Our solution
includes the image recognition necessary to determine
each ball's position, the calculation of the optimal
shot, and the presentation of that shot to the player.
The focus of the paper is on the second part -
determining the angle and force with which the player
should attempt to hit the cue ball for each shot in
order to sink all of the other balls with the fewest
shots. The solution to this problem is unique from
other game search algorithms in that it must take into
account the infinite number of possible shots given any
configuration of balls as well as the fact that the
player is not likely to hit the ball exactly how he
attempts to do so. We compare the performance of our
algorithm with one that ignores the latter fact to show
that our modifications do in fact improve performance
for a search in a continuous domain with significant
uncertainty.",
}
@TechReport{Dartmouth:TR2003-449,
author = "Lisa A. Torrey",
title = "{An Active Learning Approach to Efficiently Ranking
Retrieval Engines}",
institution = "Dartmouth College, Computer Science",
address = "Hanover, NH",
number = "TR2003-449",
year = "2003",
month = may,
URL = "http://www.cs.dartmouth.edu/reports/TR2003-449.ps.Z",
comment = "Senior Honors Thesis. Advisor: Jay Aslam.",
abstract = "Evaluating retrieval systems, such as those submitted
to the annual TREC competition, usually requires a
large number of documents to be read and judged for
relevance to query topics. Test collections are far too
big to be exhaustively judged, so only a subset of
documents is selected to form the judgment ``pool.''
The selection method that TREC uses produces pools that
are still quite large. Research has indicated that it
is possible to rank the retrieval systems correctly
using substantially smaller pools. This paper
introduces an active learning algorithm whose goal is
to reach the correct rankings using the smallest
possible number of relevance judgments. It adds one
document to the pool at a time, always trying to select
the document with the highest information gain. Several
variants of this algorithm are described, each with
improvements on the one before. Results from
experiments are included for comparison with the
traditional TREC pooling method. The best version of
the algorithm reliably outperforms the traditional
method, although its degree of improvement varies.",
}
@TechReport{Dartmouth:TR2003-450,
author = "Evan W. Richardson",
title = "{An Evaluation of the Impact of Models for Radio
Propagation on the Simulation of 802.11b Wireless
Networks}",
institution = "Dartmouth College, Computer Science",
address = "Hanover, NH",
number = "TR2003-450",
year = "2003",
month = jun,
URL = "http://www.cs.dartmouth.edu/reports/TR2003-450.ps.Z",
comment = "Senior Honors Thesis. Advisor: Felipe Perrone.",
abstract = "Working with an existing wireless network simulator,
we describe the addition of both a method for modeling
arbitrary terrain, and for calculating signal
attenuation with the Irregular Terrain Model (ITM). We
also investigate ITM's effects on upper protocol layer
in comparison to the Two-Ray Ground Reflection model.
Upon examination, it was found that aside from the
terrain between the transmitter and receiver, ITM's
various parameters are of little significance in the
computed signal attenuation. Further, examination of
the behavior of the upper protocol layers revealed that
at high traffic levels, choice of propagation model can
have significant effects on the results of the
simulation.",
}
@TechReport{Dartmouth:TR2003-451,
author = "Chris Lentz",
title = "{802.11b Wireless Network Visualization and Radiowave
Propagation Modeling }",
institution = "Dartmouth College, Computer Science",
address = "Hanover, NH",
number = "TR2003-451",
year = "2003",
month = jun,
URL = "http://www.cs.dartmouth.edu/reports/TR2003-451.pdf",
comment = "Senior thesis. Advisor: David Kotz.",
abstract = "This paper outlines the methods of creating detailed
coverage maps of 802.11b networks, with an emphasis on
minimizing the expenses and time involved. The goal of
this work is to develop and present a streamlined,
reproducible approach to wireless visualization as well
as techniques for predicting coverage area before
conducting network installations. After evaluating
these coverage maps, a repeated series of field
measurements will be checked against interpolated
values in order to improve techniques for extrapolation
of data for unsampled regions. If successful, these
extrapolation techniques will provide additional
guidelines for, and assist modeling of, new wireless
network installations. However, this paper demonstrates
that due to the microcellular structure of
indoor/outdoor 802.11b networks, accurate interpolation
and propagation prediction techniques do not exist
independent of highly specific location models. In lieu
of the creation of extensive simulation environments,
best practice guidelines for municipal wireless network
planning and deployment are presented.",
}
@TechReport{Dartmouth:TR2003-452,
author = "Brian J. Premore",
title = "{An Analysis of Convergence Properties of the Border
Gateway Protocol Using Discrete Event Simulation}",
institution = "Dartmouth College, Computer Science",
address = "Hanover, NH",
number = "TR2003-452",
year = "2003",
month = may,
URL = "http://www.cs.dartmouth.edu/reports/TR2003-452.ps.Z",
comment = "This is a Ph.D. thesis. It differs from the version of
the thesis which appears in the Dartmouth College
library in a couple of significant ways. First, it is
single-spaced. Figures have moved around in order to
accommodate this change. Second, it includes some
corrections. The primary correction is that some
bibliography entries were reordered in order to
properly alphabetize them. This has the side effect
that the numbered citations throughout the document are
different in this version than in the original
version.",
abstract = "The Internet is an enormous internetwork formed by
connecting tens of thousands of independently managed
computer networks. Though the Internet has no central
authority and is highly heterogeneous, a universally
adopted addressing scheme---defined by the Internet
Protocol (IP)---makes interaction between the
individual networks possible. Complementing IP is the
Border Gateway Protocol (BGP), which facilitates
communication between parts of the internetwork by
determining paths by which data can get from one
network to any other. Just as IP is used ubiquitously
as an addressing scheme, BGP is used ubiquitously for
the purpose of network-to-network routing. Because BGP
is universal, its well-being is the concern of
everyone. In other words, when BGP suffers, everyone
suffers. Even when just one instance of BGP on one
router is ill-behaved, it can have global effects.
Unfortunately, as the Internet has grown, the amount of
stress put on BGP has increased. For a long time, the
behavior of inter-domain routing was studied minimally
and was assumed to be working just fine. Research
eventually showed, however, that routing was not
actually functioning so smoothly, and the highly
dynamic nature of the Internet was taking its toll on
the routing infrastructure. This discovery prompted a
closer look at the behavior of BGP. Though its
underlying premise is a simple distributed
shortest-path algorithm, the dynamic nature of the
Internet, combined with some additional constraints in
the protocol, has made analytical approaches to
studying the protocol infeasible. Measurement-based
approaches have been taken, but they are difficult to
implement and have minimal leeway for allowing
exploration of the protocol's behavior under different
conditions. For these reasons we have taken the
approach of simulation in order to begin to understand
some of the complex ways in which BGP behaves.
Simulation allows one to explore the protocol more
fully, testing it under various conditions and
modifying the protocol itself to explore the
consequences of its fundamental design. We have studied
BGP behavior with respect to several parameters, some
external (network characteristics) and some internal
(protocol characteristics). We show that there is room
for improvement in the protocol, in particular with
respect to convergence following changes in
availability of an address in the network. The
rate-limiting mechanism of the protocol is a particular
parameter of concern. Although it was previously
thought to help improve convergence, we found that in
some cases it can have drastic degrading effects. As a
result of our work, we suggest ways in which BGP could
be modified in practice to reduce the instability of
the protocol.",
}
@TechReport{Dartmouth:TR2003-453,
author = "Sidharth P. Nazareth",
title = "{SPADE: SPKI/SDSI for Attribute Release Policies in a
Distributed Environment }",
institution = "Dartmouth College, Computer Science",
address = "Hanover, NH",
number = "TR2003-453",
year = "2003",
month = may,
URL = "http://www.cs.dartmouth.edu/reports/TR2003-453.ps.Z",
comment = "M.S Thesis. Advisor: Sean Smith",
abstract = "Shibboleth is a federated administrated system that
supports inter-institutional authentication and
authorization for sharing of resources. SPKI/SDSI is a
public key infrastructure whose creation was motivated
by the perception that X.509 is too complex and flawed.
This thesis addresses the problem of how users that are
part of a Public Key Infrastructure in a distributed
computing system can effectively specify, create, and
disseminate their Attribute Release Policies for
Shibboleth using SPKI/SDSI. This thesis explores
existing privacy mechanims, as well as distributed
trust management and policy based systems. My work
describes the prototype for a Trust Management
Framework called SPADE (SPKI/SDSI for Attribute Release
Policies in a Distributed Environment) that I have
designed, developed and implemented. The principal
result of this research has been the demonstration that
SPKI/SDSI is a viable approach for trust management and
privacy policy specification, especially for
minimalistic policies in a distributed environment.",
}
@TechReport{Dartmouth:TR2003-454,
author = "David M. Nicol and Guanhua Yan",
title = "{Discrete-Event Fluid Modeling of Background TCP
Traffic}",
institution = "Dartmouth College, Computer Science",
address = "Hanover, NH",
number = "TR2003-454",
year = "2003",
month = jun,
URL = "http://www.cs.dartmouth.edu/reports/TR2003-454.ps.Z",
abstract = "TCP is the most widely used transport layer protocol
used in the internet today. A TCP session adapts the
demands it places on the network to observations of
bandwidth availability on the network. Because TCP is
adaptive, any model of its behavior that aspires to be
accurate must be influenced by other network traffic.
This point is especially important in the context of
using simulation to evaluate some new network algorithm
of interest (e.g. reliable multi-cast) in an
environment where the background traffic affects---and
is affected by---its behavior. We need to generate
background traffic efficiently in a way that captures
the salient features of TCP, while the reference and
background traffic representations interact with each
other. This paper describes a fluid model of TCP and a
switching model that has flows represented by fluids
interacting with packet-oriented flows. We describe
conditions under which a fluid model produces exactly
the same behavior as a packet-oriented model, and we
quantify the performance advantages of the approach
both analytically and empirically. We observe that very
significant speedups may be attained while keeping high
accuracy.",
}
@TechReport{Dartmouth:TR2003-455,
author = "Clara E. Lee",
title = "{Persistence and Prevalence in the Mobility of
Dartmouth Wireless Network Users}",
institution = "Dartmouth College, Computer Science",
address = "Hanover, NH",
number = "TR2003-455",
year = "2003",
month = may,
URL = "http://www.cs.dartmouth.edu/reports/TR2003-455.ps.Z",
comment = "The data in this paper is highly suspect; see
TR2003-480.",
abstract = "Wireless local-area networks (WLANs) are increasing in
popularity. As more people use WLANs it is important to
understand how these users behave. We analyzed data
collected over three months of 2002 to measure the
persistence and prevalence of users of the Dartmouth
wireless network. We found that most of the users of
Dartmouth's network have short association times and a
high rate of mobility. This observation fits with the
predominantly student population of Dartmouth College,
because students do not have a fixed workplace and are
moving to and from classes all day.",
}
@TechReport{Dartmouth:TR2003-456,
author = "Daniel F. Simola",
title = "{Discovery, Visualization and Analysis of Gene
Regulatory Sequence Elements in Genomes}",
institution = "Dartmouth College, Computer Science",
address = "Hanover, NH",
number = "TR2003-456",
year = "2003",
month = may,
URL = "http://www.cs.dartmouth.edu/reports/TR2003-456.pdf",
comment = "Senior Honors Thesis. Advisor: Jay Aslam.",
abstract = "The advent of rapid DNA sequencing has produced an
explosion in the amount of available sequence
information, permitting us to ask many new questions
about DNA. There is a pressing need to design
algorithms that can provide answers to questions
related to the control of gene expression, and thus to
the structure, function, and behavior of organisms.
Such algorithms must filter through massive amounts of
informational noise to identify meaningful conserved
regulatory DNA sequence elements. We are approaching
these questions with the notion that visualization is a
key to exploring data relationships. Understanding the
exact nature of these relationships can be very
difficult by simply interpreting raw data. The ability
to look at data in a graphical form allows us to apply
our innate capacity to think visually to discern the
subtle relationships that might not be recognizable
otherwise. This thesis provides computational tools to
visually identify and analyze candidate motifs in the
DNA of a species. This includes a parsing utility to
store genomic data and an application to search for and
visually identify motifs. Using these tools, novel and
previously compiled gene sets were identified using the
genome of the plant species Arabidopsis thaliana.",
}
@TechReport{Dartmouth:TR2003-458,
author = "Michael De Rosa",
title = "{Power Conservation in the Network Stack of Wireless
Sensors}",
institution = "Dartmouth College, Computer Science",
address = "Hanover, NH",
number = "TR2003-458",
year = "2003",
month = jun,
URL = "http://www.cs.dartmouth.edu/reports/TR2003-458.ps.Z",
comment = "Senior Honors Thesis. Advisor: Bob Gray.",
abstract = "Wireless sensor networks have recently become an
incredibly active research area in the networking
community. Much attention has been given to the
construction of power-conserving protocols and
techniques, as battery life is the one factor that
prevents successful wide-scale deployment of such
networks. These techniques concentrate on the
optimization of network behavior, as the wireless
transmission of data is the most expensive operation
performed by a sensor node. Very little work has been
published on the integration of such techniques, and
their suitability to various application domains. This
paper presents an exhaustive power consumption analysis
of network stacks constructed with common algorithms,
to determine the interactions between such algorithms
and the suitability of the resulting network stack for
various applications.",
}
@TechReport{Dartmouth:TR2003-459,
author = "Ron A. Oldfield",
title = "{Efficient I/O for Computational Grid Applications}",
institution = "Dartmouth College, Computer Science",
address = "Hanover, NH",
number = "TR2003-459",
year = "2003",
month = may,
URL = "http://www.cs.dartmouth.edu/reports/TR2003-459.ps.Z",
comment = "This is a reformatted version of Ron Oldfield's Ph.D.
dissertation. Unlike the dissertation submitted to
Dartmouth College, this version is single-spaced, uses
11pt fonts, and is formatted specifically for
double-sided printing.",
abstract = "High-performance computing increasingly occurs on
{"}computational grids{"} composed of heterogeneous and
geographically distributed systems of computers,
networks, and storage devices that collectively act as
a single {"}virtual{"} computer. A key challenge in
this environment is to provide efficient access to data
distributed across remote data servers. This
dissertation explores some of the issues associated
with I/O for wide-area distributed computing and
describes an I/O system, called Armada, with the
following features: a framework to allow application
and dataset providers to flexibly compose graphs of
processing modules that describe the distribution,
application interfaces, and processing required of the
dataset before or after computation; an algorithm to
restructure application graphs to increase parallelism
and to improve network performance in a wide-area
network; and a hierarchical graph-partitioning scheme
that deploys components of the application graph in a
way that is both beneficial to the application and
sensitive to the administrative policies of the
different administrative domains. Experiments show that
applications using Armada perform well in both low- and
high-bandwidth environments, and that our approach does
an exceptional job of hiding the network latency
inherent in grid computing.",
}
@TechReport{Dartmouth:TR2003-460,
author = "Elizabeth A. Hamon",
title = "{Enhancing Asynchronous Parallel Computing}",
institution = "Dartmouth College, Computer Science",
address = "Hanover, NH",
number = "TR2003-460",
year = "2003",
month = jun,
URL = "http://www.cs.dartmouth.edu/reports/TR2003-460.ps.Z",
abstract = "In applications using large amounts of data, hiding
the latency inherent in accessing data far from the
processor is often necessary in order to achieve high
performance. Several researchers have observed that one
way to address the challenge of latency is by using a
common structure: in a series of passes, the program
reads in the data, performs various operations on it,
and writes out the data. Passes often consist of a
pipeline structure composed of different stages. In
order to achieve high performance, the stages are
frequently overlapped, for example, by using
asynchronous threads. Out-of-core parallel programs
provide one such example of this pattern. The
development and debugging time resulting from
coordinating overlapping stages, however, can be
substantial. Moreover, modifying the structure of the
overlap in an attempt to achieve higher performance can
require significant additional time on the part of the
programmer. This thesis presents FG, a Framework
Generator designed to coordinate the stages of a
pipeline and allow the programmer to easily experiment
with the pipeline's structure, thus significantly
reducing time to solution. We also discuss preliminary
results of using FG in an out-of-core sorting
program.",
}
@TechReport{Dartmouth:TR2003-461,
author = "Mindy J. Pereira",
title = "{Trusted S/MIME Gateways}",
institution = "Dartmouth College, Computer Science",
address = "Hanover, NH",
number = "TR2003-461",
year = "2003",
month = may,
URL = "http://www.cs.dartmouth.edu/reports/TR2003-461.ps.Z",
comment = "Senior Honors Thesis. Advisor: Sean Smith.",
abstract = "The utility of Web-based email clients is clear: a
user is able to access their email account from any
computer anywhere at any time. However, this option is
unavailable to users whose security depends on their
key pair being stored either on their local computer or
in their browser. Our implementation seeks to solve two
problems with secure email services. The first that of
mobility: users must have access to their key pairs in
order to perform the necessary cryptographic
operations. The second is one of transition: initially,
users would not want to give up their regular email
clients. Keeping these two restrictions in mind, we
decided on the implementation of a secure gateway
system that works in conjunction with an existing mail
server and client. Our result is PKIGate, an S/MIME
gateway that uses the DigitalNet (formerly Getronics)
S/MIME Freeware Library and IBM's 4758 secure
coprocessor. This thesis presents motivations for the
project, a comparison with similar existing products,
software and hardware selection, the design, use case
scenarios, a discussion of implementation issues, and
suggestions for future work.",
}
@TechReport{Dartmouth:TR2003-462,
author = "Zack Butler and Daniela Rus",
title = "{Distributed planning and control for modular robots
with unit-compressible modules}",
institution = "Dartmouth College, Computer Science",
address = "Hanover, NH",
number = "TR2003-462",
year = "2003",
month = jun,
URL = "http://www.cs.dartmouth.edu/reports/TR2003-462.ps.Z",
abstract = "Self-reconfigurable robots are versatile systems
consisting of large numbers of independent modules.
Effective use of these systems requires parallel
actuation and planning, both for efficiency and
independence from a central controller. This paper
presents the PacMan algorithm, a technique for
distributed actuation and planning for systems with
two- or three-dimensional unit-compressible modules. We
give two versions of the algorithm along with
correctness analysis. We also analyze the parallel
actuation capability of the algorithm, showing that it
will not deadlock and will avoid disconnecting the
robot. We have implemented PacMan on the Crystal robot,
a hardware system developed in our lab, and we present
experiments and discuss the feasibility of large-scale
implementation.",
}
@TechReport{Dartmouth:TR2003-463,
author = "Sanket Agrawal",
title = "{Investigation of Third Party Rights Service and
Shibboleth Modification to Introduce the Service }",
institution = "Dartmouth College, Computer Science",
address = "Hanover, NH",
number = "TR2003-463",
year = "2003",
month = jun,
URL = "http://www.cs.dartmouth.edu/reports/TR2003-463.ps.Z",
abstract = "Shibboleth is an architecture to support
inter-institutional sharing of electronic resources
that are subject to access control. Codifying copyright
in Shibboleth authorization policies is difficult
because of the copyright exceptions which can be highly
subjective. Third Party Rights Service is a high-level
concept that has been suggested as a solution to
approximate the exceptions of copyright law. In this
thesis, I investigate the components of the Third Party
Rights Service. I design and analyze a modified
Shibboleth architecture based on these components. The
resulting architecture allows for the phased addition
of the resources to make use of the Third Party Rights
Service, while keeping the existing resources in
Shibboleth.",
}
@TechReport{Dartmouth:TR2003-464,
author = "Li Shen and James Ford and Fillia Makedon and Andrew
Saykin",
title = "{A Surface-based Approach for Classification of 3D
Neuroanatomic Structures}",
institution = "Dartmouth College, Computer Science",
address = "Hanover, NH",
number = "TR2003-464",
year = "2003",
month = jun,
URL = "http://www.cs.dartmouth.edu/reports/TR2003-464.ps.Z",
abstract = "We present a new framework for 3D surface object
classification that combines a powerful shape
description method with suitable pattern classification
techniques. Spherical harmonic parameterization and
normalization techniques are used to describe a surface
shape and derive a dual high dimensional landmark
representation. A point distribution model is applied
to reduce the dimensionality. Fisher's linear
discriminants and support vector machines are used for
classification. Several feature selection schemes are
proposed for learning better classifiers. After showing
the effectiveness of this framework using simulated
shape data, we apply it to real hippocampal data in
schizophrenia and perform extensive experimental
studies by examining different combinations of
techniques. We achieve best leave-one-out
cross-validation accuracies of 93% (whole set, N=56)
and 90% (right-handed males, N=39), respectively, which
are competitive with the best results in previous
studies using different techniques on similar types of
data. Furthermore, to help medical diagnosis in
practice, we employ a threshold-free receiver operating
characteristic (ROC) approach as an alternative
evaluation of classification results as well as propose
a new method for visualizing discriminative patterns.",
}
@TechReport{Dartmouth:TR2003-465,
author = "Edward Wei",
title = "{Using Low Level Linear Memory Management for
Type-Preserving Mark-Sweep Garbage Collector}",
institution = "Dartmouth College, Computer Science",
address = "Hanover, NH",
number = "TR2003-465",
year = "2003",
month = jun,
URL = "http://www.cs.dartmouth.edu/reports/TR2003-465.ps.Z",
comment = "Undergraduate Honors Thesis. Advisor: Chris
Hawblitzel. Associated software release at
http://www.cs.dartmouth.edu/~hawblitz/",
abstract = "Efficient low-level systems such as garbage collectors
need more control over memory than safe high-level
languages usually provide. Due to this constraint,
garbage collectors are typically written in unsafe
languages such as C. A collector of this form usually
resides as a trusted primitive runtime service outside
the model of the programming language. The type safety
of these languages depends on the assumption that the
garbage collector will not violate any typing
invariants. However, no realistic systems provide proof
of this assumption. A garbage collector written in a
strongly typed language can guarantee not only the
safety of the garbage collector and the program being
garbage collected (mutator), but also the interaction
between the collector and the mutator. Removing the
garbage collector from the trusted computing base has
many additional benefits: Untrusted code could be given
more control over memory management without sacrificing
security. Low-level code such as device drivers could
interface in a safe way with a garbage collector. For
these and the growing prevalence of garbage collectors
in the typical programming system necessitate a safe
solution. Previous research by Wang et al introduced a
safe copying collector based on regions, where the live
graph structure of the heap is copied from an old
region to a newer region. This paper seeks to improve
the efficiency of type-preserving garbage collection
with the introduction of a type-preserving mark and
sweep garbage collector.",
}
@TechReport{Dartmouth:TR2003-467,
author = "David Kotz and Calvin Newport and Chip Elliott",
title = "{The mistaken axioms of wireless-network research}",
institution = "Dartmouth College, Computer Science",
address = "Hanover, NH",
number = "TR2003-467",
year = "2003",
month = jul,
URL = "http://www.cs.dartmouth.edu/reports/TR2003-467.ps.Z",
comment = "For more information related to this project see
http://www.cs.dartmouth.edu/~campus/.",
abstract = "Most research on ad-hoc wireless networks makes
simplifying assumptions about radio propagation. The
``Flat Earth'' model of the world is surprisingly
popular: all radios have circular range, have perfect
coverage in that range, and travel on a two-dimensional
plane. CMU's ns-2 radio models are better but still
fail to represent many aspects of realistic radio
networks, including hills, obstacles, link asymmetries,
and unpredictable fading. We briefly argue that key
``axioms'' of these types of propagation models lead to
simulation results that do not adequately reflect real
behavior of ad-hoc networks, and hence to network
protocols that may not work well (or at all) in
reality. We then present a set of 802.11 measurements
that clearly demonstrate that these ``axioms'' are
contrary to fact. The broad chasm between simulation
and reality calls into question many of results from
prior papers, and we summarize with a series of
recommendations for researchers considering analytic or
simulation models of wireless networks.",
}
@TechReport{Dartmouth:TR2003-468,
author = "Heng Huang and Lea Wittie and Chris Hawblitzel",
title = "{Formal Properties of Linear Memory Types}",
institution = "Dartmouth College, Computer Science",
address = "Hanover, NH",
number = "TR2003-468",
year = "2003",
month = aug,
URL = "http://www.cs.dartmouth.edu/reports/TR2003-468.ps.Z",
abstract = "Efficient low-level systems need more control over
memory than safe high-level languages usually provide.
As a result, run-time systems are typically written in
unsafe languages such as C. This report describes an
abstract machine designed to give type-safe code more
control over memory. It includes complete definitions
and proofs of preservation, progress, strong
normalization, erasure, and translation correctness.",
}
@TechReport{Dartmouth:TR2003-470,
author = "Anna M. Shubina and Sean W. Smith",
title = "{Using caching for browsing anonymity}",
institution = "Dartmouth College, Computer Science",
address = "Hanover, NH",
number = "TR2003-470",
year = "2003",
month = jul,
URL = "http://www.cs.dartmouth.edu/reports/TR2003-470.ps.Z",
abstract = "Privacy-providing tools, including tools that provide
anonymity, are gaining popularity in the modern world.
Among the goals of their users is avoiding tracking and
profiling. While some businesses are unhappy with the
growth of privacy-enhancing technologies, others can
use lack of information about their users to avoid
unnecessary liability and even possible harassment by
parties with contrary business interests, and to gain a
competitive market edge. Currently, users interested in
anonymous browsing have the choice only between
single-hop proxies and the few more complex systems
that are available. These still leave the user
vulnerable to long-term intersection attacks. In this
paper, we propose a caching proxy system for allowing
users to retrieve data from the World-Wide Web in a way
that would provide recipient unobservability by a third
party and sender unobservability by the recipient and
thus dispose with intersection attacks, and report on
the prototype we built using Google.",
}
@TechReport{Dartmouth:TR2003-471,
author = "Rich MacDonald and Sean W. Smith and John Marchesini
and Omen Wild",
title = "{Bear: An Open-Source Virtual Secure Coprocessor based
on TCPA}",
institution = "Dartmouth College, Computer Science",
address = "Hanover, NH",
number = "TR2003-471",
year = "2003",
month = aug,
URL = "http://www.cs.dartmouth.edu/reports/TR2003-471.ps.Z",
comment = "Superceded by TR2003-476.",
abstract = "This paper reports on our ongoing project to use TCPA
to transform a desktop Linux machine into a virtual
secure coprocessor: more powerful but less secure than
higher-end devices. We use TCPA hardware and modified
boot loaders to protect fairly static components, such
as a trusted kernel; we use an enforcer
module---configured as Linux Security Module---to
protected more dynamic system components; we use an
encrypted loopback filesystem to protect highly dynamic
components. All our code is open source and available
under GPL from http://enforcer.sourceforge.net/",
}
@TechReport{Dartmouth:TR2003-474,
author = "Anthony K. Yan and Christopher J. Langmead and Bruce
Randall Donald",
title = "{A Probability-Based Similarity Measure for Saupe
Alignment Tensors with Applications to Residual Dipolar
Couplings in NMR Structural Biology}",
institution = "Dartmouth College, Computer Science",
address = "Hanover, NH",
number = "TR2003-474",
year = "2003",
month = oct,
URL = "http://www.cs.dartmouth.edu/reports/TR2003-474.pdf",
comment = "A revised and expanded version of this paper has been
accepted at a journal and will appear as: {"}A
Probability-Based Similarity Measure for Saupe
Alignment Tensors with Applications to Residual Dipolar
Couplings in NMR Structural Biology{"}, in The
International Journal of Robotics Research
Special Issue on Robotics Techniques Applied to
Computational Biology, 2004.",
abstract = "High-throughput NMR structural biology and NMR
structural genomics pose a fascinating set of geometric
challenges. A key bottleneck in NMR structural biology
is the resonance assignment problem. We seek to
accelerate protein NMR resonance assignment and
structure determination by exploiting a priori
structural information. In particular, a method known
as Nuclear Vector Replacement (NVR) has been proposed
as a method for solving the assignment problem given a
priori structural information [24,25]. Among several
different kinds of input data, NVR uses a particular
type of NMR data known as residual dipolar couplings
(RDCs). The basic physics of residual dipolar
couplings tells us that the data should be explainable
by a structural model and set of parameters contained
within the Saupe alignment tensor. In the NVR
algorithm, one estimates the Saupe alignment tensors
and then proceeds to refine those estimates. We would
like to quantify the accuracy of such estimates, where
we compare the estimated Saupe matrix to the correct
Saupe matrix. In this work, we propose a way to
quantify this comparison. Given a correct Saupe matrix
and an estimated Saupe matrix, we compute an upper
bound on the probability that a randomly rotated Saupe
tensor would have an error smaller than the estimated
Saupe matrix. This has the advantage of being a
quantified upper bound which also has a clear
interpretation in terms of geometry and probability.
While the specific application of our rotation
probability results is given to NVR, our novel methods
can be used for any RDC-based algorithm to bound the
accuracy of the estimated alignment tensors.
Furthermore, they could also be used in X-ray
crystallography or molecular docking to quantitate the
accuracy of calculated rotations of proteins, protein
domains, nucleic acids, or small molecules.",
}
@TechReport{Dartmouth:TR2003-475,
author = "King Y. Tan",
title = "{On the Complexity of Implementing Certain Classes of
Shared Objects}",
institution = "Dartmouth College, Computer Science",
address = "Hanover, NH",
number = "TR2003-475",
year = "2003",
month = nov,
URL = "http://www.cs.dartmouth.edu/reports/TR2003-475.ps.Z",
abstract = "We consider shared memory systems in which
asynchronous processes cooperate with each other by
communicating via shared data objects, such as
counters, queues, stacks, and priority queues. The
common approach to implementing such shared objects is
based on locking: To perform an operation on a shared
object, a process obtains a lock, accesses the object,
and then releases the lock. Locking, however, has
several drawbacks, including convoying, priority
inversion, and deadlocks. Furthermore, lock-based
implementations are not fault-tolerant: if a process
crashes while holding a lock, other processes can end
up waiting forever for the lock. Wait-free linearizable
implementations were conceived to overcome most of the
above drawbacks of locking. A wait-free implementation
guarantees that if a process repeatedly takes steps,
then its operation on the implemented data object will
eventually complete, regardless of whether other
processes are slow, or fast, or have crashed. In this
thesis, we first present an efficient wait-free
linearizable implementation of a class of object types,
called closed and closable types, and then prove time
and space lower bounds on wait-free linearizable
implementations of another class of object types,
called perturbable types. (1) We present a wait-free
linearizable implementation of n-process closed and
closable types (such as swap, fetch&add,
fetch&multiply, and fetch&L, where L is any of the
boolean operations and, or, or complement) using
registers that support load-link (LL) and
store-conditional (SC) as base objects. The time
complexity of the implementation grows linearly with
contention, but is never more than O(log ^2 n). We
believe that this is the first implementation of a
class of types (as opposed to a specific type) to
achieve a sub-linear time complexity. (2) We prove
linear time and space lower bounds on the wait-free
linearizable implementations of n-process perturbable
types (such as increment, fetch&add, modulo k counter,
LL/SC bit, k-valued compare&swap (for any k >= n),
single-writer snapshot) that use resettable consensus
and historyless objects (such as registers that support
read and write) as base objects. This improves on some
previously known Omega(sqrt{n}) space complexity lower
bounds. It also shows the near space optimality of some
known wait-free linearizable implementations.",
}
@TechReport{Dartmouth:TR2003-476,
author = "John Marchesini and Sean W. Smith and Omen Wild and
Rich MacDonald",
title = "{Experimenting with TCPA/TCG Hardware, Or: How I
Learned to Stop Worrying and Love The Bear}",
institution = "Dartmouth College, Computer Science",
address = "Hanover, NH",
number = "TR2003-476",
year = "2003",
month = dec,
URL = "http://www.cs.dartmouth.edu/reports/TR2003-476.pdf",
comment = "This report, TR2003-476, supersedes TR2003-471 of
August 2003. Furthermore, the December 15, 2003 version
of TR2003476 fixes typos found in the December 4, 2003
version.",
abstract = "Over the last few years, our group has been working on
applications of secure coprocessors---but has been
frustrated by the limited computational environment and
high expense of such devices. Over the last few years,
the TCPA (now TCG) has produced a specification for a
trusted platform module (TPM)---a small hardware
addition intended to improve the overall security of a
larger machine (and tied up with a still-murky vision
of Windows-based trusted computing). Some commodity
desktops now come up with these TPMs. Consequently, we
began an experiment to see if (in the absence of a
Non-Disclosure Agreement) we could use this hardware to
transform a desktop Linux machine into a virtual secure
coprocessor: more powerful but less secure than
higher-end devices. This experiment has several
purposes: to provide a new platform for secure
coprocessor applications, to see how well the TCPA/TCG
approach works, and (by working in open source) to
provide a platform for the broader community to
experiment with alternative architectures in the
contentious area of trusted computing. This paper
reports what we have learned so far: the approach is
feasible, but effective deployment requires a more
thorough look at OS security.",
}
@TechReport{Dartmouth:TR2003-480,
author = "Tristan Henderson and David Kotz",
title = "{Problems with the Dartmouth wireless SNMP data
collection }",
institution = "Dartmouth College, Computer Science",
address = "Hanover, NH",
number = "TR2003-480",
year = "2003",
month = dec,
URL = "http://www.cs.dartmouth.edu/reports/TR2003-480-rev3.pdf",
comment = "See http://www.cs.dartmouth.edu/~campus/ for more
information. Revision 2 of 12/31/03 reflects updated
information about the Balazinska paper. Revision 3 of
10/29/04 reflects a difference between the preliminary
and final version of the Kotz/Essien journal paper.",
abstract = "The original Dartmouth wireless network study used
SNMP to query the college's Cisco 802.11b access
points. The perl scripts that performed the SNMP
queries suffered from some problems, in that they
queried inappropriate SNMP values, or misunderstood the
meaning of other values. This data was also used in a
subsequent analysis. The same scripts were used to
collect data for a subsequent study of another wireless
network. This document outlines these problems and
indicates which of the data collected by the original
scripts may be invalid.",
}
@TechReport{Dartmouth:TR2003-481,
author = "Ryan H. Lilien and Chris Bailey-Kellogg and Amy A.
Anderson and Bruce R. Donald",
title = "{A Subgroup Algorithm to Identify Cross-Rotation Peaks
Consistent with Non-Crystallographic Symmetry}",
institution = "Dartmouth College, Computer Science",
address = "Hanover, NH",
number = "TR2003-481",
year = "2003",
month = dec,
URL = "http://www.cs.dartmouth.edu/reports/TR2003-481.pdf",
comment = "A revised version of this paper has been accepted for
publication and will appear in the journal Acta
Crystallographica D: Biological Crystallography.
In press (2004).",
abstract = "Molecular replacement (MR) often plays a prominent
role in determining initial phase angles for structure
determination by X-ray crystallography. In this paper,
an efficient quaternion-based algorithm is presented
for analyzing peaks from a cross-rotation function to
identify model orientations consistent with
non-crystallographic symmetry (NCS), and to generate
NCS-consistent orientations missing from the list of
cross-rotation peaks. Our algorithm, CRANS, analyzes
the rotation differences between each pair of
cross-rotation peaks to identify finite subgroups of
NCS. Sets of rotation differences satisfying the
subgroup axioms correspond to orientations compatible
with the correct NCS. The CRANS algorithm was first
tested using cross-rotation peaks computed from
structure factor data for three test systems, and then
used to assist in the de novo structure determination
of dihydrofolate reductase-thymidylate synthase
(DHFR-TS) from Cryptosporidium hominis. In every case,
the CRANS algorithm runs in seconds to identify
orientations consistent with the observed NCS and to
generate missing orientations not present in the
cross-rotation peak list. The CRANS algorithm has
application in every molecular replacement phasing
effort with NCS.",
}
@TechReport{Dartmouth:TR2004-484,
author = "Sean Smith and Nicholas C. Goffee and Sung Hoon Kim
and Punch Taylor and Meiyuan Zhao and John Marchesini",
title = "{Greenpass: Flexible and Scalable Authorization for
Wireless Networks}",
institution = "Dartmouth College, Computer Science",
address = "Hanover, NH",
number = "TR2004-484",
year = "2004",
month = jan,
URL = "http://www.cs.dartmouth.edu/reports/TR2004-484.pdf",
abstract = "Wireless networks break the implicit assumptions that
supported authorization in wired networks (that is: if
one could connect, then one must be authorized).
However, ensuring that only authorized users can access
a campus-wide wireless network creates many challenges:
we must permit authorized guests to access the same
network resources that internal users do; we must
accommodate the de-centralized way that authority flows
in real universities; we also must work within
standards, and accommodate the laptops and systems that
users already have, without requiring additional
software or plug-ins. This paper describes our ongoing
project to address this problem, using SPKI/SDSI
delegation on top of X.509 keypair within EAP-TLS.
Within the ``living laboratory'' of Dartmouth's
wireless network, this project lets us solve real
problem with wireless networking, while also
experimenting with trust flows and testing the limits
of current tools.",
}
@TechReport{Dartmouth:TR2004-485,
author = "Sidharth Nazareth and Sean Smith",
title = "{Using SPKI/SDSI for Distributed Maintenance of
Attribute Release Policies in Shibboleth}",
institution = "Dartmouth College, Computer Science",
address = "Hanover, NH",
number = "TR2004-485",
year = "2004",
month = jan,
URL = "http://www.cs.dartmouth.edu/reports/TR2004-485.pdf",
abstract = "The Shibboleth middleware from Internet2 provides a
way for users at higher-education institutions to
access remote electronic content in compliance with the
inter-institutional license agreements that govern such
access. To protect end-user privacy, Shibboleth permits
users to construct attribute release policies that
control what user credentials a given content provider
can obtain. However, Shibboleth leaves unspecified how
to construct these policies. To be effective, a
solution needs to accommodate the typical nature of a
university: a set of decentralized fiefdoms. This need
argues for a public-key infrastructure (PKI)
approach---since public-key cryptography does not
require parties to agree on a secret beforehand, and
parties distributed throughout the institution are
unlikely to agree on anything. However, this need also
argues against the strict hierarchical structure of
traditional PKI---policy in different fiefdoms will be
decided differently, and originate within the fiefdom,
rather than from an overall root. This paper presents
our design and prototype of a system that uses the
decentralized public-key framework of SPKI/SDSI to
solve this problem.",
}
@TechReport{Dartmouth:TR2004-486,
author = "Jue Wang and Guanling Chen and David Kotz",
title = "{A meeting detector and its applications}",
institution = "Dartmouth College, Computer Science",
address = "Hanover, NH",
number = "TR2004-486",
year = "2004",
month = mar,
URL = "http://www.cs.dartmouth.edu/reports/TR2004-486.pdf",
abstract = "In this paper we present a context-sensing component
that recognizes meetings in a typical office
environment. Our prototype detects the meeting start
and end by combining outputs from pressure and motion
sensors installed on the chairs. We developed a
telephone controller application that transfers
incoming calls to voice-mail when the user is in a
meeting. Our experiments show that it is feasible to
detect high-level context changes with ``good enough''
accuracy, using low-cost, off-the-shelf hardware, and
simple algorithms without complex training. We also
note the need for better metrics to measure context
detection performance, other than just accuracy. We
propose several metrics appropriate for our application
in this paper. It may be useful, however, for the
community to define a set of general metrics as a basis
to compare different approaches of context detection.",
}
@TechReport{Dartmouth:TR2004-487,
author = "Christopher J. Langmead and Bruce R. Donald",
title = "{High-Throughput 3D Homology Detection via NMR
Resonance Assignment}",
institution = "Dartmouth College, Computer Science",
address = "Hanover, NH",
number = "TR2004-487",
year = "2003",
month = sep,
URL = "http://www.cs.dartmouth.edu/reports/TR2004-487.pdf",
comment = "A revised version of this paper will appear in the
IEEE Computational Systems Bioinformatics
Conference (CSB), Stanford CA. (August, 2004).",
abstract = "One goal of the structural genomics initiative is the
identification of new protein folds. Sequence-based
structural homology prediction methods are an important
means for prioritizing unknown proteins for structure
determination. However, an important challenge remains:
two highly dissimilar sequences can have similar folds
--- how can we detect this rapidly, in the context of
structural genomics? High-throughput NMR experiments,
coupled with novel algorithms for data analysis, can
address this challenge. We report an automated
procedure, called HD, for detecting 3D structural
homologies from sparse, unassigned protein NMR data.
Our method identifies 3D models in a protein structural
database whose geometries best fit the unassigned
experimental NMR data. HD does not use, and is thus not
limited by sequence homology. The method can also be
used to confirm or refute structural predictions made
by other techniques such as protein threading or
homology modelling. The algorithm runs in $O(pn^{5/2}
\log {(cn)} + p \log p)$ time, where $p$ is the number
of proteins in the database, $n$ is the number of
residues in the target protein and $c$ is the maximum
edge weight in an integer-weighted bipartite graph. Our
experiments on real NMR data from 3 different proteins
against a database of 4,500 representative folds
demonstrate that the method identifies closely related
protein folds, including sub-domains of larger
proteins, with as little as 10-30\% sequence homology
between the target protein (or sub-domain) and the
computed model. In particular, we report no
false-negatives or false-positives despite significant
percentages of missing experimental data.",
}
@TechReport{Dartmouth:TR2004-488,
author = "Guanling Chen and David Kotz",
title = "{Application-controlled loss-tolerant data
dissemination}",
institution = "Dartmouth College, Computer Science",
address = "Hanover, NH",
number = "TR2004-488",
year = "2004",
month = feb,
URL = "http://www.cs.dartmouth.edu/reports/TR2004-488.pdf",
abstract = "Reactive or proactive mobile applications require
continuous monitoring of their physical and
computational environment to make appropriate decisions
in time. These applications need to monitor data
streams produced by sensors and react to changes. When
mobile sensors and applications are connected by
low-bandwidth wireless networks, sensor data rates may
overwhelm the capacity of network links or of the
applications. In traditional networks and distributed
systems, flow-control and congestion-control policies
either drop data or force the sender to pause. When the
data sender is sensing the physical environment,
however, a pause is equivalent to dropping data.
Arbitrary data drops are not necessarily acceptable to
the reactive mobile applications receiving sensor data.
Data distribution systems must support
application-specific policies that selectively drop
data objects when network or application buffers
overflow. In this paper we present a data-dissemination
service, PACK, which allows applications to specify
customized data-reduction policies. These policies
define how to discard or summarize data flows wherever
buffers overflow on the dissemination path, notably at
the mobile hosts where applications often reside. The
PACK service provides an overlay infrastructure to
support mobile data sources and sinks, using
application-specific data-reduction policies where
necessary along the data path. We uniformly apply the
data-stream ``packing'' abstraction to buffer overflow
caused by network congestion, slow receivers, and the
temporary disconnections caused by end-host mobility.
We demonstrate the effectiveness of our approach with
an application example and experimental measurements.",
}
@TechReport{Dartmouth:TR2004-489,
author = "John Marchesini and Sean W. Smith and Meiyuan Zhao",
title = "{Keyjacking: The Surprising Insecurity of Client-side
SSL}",
institution = "Dartmouth College, Computer Science",
address = "Hanover, NH",
number = "TR2004-489",
year = "13,",
month = feb,
URL = "http://www.cs.dartmouth.edu/reports/TR2004-489.pdf",
comment = "This TR supercedes TR2003-443. A preliminary version
appeared in the proceedings of the 2nd Annual PKI
Research Workshop in April of 2003.",
abstract = "In theory, PKI can provide a flexible and strong way
to authenticate users in distributed information
systems. In practice, much is being invested in
realizing this vision via client-side SSL and various
client keystores. However, whether this works depends
on whether what the machines do with the private keys
matches what the humans think they do: whether a server
operator can conclude from an SSL request authenticated
with a user's private key that the user was aware of
and approved that request. Exploring this vision, we
demonstrate via a series of experiments that this
assumption does not hold with standard desktop tools,
even if the browser user does all the right things. A
fundamental rethinking of the trust, usage, and storage
model might result in more effective tools for
achieving the PKI vision.",
}
@TechReport{Dartmouth:TR2004-490,
author = "Guanling Chen and David Kotz",
title = "{A Case Study of Four Location Traces}",
institution = "Dartmouth College, Computer Science",
address = "Hanover, NH",
number = "TR2004-490",
year = "2004",
month = feb,
URL = "http://www.cs.dartmouth.edu/reports/TR2004-490.pdf",
abstract = "Location is one of the most important context
information that an ubiquitous-computing application
may leverage. Thus understanding the location systems
and how location-aware applications interact with them
is critical for design and deployment of both the
location systems and location-aware applications. In
this paper, we analyze a set of traces collected from
two small-scale one-building location system and two
large-scale campus-wide location systems. Our goal is
to study characteristics of these location systems ant
how these factors should be taken into account by a
potentially large number of location-aware applications
with different needs. We make empirical measurements of
several important metrics and compare the results
across these location systems. We discuss the
implication of these results on location-aware
applications and their supporting software
infrastructure, and how location systems could be
improved to better serve applications' needs. In places
where possible, we use location-aware applications
discussed in existing literatures as illustrating
examples.",
}
@TechReport{Dartmouth:TR2004-491,
author = "Libo Song and David Kotz and Ravi Jain and Xiaoning
He",
title = "{Evaluating next-cell predictors with extensive Wi-Fi
mobility data}",
institution = "Dartmouth College, Computer Science",
address = "Hanover, NH",
number = "TR2004-491",
year = "2004",
month = feb,
URL = "http://www.cs.dartmouth.edu/reports/TR2004-491.pdf",
comment = "A shorter,preliminary version of this paper is to
appear at IEEE Infocom, March 7-11, 2004.",
abstract = "Location is an important feature for many
applications, and wireless networks can better serve
their clients by anticipating client mobility. As a
result, many location predictors have been proposed in
the literature, though few have been evaluated with
empirical evidence. This paper reports on the results
of the first extensive empirical evaluation of location
predictors, using a two-year trace of the mobility
patterns of over 6,000 users on Dartmouth's campus-wide
Wi-Fi wireless network. We implemented and compared the
prediction accuracy of several location predictors
drawn from four major families of domain-independent
predictors, namely Markov-based, compression-based,
PPM, and SPM predictors. We found that low-order Markov
predictors performed as well or better than the more
complex and more space-consuming compression-based
predictors. Predictors of both families fail to make a
prediction when the recent context has not been
previously seen. To overcome this drawback, we added a
simple fallback feature to each predictor and found
that it significantly enhanced its accuracy in exchange
for modest effort. Thus the Order-2 Markov predictor
with fallback was the best predictor we studied,
obtaining a median accuracy of about 72\% for users
with long trace lengths. We also investigated a
simplification of the Markov predictors, where the
prediction is based not on the most frequently seen
context in the past, but the most recent, resulting in
significant space and computational savings. We found
that Markov predictors with this recency semantics can
rival the accuracy of standard Markov predictors in
some cases. Finally, we considered several seemingly
obvious enhancements, such as smarter tie-breaking and
aging of context information, and discovered that they
had little effect on accuracy. The paper ends with a
discussion and suggestions for further work.",
}
@TechReport{Dartmouth:TR2004-492,
author = "Ryan H. Lilien and Mohini Sridharan and Bruce R.
Donald",
title = "{Identification of Novel Small Molecule Inhibitors of
Core-Binding Factor Dimerization by Computational
Screening against NMR Molecular Ensembles}",
institution = "Dartmouth College, Computer Science",
address = "Hanover, NH",
number = "TR2004-492",
year = "2004",
month = mar,
URL = "http://www.cs.dartmouth.edu/reports/TR2004-492.pdf",
abstract = "The long development process of novel pharmaceutical
compounds begins with the identification of a lead
inhibitor compound. Computational screening to identify
those ligands, or small molecules, most likely to
inhibit a target protein may benefit the pharmaceutical
development process by reducing the time required to
identify a lead compound. Typically, computational
ligand screening utilizes high-resolution structural
models of both the protein and ligand to fit or `dock'
each member of a ligand database into the binding site
of the protein. Ligands are then ranked by the number
and quality of interactions formed in the predicted
protein-ligand complex. It is currently believed that
proteins in solution do not assume a single rigid
conformation but instead tend to move through a small
region of conformation space. Therefore, docking
ligands against a static snapshot of protein structure
has predictive limitations because it ignores the
inherent flexibility of the protein. A challenge,
therefore, has been the development of docking
algorithms capable of modeling protein flexibility
while balancing computational feasibility. In this
paper, we present our initial development and work on a
molecular ensemble-based algorithm to model protein
flexibility for protein-ligand binding prediction.
First, a molecular ensemble is generated from molecular
structures satisfying experimentally-measured NMR
constraints. Second, traditional protein-ligand docking
is performed on each member of the protein's molecular
ensemble. This step generates lists of ligands
predicted to bind to each individual member of the
ensemble. Finally, lists of top predicted binders are
consolidated to identify those ligands predicted to
bind multiple members of the protein's molecular
ensemble. We applied our algorithm to identify
inhibitors of Core Binding Factor (CBF) among a subset
of approximately 70,000 ligands of the Available
Chemicals Directory. Our 26 top-predicted binding
ligands are currently being tested experimentally in
the wetlab by both NMR-binding experiments (15N-edited
Heteronuclear Single-Quantum Coherence (HSQC)) and
Electrophoretic Gel Mobility Shift Assays (EMSA).
Preliminary results indicate that of approximately 26
ligands tested, three induce perturbations in the
protein's NMR chemical shifts indicative of ligand
binding and one ligand (2-amino-5-cyano-4-tertbutyl
thiazole) causes a band pattern in the EMSA indicating
the disruption of CBF dimerization.",
}
@TechReport{Dartmouth:TR2004-493,
author = "Javed Aslam and Sergey Bratus and David Kotz and Ron
Peterson and Daniela Rus and Brett Tofel",
title = "{The Kerf toolkit for intrusion analysis}",
institution = "Dartmouth College, Computer Science",
address = "Hanover, NH",
number = "TR2004-493",
year = "2004",
month = mar,
URL = "http://www.cs.dartmouth.edu/reports/TR2004-493.pdf",
abstract = "We consider the problem of intrusion analysis and
present the Kerf Toolkit, whose purpose is to provide
an efficient and flexible infrastructure for the
analysis of attacks. The Kerf Toolkit includes a
mechanism for securely recording host and network
logging information for a network of workstations, a
domain-specific language for querying this stored data,
and an interface for viewing the results of such a
query, providing feedback on these results, and
generating new queries in an iterative fashion. We
describe the architecture of Kerf, present examples to
demonstrate the power of our query language, and
discuss the performance of our implementation of this
system.",
}
@TechReport{Dartmouth:TR2004-494,
author = "Christopher J. Langmead and Bruce R. Donald",
title = "{An Improved Nuclear Vector Replacement Algorithm for
Nuclear Magnetic Resonance Assignment}",
institution = "Dartmouth College, Computer Science",
address = "Hanover, NH",
number = "TR2004-494",
year = "2003",
month = sep,
URL = "http://www.cs.dartmouth.edu/reports/TR2004-494.pdf",
abstract = "We report an improvement to the Nuclear Vector
Replacement (NVR) algorithm for high-throughput Nuclear
Magnetic Resonance (NMR) resonance assignment. The new
algorithm improves upon our earlier result in terms of
accuracy and computational complexity. In particular,
the new NVR algorithm assigns backbone resonances
without error (100% accuracy) on the same test suite
examined in [Langmead and Donald J. Biomol. NMR 2004],
and runs in $O(n^{5/2} \log {(cn)})$ time where $n$ is
the number of amino acids in the primary sequence of
the protein, and $c$ is the maximum edge weight in an
integer-weighted bipartite graph.",
}
@TechReport{Dartmouth:TR2004-495,
author = "Guanling Chen and David Kotz",
title = "{Dependency management in distributed settings}",
institution = "Dartmouth College, Computer Science",
address = "Hanover, NH",
number = "TR2004-495",
year = "2004",
month = mar,
URL = "http://www.cs.dartmouth.edu/reports/TR2004-495.pdf",
comment = "A short 2-page poster abstract of this work appears in
the International Conference on Autonomic Computing
(ICAC-04), May 2004.",
abstract = "Ubiquitous-computing environments are heterogeneous
and volatile in nature. Systems that support ubicomp
applications must be self-managed, to reduce human
intervention. In this paper, we present a general
service that helps distributed software components to
manage their dependencies. Our service proactively
monitors the liveness of components and recovers them
according to supplied policies. Our service also tracks
the state of components, on behalf of their dependents,
and may automatically select components for the
dependent to use based on evaluations of customized
functions. We believe that our approach is flexible and
abstracts away many of the complexities encountered in
ubicomp environments. In particular, we show how we
applied the service to manage dependencies of
context-fusion operators and present some experimental
results.",
}
@TechReport{Dartmouth:TR2004-496,
author = "Tristan Henderson and David Kotz and Ilya Abyzov",
title = "{The Changing Usage of a Mature Campus-wide Wireless
Network}",
institution = "Dartmouth College, Computer Science",
address = "Hanover, NH",
number = "TR2004-496",
year = "2004",
month = mar,
URL = "http://www.cs.dartmouth.edu/reports/TR2004-496.pdf",
comment = "A revised version will appear in Mobicom 2004. See
also http://www.cs.dartmouth.edu/~campus/.",
abstract = "Wireless Local Area Networks (WLANs) are now common on
academic and corporate campuses. As ``Wi-Fi''
technology becomes ubiquitous, it is increasingly
important to understand trends in the usage of these
networks. This paper analyzes an extensive network
trace from a mature 802.11 WLAN, including more than
550 access points and 7000 users over seventeen weeks.
We employ several measurement techniques, including
syslogs, telephone records, SNMP polling and tcpdump
packet sniffing. This is the largest WLAN study to
date, and the first to look at a large, mature WLAN and
consider geographic mobility. We compare this trace to
a trace taken after the networkÕs initial deployment
two years ago. We found that the applications used on
the WLAN changed dramatically. Initial WLAN usage was
dominated by Web traffic; our new trace shows
significant increases in peer-to-peer, streaming
multimedia, and voice over IP (VoIP) traffic. On-campus
traffic now exceeds offcampus traffic, a reversal of
the situation at the WLANÕs initial deployment. Our
study indicates that VoIP has been used little on the
wireless network thus far, and most VoIP calls are made
on the wired network. Most calls last less than a
minute. We saw more heterogeneity in the types of
clients used, with more embedded wireless devices such
as PDAs and mobile VoIP clients. We define a new metric
for mobility, the ``session diameter.'' We use this
metric to show that embedded devices have different
mobility characteristics than laptops, and travel
further and roam to more access points. Overall, users
were surprisingly non-mobile, with half remaining close
to home about 98% of the time.",
}
@TechReport{Dartmouth:TR2004-497,
author = "Darren Erik Vengroff and David Kotz",
title = "{A Holesome File System}",
institution = "Dartmouth College, Computer Science",
address = "Hanover, NH",
number = "TR2004-497",
year = "2004",
month = may,
URL = "http://www.cs.dartmouth.edu/reports/TR2004-497.pdf",
comment = "This paper was written in July 1995, but sat
unpublished until May 2004 when it was released as this
technical report, unchanged.",
abstract = "We present a novel approach to fully dynamic
management of physical disk blocks in Unix file
systems. By adding a single system call, zero, to an
existing file system, we permit applications to create
holes, that is, regions of files to which no physical
disk blocks are allocated, far more flexibly than
previously possible. zero can create holes in the
middle of existing files. Using zero, it is possible to
efficiently implement applications including a variety
of databases and I/O-efficient computation systems on
top of the Unix file system. zero can also be used to
implement an efficient file-system-based paging
mechanism. In some I/O-efficient computations, the
availability of zero effectively doubles disk capacity
by allowing blocks of temporary files to be reallocated
to new files as they are read. Experiments on a Linux
ext2 file system augmented by zero demonstrate that
where their functionality overlaps, zero is more
efficient than ftruncate(). Additional experiments
reveal that in exchange for added effective disk
capacity, I/O-efficient code pays only a small
performance penalty.",
}
@TechReport{Dartmouth:TR2004-498,
author = "Rachel B. Ringel",
title = "{Efficient Wait-Free Implementation of Atomic
Multi-Word Buffer}",
institution = "Dartmouth College, Computer Science",
address = "Hanover, NH",
number = "TR2004-498",
year = "2004",
month = jun # ",",
URL = "http://www.cs.dartmouth.edu/reports/TR2004-498.pdf",
comment = "Senior Honors Thesis. Advisor: Prasad Jayanti.",
abstract = "This thesis proposes algorithms for implementing a
atomic multi-word buffer, which can be accessed
concurrently by multiple readers and a single writer,
from the hardware-supported shared memory. The
algorithms are required to be wait-free: each process
reads or writes the multi-word buffer in a bounded
number of its own steps, regardless of whether other
processes are fast, slow or have crashed. Our first
algorithm is built from multi-writer, multi-reader
variables whereas the second algorithm is built from
single-writer, multi-reader variables. For either
algorithm, the worst-case running time of a read or a
write operation on the m-word buffer is O(m). The space
complexity of the algorithms is O(mn). Neither
algorithm requires hardware support for any special
synchronization instructions; the ability to read or
write into any machine word is sufficient. The
algorithms significantly improve on Peterson's
algorithm, which has O(mn) time complexity for the
write operation on the buffer.",
}
@TechReport{Dartmouth:TR2004-499,
author = "Nikita E Dubrovsky",
title = "{Mobile Agents Simulation with DaSSF}",
institution = "Dartmouth College, Computer Science",
address = "Hanover, NH",
number = "TR2004-499",
year = "2004",
month = jun,
URL = "http://www.cs.dartmouth.edu/reports/TR2004-499.pdf",
comment = "Senior Honors Thesis. Advisor: Bob Gray.",
abstract = "Mobile agents are programs that can migrate from
machine to machine in a network of computers and have
complete control over their movement. Since the
performance space of mobile agents has not been
characterized fully, assessing the effectiveness of
using mobile agents over a traditional client/server
approach currently requires implementing an agent
system and running time-consuming experiments. This
report presents a simple mobile-agent simulation that
can provide quick information on the performance and
scalability of a generic information retrieval (IR)
mobile-agent system under different network
configurations. The simulation is built using the DaSSF
and DaSSFNet frameworks, resulting in high performance
and great configuration flexibility. This report also
implements a real D'Agents mobile-agent IR system,
measuring the performance of the system. A comparison
of these real-world performance results and those given
by the simulation suggest that the simulation has good
accuracy in predicting the scalability of a
mobile-agent system. Thus this report argues that
simulation provides a good way to quickly assess the
performance and scalability of an IR mobile-agent
system under different network configurations.",
}
@TechReport{Dartmouth:TR2004-501,
author = "William Pechter",
title = "{Synchronizing Keyframe Facial Animation to Multiple
Text-to-Speech Engines and Natural Voice with Fast
Response Time}",
institution = "Dartmouth College, Computer Science",
address = "Hanover, NH",
number = "TR2004-501",
year = "2004",
month = jun,
URL = "http://www.cs.dartmouth.edu/reports/TR2004-501.pdf",
comment = "Senior Honors Thesis. Advisors: Lorie Loeb, Hany
Farid, and Stephen Linder",
abstract = "This thesis aims to create an automated
lip-synchronization system for real-time applications.
Specifically, the system is required to be fast,
consist of a limited number of keyframes with small
memory requirements, and create fluid and believable
animations that synchronize with text-to-speech engines
as well as raw voice data. The algorithms utilize
traditional keyframe animation and a novel method of
keyframe selection. Additionally, phoneme-to-keyframe
mapping, synchronization, and simple blending rules are
employed. The algorithms provide blending between
keyframe images, borrow information from neighboring
phonemes, accentuate phonemes b, p and m, differentiate
between keyframes for phonemes with allophonic
variations, and provide prosodromic variation by
including emotion while speaking. The lip-sync
animation synchronizes with multiple synthesized voices
and human speech. A fast and versatile online real-time
java chat interface is created to exhibit vivid facial
animation. Results show that the animation algorithms
are fast and show accurate lip-synchronization.
Additionally, surveys showed that the animations are
visually pleasing and improve speech understandability
96% of the time. Applications for this project include
internet chat capabilities, interactive teaching of
foreign languages, animated news broadcasting, enhanced
game technology, and cell phone messaging.",
}
@TechReport{Dartmouth:TR2004-502,
author = "Geoffrey H. Stowe",
title = "{A Secure Network Node Approach to the Policy Decision
Point in Distributed Access Control}",
institution = "Dartmouth College, Computer Science",
address = "Hanover, NH",
number = "TR2004-502",
year = "2004",
month = jun,
URL = "http://www.cs.dartmouth.edu/reports/TR2004-502.pdf",
comment = "Senior Honors Thesis. Advisor: Ed Feustel",
abstract = "To date, the vast majority of access control research
and development has been on gathering, managing, and
exchanging information about users. But an equally
important component which has yet to be fully developed
is the Policy Decision Point - the system that decides
whether an access request should be granted given
certain attributes of the requestor. This paper
describes the research and implementation of a new PDP
system for an undergraduate honors project. This PDP
system employs three unique features which
differentiate it from existing technology:
collaboration capabilities, trusted management, and
interoperability with other access control systems.
Security considerations and future research areas are
also discussed.",
}
@TechReport{Dartmouth:TR2004-503,
author = "Joseph E. Pechter",
title = "{Enhancing Expressiveness of Speech through Animated
Avatars for Instant Messaging and Mobile Phones}",
institution = "Dartmouth College, Computer Science",
address = "Hanover, NH",
number = "TR2004-503",
year = "2004",
month = jun,
URL = "http://www.cs.dartmouth.edu/reports/TR2004-503.pdf",
comment = "Senior Honors Thesis. Advisors: Lorie Loeb, Hany
Farid, Stephen Linder",
abstract = "This thesis aims to create a chat program that allows
users to communicate via an animated avatar that
provides believable lip-synchronization and expressive
emotion. Currently many avatars do not attempt to do
lip-synchronization. Those that do are not well
synchronized and have little or no emotional
expression. Most avatars with lip synch use realistic
looking 3D models or stylized rendering of complex
models. This work utilizes images rendered in a cartoon
style and lip-synchronization rules based on
traditional animation. The cartoon style, as opposed to
a more realistic look, makes the mouth motion more
believable and the characters more appealing. The
cartoon look and image-based animation (as opposed to a
graphic model animated through manipulation of a
skeleton or wireframe) also allows for fewer key frames
resulting in faster speed with more room for
expressiveness. When text is entered into the program,
the Festival Text-to-Speech engine creates a speech
file and extracts phoneme and phoneme duration data.
Believable and fluid lip-synchronization is then
achieved by means of a number of phoneme-to-image
rules. Alternatively, phoneme and phoneme duration data
can be obtained for speech dictated into a microphone
using Microsoft SAPI and the CSLU Toolkit. Once lip
synchronization has been completed, rules for
non-verbal animation are added. Emotions are appended
to the animation of speech in two ways: automatically,
by recognition of key words and punctuation, or
deliberately, by user-defined tags. Additionally, rules
are defined for idle-time animation. Preliminary
results indicate that the animated avatar program
offers an improvement over currently available
software. It aids in the understandability of speech,
combines easily recognizable and expressive emotions
with speech, and successfully enhances overall
enjoyment of the chat experience. Applications for the
program include use in cell phones for the deaf or
hearing impaired, instant messaging, video
conferencing, instructional software, and speech and
animation synthesis.",
}
@TechReport{Dartmouth:TR2004-504,
author = "Calvin Newport",
title = "{Simulating mobile ad hoc networks: a quantitative
evaluation of common MANET simulation models}",
institution = "Dartmouth College, Computer Science",
address = "Hanover, NH",
number = "TR2004-504",
year = "2004",
month = jun,
URL = "http://www.cs.dartmouth.edu/reports/TR2004-504.pdf",
comment = "Senior Honors Thesis. Advisor: David Kotz.",
abstract = "Because it is difficult and costly to conduct
real-world mobile ad hoc network experiments,
researchers commonly rely on computer simulation to
evaluate their routing protocols. However, simulation
is far from perfect. A growing number of studies
indicate that simulated results can be dramatically
affected by several sensitive simulation parameters. It
is also commonly noted that most simulation models make
simplifying assumptions about radio behavior. This
situation casts doubt on the reliability and
applicability of many ad hoc network simulation
results. In this study, we begin with a large outdoor
routing experiment testing the performance of four
popular ad hoc algorithms (AODV, APRL, ODMRP, and
STARA). We present a detailed comparative analysis of
these four implementations. Then, using the outdoor
results as a baseline of reality, we disprove a set of
common assumptions used in simulation design, and
quantify the impact of these assumptions on simulated
results. We also more specifically validate a group of
popular radio models with our real-world data, and
explore the sensitivity of various simulation
parameters in predicting accurate results. We close
with a series of specific recommendations for
simulation and ad hoc routing protocol designers.",
}
@TechReport{Dartmouth:TR2004-505,
author = "David Kotz",
title = "{Technological Implications for Privacy}",
institution = "Dartmouth College, Computer Science",
address = "Hanover, NH",
number = "TR2004-505",
year = "2004",
month = jun,
URL = "http://www.cs.dartmouth.edu/reports/TR2004-505.pdf",
comment = "Originally written in 1998; this revision was dated
January 3, 1999. The work was unofficially released,
then made a Technical Report noin June 2004.",
abstract = "The World-Wide Web is increasingly used for commerce
and access to personal information stored in databases.
Although the Web is ``just another medium'' for
information exchange, the fact that all the information
is stored in computers, and all of the activity happens
in computers and computer networks, makes it easier
(cheaper) than every to track users' activities. By
recording and analyzing user's activities in the Web,
activities that may seem to be quite private to many
users, it is more likely than ever before that a
person's privacy may be threatened. In this paper I
examine some of the technology in the Web, and how it
affects the privacy of Web users. I also briefly
summarize some of the efforts to regulate privacy on
the Internet.",
}
@TechReport{Dartmouth:TR2004-506,
author = "Paul J. Mazzuca",
title = "{Access Control in a Distributed Decentralized
Network: An XML Approach to Network Security using
XACML and SAML}",
institution = "Dartmouth College, Computer Science",
address = "Hanover, NH",
number = "TR2004-506",
year = "2004",
month = "Spring",
URL = "http://www.cs.dartmouth.edu/reports/TR2004-506.pdf",
comment = "Senior Honors Thesis. Advisor: Ed Feustel.",
abstract = "The development of eXtensible Distributed Access
Control (XDAC) systems is influenced by the
transference of data access and storage from the local
computer to the network. In this distributed system,
access control is determined by independent components
which transmit requests and decisions over a network,
utilizing XML signing capabilities found in the
Security Assertion Markup Language (SAML). All
resources in the XDAC system are protected by the first
component, a Policy Enforcement Point (PEP), which acts
as the main divider between the requesting entity and
the requested resource. The PEP grants access to a
resource only if the second component, a Policy
Decision Point (PDP), returns a permit response after
consulting a set of applicable policies based on the
requester's attributes, the resource, the action that
the requester desires to apply to that resource, and
optionally the environment. With Sun's eXtensible
Access Control Markup Language (XACML), the XML encoded
policies can be combined among multiple nodes across a
network using XACML rules and algorithms to formulate a
single decision based on an XACML request. In this
thesis project, I build a secure and efficient XDAC
System based on XACML, implement an extension to the
SAML Assertion design by including XACML Attributes and
Results, describe in-detail about the many features
that a XDAC System should embody, and show how a XDAC
System would be effectively used in modern day
computing.",
}
@TechReport{Dartmouth:TR2004-507,
author = "David Kotz and Calvin Newport and Robert S. Gray and
Jason Liu and Yougu Yuan and Chip Elliott",
title = "{Experimental evaluation of wireless simulation
assumptions}",
institution = "Dartmouth College, Computer Science",
address = "Hanover, NH",
number = "TR2004-507",
year = "2004",
month = jun,
URL = "http://www.cs.dartmouth.edu/reports/TR2004-507.pdf",
comment = "This paper is significantly revised and extended from
TR2003-467, {"}The mistaken axioms of wireless-network
research.{"}",
abstract = "All analytical and simulation research on ad~hoc
wireless networks must necessarily model radio
propagation using simplifying assumptions. Although it
is tempting to assume that all radios have circular
range, have perfect coverage in that range, and travel
on a two-dimensional plane, most researchers are
increasingly aware of the need to represent more
realistic features, including hills, obstacles, link
asymmetries, and unpredictable fading. Although many
have noted the complexity of real radio propagation,
and some have quantified the effect of overly simple
assumptions on the simulation of ad~hoc network
protocols, we provide a comprehensive review of six
assumptions that are still part of many ad~hoc network
simulation studies. In particular, we use an extensive
set of measurements from a large outdoor routing
experiment to demonstrate the weakness of these
assumptions, and show how these assumptions cause
simulation results to differ significantly from
experimental results. We close with a series of
recommendations for researchers, whether they develop
protocols, analytic models, or simulators for ad~hoc
wireless networks.",
}
@TechReport{Dartmouth:TR2004-508,
author = "Eric G. Krupski",
title = "{PPL: a Packet Processing Language}",
institution = "Dartmouth College, Computer Science",
address = "Hanover, NH",
number = "TR2004-508",
year = "2004",
month = jun,
URL = "http://www.cs.dartmouth.edu/reports/TR2004-508.pdf",
comment = "Senior Honors Thesis. Advisor: Chris Hawblitzel. Code
and other materials available at
http://www.cs.dartmouth.edu/reports/TR2004-508.tgz
(440KB).",
abstract = "Any computing device or system that uses the internet
needs to analyze and identify the contents of network
packets. Code that does this is often written in C, but
reading, identifying, and manipulating network packets
in C requires writing tricky and tedious code. Previous
work has offered specification languages for describing
the format of network packets, which would allow packet
type identification without the hassles of doing this
task in C. For example, McCann and Chandra's Packet
Types [3] system allows the programmer to define
arbitrary packet types and generates C unctions which
match given data against a specified packet type. This
paper will present a packet processing language named
PPL, which extends McCann and Chandra{\^a}s Packet
Types to allow the programmer to not only describe
arbitrary packet types, but also to control when and
how a matching is attempted, with ML-style pattern
matching. PPL is intended for multiple applications,
such as intrusion detection systems, quick prototypes
of new protocols, and IP de-multiplexing code.",
}
@TechReport{Dartmouth:TR2004-509,
author = "Nicholas C. Goffee",
title = "{Greenpass Client Tools for Delegated Authorization in
Wireless Networks}",
institution = "Dartmouth College, Computer Science",
address = "Hanover, NH",
number = "TR2004-509",
year = "2004",
month = jun,
URL = "http://www.cs.dartmouth.edu/reports/TR2004-509.pdf",
comment = "Masters thesis. Advisor: Sean Smith",
abstract = "Dartmouth's Greenpass project seeks to provide strong
access control to a wireless network while
simultaneously providing flexible guest access; to do
so, it augments the Wi-Fi Alliance's existing WPA
standard, which offers sufficiently strong user
authentication and access control, with authorization
based on SPKI certificates. SPKI allows certain local
users to delegate network access to guests by issuing
certificates that state, in essence, {"}he should get
access because I said it's okay.{"} The Greenpass
RADIUS server described in Kim's thesis [55] performs
an authorization check based on such statements so that
guests can obtain network access without requiring a
busy network administrator to set up new accounts in a
centralized database. To our knowledge, Greenpass is
the first working delegation-based solution to Wi-Fi
access control. My thesis describes the Greenpass
client tools, which allow a guest to introduce himself
to a delegator and allow the delegator to issue a new
SPKI certificate to the guest. The guest does not need
custom client software to introduce himself or to
connect to the Wi-Fi network. The guest and delegator
communicate using a set of Web applications. The guest
obtains a temporary key pair and X.509 certificate if
needed, then sends his public key value to a Web server
we provide. The delegator looks up her guest's public
key and runs a Java applet that lets her verify her
guests' identity using visual hashing and issue a new
SPKI certificate to him. The guest's new certificate
chain is stored as an HTTP cookie to enable him to
{"}push{"} it to an authorization server at a later
time. I also describe how Greenpass can be extended to
control access to a virtual private network (VPN) and
suggest several interesting future research and
development directions that could build on this work.",
}
@TechReport{Dartmouth:TR2004-510,
author = "Sung Hoon Kim",
title = "{Greenpass RADIUS Tools for Delegated Authorization in
Wireless Networks}",
institution = "Dartmouth College, Computer Science",
address = "Hanover, NH",
number = "TR2004-510",
year = "2004",
month = jun,
URL = "http://www.cs.dartmouth.edu/reports/TR2004-510.pdf",
comment = "Masters thesis. Advisor: Sean Smith",
abstract = "Dartmouth's Greenpass project extends how public key
cryptography can be used to secure the wireless LAN
with a RADIUS (Remote Authentication Dial In User
Service) server that is responsible for handling
authentication requests from clients (called
supplicants in the 802.1x authentication model). This
thesis describes the design and implementation of the
authentication process of Greenpass, specifically what
decisions are made in determining who is granted access
and how a small modification of already existing
protocols can be used to provide guest access in a way
that better reflects how delegation of authority works
in the real world. Greenpass takes advantage of the
existing PKI to authenticate local Dartmouth users via
X.509 identity certificates using EAP-TLS. We use the
flexibility of SPKI/SDSI (Simple Public Key
Infrastructure/Simple Distributed Security
Infrastructure) authorization certificates to
distribute the responsibility of delegating access to
guests to certain authorized delegators, avoiding some
of the necessary steps and paperwork associated with
having a large centralized entity responsible for the
entire institution. This thesis also discusses how our
solution can be adapted to support different methods of
guest delegation and investigates the possibility of
eliminating the cumbersome central entity and
administrative overhead traditionally associated with
public key cryptography.",
}
@TechReport{Dartmouth:TR2004-511,
author = "Robert S. Gray and David Kotz and Calvin Newport and
Nikita Dubrovsky and Aaron Fiske and Jason Liu and
Christopher Masone and Susan McGrath and Yougu Yuan",
title = "{Outdoor Experimental Comparison of Four Ad Hoc
Routing Algorithms}",
institution = "Dartmouth College, Computer Science",
address = "Hanover, NH",
number = "TR2004-511",
year = "2004",
month = jun,
URL = "http://www.cs.dartmouth.edu/reports/TR2004-511.pdf",
comment = "See also TR2004-507 and TR2004-504.",
abstract = "Most comparisons of wireless ad hoc routing algorithms
involve simulated or indoor trial runs, or outdoor runs
with only a small number of nodes, potentially leading
to an incorrect picture of algorithm performance. In
this paper, we report on the results of an outdoor
trial run of four different routing algorithms, APRL,
AODV, GPSR, and STARA, running on top of thirty-three
802.11-enabled laptops moving randomly through an
athletic field. The laptops generated random traffic
according to the traffic patterns observed in a
prototype application, and ran each routing algorithm
for a fifteen-minute period over the course of the
hour-long trial run. The 33-laptop experiment
represents one of the largest outdoor tests of wireless
routing algorithms, and three of the algorithms each
come from a different algorithmic class, providing
insight into the behavior of ad hoc routing algorithms
at larger real-world scales than have been considered
so far. In addition, we compare the outdoor results
with both indoor ({"}tabletop{"}) and simulation
results for the same algorithms, examining the
differences between the indoor results and the outdoor
reality. The paper also describes the software
infrastructure that allowed us to implement the ad hoc
routing algorithms in a comparable way, and use the
same codebase for indoor, outdoor, and simulated trial
runs.",
}
@TechReport{Dartmouth:TR2004-512,
author = "Kimberly S. Powell",
title = "{Testing the Greenpass Wireless Security System}",
institution = "Dartmouth College, Computer Science",
address = "Hanover, NH",
number = "TR2004-512",
year = "2004",
month = jun,
URL = "http://www.cs.dartmouth.edu/reports/TR2004-512.pdf",
comment = "Senior Honors Thesis. Advisors: Sean Smith and Denise
Anthony",
abstract = "Greenpass, developed by Nick Goffee, Sung Hoon Kim,
Meiyuan Zhao and John Marchesini under the supervision
of Sean Smith and Punch Taylor, is a wireless security
solution that implements SPKI/SDSI delegation on top of
X.509 keypairs within the EAP-TLS authentication
protocol. This system aims to model the decentralized
way that authorization flows in real-world enterprise
settings and provide a seamless solution that allows
for easy access to all resources in the network by both
registered users and authorized guests. These goals are
achieved through the deployment of a delegation tool,
which allows an active entity associated to the
organization's network to grant authorization to
another entity previously unauthorized to use the
network. This paper describes the testing process of
the first prototype for this system. It examines trust
and usability issues of the Greenpass Wireless Security
System and determines the accuracy of the system's
implementation in relation to its objectives. It then
addresses the planning and execution of a small-scale
demo for this prototype based on the examined issues
and makes projections for further tests on a larger
scale.",
}
@TechReport{Dartmouth:TR2004-513,
author = "Jue Wang",
title = "{Performance Evaluation of a Resource Discovery
Service}",
institution = "Dartmouth College, Computer Science",
address = "Hanover, NH",
number = "TR2004-513",
year = "2004",
month = oct # ",",
URL = "http://www.cs.dartmouth.edu/reports/TR2004-513.pdf",
abstract = "In a pervasive computing environment, the number and
variety of resources (services, devices, and contextual
information resources) make it necessary for
applications to accurately discover the best ones
quickly. Thus a resource-discovery service, which
locates specific resources and establishes network
connections as better resources become available, is
necessary for those applications. The performance of
the resource-discovery service is important when the
applications are in a dynamic and mobile environment.
In this thesis, however, we do not focus on the
resource- discovery technology itself, but the
evaluation of the scalability and mobility of the
resource discovery module in Solar, a context fusion
middleware. Solar has a naming service that provides
resource discovery, since the resource names encode
static and dynamic attributes. The results of our
experiments show that Solar's resource discovery
performed generally well in a typical dynamic
environment, although Solar can not be scaled as well
as it should. And we identify the implementation issues
related to that problem. We also discuss experience,
insights, and lessons learned from our quantitative
analysis of the experiment results.",
}
@TechReport{Dartmouth:TR2004-514,
author = "Guanling Chen",
title = "{Solar: Building A Context Fusion Network for
Pervasive Computing}",
institution = "Dartmouth College, Computer Science",
address = "Hanover, NH",
number = "TR2004-514",
year = "2004",
month = aug,
URL = "http://www.cs.dartmouth.edu/reports/TR2004-514.pdf",
comment = "This is a reformatted version of Guanling Chen's Ph.D.
dissertation. Unlike the dissertation submitted to
Dartmouth College, this version is single-spaced, uses
11pt fonts, and is formatted specifically for
double-sided printing.",
abstract = "The complexity of developing context-aware
pervasive-computing applications calls for distributed
software infrastructures that assist applications to
collect, aggregate, and disseminate contextual data. In
this dissertation, we present a Context Fusion Network
(CFN), called Solar, which is built with a scalable and
self-organized service overlay. Solar is flexible and
allows applications to select distributed data sources
and compose them with customized data-fusion operators
into a directed acyclic information flow graph. Such a
graph represents how an application computes high-level
understandings of its execution context from low-level
sensory data. To manage application-specified operators
on a set of overlay nodes called Planets, Solar
provides several unique services such as
application-level multicast with policy-driven data
reduction to handle buffer overflow, context-sensitive
resource discovery to handle environment dynamics, and
proactive monitoring and recovery to handle common
failures. Experimental results show that these services
perform well on a typical DHT-based peer-to-peer
routing substrate. In this dissertation, we also
discuss experience, insights, and lessons learned from
our quantitative analysis of the input sensors, a
detailed case study of a Solar application, and
development of other applications in different
domains.",
}
@TechReport{Dartmouth:TR2004-515,
author = "Alin C. Popescu and Hany Farid",
title = "{Exposing Digital Forgeries by Detecting Duplicated
Image Regions }",
institution = "Dartmouth College, Computer Science",
address = "Hanover, NH",
number = "TR2004-515",
year = "2004",
month = aug,
URL = "http://www.cs.dartmouth.edu/reports/TR2004-515.pdf",
abstract = "We describe an efficient technique that automatically
detects duplicated regions in a digital image. This
technique works by first applying a principal component
analysis to small fixed-size image blocks to yield a
reduced dimension representation. This representation
is robust to minor variations in the image due to
additive noise or lossy compression. Duplicated regions
are then detected by lexicographically sorting all of
the image blocks. We show the efficacy of this
technique on credible forgeries, and quantify its
robustness and sensitivity to additive noise and lossy
JPEG compression.",
}
@TechReport{Dartmouth:TR2004-517,
author = "Geeta Chaudhry",
title = "{Parallel Out-of-Core Sorting: The Third Way}",
institution = "Dartmouth College, Computer Science",
address = "Hanover, NH",
number = "TR2004-517",
year = "2004",
month = sep,
URL = "http://www.cs.dartmouth.edu/reports/TR2004-517.pdf",
comment = "Doctoral dissertation. Advisor: Thomas H. Cormen",
abstract = "Sorting very large datasets is a key subroutine in
almost any application that is built on top of a large
database. Two ways to sort out-of-core data dominate
the literature: merging-based algorithms and
partitioning-based algorithms. Within these two
paradigms, all the programs that sort out-of-core data
on a cluster rely on assumptions about the input
distribution. We propose a third way of out-of-core
sorting: oblivious algorithms. In all, we have
developed six programs that sort out-of-core data on a
cluster. The first three programs, based completely on
Leighton's columnsort algorithm, have a restriction on
the maximum problem size that they can sort. The other
three programs relax this restriction; two are based on
our original algorithmic extensions to columnsort. We
present experimental results to show that our
algorithms perform well. To the best of our knowledge,
the programs presented in this thesis are the first to
sort out-of-core data on a cluster without making any
simplifying assumptions about the distribution of the
data to be sorted.",
}
@TechReport{Dartmouth:TR2004-518,
author = "Hany Farid",
title = "{Creating and Detecting Doctored and Virtual Images:
Implications to The Child Pornography Prevention Act
}",
institution = "Dartmouth College, Computer Science",
address = "Hanover, NH",
number = "TR2004-518",
year = "2004",
month = sep,
URL = "http://www.cs.dartmouth.edu/reports/TR2004-518.pdf",
abstract = "The 1996 Child Pornography Prevention Act (CPPA)
extended the existing federal criminal laws against
child pornography to include certain types of
{"}virtual porn{"}. In 2002, the United States Supreme
Court found that portions of the CPPA, being overly
broad and restrictive, violated First Amendment rights.
The Court ruled that images containing an actual minor
or portions of a minor are not protected, while
computer generated images depicting a fictitious
{"}computer generated{"} minor are constitutionally
protected. In this report I outline various forms of
digital tampering, placing them in the context of this
recent ruling. I also review computational techniques
for detecting doctored and virtual (computer generated)
images.",
}
@TechReport{Dartmouth:TR2004-519,
author = "Robert C. Fitch",
title = "{Heterogeneous Self-Reconfiguring Robotics}",
institution = "Dartmouth College, Computer Science",
address = "Hanover, NH",
number = "TR2004-519",
year = "2004",
month = sep # ",",
URL = "http://www.cs.dartmouth.edu/reports/TR2004-519.pdf",
comment = "Doctoral dissertation. Advisor: Daniela Rus",
abstract = "Self-reconfiguring (SR) robots are modular systems
that can autonomously change shape, or reconfigure, for
increased versatility and adaptability in unknown
environments. In this thesis, we investigate planning
and control for systems of non-identical modules, known
as heterogeneous SR robots. Although previous
approaches rely on module homogeneity as a critical
property, we show that the planning complexity of
fundamental algorithmic problems in the heterogeneous
case is equivalent to that of systems with identical
modules. Primarily, we study the problem of how to plan
shape changes while considering the placement of
specific modules within the structure. We characterize
this key challenge in terms of the amount of free space
available to the robot and develop a series of
decentralized reconfiguration planning algorithms that
assume progressively more severe free space constraints
and support reconfiguration among obstacles. In
addition, we compose our basic planning techniques in
different ways to address problems in the related task
domains of positioning modules according to function,
locomotion among obstacles, self-repair, and
recognizing the achievement of distributed goal-states.
We also describe the design of a novel simulation
environment, implementation results using this
simulator, and experimental results in hardware using a
planar SR system called the Crystal Robot. These
results encourage development of heterogeneous systems.
Our algorithms enhance the versatility and adaptability
of SR robots by enabling them to use functionally
specialized components to match capability, in addition
to shape, to the task at hand.",
}
@TechReport{Dartmouth:TR2004-520,
author = "Siwei Lyu",
title = "{Mercer Kernels for Object Recognition with Local
Features}",
institution = "Dartmouth College, Computer Science",
address = "Hanover, NH",
number = "TR2004-520",
year = "2004",
month = oct,
URL = "http://www.cs.dartmouth.edu/reports/TR2004-520.pdf",
comment = "Submitted to CVPR 2005.",
abstract = "In this paper, we propose a new class of kernels for
object recognition based on local image feature
representations. Formal proofs are given to show that
these kernels satisfy the Mercer condition and reflect
similarities between sets of local features. In
addition, multiple types of local features and
semilocal constraints are incorporated to reduce
mismatches between local features, thus further improve
the classification performance. Experimental results of
SVM classifiers coupled with the proposed kernels are
reported on ecognition tasks with the standard COIL-100
database and compared with existing methods. The
proposed kernels achieved satisfactory performance and
were robust to changes in object configurations and
image degradations.",
}
@TechReport{Dartmouth:TR2004-521,
author = "Chris Hawblitzel and Heng Huang and Lea Wittie",
title = "{Composing a Well-Typed Region}",
institution = "Dartmouth College, Computer Science",
address = "Hanover, NH",
number = "TR2004-521",
year = "2004",
month = oct,
URL = "http://www.cs.dartmouth.edu/reports/TR2004-521.pdf",
abstract = "Efficient low-level systems need more control over
memory than safe high-level languages usually provide.
In particular, safe languages usually prohibit explicit
deallocation, in order to prevent dangling pointers.
Regions provide one safe deallocation mechanism;
indeed, many region calculi have appeared recently,
each with its own set of operations and often complex
rules. This paper encodes regions from lower-level
typed primitives (linear memory, coercions, and delayed
types), so that programmers can design their own region
operations and rules.",
}
@TechReport{Dartmouth:TR2004-523,
author = "Prasad Jayanti and Srdjan Petrovic",
title = "{Efficient Wait-Free Implementation of Multiword LL/SC
Variables}",
institution = "Dartmouth College, Computer Science",
address = "Hanover, NH",
number = "TR2004-523",
year = "2004",
month = oct,
URL = "http://www.cs.dartmouth.edu/reports/TR2004-523.pdf",
abstract = "Since the design of lock-free data structures often
poses a formidable intellectual challenge, researchers
are constantly in search of abstractions and primitives
that simplify this design. The multiword LL/SC object
is such a primitive: many existing algorithms are based
on this primitive, including the nonblocking and
wait-free universal constructions of Anderson and Moir
(1995), the closed objects construction of Chandra et
al.(1998) and the snapshot algorithms of Jayanti (2002,
2004). In this paper, we consider the problem of
implementing a W-word LL/SC object shared by N
processes. The previous best algorithm, due to Anderson
and Moir (1995), is time optimal (LL and SC operations
run in O(W) time), but has a space complexity of
O(N^2W). We present an algorithm that uses novel buffer
management ideas to cut down the space complexity by a
factor of N to O(NW), while still being time optimal.",
}
@TechReport{Dartmouth:TR2004-524,
author = "Kwang-Hyun Baek and Sean W. Smith and David Kotz",
title = "{A Survey of WPA and 802.11i RSN Authentication
Protocols}",
institution = "Dartmouth College, Computer Science",
address = "Hanover, NH",
number = "TR2004-524",
year = "2004",
month = nov,
URL = "http://www.cs.dartmouth.edu/reports/TR2004-524.pdf",
abstract = "In the new standards for WLAN security, many choices
exist for the authentication process. In this paper, we
list eight desired properties of WLAN authentication
protocols, survey eight recent authentication
protocols, and analyze the protocols according to the
desired properties.",
}
@TechReport{Dartmouth:TR2004-525,
author = "John Marchesini and Sean W. Smith",
title = "{Secure Hardware Enhanced MyProxy}",
institution = "Dartmouth College, Computer Science",
address = "Hanover, NH",
number = "TR2004-525",
year = "2004",
month = nov,
URL = "http://www.cs.dartmouth.edu/reports/TR2004-525.pdf",
abstract = "In 1976, Whitfield Diffie and Martin Hellman
demonstrated how {"}New Directions In Cryptography{"}
could enable secure information exchange between
parties that do not share secrets. In order for public
key cryptography to work in modern distributed
environments, we need an infrastructure for finding and
trusting other parties' public keys (i.e., a PKI). A
number of useful applications become possible with PKI.
While the applications differ in how they use keys
(e.g., S/MIME uses the key for message encryption and
signing, while client-side SSL uses the key for
authentication), all applications share one assumption:
users have keypairs. In previous work, we examined the
security aspects of some of the standard keystores and
the their interaction with the OS. We concluded that
desktops are not safe places to store private keys, and
we demonstrated the permeability of keystores such as
the default Microsoft keystore and the Mozilla
keystore. In addition to being unsafe, these desktop
keystores have the added disadvantage of being
immobile. In other previous work, we examined trusted
computing. In industry, a new trusted computing
initiative has emerged: the Trusted Computing Platform
Alliance (TCPA) (now renamed the Trusted Computing
Group (TCG)). The goal of the TCG design is
lower-assurance security that protects an entire
desktop platform and is cheap enough to be commercially
feasible. Last year, we built a trusted computing
platform based on the TCG specifications and hardware.
The picture painted by these previous projects suggests
that common desktops are not secure enough for use as
PKI clients, and trusted computing can improve the
security of client machines. The question that I
propose to investigate is: {"}Can I build a system
which applies trusted computing hardware in a
reasonable manner in order to make desktops usable for
PKI?{"} My design begins with the Grid community's
{"}MyProxy{"} credential repository, and enhances it to
take advantage of secure hardware on the clients, at
the repository, and in the policy framework. The result
is called {"}Secure Hardware Enhanced MyProxy{"}.",
}
@TechReport{Dartmouth:TR2004-526,
author = "Lea Wittie",
title = "{Type-Safe Operating System Abstractions}",
institution = "Dartmouth College, Computer Science",
address = "Hanover, NH",
number = "TR2004-526",
year = "2004",
month = jun,
URL = "http://www.cs.dartmouth.edu/reports/TR2004-526.pdf",
comment = "Doctoral dissertation. Advisor: Chris Hawblitzel",
abstract = "Operating systems and low-level applications are
usually written in languages like C and assembly, which
provide access to low-level abstractions. These
languages have unsafe type systems that allow many bugs
to slip by programmers. For example, in 1988, the
Internet Worm exploited several insecure points in Unix
including the finger command. A call to finger with an
unexpected argument caused a buffer overflow, leading
to the shutdown of most Internet traffic. A finger
application written in a type-safe language would have
prevented its exploit and limited the points the
Internet Worm could attack. Such vulnerabilities are
unacceptable in security-critical applications such as
the secure coprocessors of the Marianas network,
secStore key storage from Plan 9, and self-securing
storage. This research focuses on safe language
techniques for building OS components that cannot cause
memory or IO errors. For example, an Ethernet device
driver communicates with its device through IO
operations. The device depends on FIFO queues to send
and receive packets. A mistake in an IO operation can
overflow or underflow the FIFO queues, cause memory
errors, or cause configuration inconsistencies on the
device. Data structures such as FIFO queues can be
written safely in safe languages such as Java and ML
but these languages do not allow the access to the
low-level resources that an OS programmer needs.
Therefore, safe OS components require a language that
combines the safety of Java with the low-level control
of C. My research formalizes the concurrency, locks,
and system state needed by the safety-critical areas of
a device driver. These formal concepts are built on top
of an abstract syntax and rules that guarantees basic
memory safety using linear and singleton types to
implement safe memory load and store operations. I
proved that the improved abstract machine retains the
property of soundness, which means that all well-typed
programs will be able to execute until they reach an
approved end-state. Together, the concurrency, locks,
and state provide safety for IO operations and data
structures. Using the OSKit from the University of Utah
as a starting point, I developed a small operating
system. I ported the 3c509 Ethernet device driver from
C to Clay, a C-like type-safe language that uses a type
system powerful enough to enforce invariants about
low-level devices and data structures. The resulting
driver works safely in a multi-threaded environment. It
is guaranteed to obtain locks before using shared data.
It cannot cause a FIFO queue to overflow or underflow
and it will only call IO operations when invariants are
satisfied. This type-safe driver demonstrates an actual
working application of the theoretical components of my
research. The abstract machine is powerful enough to
encode a given OS specification and enforce a provably
matching implementation. These results lead towards
fundamentally secure computing environments.",
}
@TechReport{Dartmouth:TR2004-528,
author = "Hany Farid",
title = "{Discrete-Time Fractional Differentiation from Integer
Derivatives }",
institution = "Dartmouth College, Computer Science",
address = "Hanover, NH",
number = "TR2004-528",
year = "2004",
month = dec,
URL = "http://www.cs.dartmouth.edu/reports/TR2004-528.pdf",
abstract = "Discrete-time fractional derivative filters (1-D and
2-D) are shown to be well approximated from a small set
of integer derivatives. A fractional derivative of
arbitrary order (and, in 2-D, of arbitrary orientation)
can therefore be efficiently computed from a linear
combination of integer derivatives of the underlying
signal or image.",
}
@TechReport{Dartmouth:TR2004-529,
author = "Kazuhiro Minami and David Kotz",
title = "{Secure Context-sensitive Authorization}",
institution = "Dartmouth College, Computer Science",
address = "Hanover, NH",
number = "TR2004-529",
year = "2004",
month = dec,
URL = "http://www.cs.dartmouth.edu/reports/TR2004-529.pdf",
abstract = "There is a recent trend toward rule-based
authorization systems to achieve flexible security
policies. Also, new sensing technologies in pervasive
computing make it possible to define context-sensitive
rules, such as ``allow database access only to staff
who are currently located in the main office.''
However, these rules, or the facts that are needed to
verify authority, often involve sensitive context
information. This paper presents a secure
context-sensitive authorization system that protects
confidential information in facts or rules.
Furthermore, our system allows multiple hosts in a
distributed environment to perform the evaluation of an
authorization query in a collaborative way; we do not
need a universally trusted central host that maintains
all the context information. The core of our approach
is to decompose a proof for making an authorization
decision into a set of sub-proofs produced on multiple
different hosts, while preserving the integrity and
confidentiality policies of the mutually untrusted
principals operating these hosts. We prove the
correctness of our algorithm.",
}
@TechReport{Dartmouth:TR2005-530,
author = "Ramgopal R. Mettu and Ryan H. Lilien and Bruce R.
Donald",
title = "{High-Throughput Inference of Protein-Protein
Interaction Sites from Unassigned NMR Data by Analyzing
Arrangements Induced By Quadratic Forms on
3-Manifolds}",
institution = "Dartmouth College, Computer Science",
address = "Hanover, NH",
number = "TR2005-530",
year = "2005",
month = jan,
URL = "http://www.cs.dartmouth.edu/reports/TR2005-530.pdf",
comment = "A revised version of this paper has been accepted for
publication and will appear at ISMB (2005) and
Bioinformatics (2005).",
abstract = "We cast the problem of identifying protein-protein
interfaces, using only unassigned NMR spectra, into a
geometric clustering problem. Identifying
protein-protein interfaces is critical to understanding
inter- and intra-cellular communication, and NMR allows
the study of protein interaction in solution. However
it is often the case that NMR studies of a protein
complex are very time-consuming, mainly due to the
bottleneck in assigning the chemical shifts, even if
the apo structures of the constituent proteins are
known. We study whether it is possible, in a
high-throughput manner, to identify the interface
region of a protein complex using only unassigned
chemical shift and residual dipolar coupling (RDC)
data. We introduce a geometric optimization problem
where we must cluster the cells in an arrangement on
the boundary of a 3-manifold. The arrangement is
induced by a spherical quadratic form, which in turn is
parameterized by SO(3)xR^2. We show that this formalism
derives directly from the physics of RDCs. We present
an optimal algorithm for this problem that runs in
O(n^3 log n) time for an n-residue protein. We then use
this clustering algorithm as a subroutine in a
practical algorithm for identifying the interface
region of a protein complex from unassigned NMR data.
We present the results of our algorithm on NMR data for
7 proteins from 5 protein complexes and show that our
approach is useful for high-throughput applications in
which we seek to rapidly identify the interface region
of a protein complex.",
}
@TechReport{Dartmouth:TR2005-531,
author = "Alin C. Popescu",
title = "{Statistical Tools for Digital Image Forensics}",
institution = "Dartmouth College, Computer Science",
address = "Hanover, NH",
number = "TR2005-531",
year = "2004",
month = dec,
URL = "http://www.cs.dartmouth.edu/reports/TR2005-531.pdf",
comment = "Ph.D. thesis, advisor: Hany Farid.",
abstract = "A digitally altered image, often leaving no visual
clues of having been tampered with, can be
indistinguishable from an authentic image. The
tampering, however, may disturb some underlying
statistical properties of the image. Under this
assumption, we propose five techniques that quantify
and detect statistical perturbations found in different
forms of tampered images: (1) re-sampled images (e.g.,
scaled or rotated); (2) manipulated color filter array
interpolated images; (3) double JPEG compressed images;
(4) images with duplicated regions; and (5) images with
inconsistent noise patterns. These techniques work in
the absence of any embedded watermarks or signatures.
For each technique we develop the theoretical
foundation, show its effectiveness on credible
forgeries, and analyze its sensitivity and robustness
to simple counter-attacks.",
}
@TechReport{Dartmouth:TR2005-532,
author = "John Marchesini and Sean Smith",
title = "{SHEMP: Secure Hardware Enhanced MyProxy}",
institution = "Dartmouth College, Computer Science",
address = "Hanover, NH",
number = "TR2005-532",
year = "2005",
month = feb,
URL = "http://www.cs.dartmouth.edu/reports/TR2005-532.pdf",
abstract = "While PKI applications differ in how they use keys,
all applications share one assumption: users have
keypairs. In previous work, we established that desktop
keystores are not safe places to store private keys,
because the TCB is too large. These keystores are also
immobile, difficult to use, and make it impossible for
relying parties to make reasonable trust judgments.
Since we would like to use desktops as PKI clients and
cannot realistically expect to redesign the entire
desktop, this paper presents a system that works within
the confines of modern desktops to shrink the TCB
needed for PKI applications. Our system (called Secure
Hardware Enhanced MyProxy (SHEMP)) shrinks the TCB in
space and allows the TCB's size to vary over time and
over various application sensitivity levels, thus
making desktops usable for PKI.",
}
@TechReport{Dartmouth:TR2005-533,
author = "Soumendra Nanda",
title = "{Spatial Multipath Location Aided Routing}",
institution = "Dartmouth College, Computer Science",
address = "Hanover, NH",
number = "TR2005-533",
year = "2005",
month = feb,
URL = "http://www.cs.dartmouth.edu/reports/TR2005-533.pdf",
comment = "MS Thesis ,Originally submitted 6th June 2004, Advised
by Robert S. Gray",
abstract = "Mobile ad-hoc networks (MANETs) are
infrastructure-free networks of mobile nodes that
communicate with each other wirelessly. There are
several routing schemes that have been proposed and
several of these have been already extensively
simulated or implemented as well. The primary
applications of such networks have been in disaster
relief operations, military use, conferencing and
environment sensing. There are several ad hoc routing
algorithms at present that utilize position information
(usually in two dimensional terms) to make routing
decisions at each node. Our goal is to utilize
three-dimensional (3D) position information to provide
more reliable as well as efficient routing for certain
applications. We thus describe extensions to various
location aware routing algorithms to work in 3D. We
propose a new hierarchical, zone-based 3D routing
algorithm, based on GRID by Liao, Tseng and Sheu. Our
new algorithm called {"}Hyper-GRID{"} is a hybrid
algorithm that uses multipath routing (alternate path
caching) in 3D. We propose replacing LAR with Multipath
LAR (MLAR) in GRID. We have implemented MLAR and are
validating MLAR through simulation using ns-2 and
studying its efficiency, scalability and other
properties. We use a random waypoint mobility model and
compare our MLAR approach versus LAR, AODV and AOMDV in
both 2D and 3D for a range of traffic and mobility
scenarios. Our simulation results demonstrate the
performance benefits of MLAR over LAR and AODV in most
mobility situations. AOMDV delivers more packets than
MLAR consistently, but does so at the cost of more
frequent flooding of control packets and thus higher
bandwidth usage than MLAR.",
}
@TechReport{Dartmouth:TR2005-534,
author = "David Kotz",
title = "{Department of Computer Science Activity 1998-2004 }",
institution = "Dartmouth College, Computer Science",
address = "Hanover, NH",
number = "TR2005-534",
year = "2005",
month = mar,
URL = "http://www.cs.dartmouth.edu/reports/TR2005-534.pdf",
abstract = "This report summarizes much of the research and
teaching activity of the Department of Computer Science
at Dartmouth College between late 1998 and late 2004.
The material for this report was collected as part of
the final report for NSF Institutional Infrastructure
award EIA-9802068, which funded equipment and technical
staff during that six-year period. This equipment and
staff supported essentially all of the departmentÕs
research activity during that period.",
}
@TechReport{Dartmouth:TR2005-535,
author = "John Thomas and Naren Ramakrishnan and Chris
Bailey-Kellogg",
title = "{Graphical Models of Residue Coupling in Protein
Families}",
institution = "Dartmouth College, Computer Science",
address = "Hanover, NH",
number = "TR2005-535",
year = "2005",
month = mar,
URL = "http://www.cs.dartmouth.edu/reports/TR2005-535.pdf",
comment = "To appear in BIOKDD05.",
abstract = "Identifying residue coupling relationships within a
protein family can provide important insights into
intrinsic molecular processes, and has significant
applications in modeling structure and dynamics,
understanding function, and designing new or modified
proteins. We present the first algorithm to infer an
undirected graphical model representing residue
coupling in protein families. Such a model serves as a
compact description of the joint amino acid
distribution, and can be used for predictive (will this
newly designed protein be folded and functional?),
diagnostic (why is this protein not stable or
functional?), and abductive reasoning (what if I
attempt to graft features of one protein family onto
another?). Unlike current correlated mutation
algorithms that are focused on assessing dependence,
which can conflate direct and indirect relationships,
our algorithm focuses on assessing independence, which
modularizes variation and thus enables efficient
reasoning of the types described above. Further, our
algorithm can readily incorporate, as priors,
hypotheses regarding possible underlying
mechanistic/energetic explanations for coupling. The
resulting approach constitutes a powerful and
discriminatory mechanism to identify residue coupling
from protein sequences and structures. Analysis results
on the G-protein coupled receptor (GPCR) and PDZ domain
families demonstrate the ability of our approach to
effectively uncover and exploit models of residue
coupling.",
}
@TechReport{Dartmouth:TR2005-536,
author = "Vincent Berk and Annarita Giani and George Cybenko",
title = "{Detection of Covert Channel Encoding in Network
Packet Delays}",
institution = "Dartmouth College, Computer Science",
address = "Hanover, NH",
number = "TR2005-536",
year = "2005",
month = aug,
URL = "http://www.cs.dartmouth.edu/reports/TR2005-536-rev1.pdf",
comment = "This revision differs from the original only in the
correction of one reference.",
abstract = "Covert channels are mechanisms for communicating
information in ways that are difficult to detect. Data
exfiltration can be an indication that a computer has
been compromised by an attacker even when other
intrusion detection schemes have failed to detect a
successful attack. Covert timing channels use packet
inter-arrival times, not header or payload embedded
information, to encode covert messages. This paper
investigates the channel capacity of Internet-based
timing channels and proposes a methodology for
detecting covert timing channels based on how close a
source comes to achieving that channel capacity. A
statistical approach is then used for the special case
of binary codes.",
}
@TechReport{Dartmouth:TR2005-538,
author = "Robert Scot Drysdale and Clifford Stein and David P.
Wagner",
title = "{An O(n^{5/2} log n) Algorithm for the Rectilinear
Minimum Link-Distance Problem in Three Dimensions
(Extended Abstract)}",
institution = "Dartmouth College, Computer Science",
address = "Hanover, NH",
number = "TR2005-538",
year = "2005",
month = may,
URL = "http://www.cs.dartmouth.edu/reports/TR2005-538.pdf",
comment = "Submitted to CCCG 2005",
abstract = "In this paper we consider the Rectilinear Minimum
Link-Distance Problem in Three Dimensions. The problem
is well studied in two dimensions, but is relatively
unexplored in higher dimensions. We solve the problem
in O(B n log n) time, where n is the number of corners
among all obstacles, and B is the size of a BSP
decomposition of the space containing the obstacles. It
has been shown that in the worst case B =
Theta(n^{3/2}), giving us an overall worst case time of
O(n^{5/2} log n). Previously known algorithms have had
worst-case running times of Omega(n^3).",
}
@TechReport{Dartmouth:TR2005-539,
author = "Kwang-Hyun Baek and Sean W. Smith",
title = "{Preventing Theft of Quality of Service on Open
Platforms}",
institution = "Dartmouth College, Computer Science",
address = "Hanover, NH",
number = "TR2005-539",
year = "2005",
month = may,
URL = "http://www.cs.dartmouth.edu/reports/TR2005-539.pdf",
comment = "REVISION 1 of May 5, 2005.",
abstract = "As multiple types of traffic converge onto one network
(frequently wireless), enterprises face a tradeoff
between effectiveness and security. Some types of
traffic, such as voice-over-IP (VoIP), require certain
quality of service (QoS) guarantees to be effective.
The end client platform is in the best position to know
which packets deserve this special handling. In many
environments (such as universities), end users relish
having control over their own machines. However, if end
users administer their own machines, nothing stops
dishonest ones from marking undeserving traffic for
high QoS. How can an enterprise ensure that only
appropriate traffic receives high QoS, while also
allowing end users to retain control over their own
machines? In this paper, we present the design and
prototype of a solution, using SELinux, TCPA/TCG
hardware, Diffserv, 802.1x, and EAP-TLS.",
}
@TechReport{Dartmouth:TR2005-540,
author = "Minkyong Kim and David Kotz",
title = "{Classifying the Mobility of Users and the Popularity
of Access Points}",
institution = "Dartmouth College, Computer Science",
address = "Hanover, NH",
number = "TR2005-540",
year = "2005",
month = may,
URL = "http://www.cs.dartmouth.edu/reports/TR2005-540.pdf",
comment = "Revision of a paper that appeared at LoCA 2005.",
abstract = "There is increasing interest in location-aware systems
and applications. It is important for any designer of
such systems and applications to understand the nature
of user and device mobility. Furthermore, an
understanding of the effect of user mobility on access
points (APs) is also important for designing,
deploying, and managing wireless networks. Although
various studies of wireless networks have provided
insights into different network environments and user
groups, it is often hard to apply these findings to
other situations, or to derive useful abstract models.
In this paper, we present a general methodology for
extracting mobility information from wireless network
traces, and for classifying mobile users and APs. We
used the Fourier transform to convert time-dependent
location information to the frequency domain, then
chose the two strongest periods and used them as
parameters to a classification system based on Bayesian
theory. To classify mobile users, we computed diameter
(the maximum distance between any two APs visited by a
user during a fixed time period) and observed how this
quantity changes or repeats over time. We found that
user mobility had a strong period of one day, but there
was also a large group of users that had either a much
smaller or much bigger primary period. Both primary and
secondary periods had important roles in determining
classes of mobile users. Users with one day as their
primary period and a smaller secondary period were most
prevalent; we expect that they were mostly students
taking regular classes. To classify APs, we counted the
number of users visited each AP. The primary period did
not play a critical role because it was equal to one
day for most of the APs; the secondary period was the
determining parameter. APs with one day as their
primary period and one week as their secondary period
were most prevalent. By plotting the classes of APs on
our campus map, we discovered that this periodic
behavior of APs seemed to be independent of their
geographical locations, but may depend on the relative
locations of nearby APs. Ultimately, we hope that our
study can help the design of location-aware services by
providing a base for user mobility models that reflect
the movements of real users.",
}
@TechReport{Dartmouth:TR2005-541,
author = "Meiyuan Zhao and Sean W. Smith and David M. Nicol",
title = "{Aggregated Path Authentication for Efficient BGP
Security}",
institution = "Dartmouth College, Computer Science",
address = "Hanover, NH",
number = "TR2005-541",
year = "2005",
month = may,
URL = "http://www.cs.dartmouth.edu/reports/TR2005-541.pdf",
abstract = "The border gateway protocol (BGP) controls
inter-domain routing in the Internet. BGP is vulnerable
to many attacks, since routers rely on hearsay
information from neighbors. Secure BGP (S-BGP) uses DSA
to provide route authentication and mitigate many of
these risks. However, many performance and deployment
issues prevent S-BGP's real-world deployment. Previous
work has explored improving S-BGP processing latencies,
but space problems, such as increased message size and
memory cost, remain the major obstacles. In this paper,
we combine two efficient cryptographic
techniques---signature amortization and aggregate
signatures---to design new aggregated path
authentication schemes. We propose six constructions
for aggregated path authentication that substantially
improve efficiency of S-BGP's path authentication on
both speed and space criteria. Our performance
evaluation shows that the new schemes achieve such an
efficiency that they may overcome the space obstacles
and provide a real-world practical solution for BGP
security.",
}
@TechReport{Dartmouth:TR2005-542,
author = "Matthew P. Bell",
title = "{A toy rock climbing robot}",
institution = "Dartmouth College, Computer Science",
address = "Hanover, NH",
number = "TR2005-542",
year = "2005",
month = aug,
URL = "http://www.cs.dartmouth.edu/reports/TR2005-542.pdf",
comment = "Senior Honors Thesis. Advisor: Devin Balkcom.",
abstract = "The goal of this thesis was to build a simple toy rock
climbing robot, and to explore problems related to
grasping, path planning, and robot control. The robot
is capable of climbing a wall of pegs either under
manual control through a host system and an infrared
interface, or on the basis of a set of pre-recorded
keyframes. In addition, the robot can climb certain peg
configurations using a cyclic gait. The robot climbs in
an open-loop mode without sensor feedback. All
communications are sent through the IR connection, and
the tether to the robot consists only of two power
wires.",
}
@TechReport{Dartmouth:TR2005-543,
author = "Robert A. Savell",
title = "{On-line Metasearch, Pooling, and System Evaluation}",
institution = "Dartmouth College, Computer Science",
address = "Hanover, NH",
number = "TR2005-543",
year = "2005",
month = jun,
URL = "http://www.cs.dartmouth.edu/reports/TR2005-543.pdf",
comment = "Doctoral dissertation. Advisors: Jay Aslam (NEU), Dan
Rockmore, Chris Bailey-Kellogg, and John Lafferty
(CMU).",
abstract = "This thesis presents a unified method for simultaneous
solution of three problems in Information Retrieval---
metasearch (the fusion of ranked lists returned by
retrieval systems to elicit improved performance),
efficient system evaluation (the accurate evaluation of
retrieval systems with small numbers of relevance
judgements), and pooling or ``active sample
selection{"} (the selection of documents for manual
judgement in order to develop sample pools of high
precision or pools suitable for assessing system
quality). The thesis establishes a unified theoretical
framework for addressing these three problems and
naturally generalizes their solution to the on-line
context by incorporating feedback in the form of
relevance judgements. The algorithm--- Rankhedge for
on-line retrieval, metasearch and system evaluation---
is the first to address these three problems
simultaneously and also to generalize their solution to
the on-line context. Optimality of the Rankhedge
algorithm is developed via Bayesian and maximum entropy
interpretations. Results of the algorithm prove to be
significantly superior to previous methods when tested
over a range of TREC (Text REtrieval Conference) data.
In the absence of feedback, the technique equals or
exceeds the performance of benchmark metasearch
algorithms such as CombMNZ and Condorcet. The technique
then dramatically improves on this performance during
the on-line metasearch process. In addition, the
technique generates pools of documents which include
more relevant documents and produce more accurate
system evaluations than previous techniques. The thesis
includes an information-theoretic examination of the
original Hedge algorithm as well as its adaptation to
the context of ranked lists. The work also addresses
the concept of information-theoretic similarity within
the Rankhedge context and presents a method for
decorrelating the predictor set to improve worst case
performance. Finally, an information-theoretically
optimal method for probabilistic ``active sampling{"}
is presented with possible application to a broad range
of practical and theoretical contexts.",
}
@TechReport{Dartmouth:TR2005-544,
author = "Twum Djin",
title = "{Managing Access Control in Virtual Private
Networks}",
institution = "Dartmouth College, Computer Science",
address = "Hanover, NH",
number = "TR2005-544",
year = "2005",
month = jun,
URL = "http://www.cs.dartmouth.edu/reports/TR2005-544.pdf",
comment = "Senior honors thesis.",
abstract = "Virtual Private Network technology allows remote
network users to benefit from resources on a private
network as if their host machines actually resided on
the network. However, each resource on a network may
also have its own access control policies, which may be
completely unrelated to network access. Thus usersÕ
access to a network (even by VPN technology) does not
guarantee their access to the sought resources. With
the introduction of more complicated access privileges,
such as delegated access, it is conceivable for a
scenario to arise where a user can access a network
remotely (because of direct permissions from the
network administrator or by delegated permission) but
cannot access any resources on the network. There is,
therefore, a need for a network access control
mechanism that understands the privileges of each
remote network user on one hand, and the access control
policies of various network resources on the other
hand, and so can aid a remote user in accessing these
resources based on the user's privileges. This research
presents a software solution in the form of a
centralized access control framework called an Access
Control Service (ACS), that can grant remote users
network presence and simultaneously aid them in
accessing various network resources with varying access
control policies. At the same time, the ACS provides a
centralized framework for administrators to manage
access to their resources. The ACS achieves these
objectives using VPN technology, network address
translation and by proxying various authentication
protocols on behalf of remote users.",
}
@TechReport{Dartmouth:TR2005-547,
author = "Alexander Iliev and Sean Smith",
title = "{Towards Tiny Trusted Third Parties}",
institution = "Dartmouth College, Computer Science",
address = "Hanover, NH",
number = "TR2005-547",
year = "2005",
month = jul,
URL = "http://www.cs.dartmouth.edu/reports/TR2005-547.pdf",
abstract = "Many security protocols hypothesize the existence of a
{\em trusted third party (TTP)} to ease handling of
computation and data too sensitive for the other
parties involved. Subsequent discussion usually
dismisses these protocols as hypothetical or
impractical, under the assumption that trusted third
parties cannot exist. However, the last decade has seen
the emergence of hardware-based devices that, to high
assurance, can carry out computation unmolested;
emerging research promises more. In theory, such
devices can perform the role of a trusted third party
in real-world problems. In practice, we have found
problems. The devices aspire to be general-purpose
processors but are too small to accommodate real-world
problem sizes. The small size forces programmers to
hand-tune each algorithm anew, if possible, to fit
inside the small space without losing security. This
tuning heavily uses operations that general-purpose
processors do not perform well. Furthermore, perhaps by
trying to incorporate too much functionality, current
devices are also too expensive to deploy widely. Our
current research attempts to overcome these barriers,
by focusing on the effective use of {\em tiny} TTPs
({\em T3Ps}). To eliminate the programming obstacle, we
used our experience building hardware TTP apps to
design and prototype an efficient way to execute {\em
arbitrary} programs on T3Ps while preserving the
critical trust properties. To eliminate the performance
and cost obstacles, we are currently examining the
potential hardware design for a T3P optimized for these
operations. In previous papers, we reported our work on
the programming obstacle. In this paper, we examine the
potential hardware designs. We estimate that such a T3P
could outperform existing devices by several orders of
magnitude, while also having a gate-count of only
30K-60K, one to three orders of magnitude smaller than
existing devices.",
}
@TechReport{Dartmouth:TR2005-548,
author = "Marco D. Adelfio",
title = "{Lower Bounds on the Communication Complexity of
Shifting}",
institution = "Dartmouth College, Computer Science",
address = "Hanover, NH",
number = "TR2005-548",
year = "2005",
month = jun,
URL = "http://www.cs.dartmouth.edu/reports/TR2005-548.pdf",
comment = "Senior Honors Thesis, 2005. Awarded High Honors.",
abstract = "We study the communication complexity of the SHIFT
(equivalently, SUM-INDEX) function in a 3-party
simultaneous message model. Alice and Bob share an
n-bit string x and Alice holds an index i and Bob an
index j. They must send messages to a referee who knows
only n, i and j, enabling him to determine x[(i+j) mod
n]. Surprisingly, it is possible to achieve nontrivial
savings even with such a strong restriction: Bob can
now make do with only ceil(n/2) bits. Here we show that
this bound is completely tight, for all n. This is an
exact lower bound, with no asymptotics involved.",
}
@TechReport{Dartmouth:TR2005-549,
author = "Guanling Chen and David Kotz",
title = "{Structural Analysis of Social Networks with Wireless
Users}",
institution = "Dartmouth College, Computer Science",
address = "Hanover, NH",
number = "TR2005-549",
year = "2005",
month = jul,
URL = "http://www.cs.dartmouth.edu/reports/TR2005-549.pdf",
abstract = "Online interactions between computer users form
Internet-based social networks. In this paper we
present a structural analysis of two such networks with
wireless users. In one network the wireless users
participate in a global file-sharing system, and in the
other they interact with each other through a local
music-streaming application.",
}
@TechReport{Dartmouth:TR2005-550,
author = "Guanling Chen and Heng Huang and Minkyong Kim",
title = "{Mining Frequent and Periodic Association Patterns}",
institution = "Dartmouth College, Computer Science",
address = "Hanover, NH",
number = "TR2005-550",
year = "2005",
month = jul,
URL = "http://www.cs.dartmouth.edu/reports/TR2005-550.pdf",
abstract = "Profiling the clients' movement behaviors is useful
for mobility modeling, anomaly detection, and location
prediction. In this paper, we study clients' frequent
and periodic movement patterns in a campus wireless
network. We use offline data-mining algorithms to
discover patterns from clients' association history,
and analyze the reported patterns using statistical
methods. Many of our results reflect the common
characteristics of a typical academic campus, though we
also observed some unusual association patterns. There
are two challenges: one is to remove noise from data
for efficient pattern discovery, and the other is to
interpret discovered patterns. We address the first
challenge using a heuristic-based approach applying
domain knowledge. The second issue is harder to address
because we do not have the knowledge of people's
activities, but nonetheless we could make reasonable
interpretation of the common patterns.",
}
@TechReport{Dartmouth:TR2005-551,
author = "Alexander Iliev and Sean Smith",
title = "{More Efficient Secure Function Evaluation Using Tiny
Trusted Third Parties}",
institution = "Dartmouth College, Computer Science",
address = "Hanover, NH",
number = "TR2005-551",
year = "2005",
month = jul,
URL = "http://www.cs.dartmouth.edu/reports/TR2005-551.pdf",
abstract = "We investigate the use of trustworthy devices, which
function as trusted third parties (TTPs), to solve
general two-party Secure Function Evaluation (SFE)
problems. We assume that a really trustworthy TTP
device will have very limited protected memory and
computation environment---a \emph{tiny TTP}. This
precludes trivial solutions like {"}just run the
function in the TTP{"}. Traditional scrambled circuit
evaluation approaches to SFE have a very high overhead
in using indirectly-addressed arrays---every array
access's cost is linear in the array size. The main
gain in our approach is that array access can be
provided with much smaller overhead---$O(\sqrt{N}\log
N)$. This expands the horizon of problems which can be
efficiently solved using SFE. Additionally, our
technique provides a simple way to deploy arbitrary
programs on tiny TTPs. In our prototype, we use a
larger (and expensive) device, the IBM 4758 secure
coprocessor, but we also speculate on the design of
future tiny devices that could greatly improve the
current prototype's efficiency by being optimized for
the operations prevalent in our algorithms. We have
prototyped a compiler for the secure function
definition language (SFDL) developed in the Fairplay
project. Our compiler produces an arithmetic circuit,
augmented with \emph{array access gates} which provide
more efficient secure access to arrays. We then have a
circuit interpreter in the 4758 to evaluate such a
circuit on given inputs. It does this gate by gate,
requiring very little protected space. We report on the
performance of this prototype, which confirms our
approach's strength in handling indirectly-addressed
arrays.",
}
@TechReport{Dartmouth:TR2005-552,
author = "Yougu Yuan",
title = "{On the Design of an Immersive Environment for
Security-Related Studies}",
institution = "Dartmouth College, Computer Science",
address = "Hanover, NH",
number = "TR2005-552",
year = "2005",
month = aug,
URL = "http://www.cs.dartmouth.edu/reports/TR2005-552.pdf",
comment = "Masters thesis. Advisor: David Nicol",
abstract = "The Internet has become an essential part of normal
operations of both public and private sectors. Many
security issues are not addressed in the original
Internet design, and security now has become a large
concern for networking research and study. There is an
imperative need to have an simulation environment that
can be used to help study security-related research
problems. In the thesis we present our effort to build
such an environment: Real-time Immersive Network
Simulation Environment (RINSE). RINSE features flexible
configuration of models using various networking
protocols and real-time user interaction. We also
present the Estimate Next Infection (ENI) model we
developed for Internet scanning worms using RINSE, and
the effort of combining multiple resolutions in worm
modeling.",
}
@TechReport{Dartmouth:TR2005-553,
author = "Bruce R. Donald and Christopher G. Levey and Craig D.
McGray and Igor Paprotny and Daniela Rus",
title = "{An Untethered, Electrostatic, Globally Controllable
MEMS Micro-Robot: Supplementary videos}",
institution = "Dartmouth College, Computer Science",
address = "Hanover, NH",
number = "TR2005-553",
year = "2005",
month = aug,
comment = "This technical report is a multimedia web page,
available at
http://www.cs.dartmouth.edu/reports/TR2005-553.CD/index.html
",
abstract = "We present a steerable, electrostatic, untethered,
MEMS micro-robot, with dimensions of 60 µm
by 250 µm by 10 µm. This
micro-robot is 1 to 2 orders of magnitude
smaller in size than previous micro-robotic systems.
The device consists of a curved, cantilevered steering
arm, mounted on an untethered scratch drive actuator.
These two components are fabricated monolithically from
the same sheet of conductive polysilicon, and receive a
common power and control signal through a capacitive
coupling with an underlying electrical grid. All
locations on the grid receive the same power and
control signal, so that the devices can be operated
without knowledge of their position on the substrate
and without constraining rails or tethers. Control and
power delivery waveforms are broadcast to the device
through the capacitive power coupling, and are decoded
by the electromechanical response of the device body.
Individual control of the component actuators provides
two distinct motion gaits (forward motion and turning),
which together allow full coverage of a planar
workspace (the robot is globally controllable). These
MEMS micro-robots demonstrate turning error of less
than 3.7 °/mm during forward motion, turn with
radii as small as 176 µm, and achieve speeds
of over 200 µm/sec, with an average step
size of 12 nm. They have been shown to operate
open-loop for distances exceeding 35 cm without
failure, and can be controlled through teleoperation to
navigate complex paths. This document contains movies
showing the actuation of the micro-robots during
open-loop actuation and teleoperation experiments. The
videos have been sped up for ease of viewing. On each
video, the time-scale is noted in the lower-right
corner of the screen.",
}
@TechReport{Dartmouth:TR2005-554,
author = "Prasad Jayanti and Srdjan Petrovic",
title = "{Efficiently Implementing a Large Number of LL/SC
Objects}",
institution = "Dartmouth College, Computer Science",
address = "Hanover, NH",
number = "TR2005-554",
year = "2005",
month = aug,
URL = "http://www.cs.dartmouth.edu/reports/TR2005-554.pdf",
abstract = "Over the past decade, a pair of instructions called
load-linked (LL) and store-conditional (SC) have
emerged as the most suitable synchronization
instructions for the design of lock-free algorithms.
However, current architectures do not support these
instructions; instead, they support either CAS (e.g.,
UltraSPARC, Itanium) or restricted versions of LL/SC
(e.g., POWER4, MIPS, Alpha). Thus, there is a gap
between what algorithm designers want (namely, LL/SC)
and what multiprocessors actually support (namely, CAS
or RLL/RSC). To bridge this gap, a flurry of algorithms
that implement LL/SC from CAS have appeared in the
literature. The two most recent algorithms are due to
Doherty, Herlihy, Luchangco, and Moir (2004) and
Michael (2004). To implement M LL/SC objects shared by
N processes, Doherty et al.'s algorithm uses only O(N +
M) space, but is only non-blocking and not wait-free.
Michael's algorithm, on the other hand, is wait-free,
but uses O(N^2 + M) space. The main drawback of his
algorithm is the time complexity of the SC operation:
although the expected amortized running time of SC is
only O(1), the worst-case running time of SC is O(N^2).
The algorithm in this paper overcomes this drawback.
Specifically, we design a wait-free algorithm that
achieves a space complexity of O(N^2 + M), while still
maintaining the O(1) worst-case running time for LL and
SC operations.",
}
@TechReport{Dartmouth:TR2005-555,
author = "Valentino Crespi and George V. Cybenko and Guofei
Jiang",
title = "{The Theory of Trackability with Applications to
Sensor Networks}",
institution = "Dartmouth College, Computer Science",
address = "Hanover, NH",
number = "TR2005-555",
year = "2005",
month = aug,
URL = "http://www.cs.dartmouth.edu/reports/TR2005-555.pdf",
abstract = "In this paper, we formalize the concept of tracking in
a sensor network and develop a rigorous theory of {\em
trackability} that investigates the rate of growth of
the number of consistent tracks given a sequence of
observations made by the sensor network. The phenomenon
being tracked is modelled by a nondeterministic finite
automaton and the sensor network is modelled by an
observer capable of detecting events related, typically
ambiguously, to the states of the underlying automaton.
More formally, an input string, $Z^t$, of $t+1$ symbols
(the sensor network observations) that is presented to
a nondeterministic finite automaton, $M$, (the model)
determines a set, ${\cal H}_M(Z^t)$, of state sequences
(the tracks or hypotheses) that are capable of
generating the input string $Z^t$. We study the growth
of the size of this set, $|{\cal H}_M(Z^t)|$, as a
function of the length of the input string, $t+1$. Our
main result is that for a given automaton and sensor
coverage, the worst-case rate of growth is either
polynomial or exponential in $t$, indicating a kind of
phase transition in tracking accuracy. The techniques
we use include the Joint Spectral Radius,
$\rho(\Sigma)$, of a finite set, $\Sigma$, of
$(0,1)$-matrices derived from $M$. Specifically, we
construct a set of matrices, $\Sigma$, corresponding to
$M$ with the property that $\rho(\Sigma) \leq 1$ if and
only if $|{\cal H}_M(Z^t)|$ grows polynomially in $t$.
We also prove that for $(0,1)$-matrices, the decision
problem $\rho(\Sigma)\leq 1$ is Turing decidable and,
therefore, so is the problem of deciding whether worst
case state sequence growth for a given automaton is
polynomial or exponential. These results have
applications in sensor networks, computer network
security and autonomic computing as well as various
tracking problems of recent interest involving
detecting phenomena using noisy observations of hidden
states.",
}
@TechReport{Dartmouth:TR2005-556,
author = "Srdjan Petrovic",
title = "{Efficient Wait-Free Algorithms for Implementing LL/SC
Objects}",
institution = "Dartmouth College, Computer Science",
address = "Hanover, NH",
number = "TR2005-556",
year = "2005",
month = aug,
URL = "http://www.cs.dartmouth.edu/reports/TR2005-556.pdf",
abstract = "Over the past decade, a pair of instructions called
load-linked (LL) and store-conditional (SC) have
emerged as the most suitable synchronization
instructions for the design of lock-free algorithms.
However, current architectures do not support these
instructions; instead, they support either CAS (e.g.,
UltraSPARC, Itanium, Pentium) or restricted versions of
LL/SC (e.g., POWER4, MIPS, Alpha). Thus, there is a gap
between what algorithm designers want (namely, LL/SC)
and what multiprocessors actually support (namely, CAS
or restricted LL/SC). To bridge this gap, this thesis
presents a series of efficient, wait-free algorithms
that implement LL/SC from CAS or restricted LL/SC.",
}
@TechReport{Dartmouth:TR2005-558,
author = "Guanhua Yan",
title = "{Improving Large-Scale Network Traffic Simulation with
Multi-Resolution Models }",
institution = "Dartmouth College, Computer Science",
address = "Hanover, NH",
number = "TR2005-558",
year = "2005",
month = sep,
URL = "http://www.cs.dartmouth.edu/reports/TR2005-558.pdf",
comment = "Ph.D dissertation. 183 pages. Advisor: David Nicol.",
abstract = "Simulating a large-scale network like the Internet is
a challenging undertaking because of the sheer volume
of its traffic. Packet-oriented representation provides
high-fidelity details but is computationally expensive;
fluid-oriented representation offers high simulation
efficiency at the price of losing packet-level details.
Multi-resolution modeling techniques exploit the
advantages of both representations by integrating them
in the same simulation framework. This dissertation
presents solutions to the problems regarding the
efficiency, accuracy, and scalability of the traffic
simulation models in this framework. The ``ripple
effect'' is a well-known problem inherent in
event-driven fluid-oriented traffic simulation, causing
explosion of fluid rate changes. Integrating
multi-resolution traffic representations requires
estimating arrival rates of packet-oriented traffic,
calculating the queueing delay upon a packet arrival,
and computing packet loss rate under buffer overflow.
Real time simulation of a large or ultra-large network
demands efficient background traffic simulation. The
dissertation includes a rate smoothing technique that
provably mitigates the ``ripple effect'', an accurate
and efficient approach that integrates traffic models
at multiple abstraction levels, a sequential algorithm
that achieves real time simulation of the
coarse-grained traffic in a network with 3 tier-1 ISP
(Internet Service Provider) backbones using an ordinary
PC, and a highly scalable parallel algorithm that
simulates network traffic at coarse time scales.",
}
@TechReport{Dartmouth:TR2005-559,
author = "Meiyuan Zhao",
title = "{Performance Evaluation of Distributed Security
Protocols Using Discrete Event Simulation}",
institution = "Dartmouth College, Computer Science",
address = "Hanover, NH",
number = "TR2005-559",
year = "2005",
month = oct,
URL = "http://www.cs.dartmouth.edu/reports/TR2005-559.pdf",
comment = "Ph.D. Thesis",
abstract = "The Border Gateway Protocol (BGP) that manages
inter-domain routing on the Internet lacks security.
Protective measures using public key cryptography
introduce complexities and costs. To support
authentication and other security functionality in
large networks, we need public key infrastructures
(PKIs). Protocols that distribute and validate
certificates introduce additional complexities and
costs. The certification path building algorithm that
helps users establish trust on certificates in the
distributed network environment is particularly
complicated. Neither routing security nor PKI come for
free. Prior to this work, the research study on
performance issues of these large-scale distributed
security systems was minimal. In this thesis, we
evaluate the performance of BGP security protocols and
PKI systems. We answer the questions about how the
performance affects protocol behaviors and how we can
improve the efficiency of these distributed protocols
to bring them one step closer to reality. The
complexity of the Internet makes an analytical approach
difficult; and the scale of Internet makes empirical
approaches also unworkable. Consequently, we take the
approach of simulation. We have built the simulation
frameworks to model a number of BGP security protocols
and the PKI system. We have identified performance
problems of Secure BGP (S-BGP), a primary BGP security
protocol, and proposed and evaluated Signature
Amortization (S-A) and Aggregated Path Authentication
(APA) schemes that significantly improve efficiency of
S-BGP without compromising security. We have also built
a simulation framework for general PKI systems and
evaluated certification path building algorithms, a
critical part of establishing trust in Internet-scale
PKI, and used this framework to improve algorithm
performance.",
}
@TechReport{Dartmouth:TR2005-560,
author = "Amit Chakrabarti and Subhash Khot",
title = "{Combinatorial Theorems about Embedding Trees on the
Real Line}",
institution = "Dartmouth College, Computer Science",
address = "Hanover, NH",
number = "TR2005-560",
year = "2005",
month = oct,
URL = "http://www.cs.dartmouth.edu/reports/TR2005-560.pdf",
abstract = "We consider the combinatorial problem of embedding a
tree metric into the real line with low distortion. For
two special families of trees --- the family of
complete binary trees and the family of subdivided
stars --- we provide embeddings whose distortion is
provably optimal, up to a constant factor. We also
prove that the optimal distortion of a linear embedding
of a tree can be arbitrarily low or high even when it
has bounded degree.",
}
@TechReport{Dartmouth:TR2005-561,
author = "Nikhil Bansal and Amit Chakrabarti and Amir Epstein
and Baruch Schieber",
title = "{A Quasi-PTAS for Unsplittable Flow on Line Graphs}",
institution = "Dartmouth College, Computer Science",
address = "Hanover, NH",
number = "TR2005-561",
year = "2005",
month = oct,
URL = "http://www.cs.dartmouth.edu/reports/TR2005-561.pdf",
abstract = "We study the Unsplittable Flow Problem (UFP) on a line
graph, focusing on the long-standing open question of
whether the problem is APX-hard. We describe a
deterministic quasi-polynomial time approximation
scheme for UFP on line graphs, thereby ruling out an
APX-hardness result, unless NP is contained in
DTIME(2^polylog(n)). Our result requires a
quasi-polynomial bound on all edge capacities and
demands in the input instance. Earlier results on this
problem included a polynomial time
(2+epsilon)-approximation under the assumption that no
demand exceeds any edge capacity (the {"}no-bottleneck
assumption{"}) and a super-constant integrality gap if
this assumption did not hold. Unlike most earlier work
on UFP, our results do not require a no-bottleneck
assumption.",
}
@TechReport{Dartmouth:TR2005-563,
author = "Anne Loomis",
title = "{Computation reuse in stacking and unstacking}",
institution = "Dartmouth College, Computer Science",
address = "Hanover, NH",
number = "TR2005-563",
year = "2005",
month = nov # ",",
URL = "http://www.cs.dartmouth.edu/reports/TR2005-563.pdf",
comment = "Master's thesis proposal.",
abstract = "Algorithms for dynamic simulation and control are
fundamental to many applications, including computer
games and movies, medical simulation, and mechanical
design. I propose to explore efficient algorithms for
finding a stable unstacking sequence -- an order in
which we can remove every object from a structure
without causing the structure to collapse under gravity
at any step. We begin with a basic unstacking sequence
algorithm: consider the set of all objects in a
structure. Collect all possible subsets into a
disassembly graph. Search the graph, testing the
stability of each node as it is visited. Any path of
stable nodes from start to goal is a stable unstacking
sequence. I propose to show how we can improve the
performance of individual stability tests for
three-dimensional structures with Coulomb friction, and
give effective methods for searching the disassembly
graph. I will also analyze the computational complexity
of stable unstacking problems, and explore a
classification of structures based on characteristics
of their stable unstacking sequences. In preliminary
work, I have shown that we can reuse computation from
one stability test of a planar subassembly to the next.
The implementation, which solves the system dynamics as
a linear complementarity problem (LCP), outperforms an
implementation that solves the system statics as a
linear program (LP). This is surprising because LCPs
are more complex than LPs, and dynamics equations are
more complex than statics equations.",
}
@TechReport{Dartmouth:TR2005-564,
author = "Bruce R. Donald and Christopher G. Levey and Craig D.
McGray and Igor Paprotny and Daniela Rus",
title = "{A Steerable, Untethered, 250x60 micron MEMS Mobile
Micro-Robot}",
institution = "Dartmouth College, Computer Science",
address = "Hanover, NH",
number = "TR2005-564",
year = "2005",
month = dec,
URL = "http://www.cs.dartmouth.edu/reports/TR2005-564.pdf",
comment = "A revised version of this paper has appeared in the
proceedings of the 12th International Symposium of
Robotics Research (ISRR 2005), San Francisco, CA,
October 12th-15th, 2005.",
abstract = "We present a steerable, electrostatic, untethered,
MEMS micro-robot, with dimensions of 60 µm by 250
µm by 10 µm. This micro-robot is 1 to 2
orders of magnitude smaller in size than previous
micro-robotic systems. The device consists of a curved,
cantilevered steering arm, mounted on an untethered
scratch drive actuator. These two components are
fabricated monolithically from the same sheet of
conductive polysilicon, and receive a common power and
control signal through a capacitive coupling with an
underlying electrical grid. All locations on the grid
receive the same power and control signal, so that the
devices can be operated without knowledge of their
position on the substrate and without constraining
rails or tethers. Control and power delivery waveforms
are broadcast to the device through the capacitive
power coupling, and are decoded by the
electromechanical response of the device body.
Individual control of the component actuators provides
two distinct motion gaits (forward motion and turning),
which together allow full coverage of a planar
workspace (the robot is globally controllable). These
MEMS micro-robots demonstrate turning error of less
than 3.7 °/mm during forward motion, turn with
radii as small as 176 µm, and achieve speeds of
over 200 µm/sec, with an average step size of 12
nm. They have been shown to operate open-loop for
distances exceeding 35 cm without failure, and can be
controlled through teleoperation to navigate complex
paths.",
}
@TechReport{Dartmouth:TR2005-565,
author = "Chien-Chung Huang",
title = "{How hard is it to cheat in the Gale-Shapley Stable
Matching Algorithm}",
institution = "Dartmouth College, Computer Science",
address = "Hanover, NH",
number = "TR2005-565",
year = "2005",
month = dec,
URL = "http://www.cs.dartmouth.edu/reports/TR2005-565.pdf",
abstract = "We study strategy issues surrounding the stable
marriage problem. Under the Gale-Shapley algorithm
(with men proposing), a classical theorem says that it
is impossible for every liar to get a better partner.
We try to challenge this theorem. First, observing a
loophole in the statement of the theorem, we devise a
coalition strategy in which a non-empty subset of the
liars gets a better partner and no man is worse off
than before. This strategy is restricted in that not
everyone has the incentive to cheat. We attack the
classical theorem further by means of randomization.
However, this theorem shows surprising robustness: it
is impossible that every liar has the chance to improve
while no one gets hurt. Hence, this impossibility
result indicates that it is always hard to induce some
people to falsify their lists. Finally, to overcome the
problem of lacking motivation, we exhibit another
randomized lying strategy in which every liar can
expect to get a better partner, though with a chance of
getting a worse one.",
}
@TechReport{Dartmouth:TR2005-566,
author = "Zhenhui Jiang",
title = "{A Combined Routing Method for Ad hoc Wireless
Networks}",
institution = "Dartmouth College, Computer Science",
address = "Hanover, NH",
number = "TR2005-566",
year = "2005",
month = dec,
URL = "http://www.cs.dartmouth.edu/reports/TR2005-566.pdf",
comment = "Masters thesis. Advisor: David Kotz. A shortened and
updated version of this work appears as TR2007-588.",
abstract = "To make ad hoc wireless networks adaptive to different
mobility and traffic patterns, we studied in this
thesis an approach to swap from one protocol to another
protocol dynamically, while routing continues. By the
insertion of a new layer, we were able to make each
node in the ad hoc wireless network notify each other
about the protocol swap. To ensure that routing works
efficiently after the protocol swap, we initialized the
destination routing protocolÕs data structures and
reused the previous routing information to build the
new routing table. We also tested our approach under
different network topologies and traffic patterns in
static networks to learn whether the swap is fast and
whether the swap incurs too much overload . We found
that the swap latency is related to the destination
protocol and the topology of the network. We also found
that the control packet ratio after swap is close to
the protocol running without swap, which means our
method does not incur too many control packets for
swap.",
}
@TechReport{Dartmouth:TR2006-570,
author = "Ivelin Georgiev and Ryan H. Lilien and Bruce R.
Donald",
title = "{A Novel Minimized Dead-End Elimination Criterion and
Its Application to Protein Redesign in a Hybrid Scoring
and Search Algorithm for Computing Partition Functions
over Molecular Ensembles}",
institution = "Dartmouth College, Computer Science",
address = "Hanover, NH",
number = "TR2006-570",
year = "2006",
month = jan,
URL = "http://www.cs.dartmouth.edu/reports/TR2006-570.pdf",
comment = "A revised version of this paper will appear in the
Proceedings of the Tenth Annual International
Conference on Research in Computational Molecular
Biology (RECOMB), Venice Lido, Italy, April 2006.",
abstract = "Novel molecular function can be achieved by
redesigning an enzyme's active site so that it will
perform its chemical reaction on a novel substrate. One
of the main challenges for protein redesign is the
efficient evaluation of a combinatorial number of
candidate structures. The modeling of protein
flexibility, typically by using a rotamer library of
commonly-observed low-energy side-chain conformations,
further increases the complexity of the redesign
problem. A dominant algorithm for protein redesign is
Dead-End Elimination (DEE), which prunes the majority
of candidate conformations by eliminating rigid
rotamers that provably are not part of the Global
Minimum Energy Conformation (GMEC). The identified GMEC
consists of rigid rotamers (i.e., rotamers that have
not been energy-minimized) and is thus referred to as
the rigid-GMEC. As a post-processing step, the
conformations that survive DEE may be energy-minimized.
When energy minimization is performed after pruning
with DEE, the combined protein design process becomes
heuristic, and is no longer provably accurate: a
conformation that is pruned using rigid-rotamer
energies may subsequently minimize to a lower energy
than the rigid-GMEC. That is, the rigid-GMEC and the
conformation with the lowest energy among all
energy-minimized conformations (the minimized-GMEC) are
likely to be different. While the traditional DEE
algorithm succeeds in not pruning rotamers that are
part of the rigid-GMEC, it makes no guarantees
regarding the identification of the minimized-GMEC. In
this paper we derive a novel, provable, and efficient
DEE-like algorithm, called minimized-DEE (MinDEE), that
guarantees that rotamers belonging to the
minimized-GMEC will not be pruned, while still pruning
a combinatorial number of conformations. We show that
MinDEE is useful not only in identifying the
minimized-GMEC, but also as a filter in an
ensemble-based scoring and search algorithm for protein
redesign that exploits energy-minimized conformations.
We compare our results both to our previous
computational predictions of protein designs and to
biological activity assays of predicted protein
mutants. Our provable and efficient minimized-DEE
algorithm is applicable in protein redesign,
protein-ligand binding prediction, and computer-aided
drug design.",
}
@TechReport{Dartmouth:TR2006-571,
author = "Kazuhiro Minami",
title = "{Secure Context-sensitive Authorization }",
institution = "Dartmouth College, Computer Science",
address = "Hanover, NH",
number = "TR2006-571",
year = "2006",
month = feb,
URL = "http://www.cs.dartmouth.edu/reports/TR2006-571.pdf",
comment = "Doctoral dissertation. Advisor: David Kotz",
abstract = "Pervasive computing leads to an increased integration
between the real world and the computational world, and
many applications in pervasive computing adapt to the
user's context, such as the location of the user and
relevant devices, the presence of other people, light
or sound conditions, or available network bandwidth, to
meet a user's continuously changing requirements
without taking explicit input from the users. We
consider a class of applications that wish to consider
a user's context when deciding whether to authorize a
user's access to important physical or information
resources. Such a context-sensitive authorization
scheme is necessary when a mobile user moves across
multiple administrative domains where they are not
registered in advance. Also, users interacting with
their environment need a non-intrusive way to access
resources, and clues about their context may be useful
input into authorization policies for these resources.
Existing systems for context-sensitive authorization
take a logic-based approach, because a logical language
makes it possible to define a context model where a
contextual fact is expressed with a boolean predicate
and to derive higher-level context information and
authorization decisions from contextual facts. However,
those existing context-sensitive authorization systems
have a central server that collects context
information, and evaluates policies to make
authorization decisions on behalf of a resource owner.
A centralized solution assumes that all resource owners
trust the server to make correct decisions, and all
users trust the server not to disclose private context
information. In many realistic applications of
pervasive computing, however, the resources, users, and
sources of context information are inherently
distributed among many organizations that do not
necessarily trust each other. Resource owners may not
trust the integrity of context information produced by
another domain, and context sensors may not trust
others with the confidentiality of data they provide
about users. In this thesis, we present a secure
distributed proof system for context-sensitive
authorization. Our system enables multiple hosts to
evaluate an authorization query in a peer-to-peer way,
while preserving the confidentiality and integrity
policies of mutually untrusted principals running those
hosts. We also develop a novel caching and revocation
mechanism to support context-sensitive policies that
refer to information in dozens of different
administrative domains. Contributions of this thesis
include the definition of fine-grained security
policies that specify trust relations among principals
in terms of information confidentiality and integrity,
the design and implementation of a secure distributed
proof system, a proof for the correctness of our
algorithm, and a performance evaluation showing that
the amortized performance of our system scales to
dozens of servers in different domains.",
}
@TechReport{Dartmouth:TR2006-573,
author = "Gregory Leibon and Dan Rockmore and Martin R. Pollak",
title = "{A simple computational method for the identification
of disease-associated loci in complex, incomplete
pedigrees}",
institution = "Dartmouth College, Computer Science",
address = "Hanover, NH",
number = "TR2006-573",
year = "2006",
month = mar,
URL = "http://www.cs.dartmouth.edu/reports/TR2006-573.pdf",
abstract = "We present an approach, called the Shadow Method, for
the identification of disease loci from dense genetic
marker maps in complex, potentially incomplete
pedigrees. Shadow is a simple method based on an
analysis of the patterns of obligate meiotic
recombination events in genotypic data. This method can
be applied to any high density marker map and was
specifically designed to explore the fact that
extremely dense marker maps are becoming more readily
available. We also describe how to interpret and
associated meaningful P-Values to the results. Shadow
has significant advantages over traditional parametric
linkage analysis methods in that it can be readily
applied even in cases in which the topology of a
pedigree or pedigrees can only be partially determined.
In addition, Shadow is robust to variability in a range
of parameters and in particular does not require prior
knowledge of mode of inheritance, penetrance, or
clinical misdiagnosis rate. Shadow can be used for any
SNP data, but is especially effective when applied to
dense samplings. Our primary example uses data from
Affymetrix 100k SNPChip samples in which we illustrate
our approach by analyzing simulated data as well as
genome-wide SNP data from two pedigrees with inherited
forms of kidney failure, one of which is compared with
a typical LOD score analysis.",
}
@TechReport{Dartmouth:TR2006-574,
author = "Nicholas J. Santos",
title = "{Limited Delegation (Without Sharing Secrets) in Web
Applications}",
institution = "Dartmouth College, Computer Science",
address = "Hanover, NH",
number = "TR2006-574",
year = "2006",
month = may,
URL = "http://www.cs.dartmouth.edu/reports/TR2006-574.pdf",
comment = "Senior Honors Thesis. Advisor: Sean W. Smith.",
abstract = "Delegation is the process wherein an entity Alice
designates an entity Bob to speak on her behalf. In
password-based security systems, delegation is easy:
Alice gives Bob her password. This is a useful feature,
and is used often in the real world. But it's also
problematic. When Alice shares her password, she must
delegate all her permissions, but she may wish to
delegate a limited set. Also, as we move towards
PKI-based systems, secret-sharing becomes impractical.
This thesis explores one solution to these problems. We
use proxy certificates in a non-standard way so that
user Alice can delegate a subset of her privileges to
user Bob in a secure, decentralized way for web
applications. We identify how delegation changes the
semantics of access control, then build a system to
demonstrate these possibilities in action. An extension
on top of Mozilla's Firefox web browser allows a user
to create and use proxy certificates for delegation,
and a module on top of the Apache web server accepts
multiple chains of these certificates. This is done in
a modified SSL session that should not break current
SSL implementations.",
}
@TechReport{Dartmouth:TR2006-576,
author = "Anne Loomis",
title = "{Computation Reuse in Statics and Dynamics Problems
for Assemblies of Rigid Bodies}",
institution = "Dartmouth College, Computer Science",
address = "Hanover, NH",
number = "TR2006-576",
year = "2006",
month = jun # ",",
URL = "http://www.cs.dartmouth.edu/reports/TR2006-576.pdf",
comment = "Master's thesis.",
abstract = "The problem of determining the forces among contacting
rigid bodies is fundamental to many areas of robotics,
including manipulation planning, control, and dynamic
simulation. For example, consider the question of how
to unstack an assembly, or how to find stable regions
of a rubble pile. In considering problems of this type
over discrete or continuous time, we often encounter a
sequence of problems with similar substructure. The
primary contribution of our work is the observation
that in many cases, common physical structure can be
exploited to solve a sequence of related problems more
efficiently than if each problem were considered in
isolation. We examine three general problems concerning
rigid-body assemblies: dynamic simulation, assembly
planning, and assembly stability given limited
knowledge of the structure's geometry. To approach the
dynamic simulation and assembly planning applications,
we have optimized a known method for solving the system
dynamics. The accelerations of and forces among
contacting rigid bodies may be computed by formulating
the dynamics equations and contact constraints as a
complementarity problem. Dantzig's algorithm, when
applicable, takes n or fewer major cycles to find a
solution to the linear complementarity problem
corresponding to an assembly with n contacts. We show
that Dantzig's algorithm will find a solution in n - k
or fewer major cycles if the algorithm is initialized
with a solution to the dynamics problem for a
subassembly with k internal contacts. Finally, we show
that if we have limited knowledge of a structure's
geometry, we can still learn about stable regions of
its surface by physically pressing on it. We present an
approach for finding stable regions of planar
assemblies: sample presses on the surface to identify a
stable cone in wrench space, partition the space of
applicable wrenches",
intos
?? Expected "=" after field ``into''.
table and unstable regions, and map these
back to the surface of the structure.
}
}
@TechReport{Dartmouth:TR2006-577,
author = "Constantinos C. Neophytou",
title = "{SAMPLED: Shared Anonymous Music PLayback using
wirelEss Devices}",
institution = "Dartmouth College, Computer Science",
address = "Hanover, NH",
number = "TR2006-577",
year = "2006",
month = jun,
URL = "http://www.cs.dartmouth.edu/reports/TR2006-577.pdf",
comment = "Undergraduate project; advisor Tristan Henderson.",
abstract = "Recent advances in mobile computing enable many new
applications, yet at the same time create privacy
implications caused by the increasing amount of data
that becomes available. This thesis will explore the
possibilities of wireless-enabled portable devices and
their attending privacy implications. We will describe
how such a device containing personal information about
the musical preferences of its user can help improve
the user's experience in a social setting where music
is played for all, and at the same time preserve each
user's privacy.",
}
}
@TechReport{Dartmouth:TR2006-578,
author = "Khanh Do Ba",
title = "{Wait-Free and Obstruction-Free Snapshot}",
institution = "Dartmouth College, Computer Science",
address = "Hanover, NH",
number = "TR2006-578",
year = "2006",
month = jun,
URL = "http://www.cs.dartmouth.edu/reports/TR2006-578.pdf",
comment = "Senior Honors Thesis. Advisor: Prasad Jayanti.",
abstract = "The snapshot problem was first proposed over a decade
ago and has since been well-studied in the distributed
algorithms community. The challenge is to design a data
structure consisting of $m$ components, shared by upto
$n$ concurrent processes, that supports two operations.
The first, $Update(i,v)$, atomically writes $v$ to the
$i$th component. The second, $Scan()$, returns an
atomic snapshot of all $m$ components. We consider two
termination properties: wait-freedom, which requires a
process to always terminate in a bounded number of its
own steps, and the weaker obstruction-freedom, which
requires such termination only for processes that
eventually execute uninterrupted. First, we present a
simple, time and space optimal, obstruction-free
solution to the single-writer, multi-scanner version of
the snapshot problem (wherein concurrent Updates never
occur on the same component). Second, we assume
hardware support for compare&swap (CAS) to give a
time-optimal, wait-free solution to the multi-writer,
single-scanner snapshot problem (wherein concurrent
Scans never occur). This algorithm uses only $O(mn)$
space and has optimal CAS, write and remote-reference
complexities. Additionally, it can be augmented to
implement a general snapshot object with the same time
and space bounds, thus improving the space complexity
of $O(mn^2)$ of the only previously known time-optimal
solution.",
}
@TechReport{Dartmouth:TR2006-579,
author = "Micah K. Johnson and Hany Farid",
title = "{Metric Measurements on a Plane from a Single Image}",
institution = "Dartmouth College, Computer Science",
address = "Hanover, NH",
number = "TR2006-579",
year = "2006",
month = aug,
URL = "http://www.cs.dartmouth.edu/reports/TR2006-579.pdf",
abstract = "The past decade has seen considerable advances in the
application of principles from projective geometry to
problems in image analysis and computer vision. In this
paper, we review a subset of this work, and leverage
these results for the purpose of forensic analysis.
Specifically, we review three techniques for making
metric measurements on planar surfaces from a single
image. The resulting techniques should prove useful in
forensic settings where real-world measurements are
required.",
}
@TechReport{Dartmouth:TR2006-580,
author = "Fabio Pellacini and Lori Lorigo and Geri Gay",
title = "{Visualizing Paths in Context}",
institution = "Dartmouth College, Computer Science",
address = "Hanover, NH",
number = "TR2006-580",
year = "2006",
month = apr,
URL = "http://www.cs.dartmouth.edu/reports/TR2006-580.pdf",
abstract = "Data about movement through a space is increasingly
becoming available for capture and analysis. In many
applications, this data is captured or modeled as
transitions between a small number of areas of
interests, or a finite set of states, and these
transitions constitute paths in the space. Similarities
and differences between paths are of great importance
to such analyses, but can be difficult to assess. In
this work we present a visualization approach for
representing paths in context, where individual paths
can be compared to other paths or to a group of paths.
Our approach summarizes path behavior using a simple
circular layout, including information about state and
transition likelihood using Markov random models,
together with information about specific path and state
behavior. The layout avoids line crossovers entirely,
making it easy to observe patterns while reducing
visual clutter. In our tool, paths can either be
compared in their natural sequence or by aligning
multiple paths using Multiple Sequence Alignment, which
can better highlight path similarities. We applied our
technique to eye tracking data and cell phone tower
data used to capture human movement.",
}
@TechReport{Dartmouth:TR2006-582,
author = "Chien-Chung Huang",
title = "{Cheating to Get Better Roommates in a Random Stable
Matching}",
institution = "Dartmouth College, Computer Science",
address = "Hanover, NH",
number = "TR2006-582",
year = "2006",
month = dec # ",",
URL = "http://www.cs.dartmouth.edu/reports/TR2006-582.pdf",
abstract = "This paper addresses strategies for the stable
roommates problem, assuming that a stable matching is
chosen at random. We investigate how a cheating man
should permute his preference list so that he has a
higher-ranking roommate probabilistically. In the first
part of the paper, we identify a necessary condition
for creating a new stable roommate for the cheating
man. This condition precludes any possibility of his
getting a new roommate ranking higher than all his
stable roommates when everyone is truthful.
Generalizing to the case that multiple men collude, we
derive another impossibility result: given any stable
matching in which a subset of men get their best
possible roommates, they cannot cheat to create a new
stable matching in which they all get strictly better
roommates than in the given matching. Our impossibility
result, considered in the context of the stable
marriage problem, easily re-establishes the celebrated
Dubins-Freedman Theorem. The more generalized
Demange-Gale-Sotomayor Theorem states that a coalition
of men and women cannot cheat to create a stable
matching in which everyone of them gets a strictly
better partner than in the Gale-Shapley algorithm (with
men proposing). We give a sharper result: a coalition
of men and women cannot cheat together so that, in a
newly-created stable matching, every man in the
coalition gets a strictly better partner than in the
Gale-Shapley algorithm while none of the women in the
coalition is worse off. In the second part of the
paper, we present two cheating strategies that
guarantee that the cheating man's new probability
distribution over stable roommates majorizes the
original one. These two strategies do not require the
knowledge of the probability distribution of the
cheating man. This is important because the problem of
counting stable matchings is \#P-complete. Our
strategies only require knowing the set of stable
roommates that the cheating man has and can be
formulated in polynomial time. Our second cheating
strategy has an interesting corollary in the context of
stable marriage with the Gale-Shapley algorithm. Any
woman-optimal strategy will ensure that every woman,
cheating or otherwise, ends up with a partner at least
as good as when everyone is truthful.",
}
@TechReport{Dartmouth:TR2006-583,
author = "Hany Farid",
title = "{Digital Image Ballistics from JPEG Quantization}",
institution = "Dartmouth College, Computer Science",
address = "Hanover, NH",
number = "TR2006-583",
year = "2006",
month = sep,
URL = "http://www.cs.dartmouth.edu/reports/TR2006-583.pdf",
abstract = "Most digital cameras export images in the JPEG file
format. This lossy compression scheme employs a
quantization table that controls the amount of
compression achieved. Different cameras typically
employ different tables. A comparison of an image's
quantization scheme to a database of known cameras
affords a simple technique for confirming or denying an
image's source. Similarly, comparison to a database of
photo-editing software can be used in a forensic
setting to determine if an image was edited after its
original recording.",
}
@TechReport{Dartmouth:TR2006-584,
author = "Javed Aslam and Sergey Bratus and Virgil Pavlu",
title = "{Tools and algorithms to advance interactive intrusion
analysis via Machine Learning and Information
Retrieval}",
institution = "Dartmouth College, Computer Science",
address = "Hanover, NH",
number = "TR2006-584",
year = "2006",
month = sep,
URL = "http://www.cs.dartmouth.edu/reports/TR2006-584.pdf",
abstract = "We consider typical tasks that arise in the intrusion
analysis of log data from the perspectives of Machine
Learning and Information Retrieval, and we study a
number of data organization and interactive learning
techniques to improve the analyst's efficiency. In
doing so, we attempt to translate intrusion analysis
problems into the language of the abovementioned
disciplines and to offer metrics to evaluate the effect
of proposed techniques. The Kerf toolkit contains
prototype implementations of these techniques, as well
as data transformation tools that help bridge the gap
between the real world log data formats and the ML and
IR data models. We also describe the log representation
approach that Kerf prototype tools are based on. In
particular, we describe the connection between decision
trees, automatic classification algorithms and log
analysis techniques implemented in Kerf.",
}
@TechReport{Dartmouth:TR2006-585,
author = "David P. Wagner",
title = "{Path Planning Algorithms under the Link-Distance
Metric}",
institution = "Dartmouth College, Computer Science",
address = "Hanover, NH",
number = "TR2006-585",
year = "2006",
month = feb,
URL = "http://www.cs.dartmouth.edu/reports/TR2006-585.pdf",
comment = "Doctoral dissertation. Co-Advisors: Robert Scot
Drysdale, Clifford Stein; Thesis Committee: Amit
Chakrabarti, Joseph S. B. Mitchell",
abstract = "The Traveling Salesman Problem and the Shortest Path
Problem are famous problems in computer science which
have been well studied when the objective is measured
using the Euclidean distance. Here we examine these
geometric problems under a different set of
optimization criteria. Rather than considering the
total distance traversed by a path, this thesis looks
at reducing the number of times a turn is made along
that path, or equivalently, at reducing the number of
straight lines in the path. Minimizing this objective
value, known as the link-distance, is useful in
situations where continuing in a given direction is
cheap, while turning is a relatively expensive
operation. Applications exist in VLSI, robotics,
wireless communications, space travel, and other fields
where it is desirable to reduce the number of turns.
This thesis examines rectilinear and non-rectilinear
variants of the Traveling Salesman Problem under this
metric. The objective of these problems is to find a
path visiting a set of points which has the smallest
number of bends. A 2-approximation algorithm is given
for the rectilinear problem, while for the
non-rectilinear problem, an O(log n)-approximation
algorithm is given. The latter problem is also shown to
be NP-Complete. Next, the Rectilinear Minimum
Link-Distance Problem, also known as the Minimum Bends
Path Problem, is considered. Here the objective is to
find a rectilinear path between two points among
rectilinear obstacles which has the minimum number of
bends, while avoiding passing through any of the
obstacles. The problem has been well studied in two
dimensions, but is relatively unexplored in higher
dimensions. A main result of this thesis is an
O(n^{5/2} log n) time algorithm solving this problem in
three dimensions. Previously known algorithms have had
worst-case running times of Omega(n^3). This algorithm
requires a data structure that supports efficient
operations on pointsets within rectangular regions of
the Euclidean plane. We design a new data structure,
which is a variation on the segment tree, in order to
support these operations. Finally, an implementation of
the data structure and of the algorithm solving the
Minimum Link-Distance Problem demonstrates their
experimental running times and ease of
implementation.",
}
@TechReport{Dartmouth:TR2007-586,
author = "Peter Johnson and Apu Kapadia and David Kotz and Nikos
Triandopoulos",
title = "{People-Centric Urban Sensing: Security Challenges for
the New Paradigm}",
institution = "Dartmouth College, Computer Science",
address = "Hanover, NH",
number = "TR2007-586",
year = "2007",
month = feb,
URL = "http://www.cs.dartmouth.edu/reports/TR2007-586.pdf",
abstract = "We study the security challenges that arise in
\emph{people-centric urban sensing}, a new
sensor-networking paradigm that leverages humans as
part of the sensing infrastructure. Most prior work on
sensor networks has focused on collecting and
processing ephemeral data about the environment using a
static topology and an application-aware
infrastructure. People-centric urban sensing, however,
involves collecting, storing, processing and fusing
large volumes of data related to every-day human
activities. Sensing is performed in a highly dynamic
and mobile environment, and supports (among other
things) pervasive computing applications that are
focused on enhancing the user's experience. In such a
setting, where humans are the central focus, there are
new challenges for information security; not only
because of the complex and dynamic communication
patterns, but also because the data originates from
sensors that are carried by a person---not a tiny
sensor thrown in the forest or mounted on the neck of
an animal. In this paper we aim to instigate discussion
about this critical issue---because people-centric
sensing will never succeed without adequate provisions
for security and privacy. To that end, we outline
several important challenges and suggest general
solutions that hold promise in this new paradigm of
sensor networks.",
}
@TechReport{Dartmouth:TR2007-587,
author = "John Thomas and Naren Ramakrishnan and Chris
Bailey-Kellogg",
title = "{Protein Design by Mining and Sampling an Undirected
Graphical Model of Evolutionary Constraints}",
institution = "Dartmouth College, Computer Science",
address = "Hanover, NH",
number = "TR2007-587",
year = "2007",
month = mar,
URL = "http://www.cs.dartmouth.edu/reports/TR2007-587.pdf",
comment = "Submitted to KDD 2007.",
abstract = "Evolutionary pressures on proteins to maintain
structure and function have constrained their sequences
over time and across species. The sequence record thus
contains valuable information regarding the acceptable
variation and covariation of amino acids in members of
a protein family. When designing new members of a
protein family, with an eye toward modified or improved
stability or functionality, it is incumbent upon a
protein engineer to uncover such constraints and design
conforming sequences. This paper develops such an
approach for protein design: we first mine an
undirected probabilistic graphical model of a given
protein family, and then use the model generatively to
sample new sequences. While sampling from an undirected
model is difficult in general, we present two
complementary algorithms that effectively sample the
sequence space constrained by our protein family model.
One algorithm focuses on the high-likelihood regions of
the space. Sequences are generated by sampling the
cliques in a graphical model according to their
likelihood while maintaining neighborhood consistency.
The other algorithm designs a fixed number of
high-likelihood sequences that are reflective of the
amino acid composition of the given family. A set of
shuffled sequences is iteratively improved so as to
increase their mean likelihood under the model. Tests
for two important protein families, WW domains and PDZ
domains, show that both sampling methods converge
quickly and generate diverse high-quality sets of
sequences for further biological study.",
}
@TechReport{Dartmouth:TR2007-588,
author = "Soumendra Nanda and Zhenhui Jiang and David Kotz",
title = "{A Combined Routing Method for Wireless Ad Hoc
Networks}",
institution = "Dartmouth College, Computer Science",
address = "Hanover, NH",
number = "TR2007-588",
year = "2007",
month = jun,
URL = "http://www.cs.dartmouth.edu/reports/TR2007-588.pdf",
comment = "This report is a shortened and updated version of the
M.S. thesis that appeared as TR2005-566.",
abstract = "To make ad hoc wireless networks adaptive to different
mobility and traffic patterns, this paper proposes an
approach to swap from one protocol to another protocol
dynamically, while routing continues. By the insertion
of a thin new layer, we were able to make each node in
the ad hoc wireless network notify each other about the
protocol swap. To ensure that routing works efficiently
after the protocol swap, we initialized the destination
routing protocol's data structures and reused the
previous routing information to build the new routing
table. We also tested our approach under different
network topologies and traffic patterns in static
networks to learn whether the swap was fast and whether
the swap incurred too much overhead. We found that the
swap latency was related to the nature of the
destination protocol and the topology of the network.
We also found that the control packet ratio after swap
was close to that of the protocol running without swap,
which indicates that our method does not incur too much
overhead for the swap.",
}
@TechReport{Dartmouth:TR2007-589,
author = "Alexander Wakefield Steinberg",
title = "{Lighting with Sketches}",
institution = "Dartmouth College, Computer Science",
address = "Hanover, NH",
number = "TR2007-589",
year = "2007",
month = may,
URL = "http://www.cs.dartmouth.edu/reports/TR2007-589.pdf",
comment = "Advisor: Fabio Pellacini",
abstract = "Lighting design is a fundamental aspect of computer
cinematography, where it is used to support
storytelling by affecting the mood, style, and
believability of a scene. Traditionally, lighting has
requred the tedious adjustment of large set parameters
that describe complex lighting setups, including lights
positions, colors, shapes, etc. This work presents an
interactive user interface that facilitates lighting
workflow by using a sketching paradigm for light
creation. Lights are specified by a series of strokes
that define various properties of illumination such as
shape of the light and position of illuminated and
shadowed areass. The system will them perform a
nonlinear optimization over all the light parameters to
find a match to the controlling sketches. To
demonstrate our prototype system, we lit a simple scene
fully with our application, showing that sketching
paradigms ar promising to facilitate the lighting
workflow.",
}
@TechReport{Dartmouth:TR2007-590,
author = "Patrick P. Tsang and Sean W. Smith",
title = "{Secure Cryptographic Precomputation with Insecure
Memory}",
institution = "Dartmouth College, Computer Science",
address = "Hanover, NH",
number = "TR2007-590",
year = "2007",
month = jul,
URL = "http://www.cs.dartmouth.edu/reports/TR2007-590.pdf",
abstract = "Precomputation dramatically reduces the execution
latency of many cryptographic algorithms. To sustain
the reduced latency over time during which these
algorithms are routinely invoked, however, a pool of
precomputation results must be stored and be readily
available. While precomputation is an old and
well-known technique, how to securely and yet
efficiently store these precomputation results has
largely been ignored. For instance, requiring
tamper-proof memory would be too expensive, if not
unrealistic, for precomputation to be cost-effective.
In this paper, we propose an architecture that provides
secure storage for cryptographic precomputation using
only insecure memory, which may be eavesdropped or even
tampered with. Specifically, we design a small
tamper-resistant hardware module that we call the {\em
Queue Security Proxy (QSP)}, which situates on the
data-path between the processor and the insecure
memory. Our analysis shows that our design is secure,
efficient, flexible and yet inexpensive. In particular,
our design's timing overhead and hardware cost are
independent of the storage size. We also discuss in
this paper several interesting extensions to our
proposed architecture. We plan to prototype our design
assuming the scenario of precomputing DSA signatures,
effectively building a cost-effective low-latency DSA
signing secure coprocessor.",
}
@TechReport{Dartmouth:TR2007-591,
author = "Kwang-Hyun Baek and Sergey Bratus and Sara Sinclair
and Sean W. Smith",
title = "{Dumbots: Unexpected Botnets through Networked
Embedded Devices}",
institution = "Dartmouth College, Computer Science",
address = "Hanover, NH",
number = "TR2007-591",
year = "2007",
month = may,
URL = "http://www.cs.dartmouth.edu/reports/TR2007-591.pdf",
abstract = "Currently, work on botnets focuses primarily on PCs.
However, as lightweight computing devices with embedded
operating systems become more ubiquitous, they present
a new and very disturbing target for botnet developers.
In this paper, we present both an empirical
demonstration on a widely deployed multimedia box, as
well as an evaluation of the deeper potential of these
dumbots.",
}
@TechReport{Dartmouth:TR2007-592,
author = "Daniel G. Peebles",
title = "{SCML: A Structural Representation for Chinese
Characters}",
institution = "Dartmouth College, Computer Science",
address = "Hanover, NH",
number = "TR2007-592",
year = "2007",
month = may,
URL = "http://www.cs.dartmouth.edu/reports/TR2007-592.pdf",
comment = "Senior Honors Thesis. Advisor: Devin Balkcom.",
abstract = "Chinese characters are used daily by well over a
billion people. They constitute the main writing system
of China and Taiwan, form a major part of written
Japanese, and are also used in South Korea. Anything
more than a cursory glance at these characters will
reveal a high degree of structure to them, but
computing systems do not currently have a means to
operate on this structure. Existing character databases
and dictionaries treat them as numerical code points,
and associate with them additional `hand-computed'
data, such as stroke count, stroke order, and other
information to aid in specific searches. Searching by a
character's `shape' is effectively impossible in these
systems. I propose a new approach to representing these
characters, through an XML-based language called SCML.
This language, by encoding an abstract form of a
character, allows the direct retrieval of important
information such as stroke count and stroke order, and
permits useful but previously impossible automated
analysis of characters. In addition, the system allows
the design of a view that takes abstract SCML
representations as character models and outputs glyphs
based on an aesthetic, facilitating the creation of
`meta-fonts' for Chinese characters. Finally, through
the creation of a specialized database, SCML allows for
efficient structural character queries to be performed
against the body of inserted characters, thus allowing
people to search by the most obvious of a character's
characteristics: its shape.",
}
@TechReport{Dartmouth:TR2007-593,
author = "Mark C. Henle",
title = "{Closest and Farthest-Line Voronoi Diagrams in the
Plane}",
institution = "Dartmouth College, Computer Science",
address = "Hanover, NH",
number = "TR2007-593",
year = "2007",
month = jun,
URL = "http://www.cs.dartmouth.edu/reports/TR2007-593.pdf",
comment = "Senior Honors Thesis. Advisor: Robert L. Scot
Drysdale",
abstract = "Voronoi diagrams are a geometric structure containing
proximity information useful in efficiently answering a
number of common geometric problems associated with a
set of points in the plane.. They have applications in
fields ranging from crystallography to biology.
Diagrams of sites other than points and with different
distance metrics have been studied. This paper examines
the Voronoi diagram of a set of lines, which has
escaped study in the computational geometry literature.
The combinatorial and topological properties of the
closest and farthest Voronoi diagrams are analyzed and
O(n^2) and O(n log n) algorithms are presented for
their computation respectively.",
}
@TechReport{Dartmouth:TR2007-594,
author = "Nihal A. D'Cunha",
title = "{Exploring the Integration of Memory Management and
Trusted Computing}",
institution = "Dartmouth College, Computer Science",
address = "Hanover, NH",
number = "TR2007-594",
year = "2007",
month = may,
URL = "http://www.cs.dartmouth.edu/reports/TR2007-594.pdf",
comment = "M.S. Thesis. Advisor: Sean Smith.",
abstract = "This thesis addresses vulnerabilities in current
Trusted Computing architecture by exploring a design
for a better Trusted Platform Module (TPM); one that
integrates more closely with the CPUÕs Memory
Management Unit (MMU). We establish that software-based
attacks on trusted memory can be carried out
undetectably by an adversary on current TCG/TPM
implementations. We demonstrate that an attacker with
sufficient privileges can compromise the integrity of a
TPM-protected system by modifying critical loaded code
and static data after measurement has taken place. More
specifically, these attacks illustrate the Time Of
Check vs. Time of Use (TOCTOU) class of attacks. We
propose to enhance the MMU, enabling it to detect when
memory containing trusted code or data is being
maliciously modified at run-time. On detection, it
should be able to notify the TPM of these
modifications. We seek to use the concepts of selective
memory immutability as a security tool to harden the
MMU, which will result in a more robust TCG/TPM
implementation. To substantiate our ideas for this
proposed hardware feature, we designed and implemented
a software prototype system, which employs the
monitoring capabilities of the Xen virtual machine
monitor. We performed a security evaluation of our
prototype and validated that it can detect all our
software-based TOCTOU attacks. We applied our prototype
to verify the integrity of data associated with an
application, as well as suggested and implemented ways
to prevent unauthorized use of data by associating it
with its owner process. Our performance evaluation
reveals minimal overhead.",
}
@TechReport{Dartmouth:TR2007-596,
author = "Thomas H. Cormen and Priya Natarajan and Elena Riccio
Davidson",
title = "{When One Pipeline Is Not Enough}",
institution = "Dartmouth College, Computer Science",
address = "Hanover, NH",
number = "TR2007-596",
year = "2007",
month = jun,
URL = "http://www.cs.dartmouth.edu/reports/TR2007-596.pdf",
abstract = "Pipelines that operate on buffers often work well to
mitigate the high latency inherent in interprocessor
communication and in accessing data on disk. Running a
single pipeline on each node works well when each
pipeline stage consumes and produces data at the same
rate. If a stage might consume data faster or slower
than it produces data, a single pipeline becomes
unwieldy. We describe how we have extended the FG
programming environment to support multiple pipelines
in two forms. When a node might send and receive data
at different rates during interprocessor communication,
we use disjoint pipelines that send and receive on each
node. When a node consumes and produces data from
different streams on the node, we use multiple
pipelines that intersect at a particular stage.
Experimental results for two out-of-core sorting
algorithms---one based on columnsort and the other a
distribution-based sort---demonstrate the value of
multiple pipelines.",
}
@TechReport{Dartmouth:TR2007-597,
author = "Evan R. Sparks",
title = "{A Security Assessment of Trusted Platform Modules}",
institution = "Dartmouth College, Computer Science",
address = "Hanover, NH",
number = "TR2007-597",
year = "2007",
month = jun,
URL = "http://www.cs.dartmouth.edu/reports/TR2007-597.ps.Z",
comment = "Senior Honors Thesis. Advisor: Sean Smith.",
abstract = "Trusted Platform Modules (TPMs) are becoming
ubiquitous devices included in newly released personal
computers. Broadly speaking, the aim of this technology
is to provide a facility for authenticating the
platform on which they are running: they are able to
measure attest to the authenticity of a hardware and
software configuration. Designed to be cheap, commodity
devices which motherboard and processor vendors can
include in their products with minimal marginal cost,
these devices have a good theoretical design.
Unfortunately, there exist several practical
constraints on the effectiveness of TPMs and the
architectures which employ them which leave them open
to attack. We demonstrate some hardware and software
attacks against these devices and architectures. These
attacks include Time of Check/Time of Use attacks on
the Integrity Measurment Architecture, and a bus attack
against the Low Pin Count bus. Further, we explore the
possibility of side-channel attacks against TPMs.",
}
@TechReport{Dartmouth:TR2007-598,
author = "Chien-Chung Huang",
title = "{Two's Company, Three's a Crowd: Stable Family and
Threesome Roommates Problems}",
institution = "Dartmouth College, Computer Science",
address = "Hanover, NH",
number = "TR2007-598",
year = "2007",
month = dec # ",",
URL = "http://www.cs.dartmouth.edu/reports/TR2007-598.pdf",
abstract = "We investigate Knuth's eleventh open question on
stable matchings. In the stable family problem, sets of
women, men, and dogs are given, all of whom state their
preferences among the other two groups. The goal is to
organize them into family units, so that no three of
them have the incentive to desert their assigned family
members to form a new family. A similar problem, called
the threesome roommates problem, assumes that a group
of persons, each with their preferences among the
combinations of two others, are to be partitioned into
triples. Similarly, the goal is to make sure that no
three persons want to break up with their assigned
roommates. Ng and Hirschberg were the first to
investigate these two problems. In their formulation,
each participant provides a strictly-ordered list of
all combinations. They proved that under this scheme,
both problems are NP-complete. Their paper reviewers
pointed out that their reduction exploits
\emph{inconsistent} preference lists and they wonder
whether these two problems remain NP-complete if
preferences are required to be consistent. We answer in
the affirmative. In order to give these two problems a
broader outlook, we also consider the possibility that
participants can express indifference, on the condition
that the preference consistency has to be maintained.
As an example, we propose a scheme in which all
participants submit two (or just one in the roommates
case) lists ranking the other two groups separately.
The order of the combinations is decided by the sum of
their ordinal numbers. Combinations are tied when the
sums are equal. By introducing indifference, a
hierarchy of stabilities can be defined. We prove that
all stability definitions lead to NP-completeness for
existence of a stable matching.",
}
@TechReport{Dartmouth:TR2007-600,
author = "William B. Kerr and Fabio Pellacini",
title = "{Light-Based Sample Reduction Methods for Interactive
Relighting of Scenes with Minute Geometric Scale}",
institution = "Dartmouth College, Computer Science",
address = "Hanover, NH",
number = "TR2007-600",
year = "2007",
month = jul,
URL = "http://www.cs.dartmouth.edu/reports/TR2007-600.pdf",
abstract = "Rendering production-quality cinematic scenes requires
high computational and temporal costs. From an artist's
perspective, one must wait for several hours for
feedback on even minute changes of light positions and
parameters. Previous work approximates scenes so that
adjustments on lights may be carried out with
interactive feedback, so long as geometry and materials
remain constant. We build on these methods by proposing
means by which objects with high geometric complexity
at the subpixel level, such as hair and foliage, can be
approximated for real-time cinematic relighting. Our
methods make no assumptions about the geometry or
shaders in a scene, and as such are fully generalized.
We show that clustering techniques can greatly reduce
multisampling, while still maintaining image fidelity
at an error significantly lower than sparsely sampling
without clustering, provided that no shadows are
computed. Scenes that produce noise-like shadow
patterns when sparse shadow samples are taken suffer
from additional error introduced by those shadows. We
present a viable solution to scalable scene
approximation for lower sampling reolutions, provided a
robust solution to shadow approximation for sub-pixel
geomery can be provided in the future.",
}
@TechReport{Dartmouth:TR2007-601,
author = "Patrick P. Tsang and Man Ho Au and Apu Kapadia and
Sean W. Smith",
title = "{Blacklistable Anonymous Credentials: Blocking
Misbehaving Users without TTPs (Extended Version)}",
institution = "Dartmouth College, Computer Science",
address = "Hanover, NH",
number = "TR2007-601",
year = "2007",
month = sep,
URL = "http://www.cs.dartmouth.edu/reports/TR2007-601.pdf",
comment = "This technical report is the extended version of the
paper to appear in CCS '07 under the same title.",
abstract = "Several credential systems have been proposed in which
users can authenticate to services anonymously. Since
anonymity can give users the license to misbehave, some
variants allow the selective deanonymization (or
linking) of misbehaving users upon a complaint to a
trusted third party (TTP). The ability of the TTP to
revoke a user's privacy at any time, however, is too
strong a punishment for misbehavior. To limit the scope
of deanonymization, systems such as ``e-cash'' have
been proposed in which users are deanonymized under
only certain types of well-defined misbehavior such as
``double spending.'' While useful in some applications,
it is not possible to generalize such techniques to
more subjective definitions of misbehavior. We present
the first anonymous credential system in which services
can ``blacklist'' misbehaving users without contacting
a TTP. Since blacklisted users remain anonymous,
misbehaviors can be judged subjectively without users
fearing arbitrary deanonymization by a TTP.",
}
@TechReport{Dartmouth:TR2007-602,
author = "Richard Cole and Lisa Fleischer",
title = "{Fast-Converging Tatonnement Algorithms for the Market
Problem}",
institution = "Dartmouth College, Computer Science",
address = "Hanover, NH",
number = "TR2007-602",
year = "2007",
month = aug,
URL = "http://www.cs.dartmouth.edu/reports/TR2007-602.pdf",
abstract = "Why might markets tend toward and remain near
equilibrium prices? In an effort to shed light on this
question from an algorithmic perspective, this paper
defines and analyzes two simple tatonnement algorithms
that differ from previous algorithms that have been
subject to asymptotic analysis in three significant
respects: the price update for a good depends only on
the price, demand, and supply for that good, and on no
other information; the price update for each good
occurs distributively and asynchronously; the
algorithms work (and the analyses hold) from an
arbitrary starting point. Our algorithm introduces a
new and natural update rule. We show that this update
rule leads to fast convergence toward equilibrium
prices in a broad class of markets that satisfy the
weak gross substitutes property. These are the first
analyses for computationally and informationally
distributed algorithms that demonstrate polynomial
convergence. Our analysis identifies three parameters
characterizing the markets, which govern the rate of
convergence of our protocols. These parameters are,
broadly speaking: 1. A bound on the fractional rate of
change of demand for each good with respect to
fractional changes in its price. 2. A bound on the
fractional rate of change of demand for each good with
respect to fractional changes in wealth. 3. The
relative demand for money at equilibrium prices. We
give two protocols. The first assumes global knowledge
of only the first parameter. For this protocol, we also
provide a matching lower bound in terms of these
parameters. Our second protocol assumes no global
knowledge whatsoever.",
}
@TechReport{Dartmouth:TR2007-603,
author = "Patrick P. Tsang and Sean W. Smith",
title = "{YASIR: A Low-Latency, High-Integrity Security
Retrofit for Legacy SCADA Systems}",
institution = "Dartmouth College, Computer Science",
address = "Hanover, NH",
number = "TR2007-603",
year = "2007",
month = sep,
URL = "http://www.cs.dartmouth.edu/reports/TR2007-603.pdf",
abstract = "We construct a bump-in-the-wire (BITW) solution that
retrofits security into time-critical communications
over bandwidth-limited serial links between devices in
Supervisory Control And Data Acquisition (SCADA)
systems. Previous BITW solutions fail to provide the
necessary security within timing constraints; the
previous solution that does provide the necessary
security is not BITW. At a comparable hardware cost,
our BITW solution provides sufficient security, and yet
incurs minimal end-to-end communication latency. A
microcontroller prototype of our solution is under
development.",
}
@TechReport{Dartmouth:TR2007-605,
author = "Hany Farid and Jeffrey B. Woodward",
title = "{Video Stabilization and Enhancement}",
institution = "Dartmouth College, Computer Science",
address = "Hanover, NH",
number = "TR2007-605",
year = "2007",
month = sep,
URL = "http://www.cs.dartmouth.edu/reports/TR2007-605.pdf",
abstract = "We describe a simple and computationally efficient
approach for video stabilization and enhancement. By
combining multiple low-quality video frames, it is
possible to extract a high-quality still image. This
technique is particularly helpful in identifying
people, license plates, etc. from low-quality video
surveillance cameras.",
}
@TechReport{Dartmouth:TR2007-606,
author = "Denise Anthony and Sean W. Smith and Tim Williamson",
title = "{The Quality of Open Source Production: Zealots and
Good Samaritans in the Case of Wikipedia}",
institution = "Dartmouth College, Computer Science",
address = "Hanover, NH",
number = "TR2007-606",
year = "2007",
month = sep,
URL = "http://www.cs.dartmouth.edu/reports/TR2007-606.pdf",
comment = "A preliminary version of this paper was published
online in November 2005.",
abstract = "New forms of production based in electronic
technology, such as open-source and open-content
production, convert private commodities (typically
software) into essentially public goods. A number of
studies find that, like in other collective goods,
incentives for reputation and group identity motivate
contributions to open source goods, thereby overcoming
the social dilemma inherent in producing such goods. In
this paper we examine how contributor motivations
affect the quality of contributions to the open-content
online encyclopedia Wikipedia. We find that quality is
associated with contributor motivations, but in a
surprisingly inconsistent way. Registered users'
quality increases with more contributions, consistent
with the idea of participants motivated by reputation
and commitment to the Wikipedia community.
Surprisingly, however, we find the highest quality from
the vast numbers of anonymous {"}Good Samaritans{"} who
contribute only once. Our findings that Good Samaritans
as well as committed {"}zealots{"} contribute high
quality content to Wikipedia suggest that it is the
quantity as well as the quality of contributors that
positively affects the quality of open source
production.",
}
@TechReport{Dartmouth:TR2007-608,
author = "Yih-Kuen Tsay and Chien-Chung Huang",
title = "{Exclusion and Object Tracking in a Network of
Processes}",
institution = "Dartmouth College, Computer Science",
address = "Hanover, NH",
number = "TR2007-608",
year = "2007",
month = dec,
URL = "http://www.cs.dartmouth.edu/reports/TR2007-608.pdf",
abstract = "This paper concerns two fundamental problems in
distributed computing---mutual exclusion and mobile
object tracking. For a variant of the mutual exclusion
problem where the network topology is taken into
account, all existing distributed solutions make use of
tokens. It turns out that these token-based solutions
for mutual exclusion can also be adapted for object
tracking, as the token behaves very much like a mobile
object. To handle objects with replication, we go
further to consider the more general $k$-exclusion
problem which has not been as well studied in a network
setting. A strong fairness property for $k$-exclusion
requires that a process trying to enter the critical
section will eventually succeed even if \emph{up to}
$k-1$ processes stay in the critical section
indefinitely. We present a comparative survey of
existing token-based mutual exclusion algorithms, which
have provided much inspiration for later $k$-exclusion
algorithms. We then propose two solutions to the
$k$-exclusion problem, the second of which meets the
strong fairness requirement. Fault-tolerance issues are
also discussed along with the suggestion of a third
algorithm that is also strongly fair. Performances of
the three algorithms are compared by simulation.
Finally, we show how the various exclusion algorithms
can be adapted for tracking mobile objects.",
}
@TechReport{Dartmouth:TR2008-612,
author = "Soumendra Nanda and David Kotz",
title = "{Localized Bridging Centrality for Distributed Network
Analysis }",
institution = "Dartmouth College, Computer Science",
address = "Hanover, NH",
number = "TR2008-612",
year = "2008",
month = jan,
URL = "http://www.cs.dartmouth.edu/reports/TR2008-612.pdf",
abstract = "Centrality is a concept often used in social network
analysis to study different properties of networks that
are modeled as graphs. We present a new centrality
metric called Localized Bridging Centrality (LBC). LBC
is based on the Bridging Centrality (BC) metric that
Hwang et al. recently introduced. Bridging nodes are
nodes that are located in between highly connected
regions. LBC is capable of identifying bridging nodes
with an accuracy comparable to that of the BC metric
for most networks. As the name suggests, we use only
local information from surrounding nodes to compute the
LBC metric, while, global knowledge is required to
calculate the BC metric. The main difference between
LBC and BC is that LBC uses the egocentric definition
of betweenness centrality to identify bridging nodes,
while BC uses the sociocentric definition of
betweenness centrality. Thus, our LBC metric is
suitable for distributed computation and has the
benefit of being an order of magnitude faster to
calculate in computational complexity. We compare the
results produced by BC and LBC in three examples. We
applied our LBC metric for network analysis of a real
wireless mesh network. Our results indicate that the
LBC metric is as powerful as the BC metric at
identifying bridging nodes that have a higher flow of
information through them (assuming a uniform
distribution of network flows) and are important for
the robustness of the network.",
}
@TechReport{Dartmouth:TR86-101,
author = "Mark Sherman",
title = "{Maze Game for the Macintosh}",
institution = "Dartmouth College, Computer Science",
address = "Hanover, NH",
number = "DCS-TR86-101",
year = "1986",
abstract = "Maze is a multiperson game using a broadcast protocol
on the Macintosh. This disk contains the sources (in
TML Pascal) for a Maze game.",
}
@TechReport{Dartmouth:TR86-102,
author = "John W. Scott",
title = "{Instructions for Using Logic}",
institution = "Dartmouth College, Computer Science",
address = "Hanover, NH",
number = "PCS-TR86-102",
year = "1986",
abstract = "This document provides instructions on the use of
{"}Logic{"}, a digital logic simulator for the
Macintosh written for Dartmouth students in the Machine
Architecture and Digital Electronics courses.",
}
@TechReport{Dartmouth:TR86-103,
author = "John W. Scott",
title = "{Digital Logic Simulator}",
institution = "Dartmouth College, Computer Science",
address = "Hanover, NH",
number = "DCS-TR86-103",
year = "1986",
abstract = "Logic is a Macintosh program that simulates discrete,
digital logic circuits. The two disks contain an
executable version of the program, MacApp sources and
brief documentation (which is also available separately
in hardcopy).",
}
@TechReport{Dartmouth:TR86-104,
author = "Mark Sherman",
title = "{Uses of Generics in Ada}",
institution = "Dartmouth College, Computer Science",
address = "Hanover, NH",
number = "PCS-TR86-104",
year = "1986",
abstract = "This paper discusses how Ada generic procedures and
packages can be used in novel ways to provide general
initialization of records, expressions using
discriminants, record field hiding and explicit control
of parameter binding.",
}
@TechReport{Dartmouth:TR86-105,
author = "Shinji Nakamura",
title = "{Parallel Accessible Memory}",
institution = "Dartmouth College, Computer Science",
address = "Hanover, NH",
number = "PCS-TR86-105",
year = "1986",
abstract = "A new design of a memory device which allows
simultaneous access to more than one location is
proposed. The unique feature of this multiple
accessibility of the memory is realized by applying a
binomial concentrator, a type of sparse crossbar
interconnection network, to content-addressable memory.
The organization of the memory system and the
concentration network structure as well as the network
characteristics are described along with a distributive
control algorithm. Applications of the memory system to
parallel processing environments are also included.",
}
@TechReport{Dartmouth:TR86-106,
author = "Shinji Nakamura",
title = "{Algorithms for Iterative Array Multiplication}",
institution = "Dartmouth College, Computer Science",
address = "Hanover, NH",
number = "PCS-TR86-106",
year = "1986",
abstract = "Algorithms for the parallel multiplication of two n
bit binary numbers by an iterative array of logic cells
are discussed. The regular interconnection structures
of the multiplier array cell elements, which are ideal
for VLSI implementation, are described. The speed and
hardware complexity of two new iterative array
algorithms, both of which require n cell delays for one
n by n bit multiplication, are compared with a
straight-forward iterative array algorithm having a 2n
cell delay and its higher radix version having an n
cell delay.",
}
@TechReport{Dartmouth:TR86-107,
author = "Kenneth P. Bogart",
title = "{What Should a Discrete Mathematics Course Be?}",
institution = "Dartmouth College, Computer Science",
address = "Hanover, NH",
number = "PCS-TR86-107",
year = "1986",
abstract = "This paper presents the results of a survey of
mathematics and computer science departments on their
needs and intentions for survey courses in discrete
mathematics. The paper then presents an idealized
syllabus for such a course, recognizing that many
topics in the syllabus should be regarded as optional.
The paper concludes with a brief summary of the
experience at Dartmouth in teaching such a course.",
}
@TechReport{Dartmouth:TR86-108,
author = "Joon Sup Lee",
title = "{Dartmouth-Smalltalk: An Exercise in Implementation}",
institution = "Dartmouth College, Computer Science",
address = "Hanover, NH",
number = "PCS-TR86-108",
year = "1986",
abstract = "This report discusses a preliminary implementation of
the Smalltalk-80 virtual machine for Vax/Unix.",
}
@TechReport{Dartmouth:TR86-109,
author = "Mark Sherman and Tim Maroney",
title = "{MacIP Sources and Applications}",
institution = "Dartmouth College, Computer Science",
address = "Hanover, NH",
number = "DCS-TR86-109",
year = "1986",
abstract = "The MacIP set consists of three disks, all
single-sided, MFS formatted. Two disks contain the Lisa
Pascal/Lisa Assembler sources for the network libraries
and application programs; the third disk contains the
runnable applications along with an AppleTalk
configured system. The current version by Tim Maroney
fixes all reported bugs mentioned in the MacIP
Technical Report and includes the TCP library and
Telnet program.",
}
@TechReport{Dartmouth:TR86-110,
author = "Mark Sherman",
title = "{Stack Package Implementing Tasks and Coroutines for
TML Pascal on the Macintosh}",
institution = "Dartmouth College, Computer Science",
address = "Hanover, NH",
number = "DCS-TR86-110",
year = "1986",
abstract = "This disk contains the necessary TML Pascal and MDS
Assembler files for implementing tasking and coroutines
in TML Pascal Programs. Two example programs and brief
documentation are provided. MDS format disk.",
}
@TechReport{Dartmouth:TR86-111,
author = "Mark Sherman",
title = "{QDT (Quickdraw Terminal) Disks}",
institution = "Dartmouth College, Computer Science",
address = "Hanover, NH",
number = "DCS-TR86-111",
year = "1986",
abstract = "This disk set consists of one disk containing a
running version of QDT over a serial line, one disk
containing a running version of QDT over Apple Talk
(using KSP), and one disk containing the Lisa Pascal
sources for creating QDT (either version).",
}
@TechReport{Dartmouth:TR86-112,
author = "Mark Sherman and Ann Marks",
title = "{QDT (Quickdraw Terminal) Libraries}",
institution = "Dartmouth College, Computer Science",
address = "Hanover, NH",
number = "TCS-TR86-112",
year = "1986",
abstract = "This Unix tar-tape contains the C libraries used on
Unix and the PL/1 Libraries used on DCTS for
communicating with QDT. (No longer available.)",
}
@TechReport{Dartmouth:TR86-113,
author = "Joe Bergin and Robert L. Scot Drysdale and Jerry
Keough and Larry Gallagher and Vivian Sewelson and Mark
Sherman",
title = "{A Collection of MDS Example Programs}",
institution = "Dartmouth College, Computer Science",
address = "Hanover, NH",
number = "DCS-TR86-113",
year = "1986",
abstract = "This MFS formatted disk contains a collection of
example programs written for teaching machine
architecture concepts using the Macintosh Development
System. Sample programs illustrate how instructions can
be treated as data, computer arithmetic, looping
features, interrupt handling, coroutines, recursive
subprograms and stack frames, traps and direct
manipulation of the screen. In addition, a supervisor
program is provided that implements basic,
line-oriented input and output facilities for the 68000
assembly language programs on the Macintosh.",
}
@TechReport{Dartmouth:TR86-114,
author = "Ed Grosz",
title = "{Music Editor}",
institution = "Dartmouth College, Computer Science",
address = "Hanover, NH",
number = "DCS-TR86-114",
year = "1986",
abstract = "This disk contains a simple music editor that creates
resources that can be used directly by the Macintosh
Sound Driver. The MFS formatted disk contains both the
runnable program and the Lisa Object Pascal/MacApp
Sources.",
}
@TechReport{Dartmouth:TR86-115,
author = "Ed Grosz",
title = "{KD Tree Simulator}",
institution = "Dartmouth College, Computer Science",
address = "Hanover, NH",
number = "DCS-TR86-115",
year = "1986",
abstract = "This MFS formatted disk contains an animation program
for illustrating KD-Trees (D-dimensional search trees)
(actually, only 2 dimensions are shown). Both the
runnable application and the Lisa Object Pascal/MacApp
sources are included.",
}
@TechReport{Dartmouth:TR86-116,
author = "Mark Sherman and Ann Marks and Rob Collins and Heather
Anderson and Jerry Godes and Denis Devlin and Leonid
Spector and Vivian Sewelson",
title = "{A Practical, Distributed Environment for Macintosh
Software Development}",
institution = "Dartmouth College, Computer Science",
address = "Hanover, NH",
number = "PCS-TR86-116",
year = "1986",
abstract = "We describe a development environment we created for
prototyping software for the Macintosh. The programs
are developed and executed on a large time-shared
computer but can use the full facilities of the
Macintosh. By using this system, we combine the
advantages of the large system, such as large amounts
of disk storage and automatic file backups, with the
advantages of the Macintosh, such as advanced graphics,
mouse control and sound synthesis. We also describe
several projects that used the distributed development
system. We conclude with a description of our future
plans for this environment.",
}
@TechReport{Dartmouth:TR86-117,
author = "Ann Kratzer and Mark Sherman",
title = "{View-3 and Ada: Tools for Building Systems with Many
Tasks}",
institution = "Dartmouth College, Computer Science",
address = "Hanover, NH",
number = "PCS-TR86-117",
year = "1986",
abstract = "This paper discusses some useful features for tools
that are intended to be used for developing systems
with multiple tasks. We include a description of one
tool that has been built, View-3. We also describe some
problems that might be encountered when trying to fit
this kind of tool into an APSE system.",
}
@TechReport{Dartmouth:TR86-118,
author = "Ann Kratzer",
title = "{A Distributed Strategy for Resource Allocation}",
institution = "Dartmouth College, Computer Science",
address = "Hanover, NH",
number = "PCS-TR86-118",
year = "1986",
abstract = "In this paper, we present a decentralized algorithm
for determining how resources should be allocated to
sites. This algorithm is general in the sense that it
can be used for allocating different kinds of
resources. This algorithm can be applied either
statically, used on a quiescent system, or used
dynamically as the system runs. Throughout, we consider
only systems in which a resource has a fixed cost
associated with it regardless of where it may be
located (i.e. the system is homogeneous).",
}
@TechReport{Dartmouth:TR86-119,
author = "Ann Kratzer",
title = "{Task Queues: A General Model for the Implementation
of Communications Protocols}",
institution = "Dartmouth College, Computer Science",
address = "Hanover, NH",
number = "PCS-TR86-119",
year = "1986",
abstract = "When any computer communications network is built, its
communications protocol must always be implemented. The
protocol is implementetd on the switching nodes of the
network. The node software must respond in real time to
events generated external to the switching node. Thus,
the software running on a switching node constitutes a
concurrent program; this complicates the design,
implementation and testing of the switching node
software. The task queue model presented in this paper
defines a structure for this software that facilitates
the design, implementation and testing of
communications protocols.",
}
@TechReport{Dartmouth:TR86-120,
author = "Ann Kratzer",
title = "{View 3: A Programming Environment for Distributed
Programming}",
institution = "Dartmouth College, Computer Science",
address = "Hanover, NH",
number = "PCS-TR86-120",
year = "1986",
abstract = "View 3 is an experimental programming environment to
support the development and use of distributed
programs. It builds upon three major concepts. First,
distributed programs and distributed processes are
basic objects. Second, the port mechanism allows a
process to exchange information with another process, a
file or an I/O device without concern for the type of
the object on the other end of the port. Third, test
and use of distributed programs are facilitated by the
user interface program screen format that allows the
user to control both the format and contents of the
physical terminal.",
}
@TechReport{Dartmouth:TR86-121,
author = "David Cohn and Stephen Madancy",
title = "{Creating Havoc: Havoc Development Program}",
institution = "Dartmouth College, Computer Science",
address = "Hanover, NH",
number = "PCS-TR86-121",
year = "1986",
abstract = "One area where use of the computer is essential is in
the modern scientific laboratory. High speed
computation, data storage and data analysis enable
scientists to perform experiments that would otherwise
be impractical. A problem inherent to the effective use
of special purpose laboratory computers, however, is
the fact that this equipment has generally been
developed for highly specific uses, and has either
tried to cope with existing high-level languages or has
abandoned the attempt and required the user to program
in a low-level assembly or machine language. Our idea
was to design, develop and implement a programming
language that is suited to the needs of a laboratory
scientist. Our results have led us to believe that the
best way to achieve our goals was using an
interpretive/compiled programming environment (similar
in spirit to FORTH) in which large programs could be
built in small, coherent pieces, that could easily be
tested on as high or low a level as the programmer
desired. Our language, Havoc, adheres to these
principles while providing many of the more widespread
and useful language features not found in FORTH.
Besides giving it motivation, this preliminary report
describes the current design and implementation status
of the HAVOC system. The current version of the HAVOC
system is available for the Macintosh.",
}
@TechReport{Dartmouth:TR86-122,
author = "David Cohn and Stephen Madancy",
title = "{Havoc V.85 Software}",
institution = "Dartmouth College, Computer Science",
address = "Hanover, NH",
number = "DCS-TR86-122",
year = "1986",
abstract = "This disk contains alpha release 85 of the HAVOC
system, with examples. It is written in C and 68000
assembler.",
}
@TechReport{Dartmouth:TR86-123,
author = "Keith Vetter and Christopher Roche",
title = "{BRUCE: A Graphics System with Hidden Line and Hidden
Surface Algorithms}",
institution = "Dartmouth College, Computer Science",
address = "Hanover, NH",
number = "PCS-TR86-123",
year = "1986",
abstract = "Accurately representing the physical world by computer
is a topic which has direct benefits to fields like
chemistry and architecture, and is a source of much
research in computer science. This paper examines the
steps necessary to develop and implement a graphical
system that will allow for the modeling of physical
world objects. In particular, this is a description of
BRUCE: a graphical system that will describe a world of
three dimensional polyhedra, implementing algorithms
for hidden line and hidden surface removal. This paper
also deals with the problems incurred along the way and
suggestions for further improvement of BRUCE.",
}
@TechReport{Dartmouth:TR86-124,
author = "Mark Sherman",
title = "{A Network Package for the Macintosh Using the DoD
Internet Protocols}",
institution = "Dartmouth College, Computer Science",
address = "Hanover, NH",
number = "PCS-TR86-124",
year = "1986",
abstract = "This memo describes the design, implementation and use
of the MacIP libraries and programs for running DoD
Internet Protocols on the Macintosh over Apple Talk. It
is preliminary documentation and out of date, but it is
all that exists.",
}
@TechReport{Dartmouth:TR86-125,
author = "Mark Sherman and Andy Hisgen and Jonathan Rosenberg
and David Alex Lamb",
title = "{Functions Returning Values of Dynamic Size}",
institution = "Dartmouth College, Computer Science",
address = "Hanover, NH",
number = "PCS-TR86-125",
year = "1986",
abstract = "Modern programming languages, such as Ada (Ichbiah
80), permit the definition of functions that return
values whose size can not be determined until the
function returns. This paper discusses five
implementation techniques that can be used to implement
this capability. Comparisons of the techniques are
provided and guidelines for selecting a particular
technique for a compiler are given.",
}
@TechReport{Dartmouth:TR86-126,
author = "Mark Sherman and Ann Marks",
title = "{Using Low-Cost Workstations to Investigate Computer
Networks and Distributed Systems}",
institution = "Dartmouth College, Computer Science",
address = "Hanover, NH",
number = "PCS-TR86-126",
year = "1986",
abstract = "A quality education in contemporary computer science
requires that students gain experience with realistic
systems. Many efforts at bringing empirical computer
science to undergraduates focus on rather old
technologies, for example, building a compiler or
simulating a disk scheduler. Although efforts are being
made to use some newer technologies, the efforts are
concentrating on teaching traditional material in a new
medium. However, the medium itself -- networked
workstations in a server environment -- is worthy of
exploration by undergraduate students in a laboratory
setting. At Dartmouth, we developed a Computer Network
Laboratory to let students experiment with computer
networks, protocols and distributed systems. Through
this article, we wish to share our experiences in the
design of the laboratory and give an example of how the
laboratory was used in a computer network course.",
}
@TechReport{Dartmouth:TR86-127,
author = "John Glenn",
title = "{Binary Trees (v. 2.1 -- September 25, 1985)}",
institution = "Dartmouth College, Computer Science",
address = "Hanover, NH",
number = "DCS-TR86-127",
year = "1986",
abstract = "Binary Tree is a program that uses animation to
illustrate insertion, deletion and searching of nodes
in a binary search tree. Pre-order, in-order, and
post-order tree walks are supported. Binary Tree can
also perform a recursive descent parse of arithmetic
expressions and show the resulting abstract syntax
tree. Lisa Pascal source and application available on a
single-sided, MFS format microdisk.",
}
@TechReport{Dartmouth:TR86-128,
author = "William J. Murray",
title = "{An Image Processing Software Package for the Laser
Scanning Phase Modulation Microscope}",
institution = "Dartmouth College, Computer Science",
address = "Hanover, NH",
number = "PCS-TR86-128",
year = "1986",
abstract = "This thesis documents the most recent effort to
develop a user-friendly image processing software
package for the Laser Scanning Phase Modulation
Microscope (LSPMM). The LSPMM is composed of three
integrated subsystems, the Laser Scanning (LS) system,
the Phase Modulation (PM) system, and Digital Image
Acquisition (DIA) system. Under the control of the
image processing software, the DIA system can receive
and store the digital image data, display the image on
a monochrome monitor, and process the image to provide
the microscopist with quantitative information
regarding the image. The implementation of this image
processing software package required the specification
of a four level software hierarchy to serve as an
organizational framework, with the highest level
interacting with the LSPM microscopist, and the lowest
level performing hardware control. This framework
should prove useful for the development and
implementation of additional software in the future.
The programs that were developed accept command line
arguments; however, most will interactively query the
user if the command line arguments are not known. This
software provides the microscopist with the capability
to scan, save, and display a 512 by 512 pixel image.
The image may be scanned to, saved from, or displayed
in either of the two DeAnza image display memory
planes. Considerable effort has been made to
incorporate all of the devices useful for image
processing into a single operating system kernel. This
alleviates the problem of taking down one operating
system and bringing up another version in order to dump
image files on magnetic tape.",
}
@TechReport{Dartmouth:TR86-129,
author = "Ann Marks",
title = "{An Algorithm for Resource Allocation Requiring Low
Overhead Communication}",
institution = "Dartmouth College, Computer Science",
address = "Hanover, NH",
number = "PCS-TR86-129",
year = "1986",
abstract = "A heuristic algorithm for allocating resource units to
sites in a distributed system is presented. Starting
with a given allocation of sites, the algorithm
performs a series of optimizations involving pairs of
sites in an attempt to improve the worst pair-wise
imbalance present in the system; termination occurs
when no further improvement is possible. After
outlining the general form of the algorithm, which
effectively defines an entire family of algorithms, we
present theoretical results that speak to the
performance of the algorithm as measured in the number
of optimizations that can be done, the amount of
control communication required and the worst case
imbalance of the resulting allocation. Subsequently,
two particular algorithms in the family are given and
the results of a simulation study of their performance
is presented.",
}
@TechReport{Dartmouth:TR86-130,
author = "L. Paul Chew and Robert L. Scot Drysdale",
title = "{Finding Largest Empty Circles with Location
Constraints}",
institution = "Dartmouth College, Computer Science",
address = "Hanover, NH",
number = "PCS-TR86-130",
year = "1986",
abstract = "Let S be a set of n points in the plane and let CH(S)
represent the convex hull of S. The Largest Empty
Circle (LEC) problem is the problem of finding the
largest circle centered with CH(S) such that no point
of S lies within the circle. Shamos and Hoey (SH75)
outlined an algorithm for solving this problem in time
O(n log n) by first computing the Voronoi diagram,
V(S), in time O(n log n), then using V(S) and CH(S) to
compute the largest empty circle in time O(n). In a
recent paper [Tou83], Toussaint pointed out some
problems with the algorithm as outlined by Shamos and
presented an algorithm which, given V(S) and CH(S),
solves the LEC problem in time O(n log n). In this note
we show that Shamos' original claim was correct: given
V(S) and CH(S), the LEC problem can be solved in time
O(n). More generally, given V(S) and a convex k-gon P,
the LEC centered within P can be found in time O(k+n).
We also improve on an algorithm given by Toussaint for
computing the LEC when the center is constrained to lie
within an arbitrary simple polygon. Given a set S of n
points and an arbitrary simple k-gon P, the largest
empty circle centered within P can be found in time
O(kn + n log n). This becomes O(kn) if the Voronoi
diagram of S is already given.",
}
@TechReport{Dartmouth:TR86-131,
author = "David B. Levine",
title = "{The Pairwise Intersection Problem for Monotone
Polygons}",
institution = "Dartmouth College, Computer Science",
address = "Hanover, NH",
number = "PCS-TR86-131",
year = "1986",
abstract = "Geometric intersection problems arise in a number of
areas of computer science including graphics and VLSI
design rule checking. Previous work has concentrated on
solving the pairwise intersection problem for line
segments and iso-oriented rectangles. This thesis
extends that work by presenting efficient algorithms to
solve the pairwise intersection problem for monotone
polygons. For general segments, the problem has been
solved in O(N+I)*logN) time using a sweeping line
technique, where N is the number of segments and I is
the number of intersections reported. We combine this
technique with approaches taken to solve the
iso-oriented rectangle problem to yield an algorithm
which solves the pairwise intersection problem for
monotone polygons in the same asymptotic time. In
addition, there are certain classes of line segments
for which the pairwise intersection problem may be
solved in O(N*logN + I) time, the best possible. We
generalize each such class of line segments to a class
of polygons and present algorithms to solve the
associated polygon problem. Finally, we discuss the
impacts which possible improvements to the line segment
problem would have on our results.",
}
@TechReport{Dartmouth:TR86-132,
author = "L. Paul Chew and Robert L. Scot Drysdale",
title = "{Voronoi Diagrams Based on Convex Distance
Functions}",
institution = "Dartmouth College, Computer Science",
address = "Hanover, NH",
number = "PCS-TR86-132",
year = "1986",
abstract = "We present an {"}expanding waves{"} view of Voronoi
diagrams that allows such diagrams to be defined for
very general metrics and for distance measures that do
not qualify as matrics. If a pebble is dropped into a
still pond, circular waves move out from the point of
impact. If n pebbles are dropped simultaneously, the
paces where wave fronts meet define the Voronoi diagram
on the n points of impact. The Voronoi diagram for any
normed matric, including the Lp metrics, can be
obtained by changing the shape of the wave front from a
circle to the shape of the {"}circle{"} in that metric.
(For example, the {"}circle{"} in the L1 metric is
diamond shaped.) For any convex wave shape there is a
corresponding convex distance function. Even if the
shape is not symmetric about its center (a triangle,
for example), although the resulting distance function
is not a metric, it can still be used to define a
Voronoi diagram. Like Voronoi diagrams based on the
Euclidean metric, the Voronoi diagrams based on other
nomed metrics can be used to solve various
closest-point problems (all-nearest-neighbors, minimum
spanning trees, etc.). Some of these problems also make
sense for convex distance functions which are not
metrics. In particular, the {"}largest empty circle{"}
problem becomes the {"}largest empty convex shape{"}
problem, and {"}motion planning for a disc{"} becomes
{"}motion planning for a convex shape{"}. These
problems can both be solved quickly given the Voronoi
diagram. We present an asymptotically optimal algorithm
for computing Voronoi diagrams based on convex distance
functions.",
}
@TechReport{Dartmouth:TR86-134,
author = "Mark Sherman and Robert L. Scot Drysdale",
title = "{Producing Software Using Tools in a Workstation
Environment}",
institution = "Dartmouth College, Computer Science",
address = "Hanover, NH",
number = "PCS-TR86-134",
year = "1986",
abstract = "We discuss how we taught students to build and use
translation, interpretive, editing and monitoring tools
in an undergraduate software engineering course.
Students used the tools on low-cost workstations
(Macintoshes) to build large, group projects. The
students' projects used all available features of
workstation environments, including graphics, windows,
fonts, mice, networks, and sound generators. We found
that 1) the use of tools increased student
productivity, 2) a shift in a data structure and
algorithm topics is needed to cover material relevant
for workstation environments, 3) new topics in system
design are required for a workstation environment, 4)
traditional material can be easily illustrated with a
workstation environment and 5) students enjoyed being
able to manipulate the advanced features of
workstations in their work, which in turn increased
their motivation for and concentration on the course
material.",
}
@TechReport{Dartmouth:TR86-135,
author = "John R. Meier",
title = "{Making Mail Friendlier: Adding Macintosh features and
multimedia documents in UNIX mail}",
institution = "Dartmouth College, Computer Science",
address = "Hanover, NH",
number = "PCS-TR86-135",
year = "1986",
abstract = "This paper describes a Macintosh application which
acts as a front-end to Unix mail. Features of the
Macintosh interface such as icons, menus, and windows
replace the command driven interface. Complicated
editing commands are replaced with mouse selection and
cut, copy, and paste. Message can be composed of text,
pictures, and any Macintosh file, because they are
encoded into plain text, sent through the mail
system,and then unencoded by the receiving end. The
designs of the mail server and communications interface
are such that mail servers and communications other
than Unix mail and a serial line may be easily
implemented.",
}
@TechReport{Dartmouth:TR87-139,
author = "Peter A. Sandon",
title = "{Learning Object-Centered Representations}",
institution = "Dartmouth College, Computer Science",
address = "Hanover, NH",
number = "PCS-TR87-139",
year = "1987",
abstract = "When we look at a familiar object from a novel
viewpoint, we are usually able to recognize it. In this
thesis, we address the problem of learning to recognize
objects under transformations associated with
viewpoint. Our vision model combines a hierarchical
representation of shape features with an explicit
representation of the transformation. Shape features
are represented in a layered pyramid-shaped subnetwork,
while the transformation is explicitly represented in
an auxiliary subnetwork. The two connectionist networks
are conjunctively combined to allow object- centered
shape features to be computed in the upper layers of
the network. A simulation of a 2-D translation
subnetwork demonstrates the ability to learn to
recognize shapes in different locations in an image,
such that those same shapes can be recognized in novel
locations. Two new learning methods are presented,
which provide improved behavior over previous
backpropagation methods. Both methods involve
ciompetitive interactions among clusters of nodes. The
new learning methods demonstrate improved learning over
the generalized delta rule when applied to a number of
network tasks. In the first method, called error
modification, competition is based on the error signals
computed from the gradient of the output error. The
result of this competition is a set of midified error
signals representing a contrast enhanced version of the
original errors. The error modification method reduces
the occurrence of network configurations that
correspond to local error minima. In the second method,
called error augmentation, competition is based on that
activations of the nodes in the cluster. Network
changes resulting from this competition augment those
specified by the error gradient computation. This
competition is implemented by the trace comparison
rule, a new self-organizing mechanism that is effective
in developing highly discriminating features within the
cluster. The error augmentation method improves
learning in the lower network layers when backpropagged
error is weak.",
}
@TechReport{Dartmouth:TR88-136,
author = "Matt Bishop",
title = "{The Sharing of Rights and Information in a
Capability-Based Protection System}",
institution = "Dartmouth College, Computer Science",
address = "Hanover, NH",
number = "PCS-TR88-136",
year = "1988",
abstract = "The paper examines the question of sharing of rights
and information in the Take-Grant Protection Model by
concentrating on the similarities between the two; in
order to do this, we state and prove new theorems for
each that specifically show the similarities. The proof
for one of the original theorems is also provided.
These statements of necessary and sufficient conditions
are contrasted to illustrate the proposition that
transferring rights and transferring information are
fundamentally the same, as one would expect in a
capability-based system. We then discuss directions for
future research in light of these results.",
}
@TechReport{Dartmouth:TR88-137,
author = "Matt Bishop",
title = "{Theft of Information in the Take-Grant Protection
Model}",
institution = "Dartmouth College, Computer Science",
address = "Hanover, NH",
number = "PCS-TR88-137",
year = "1988",
abstract = "(Revised 5/90). Questions of information flow are in
many ways more important than questions of access
control, because the goal of many security policies is
to thwart the unauthorized release of information, not
merely the illicit obtaining of access rights to that
information. The Take-Grant Protection Model is an
excellent theoretical tool for examining such issues
because conditions necessary and sufficienct for
information to flow between tow objects, and for rights
to object to be obtained or stolen, are known. In this
paper we extend these results by examinig the question
of information flow from an object the owner of which
is unwilling to release that information. Necessary and
sufficient conditions for such {"}theft of
information{"} to occur are derived, and bounds on the
number of subjects that must take action for the theft
to occur are presented. To emphasize the usefulness of
these results, the security policies of complete
isolation,transfer of rights with the cooperation of an
owner, and transfer of information (but not rights)
with the cooperation of the owner are presented; the
last is usedto model a simple reference monitor
guarding a resource.",
}
@TechReport{Dartmouth:TR88-138,
author = "Matt Bishop",
title = "{An Application of a Fast Data Encryption Standard
Implementation}",
institution = "Dartmouth College, Computer Science",
address = "Hanover, NH",
number = "PCS-TR88-138",
year = "1988",
abstract = "The Data Encryption Standard is used as the basis for
the UNIX password encryption scheme. Some of the
security of that scheme depends on the speed of the
implementation. This paper presents a mathematical
formulation of a fast implementation of the DES in
software, discusses how the mathematics can be
translated into code, and then analyzes the UNIX
password scheme to show how these results can be used
to implement it. Experimental results are provided for
several computers to show that the given method speeds
up the computation of a password by roughly 20 times
(depending on the specific computer).",
}
@TechReport{Dartmouth:TR89-140,
author = "Jeffrey Shallit",
title = "{On the Worst Case of Three Algorithms for Computing
the Jacobi Symbol}",
institution = "Dartmouth College, Computer Science",
address = "Hanover, NH",
number = "PCS-TR89-140",
year = "1989",
abstract = "We study the worst-case behavior of three iterative
algorithms- Eisenstein's algorithm, Lebesgue's
algorithm, and the {"}ordinary{"} Jacobi symbol
algorithm - for computing the Jacobi symbol. Each
algorithm is similar in format to the Euclidean
algorithm for computing gcd (u,v).",
}
@TechReport{Dartmouth:TR89-141,
author = "James R. Driscoll and Dennis M. Healy",
title = "{Asymptotically Fast Algorithms for Spherical and
Related Transforms}",
institution = "Dartmouth College, Computer Science",
address = "Hanover, NH",
number = "PCS-TR89-141",
year = "1989",
abstract = "This paper considers the problem of computing the
harmonic expansion of functions defined on the sphere.
We begin by proving convolution theorems that relate
the convolution of two functions on the sphere to a
{"}multiplication{"} in the sprectral domain, as well
as the multiplication of two functions on the sphere to
a {"}convolution{"} in the spectral domain. These
convolution theorems are then used to develop a
sampling theorem on the sphere.",
}
@TechReport{Dartmouth:TR89-142,
author = "Michael Goldweber and Donald B. Johnson and Larry
Raab",
title = "{A Comparison of Consistency Control Protocols}",
institution = "Dartmouth College, Computer Science",
address = "Hanover, NH",
number = "PCS-TR89-142",
year = "1989",
abstract = "In this paper we analyze three protocols for
maintaining the mutual consistency of replicated
objects in a distributed computing environment and
compare their performance with that of an oracle
protocol whose performance is optimal. We examine these
protocols, two dynamic protocols and the majority
consensus protocol, via simulations using two measures
of availability. The analysis shows that the dynamic
protocols, under realistic assumptions, do not perform
significantly better than the static voting scheme.
Finally we demonstrate that none of these approaches
perform as well as our oracle protocol which is shown
to be an upper bound on availability.",
}
@TechReport{Dartmouth:TR90-143,
author = "Samuel W. Bent",
title = "{Matching Multiple Patterns From Right to Left}",
institution = "Dartmouth College, Computer Science",
address = "Hanover, NH",
number = "PCS-TR90-143",
year = "1990",
abstract = "We address the problem of matching multiple pattern
strings against a text string. Just as the Aho-Corasick
algorithm generalizes the Knuth-Morris-Pratt
single-pattern algorithm to handle multiple patterns,
we exhibit two generalizations of the Boyer-Moore
algorithm to handle multiple patterns. In order to
obtain worst-case time bounds better than quadratic,
our algorithms remember some of the previous history of
the matching.",
}
@TechReport{Dartmouth:TR90-145,
author = "Michael Goldweber and Donald B. Johnson",
title = "{A Bound of Data Availability when Networks
Partition}",
institution = "Dartmouth College, Computer Science",
address = "Hanover, NH",
number = "PCS-TR90-145",
year = "1990",
month = mar,
URL = "http://www.cs.dartmouth.edu/reports/TR90-145.pdf",
abstract = "Many consistency or replication control schemes that
increase data availability in distributed systems
exist, and the search for improvements continues,
though there have been no good nontrivial upper bound
demonstrating how much improvement is possible. We
present a new upper bound for data availability under
replication for general networks. In addition we also
describe a new technique that yields near optimal
levels of data availability with respect to this
bound.",
}
@TechReport{Dartmouth:TR90-146,
author = "L. Paul Chew",
title = "{Planar Graphs and Sparse Graphs from Efficient Motion
Planning in the Plane}",
institution = "Dartmouth College, Computer Science",
address = "Hanover, NH",
number = "PCS-TR90-146",
year = "1990",
abstract = "Given a source, a destination, and a number of
obstacles in the plane, the Motion Planning Program is
to determine the best path to move an object (a robot)
from the source to the destination without colliding
with any of the obstacles. For us, motion is restricted
to the plane, the robot is represented by a point, and
the obstacles are represented by a set of polygons with
a total of n vertices among all the polygonal
obstacles.",
}
@TechReport{Dartmouth:TR90-147,
author = "L. Paul Chew",
title = "{Building Voronoi Diagrams for Convex Polygons in
Linear Expected Time}",
institution = "Dartmouth College, Computer Science",
address = "Hanover, NH",
number = "PCS-TR90-147",
year = "1990",
abstract = "Let P be a list of points in the plane such that the
points of P taken in order form the vertices of a
convex polygon. We introduce a simple, linear
expected-time algorithm for finding the Voronoi diagram
of the points in P. Unlike previous results on
expected-time algorithms for Voronoi diagrams, this
method does not require any assumptions about the
distribution of points. With minor modifications, this
method can be used to design fast algorithms for
certain problems involving unrestricted sets of points.
For example, fast expected-time algorithms can be
designed to delete a point from a Voronoi diagram, to
build an order k Voronoi diagram for an arbitrary set
of points, and to determine the smallest enclosing
circle for points at the vertices of a convex hull.",
}
@TechReport{Dartmouth:TR90-148,
author = "L. Paul Chew",
title = "{There is a Planar Graph Almost as Good as the
Complete Graph}",
institution = "Dartmouth College, Computer Science",
address = "Hanover, NH",
number = "PCS-TR90-148",
year = "1990",
abstract = "Given a set S of points in the plane, there is a
triangulation of S such that a path found within this
triangulation has length bounded by a constant times
the straight-line distance between the endpoints of the
path. Specifically, for any two points a and b of S
there is a path along edges of the triangulation with
length less that Ã10 times [ab], where [ab] is the
straight-line Euclidean distance between a and b. The
triangulation that has this property is the L1 metric
Delauney triangulation for the set S. This result can
be applied to motion planning in the plane. Given a
source, a destination, and a set of polygonal obstacles
of size n, an O(n) size data structure can be used to
find a reasonable approximation to the shortest path
between the source and the destination in O (n log n)
time.",
}
@TechReport{Dartmouth:TR90-149,
author = "L. Paul Chew",
title = "{Term Reduction Using Directed Congruence Closure}",
institution = "Dartmouth College, Computer Science",
address = "Hanover, NH",
number = "PCS-TR90-149",
year = "1990",
abstract = "Many problems in computer science can be described in
terms of reduction rules that tell how to transform
terms. Problems that can be handled in this way include
interpreting programs, implementing abstract data
types, and proving certain kinds of theorems. A terms
is said to have a normal form if it can be transformed,
using the reduction rules, into a term to which no
further reduction rules apply. In this paper, we extend
the Congruence Closure Algorithm, an algorithm for
finding the consequences of a finite set of equations,
to develop Directed Congruence Closure, a technique for
finding the normal form of a term provided the
reduction rules satisfy the conditions for a regular
term rewriting system. This technique is particularly
efficient because it inherits, from the Congruence
Closure Algorithm, the ability to remember all objects
that have already been proved equivalent.",
}
@TechReport{Dartmouth:TR90-151,
author = "Matt Bishop",
title = "{Applying the Take-Grant Protection Model}",
institution = "Dartmouth College, Computer Science",
address = "Hanover, NH",
number = "PCS-TR90-151",
year = "1990",
abstract = "The Take-Grant Protection Model has in the past been
used to model multilevel security hierarchies and
simple protection systems. The models are extended to
include theft of rights and sharing of information, and
additional security policies are examined. The analysis
suggests that in some cases the basic rules of the
Take-Grant Protection Model should be augmented to
represent the policy properly; when appropriate, such
modifications are made and their effects with respect
to the policy and its Take-Grant representations are
discussed",
}
@TechReport{Dartmouth:TR90-152,
author = "Matt Bishop",
title = "{A Proactive Password Checker}",
institution = "Dartmouth College, Computer Science",
address = "Hanover, NH",
number = "PCS-TR90-152",
year = "1990",
abstract = "Password selection has long been a difficult issue;
traditionally, passwords are either assigned by the
computer or chosen by the user. When the computer does
the assignments, the passwords are often hard to
remember; when the User makes the selection, the
passwords are often easy to guess. This paper describes
a technique, and a mechanism, to allow users to select
passwords which to them are easy to remember but to
others would be very difficult to guess. The technique
is site, user, and group configurable, and allows rapid
changing of constraints impossed upon the passwords.
Although experience with this technique has been
limited, it appears to have much promise.",
}
@TechReport{Dartmouth:TR90-153,
author = "Matt Bishop",
title = "{Administrator's Guide to the Digital Signature
Facility "Rover"}",
institution = "Dartmouth College, Computer Science",
address = "Hanover, NH",
number = "PCS-TR90-153",
year = "1990",
abstract = "This document describes the installation and
maintenance of the rover utility, which provides a
digital signature capability for internet messages.",
}
@TechReport{Dartmouth:TR90-155,
author = "Donald B. Johnson and Larry Raab",
title = "{Effects of Replication on Data Availability}",
institution = "Dartmouth College, Computer Science",
address = "Hanover, NH",
number = "PCS-TR90-155",
year = "1990",
abstract = "In this paper we examine the effects of replication on
the availability of data in a large network. This
analysis differs from previous analyses in that it
compares the performance of a dynamic consistency
control protocol not only to that of other consistency
control protocols, but also to the performance of
non-replication and to an upper bound on data
availability. This analysis also differes in that we
gather extensive simulations on large networks subject
to partitions at realistically high component
reliabilities. We examine the dynamic consistency
protocol presented by Jajodia and Mutchler [9, 12] and
by Long and Paris[18] along with two proposed
enhancements to this protocol[10,11]. We study networks
of 101 sites and up to 5050 links (fully-connected) in
which all components, although highly reliable, are
subject to failure. We demonstrate the importance in
this realistic environment of an oft neglected
parameter of the system model, the ratio of transaction
submissions to component failures. We also show the
impact of the number of copies on both the protocol
performance and the potential of replicaion as measured
by the upper bound. Our simulations show that the
majority of current protocol performs optimally for
topologies that yield availabilities of at least 65%.
On the other hand, the availability provided by
non-replicaion is inferior to that of the majority of
current protocol by a most 5.9 percentage points for
these same topologies. At this point of maximum
difference, theprimary copy protocol yields
availability 59.1% and the majority of current protocol
yields availability 65.0%. We discuss the
characteristics of the model limiting the performance
of replication.",
}
@TechReport{Dartmouth:TR90-157,
author = "Donald B. Johnson and Larry Raab",
title = "{A Tight Upper Bound on the Benefits of Replication
and Consistency Control Protocols}",
institution = "Dartmouth College, Computer Science",
address = "Hanover, NH",
number = "PCS-TR90-157",
year = "1990",
abstract = "We present an upper bound on the performance provided
by a protocol guaranteeing mutually exclusive access to
a replicated resource in a network subject to component
failure and subsequent partitioning. The bound is
presented in terms of the performance of a single
resource in the same network. The bound is tight and is
the first such bound known to us. Since mutual
exclusion is one of the requirements for maintaining
the consistency of a database object, this bound
provides an upper limit on the availability provided by
any database consistency control protocol, including
those employing dynamic data relocation and
replication. We show that if a single copy provides
availability A for 0 ² A ² 1, then no scheme can
achieve availability greater than ÃA in the same
network. We show this bound to be the best possible for
any network with availability greater than .25.
Although, as we proved, the problem of calculating A is
#P-complete, we describe a method for approximating the
optimal location for a single copy which adjusts
dynamically to current network characteristcs. This
bound is most useful for high availabilities, which
tend to be obtainable with modern networks and their
constituent components.",
}
@TechReport{Dartmouth:TR90-158,
author = "Donald B. Johnson and Larry Raab",
title = "{Finding Optimal Quorum Assigments for Distributed
Databases}",
institution = "Dartmouth College, Computer Science",
address = "Hanover, NH",
number = "PCS-TR90-158",
year = "1990",
abstract = "Replication has been studied as a method of increasing
the availability of a data item in a distributed
database subject to component failures and consequent
partitioning. The potential for partitioning requires
that a protocol be employed which guarantees that any
access to a data item is aware of the most recent
update to that data item. By minimizing the number of
access requests denied due to this constraint, we
maximize availability. In the event that all access
requests are reads, placing one copy of the data item
at each site clearly leads to maximum availability. The
other extreme, all access requests are write requests
or are treated as such, has been studied extensively in
the literature. In this paper we investigate the
performance of systems with both read and write
requests. We describe a distributed on-line algorithm
for determining the optimal parameters, or optimal
quorum assignments, for a commonly studied protocol,
the quorum consensus protocol[9]. We also show how to
incorporate these optimization techniques into a
dynamic quorum reassignment protocol. In addition, we
demonstrate via simulation both the value of this
algorithm and the effect of various read-write rations
on availability. This simulation, on 101 sites and up
to 5050 links(fully- connected), demonstrates that the
techniques described here can greatly increase data
availability, and that the best quorum assignments are
frequently realized at the extreme values of the quorum
parameters.",
}
@TechReport{Dartmouth:TR91-150,
author = "Matt Bishop",
title = "{Privacy-Enhanced Electronic Mail}",
institution = "Dartmouth College, Computer Science",
address = "Hanover, NH",
number = "PCS-TR91-150",
year = "1991",
URL = "http://www.cs.dartmouth.edu/reports/TR91-150.pdf",
abstract = "(Revision 3). The security of electronic mail sent
through the Internet may be described in exactly three
words: there is none. The Privacy and Security Research
Group has recommended implementing mechanisms designed
to provide security enhancements. The first set of
mechanisms provides a protocol to provide privacy,
integrity, and authentication for electronic mail; the
second provides a certificate-based key management
infrastructure to support key distribution throughout
the internet, to support the first set of mechanisms.
This paper describes these mechanisms, as well as the
reasons behind their selection and how these mechanisms
can be used to provide some measure of securtiy in the
exchange of electronic mail.",
}
@TechReport{Dartmouth:TR91-154,
author = "Matt Bishop",
title = "{A Security Analysis of Version 2 of the Network Time
Protocol NTP: A Report to the Privacy and Security
Research Group}",
institution = "Dartmouth College, Computer Science",
address = "Hanover, NH",
number = "PCS-TR91-154",
year = "1991",
abstract = "The Network Time Protocol is being used throughout the
Internet to provide an accurate time service. This
paper examines the security requirements of such a
service, analyzes version 2 of the NTP protocol to
determine how well it meets these requirements, and
suggests improvements where appropriate.",
}
@TechReport{Dartmouth:TR91-156,
author = "Matt Bishop",
title = "{An Overview of Computer Viruses in a Research
Environment}",
institution = "Dartmouth College, Computer Science",
address = "Hanover, NH",
number = "PCS-TR91-156",
year = "1991",
abstract = "The threat of attack by computer viruses is in reality
a very small part of a much more general threat,
specifically attacks aimed at subverting computer
security. This paper examines computer viruses as
malicious logic in a research and development
environment, relates them to various models of security
and integrity, and examines current research techniques
aimed at controlling the threats viruses in particular,
and malicious logic in gerneral, pose to computer
systems. Finally, a brief examination of the
vulnerabilities of research and development systems
that malicious logic and computer viruses may exploit
is undertaken.",
}
@TechReport{Dartmouth:TR91-158,
author = "Matt Bishop",
title = "{Implementation Notes on bdes(1)}",
institution = "Dartmouth College, Computer Science",
address = "Hanover, NH",
number = "PCS-TR91-158",
year = "1991",
abstract = "This note describes the implementation of bdes, the
file encryption program being distributed in the 4.4
release of the Berkeley Software Distribution. It
implements all modes of the Data Encryption Standard
program.",
}
@TechReport{Dartmouth:TR91-159,
author = "Donald B. Johnson and Panagiotis Metaxas",
title = "{Optimal Parallel and Sequential Algorithms for the
Vertex Updating Problem of a Minimum Spanning Tree}",
institution = "Dartmouth College, Computer Science",
address = "Hanover, NH",
number = "PCS-TR91-159",
year = "1991",
abstract = "We present a set of rules that can be used to give
optimal solutions to the vertex updating problem for a
minimum spanning tree: Update a given MST when a new
vertex z is introducted, along with weighted edges that
connect z with the vertices of the graph. These rules
lead to simple parallel algorithms that run in O(lg n)
parallel time using n/lg n EREW PRAMs. They can also be
used to derive simple linear-time sequential algorithms
for the same problem. Furthermore, we show how our
solution can be used to solve the multiple vertex
updating problem.",
}
@TechReport{Dartmouth:TR91-160,
author = "Donald B. Johnson and Panagiotis Metaxas",
title = "{Connected Components in O(lg3/2|V|) Parallel Time for
the CREW PRAM}",
institution = "Dartmouth College, Computer Science",
address = "Hanover, NH",
number = "PCS-TR91-160",
year = "1991",
abstract = "Computing the connected components of an undirected
graph G = (V,E) on |V| = n vertices and |E| = m edges
is a fundamental computational problem. The best known
parallel algorithm for the CREW PRAM model runs on
O(lg2n) time using n2/lg2n processors [CLC82,HCS79].
For the CRCW PRAM model in which concurrent writing is
permitted, the best known algorithm runs in O(lg n)
time using almost (n+m)/lg n processors
[SV82,CV86,AS87]. Unfortunately, simulating this
algorithm on the weaker CREW model increases its
running time to O(lg2n) [CDR86, KR90,Vis83]. We present
here an efficient and simple algorithm that runs in
O(lg 3/2n) time using n+m CREW processors.",
}
@TechReport{Dartmouth:TR91-161,
author = "Dimitrios Kagaris and Fillia Makedon",
title = "{On Minimizing Hardware Overhead for Exhaustive
Circuit Testability}",
institution = "Dartmouth College, Computer Science",
address = "Hanover, NH",
number = "PCS-TR91-161",
year = "1991",
abstract = "Exhaustive built-in self testing is given much
attention as a viable technique in the context of VLSI
technology. In this paper, we present heuristic in
order to make exhaustive testing of combinational
circuits practical. The goal is to place a small number
of register cells on the nets of the input circuit so
that the input dependency of combinational elements in
the circuit is less than a small given integer k. Our
heuristic guarantees that each output can be
individually tested with 2k test patterns and can be
used as a subroutine to generat efficient test patterns
to test all the outputs of the circuit simultaneously.
For example, we can connect the register cells in a
Linear Feedback Shift Register(LFSR). Minimizing the
number of the inserted register cells reduces the
hardware overhead as well as the upper bound on the
number of test patterns generated. A heuristic approach
has been proposed only for the case when an element in
the circuit schematic denotes a boolean gate. An
element may, however, also be used to represent a
combinatorial circuit model. Our heuristic applies to
this case as well. Extensive experimentation indicates
that the proposed technique is very efficient.",
}
@TechReport{Dartmouth:TR91-162,
author = "Dimitrios Kagaris and Fillia Makedon",
title = "{A Metric Towards Efficient Exhaustive Test Pattern
Generation}",
institution = "Dartmouth College, Computer Science",
address = "Hanover, NH",
number = "PCS-TR91-162",
year = "1991",
abstract = "A viable technique [7] in built-in self-test (BIST)[2]
is to generate test patterns pseudo-exhaustively by
using linear feedback shift registers (LFSR's). The
goal is to find an appropriate primitive polynomial of
degree d that will generat 2d test patterns in order to
exercise all circuit outputs simultaneously. In an
attempt to reduce the degree d of the polynomial the
following strategy was proposed in [6,5]. In the first
phase, partition the circuit into segments by inserting
a small number of register cells, so that the input
dependency of any circuit element in the segments is no
more than d. Then, obain an appropriate primitive
polynomial of degree d by inserting additional register
cells. In [12] we have proposed a heuristic for phase
one that does not necessarily partition the circuit.
Extensive experimentation has shown that this results
in a considerably smaller cell overhead. In this paper
we extend our heuristic in [12], so that the
minimization of the number of register cells is done in
conjunction with a quantity that naturally reflects the
difficulty of deriving an appropriate primitive
polynomial of degree d. Experimentation shows that the
proposed heuristic results again in an overall smaller
number of register cells than a partition based
approach and in an efficient framework for test pattern
generation.",
}
@TechReport{Dartmouth:TR91-163,
author = "Fillia Makedon and Adononios Simvonis",
title = "{Multipacket Routing on Rings}",
institution = "Dartmouth College, Computer Science",
address = "Hanover, NH",
number = "PCS-TR91-163",
year = "1991",
abstract = "We study multipacket routing problems. We divide the
multipacket routing problem into two classes, namely,
distance limited and bisection limited routing
problems. Then, we concentrate on rings of processors.
Having a full understanding of the multipacket routing
problem on rings is essential before trying to attack
the problem for the more general case of r-dimensional
meshes and tori. We prove a new lower bound of 2n/3
routing steps for the case of distance limited routing
problems. We also give an algorithm that tightens this
lower bound. For bisection limited problems, we present
an algorithm that completes the routing in near optimal
time.",
}
@TechReport{Dartmouth:TR91-164,
author = "Otto Mayer and Graham E. Oberem and Fillia Makedon",
title = "{Ilona: An advanced CAI Tutorial System for the
Fundamentals of Logic}",
institution = "Dartmouth College, Computer Science",
address = "Hanover, NH",
number = "PCS-TR91-164",
year = "1991",
abstract = "An advanced tutorial system for teaching the
fundamentals of logic has been developed to run on UNIX
work stations and commonly available micro-computers.
An important part of this tutorial is the intelligent
problem solving environment which allows students to
practise wiriting logical sentences in mathematical
notation. A natural language system for intelligent
logic narrative analysis (ILONA) allows students to
type in their own logical sentences in plain English
and then have the computer check their working when
they write these in mathematical form. ILONA is an
intelligent tutoring system which allows students a
great deal of initiative in problem solving and
provides a degree of flexibility in answer evaluation
not found in traditional CAI systems. The concepts and
structures used in the development of ILONA are easily
transferable to other domains.",
}
@TechReport{Dartmouth:TR91-165,
author = "Jill P. David and Julie C. Jumes and Fillia Makedon",
title = "{An Object-Oriented Learning/Design Support
Environment}",
institution = "Dartmouth College, Computer Science",
address = "Hanover, NH",
number = "PCS-TR91-165",
year = "1991",
abstract = "We present an object-oriented experimental learning
and design support environment, call AVT, for an
Algorithm Visualization Tool, implemented in Digitalk's
Smalltalk/V1 on a Macintosh II2, AVT provides a domain-
independent visualization tool, an exploratory learning
environment, and an experimental heuristic design
environment. Algorithm visualization is the exploration
of ways to visualize intuitively the computational
behavior of an algorithm using multiple views, some of
which are visual in the graphical sense [2,4]. AVT
employs other views (combining text and graphics) to
explain the problem, the strategy, the heuristics, and
the reasoning process behind the solutions. User
interaction in AVT includes not only passive viewingof
the animated algorithmic process but also active
participation in the design of the steps of the
algorithm. Object-Oriented Programming(OOP)offers an
attractive paradigm for rapidly implementing heuristics
as well as more coherent and understandable code
[1,12]. Inheritance properties of OOP languages capture
natural mechanisms such as specialization, abstraction,
and evolution allowing us to model our environment in a
more natural manner[11].",
}
@TechReport{Dartmouth:TR91-166,
author = "Donald B. Johnson and Panagiotis Metaxas",
title = "{A Parallel Algorithm for the Minimum Spanning Tree}",
institution = "Dartmouth College, Computer Science",
address = "Hanover, NH",
number = "PCS-TR91-166",
year = "1991",
}
@TechReport{Dartmouth:TR91-167,
author = "Donald B. Johnson and Larry Raab",
title = "{Complexity of Network Reliability and Optimal
Database Placement Problems}",
institution = "Dartmouth College, Computer Science",
address = "Hanover, NH",
number = "PCS-TR91-167",
year = "1991",
abstract = "A fundamental problem of distributed database design
in an existing network where components can fail is
finding an optimal location at which to place the
database in a centralized system or copies of each data
item in a decentralized or replicated system. In this
paper it is proved for the first time exactly how hard
this placement problem is under the measure of data
availability. Specifically, we show that the optimal
placement problem for availability is #P- complete, a
measure of intractability at least as severe as
NP-completeness. Given the anticipated computational
difficulty of finding an exact solution, we go on to
describe an effective, practical method for
approximating the optimal copy placement. To obtain
these results, we model the environment in which a
distributed database operates by a probabilistic graph,
which is a set of fully-reliable vertices representing
sites, and a set of edges representing communication
links, each operational with a rational probability. We
prove that finding the optimal copy placement in a
probabilistic graph is #P-complete by giving a sequence
of reductions from #Satisfiability. We generalize this
result to networks in which each site and each link has
an independent, rational operational probability and to
networks in which all the sites or all the links have a
fixed, uniform operational probabilities.",
}
@TechReport{Dartmouth:TR91-168,
author = "Donald B. Johnson and Larry Raab",
title = "{Availability Issues in Data Replication in
Distributed Database}",
institution = "Dartmouth College, Computer Science",
address = "Hanover, NH",
number = "PCS-TR91-168",
year = "1991",
abstract = "Replication of data at more than one site in a
distributed database has been reported to increase the
availability in data in systems where sites and links
are subject to failure. We have shown in results
summarized in this paper that in many interesting cases
the advantage is slight. A well-placed single copy is
available to transactions almost as much of the time as
is correct replicated data no matter how ingeniously it
is managed. We explain these findings in terms of the
behavior of the partitions that form in networks where
components fail. We also show that known and rather
simple protocols for the maintenance of multiple copies
are essentially best possible by comparing them against
an unrealizable {"}protocol{"} that knows the future.
We complete our study of these questions by reporting
that while computing the availability of data is
#P-complete, nonetheless there is a tight analytical
bound on the amount replication can improve over a
well-located single copy. We close with some
observations regarding system design motivated by this
work.",
}
@TechReport{Dartmouth:TR91-169,
author = "Donald B. Johnson and Larry Raab",
title = "{Effects of Replication on the Duration of Failure in
Distributed Databases}",
institution = "Dartmouth College, Computer Science",
address = "Hanover, NH",
number = "PCS-TR91-169",
year = "1991",
abstract = "Replicating data objects has been suggested as a means
of increasing the performance of a distributed database
system in a network subject to link and site failures.
Since a network may partition as a consequence of such
failures, a data object may become unavailable from a
given site for some period of time. In this paper we
study duration failure, which we define as the length
of time, once the object becomes unavailable from a
particular site, that the object remains unavailable.
We show that, for networks composed of highly-reliable
components, replication does not substantially reduce
the duration of failure. We model a network as a
collection of sites and links, each failing and
recovering independently according to a Poisson
process. Using this model, we demonstrate via
simulation that the duration of failure incurred using
a non-replicated data object is nearly as short as that
incurred using a replicated object and a replication
control protocol, including an unrealizable protocol
which is optimal with respect to availability. We then
examine analytically a simplified system in which the
sites but not the links are subject to failure. We
prove that if each site operates with probability p,
then the optimal replication protocol, Available Copies
[5,26], reduces the duration of failure by at most a
factor of 1-p/1+p. Lastly, we present bounds for
general systems, those in which both the sites and the
communications between the sites may fail. We prove,
for example, that if sites are 95% reliable and a
communications failure is sufficiently short (either
infallible or satisfying a function specified in the
paper) then replication can improve the duration of
failure by at most 2.7% of that experienced using a
single copy. These results show that replication has
only a small effect of the duration of failure in
present-day partitionable networks comprised of
realistically reliable components.",
}
@TechReport{Dartmouth:TR91-174,
author = "Fillia Makedon and Antonios Symvonis",
title = "{Optimal Algorithms for Multipacket Routing Problems
on Rings}",
institution = "Dartmouth College, Computer Science",
address = "Hanover, NH",
number = "PCS-TR91-174",
year = "1991",
abstract = "We study multipacket routing problems. We divide the
multipacket routing problem into two classes, namely,
distance limited and bisection limited routing
problems. Then, we concentrate on rings of processors.
We prove a new lower bound of 2n/ 3 routing steps for
the case of distance limited routing problems. We also
give an algorithm that tightens this lower bound. For
bisection limited problems the lower bound is kn/ 4,k
>2, where k is the number of packets per processor. The
trivial algorithm needs in the worst case k | n /2|
steps to terminate. An algorithm that completes the
routing in kn /4 + 2.5 n routing steps is given. We
define the class of pure routing algorithms and we
demonstrate that new lower bounds hold if the routing
is to be done by an algorithm in this class.",
}
@TechReport{Dartmouth:TR92-176,
author = "David Kotz and Fillia Makedon and Matt Bishop and
Robert L. Scot Drysdale and Donald B. Johnson and
Panagiotis Metaxas",
title = "{Parallel Computer Needs at Dartmouth College}",
institution = "Dartmouth College, Computer Science",
address = "Hanover, NH",
number = "PCS-TR92-176",
year = "1992",
URL = "http://www.cs.dartmouth.edu/reports/TR92-176.ps.Z",
abstract = "To determine the need for a parallel computer on
campus, a committee of the Graduate Program in Computer
Science surveyed selected Dartmouth College faculty and
students in December, 1991, and January, 1992. We hope
that the information in this report can be used by many
groups on campus, including the Computer Science
graduate program and DAGS summer institute, Kiewit's NH
Supercomputer Initiative, and by numerous researchers
hoping to collaborate with people in other disciplines.
We found significant interest in parallel
supercomputing on campus. An on-campus parallel
supercomputing facility would not only support numerous
courses and research projects, but would provide a
locus for intellectual activity in parallel computing,
encouraging interdisciplinary collaboration. We believe
that this report is a first step in that direction.",
}
@TechReport{Dartmouth:TR92-177,
author = "Barry F. Schaudt",
title = "{Multiplicatively Weighted Crystal Growth Voronoi
Diagrams (Thesis)}",
institution = "Dartmouth College, Computer Science",
address = "Hanover, NH",
number = "PCS-TR92-177",
year = "1992",
abstract = "Voronoi diagrams and variants of Voronoi diagrams have
been used for many years to model crystal growth. If
the boundary of the growing crystals are circular and
all the crystals start at the same time and have the
same constant growth rate, then the Voronoi diagram is
used to model the growth. If the crystals start at
different times, the additively weighted Voronoi
diagram is used to model the crystal growth. In this
thesis, I propose a new type of Voronoi diagram called
the multiplicatively weighted crystal growth Voronoi
diagram, that can be used to model crystal growth when
the crystals have different constant growth rates. In
this new model, the distance from a site to a point in
its region is measured along a shortest path lying
entirely within the region. In the multiplicatively
weighted crystal growth Voronoi diagram, a growing
crystal (or region) may {"}wrap around{"} another
site's region. When a region wraps around, distances
from the site are in part measured along the boundary
of the two regions, treating one of the regions as an
obstacle, rather than along a straight line that passes
through the region. The worst case size of the
multiplicatively weighted crystal growth Voronoi,
diagram is 0(n 2). To construct the diagram, techniques
from numerical analysis are used to approximate and to
intersect curves described by a system of first order
differential equations. Numerical methods to
approximated a curve construct a polygonal
approximation of the curve. One step of the numerical
methods constructs an edge of the polygonal
approximation. In the new Voronoi diagram, a step may
require 0(n ) constant time operations. Let S be the
number of steps required by the numerical method used
just to draw the diagram. In the worst case, the
algorithm presented in this thesis requires O (n 3)
intersection calculations plus O (nS lg S ) time using
O (n 3 + S ) space. A variant of this algorithm
requires O (n 3) intersection calculations plus O (nS 2
+ n 2S ) time using O (n 2) space. Also presented are
some variants of the new Voronoi diagram. One of these
variants uses a convex polygon distance function. The
multiplicatively weighted crystal growth Voronoi
diagram using a convex polygon distance function does
not require numerical methods to construct.",
}
@TechReport{Dartmouth:TR92-178,
author = "Panagiotis Metaxas",
title = "{Parallel Algorithms For Graph Problems (Thesis)}",
institution = "Dartmouth College, Computer Science",
address = "Hanover, NH",
number = "PCS-TR92-178",
year = "1992",
abstract = "In this thesis we examine three problems in graph
theory and propose efficient parallel algorithms for
solving them. We also introduce a number of parallel
algorithmic techniques.",
}
@TechReport{Dartmouth:TR92-179,
author = "David Kotz",
title = "{Multiprocessor File System Interfaces}",
institution = "Dartmouth College, Computer Science",
address = "Hanover, NH",
number = "PCS-TR92-179",
year = "1992",
URL = "http://www.cs.dartmouth.edu/reports/TR92-179.ps.Z",
abstract = "Increasingly, file systems for multiprocessors are
designed with parallel access to multiple disks, to
keep I/O from becoming a serious bottleneck for
parallel applications. Although file system software
can transparently provide high-performance access to
parallel disks, a new file system interface is needed
to facilitate parallel access to a file from a parallel
application. We describe the difficulties faced when
using the conventional (Unix-like) interface in
parallel applications, and then outline ways to extend
the conventional interface to provide convenient access
to the file for parallel programs, while retaining the
traditional interface for programs that have no need
for explicitly parallel file access. Our interface
includes a single naming scheme, a multiopen operation,
local and global file pointers, mapped file pointers,
logical records, multifiles, and logical coercion for
backward compatibility.",
}
@TechReport{Dartmouth:TR92-180,
author = "Peter A. Gloor and Donald B. Johnson and Fillia
Makedon and Panagiotis Metaxas",
title = "{A Visualization System for Correctness Proofs of
Graph Algorithms}",
institution = "Dartmouth College, Computer Science",
address = "Hanover, NH",
number = "PCS-TR92-180",
year = "1992",
abstract = "In this paper we describe a system for visualizing
correctness proofs of graph algorithms. The system has
been demonstrated for a greedy algorithm. PrimÕs
algorithm for finding a minimum spanning tree of an
undirected, weighted graph. We believe that our system
is particularly appropriate for greedy algorithms,
though much of what we discuss can guide visualization
of proofs in other contexts. While an example is not a
proof, our system provides concrete examples to
illustrate the operation of the algorithm. These
examples can be referred to by the user interactively
and alternatively with the visualization of the proof
where the general case is portrayed abstractly.",
}
@TechReport{Dartmouth:TR92-181,
author = "Glenn Hurlbert and Garth Isaak",
title = "{On The De Bruijn Torus Problem}",
institution = "Dartmouth College, Computer Science",
address = "Hanover, NH",
number = "PCS-TR92-181",
year = "1992",
abstract = "A (kn;n)k-de Bruijn Cycle is a cyclic k-ary sequence
with the property that every k-ary n-tuple appears
exactly once contiguously on the cycle. A (kr, ks; m,
n)k-de Bruijn Torus is a k-ary krXks toroidal array
with the property that every k-ary m x n matrix appears
exactly once contiguously on the torus. As is the case
with de Bruijn cycles, the 2-dimensional version has
many interesting applications, from coding and
communications to pseudo-random arrays, spectral
imaging, and robot self-location. J.C. Cock proved the
existence of such tori for all m, n, and k, and Chung,
Diaconis, and Graham asked if it were possible that r =
s and m -= n for n even. Fan, Fan, Ma and Siu showed
this was possible for k - 2. Combining new techniques
with old, we prove the result for k > 2 and show that
actually much more is possible. The cases in 3 or more
dimensions remain.",
}
@TechReport{Dartmouth:TR92-182,
author = "Peter Su and Matt Bishop",
title = "{How to Encrypt /usr/dict/words in About a Second}",
institution = "Dartmouth College, Computer Science",
address = "Hanover, NH",
number = "PCS-TR92-182",
year = "1992",
abstract = "We present an implementation of the Data Encryption
Standard on the Connection Machine architecture. The
DES encryption algorithm is ideally suited to the
Connection Machine because it consists of bit serial
operations, and thousands of encryptions can be done in
parallel, independently of one another. Thus, our code
encrypts passwords about ten times faster than the
fastest competition that we know about. In addition,
the nature of the Connection Machine's architecture is
such that some of the optimizations that make DES run
much faster on conventional architectures have no
effect on the performance of the Connection Machine.
Our comparison of a simple implementation along with
one that uses many optimizations illustrates this
fact.",
}
@TechReport{Dartmouth:TR92-183,
author = "Peter Su",
title = "{Concurrent Local Search for Fast Proximity Algorithms
on Parallel and Vector Architectures}",
institution = "Dartmouth College, Computer Science",
address = "Hanover, NH",
number = "PCS-TR92-183",
year = "1992",
abstract = "This paper presents a fast algorithm for solving the
all-nearest-neighbors problem. The algorithm uses a
data parallel style of programming which can be
efficiently utilized on a variety of parallel and
vector architectures [4,21,26]. I have implemented the
algorithm in C on one such architecture, the Cray Y-MP.
On one Cray CPU, the implementation is about 19 times
faster than a fast sequential algorithm running on a
Sparc workstation. The main idea in the algorithm is to
divide the plane up into a fixed grid of cells, or
buckets. When the points are well distributed, the
algorithm processes each query point, q, by searching a
small number of cells close to q. Bentley, WEide and
Yao first presented this idea for conventional
architectures [3], but the technique works equally well
on parallel and vector machines, leading to a simple,
efficient algorithm. We can also use the cell technique
to solve a wide variety of basic computational problems
such as finding closest pairs, sorting and constructing
Voronoi diagrams and Delaunay triangulations.",
}
@TechReport{Dartmouth:TR92-184,
author = "Peter Su and Robert L. Scot Drysdale",
title = "{Building Segment Trees in Parallel}",
institution = "Dartmouth College, Computer Science",
address = "Hanover, NH",
number = "PCS-TR92-184",
year = "1992",
abstract = "The segment tree is a simple and important data
structure in computational geometry [7,11]. We present
an experimental study of parallel algorithms for
building segment trees. We analyze the algorithms in
the context of both the PRAM (Parallel Random Access
Machine) and hypercube architectures. In addition, we
present performance data for implementations developed
on the Connection Machine. We compare two different
parallel alforitms, and we also compare our parallel
algorithms to a good sequential algorithm for doing the
same job. In this way, we evaluate the overall
efficiency of our parallel methods. Our performance
results illustrates the problems involved in using
popular machine models(PRAM) and analysis techniques
(asymptotic efficiency) to predict the performance of
parallel algorithms on real machines. We present two
different analyses of our algorithms and show that
neither is effective in predicting the actual
performance numbers that we obtained.",
}
@TechReport{Dartmouth:TR92-185,
author = "Peter Su",
title = "{Algorithms for Closest Point Problems: Practice and
Theory}",
institution = "Dartmouth College, Computer Science",
address = "Hanover, NH",
number = "PCS-TR92-185",
year = "1992",
abstract = "This paper describes and evaluates know sequential
algorithms for constructing planar Voronoi diagrams and
Delaunay triangulations. In addition, it describes a
new incremental algorithm which is simple to understand
and implement, but whose performance is competitive
with all known methods. The experiments in this paper
are more than just simple benchmarks, they evaluate the
expected performance of the algorithms in a precise and
machine independent fashion. Thus, the paper also
illustrates how to use experimental tools to both
understand the behaviour of different algorithms and to
guide the algorithm design process.",
}
@TechReport{Dartmouth:TR92-186,
author = "Deb Banerjee",
title = "{Formal Implementation of High-Level Languages for
Data-Parallel Programming}",
institution = "Dartmouth College, Computer Science",
address = "Hanover, NH",
number = "PCS-TR92-186",
year = "1992",
abstract = "The success of parallel architectures has been limited
by the lack of high-level parallel programming
languages and useful programming models. The
data-parallel model of programming has been
demonstrated to be useful and natural on a wide variet
of parallel architectures. This dissertation presents a
set of formal techniques for compiling high- level
languages based on data-parallelism.",
}
@TechReport{Dartmouth:TR93-187,
author = "James Matthews and Peter A. Gloor and Fillia Makedon",
title = "{VideoScheme: A Programmable Video Editing System for
Automation and Media Recognition}",
institution = "Dartmouth College, Computer Science",
address = "Hanover, NH",
number = "PCS-TR93-187",
year = "1993",
abstract = "The recent development of powerful, inexpensive
hardware and software support had made digital video
editing possible on personal computers and
workstations. To date the video editing application
category has been dominated by visual, easy-to-use,
direct manipulation interfaces. These systems bring
high-bandwidth human-computer interaction to a task
formerly characterized by slow, inflexible,
indirectly-operated machines. However, the direct
manipulation computer interfaces are limited by their
manual nature, and can not easily accommodate
algorithmically- defined operations. This paper
proposes a melding of the common direct manipulation
interfaces with a programming language which we have
enhanced to manipulate digital audio and video. The
result is a system which can automate routine tasks as
well as perform tasks based on sophisticated media
recognition algorithms.",
}
@TechReport{Dartmouth:TR93-188,
author = "Thomas H. Cormen and David Kotz",
title = "{Integrating Theory and Practice in Parallel File
Systems}",
institution = "Dartmouth College, Computer Science",
address = "Hanover, NH",
number = "PCS-TR93-188",
year = "1993",
URL = "http://www.cs.dartmouth.edu/reports/TR93-188-update.ps.Z",
comment = "The original 1993 tech report was superceded by the
conference version. The paper has since been
revised, re-issued on 9/20/94 as an updated technical
report.",
abstract = "Several algorithms for parallel disk systems have
appeared in the literature recently, and they are
asymptotically optimal in terms of the number of disk
accesses. Scalable systems with parallel disks must be
able to run these algorithms. We present a list of
capabilities that must be provided by the system to
support these optimal algorithms: control over
declustering, querying about the configuration,
independent I/O, turning off file caching and
prefetching, and bypassing parity. We summarize recent
theoretical and empirical work that justifies the need
for these capabilities.",
}
@TechReport{Dartmouth:TR93-189,
author = "J. Diaz and A. Gibbons and Grammati E. Pantziou and M.
Serna and Paul G. Spirakis and J. Toran",
title = "{Efficient Parallel Algorithms for some Tree Layout
Problems}",
institution = "Dartmouth College, Computer Science",
address = "Hanover, NH",
number = "PCS-TR93-189",
year = "1993",
abstract = "The minimum cut and minimum length linear arrangement
problems usually occur in solving wiring problems and
have a lot in common with job sequencing questions.
Both problems are NP-complete for general graphs and in
P for trees. We present here two algorithms in NC. The
first solves the minimum length linear arrangement
problem for unrooted trees in $O(\log^2 n)$ time and
$O(n^2 3^{\log n})$ CREW PRAM processors. The second
algorithm solves the minimum cut arrangement for
unrooted trees of maximum degree $d$ in $O(d \log^2 n)$
time and $O(n^2 /\log n)$ CREW PRAM processors.",
}
@TechReport{Dartmouth:TR93-190,
author = "David Kotz",
title = "{Throughput of Existing Multiprocessor File Systems
(An Informal Study)}",
institution = "Dartmouth College, Computer Science",
address = "Hanover, NH",
number = "PCS-TR93-190",
year = "1993",
URL = "http://www.cs.dartmouth.edu/reports/TR93-190.ps.Z",
abstract = "Fast file systems are critical for high-performance
scientific computing, since many scientific
applications have tremendous I/O requirements. Many
parallel supercomputers have only recently obtained
fully parallel I/O architectures and file systems,
which are necessary for scalable I/O performance.
Scalability aside, I show here that many systems lack
sufficient absolute performance. I do this by surveying
the performance reported in the literature, summarized
in an informal table.",
}
@TechReport{Dartmouth:TR93-191,
author = "Jerome L. Quinn",
title = "{Accurate Verification of Five-Axis Numerically
Controlled Machining}",
institution = "Dartmouth College, Computer Science",
address = "Hanover, NH",
number = "PCS-TR93-191",
year = "1993",
}
@TechReport{Dartmouth:TR93-192,
author = "Berrin A. Yanikoglu and Peter A. Sandon",
title = "{Off-line Cursive Handwriting Recognition Using Style
Parameters}",
institution = "Dartmouth College, Computer Science",
address = "Hanover, NH",
number = "PCS-TR93-192",
year = "1993",
URL = "http://www.cs.dartmouth.edu/reports/TR93-192.ps.Z",
abstract = "(No abstract available).",
}
@TechReport{Dartmouth:TR93-193,
author = "Thomas H. Cormen and Leonard F. Wisniewski",
title = "{Asymptotically Tight Bounds for Performing BMMC
Permutations on Parallel Disk Systems}",
institution = "Dartmouth College, Computer Science",
address = "Hanover, NH",
number = "PCS-TR93-193",
year = "1993",
comment = "This TR is superceded by TR94-223.",
}
@TechReport{Dartmouth:TR93-194,
author = "Thomas H. Cormen",
title = "{Vector Layout in Virtual-Memory Systems for
Data-Parallel Computing}",
institution = "Dartmouth College, Computer Science",
address = "Hanover, NH",
number = "PCS-TR93-194",
year = "1993",
}
@TechReport{Dartmouth:TR93-196,
author = "Tim Olson and Joe Destefano",
title = "{Wavelet Localization of the Radon Transform}",
institution = "Dartmouth College, Computer Science",
address = "Hanover, NH",
number = "PCS-TR93-196",
year = "1993",
}
@TechReport{Dartmouth:TR93-198,
author = "David Kotz and Preston Crow",
title = "{The Expected Lifetime of "Single-Address-Space"
Operating Systems}",
institution = "Dartmouth College, Computer Science",
address = "Hanover, NH",
number = "PCS-TR93-198",
year = "1993",
URL = "http://www.cs.dartmouth.edu/reports/TR93-198.ps.Z",
comment = "The on-line version is a revision of March 15, 1996.
An earlier revised version appeared in SIGMETRICS '94.
The original technical report is not available
on-line.",
abstract = "Trends toward shared-memory programming paradigms,
large (64-bit) address spaces, and memory-mapped files
have led some to propose the use of a single
virtual-address space, shared by all processes and
processors. Typical proposals require the single
address space to contain all process-private data,
shared data, and stored files. To simplify management
of an address space where stale pointers make it
difficult to re-use addresses, some have claimed that a
64-bit address space is sufficiently large that there
is no need to ever re-use addresses. Unfortunately,
there has been no data to either support or refute
these claims, or to aid in the design of appropriate
address-space management policies. In this paper, we
present the results of extensive kernel-level tracing
of the workstations in our department, and discuss the
implications for single-address-space operating
systems. We found that single-address-space systems
will not outgrow the available address space, but only
if reasonable space-allocation policies are used, and
only if the system can adapt as larger address spaces
become available.",
}
@TechReport{Dartmouth:TR93-200,
author = "Hristo N. Djidjev and Grammati E. Pantziou and
Christos D. Zaroliagis",
title = "{On-Line and Dynamic Shortest Paths Through Graph
Decompositions}",
institution = "Dartmouth College, Computer Science",
address = "Hanover, NH",
number = "PCS-TR93-200",
year = "1993",
abstract = "We describe algorithms for finding shortest paths and
distances in a planar digraph which exploit the
particular topology of the input graph. An important
feature of our algorithms is that they can work in a
dynamic environment, where the cost of any edge can be
changed or the edge can be deleted. For outerplanar
digraphs, for instance, the data structures can be
updated after any such change in only $O(\log n)$ time,
where $n$ is the number of vertices of the digraph. We
also describe the first parallel algorithms for solving
the dynamic version of the shortest path problem. Our
results can be extended to hold for digraphs of genus
$o(n)$.",
}
@TechReport{Dartmouth:TR93-201,
author = "Grammati E. Pantziou and Paul G. Spirakis and Christos
D. Zaroliagis",
title = "{Parallel Max Cut Approximations}",
institution = "Dartmouth College, Computer Science",
address = "Hanover, NH",
number = "PCS-TR93-201",
year = "1993",
abstract = "Given a graph with positive integer edge weights one
may ask whether there exists an edge cut whose weight
is bigger than a given number. This problem is
NP-complete. We present here an approximation algorithm
in NC which provides tight upper bounds to the
proportion of edge cuts whose size is bigger than a
given number. Our technique is based on the methods to
convert randomized parallel algorithms into
deterministic ones introduced by Karp and Wigderson.
The basic idea of those methods is to replace an
exponentially large sample space by one of polynomial
size. In this work, we prove the interesting result
that the statistical distance of random variables of
the small sample space is bigger than the statistical
distance of corresponding variables of the
exponentially large space, which is the space of all
edge cuts taken equiprobably.",
}
@TechReport{Dartmouth:TR93-202,
author = "Panagiotis Metaxas and Grammati E. Pantziou and
Antonios Symvonis",
title = "{Parallel h-v Drawings of Binary Trees}",
institution = "Dartmouth College, Computer Science",
address = "Hanover, NH",
number = "PCS-TR93-202",
year = "1993",
abstract = "In this paper we present a method to obtain optimal
h-v and inclusion drawings in parallel. Based on
parallel tree contraction, our method computes optimal
(with respect to a class of cost functions of the
enclosing rectangle) drawings in $O(\log^2 n)$ parallel
time by using a polynomial number of EREW processors.
The number of processors reduces substantially when we
study minimum area drawings. The method can be extended
to compute optimal inclusion layouts in the case where
each leaf $l$ of the tree is represented by rectangle
$l_x \times l_y$ (the dimensions of which are part of
the input). For polynomial area layouts, our work
places the problem of obtaining optimal size h-v or
inclusion drawings in NC, presenting the first
algorithm with polylogarithmic time complexity. Our
method also yields an NC algorithm for the slicing
floorplanning problem. Whether this problems was in NC
was an open question~\cite{CT90}.",
}
@TechReport{Dartmouth:TR94-204,
author = "Dimitrios Kagaris and Grammati E. Pantziou and Spyros
Tragoudas and Christos D. Zaroliagis",
title = "{Quickest Paths: Faster Algorithms and Dynamization}",
institution = "Dartmouth College, Computer Science",
address = "Hanover, NH",
number = "PCS-TR94-204",
year = "1994",
abstract = "Given a network $N=(V,E,{c},{l})$, where $G=(V,E)$,
$|V|=n$ and $|E|=m$, is a directed graph, ${c}(e) > 0$
is the capacity and ${l}(e) \ge 0$ is the lead time (or
delay) for each edge $e\in E$, the quickest path
problem is to find a path for a given
source--destination pair such that the total lead time
plus the inverse of the minimum edge capacity of the
path is minimal. The problem has applications to fast
data transmissions in communication networks. The best
previous algorithm for the single--pair quickest path
problem runs in time $O(r m+r n \log n)$, where $r$ is
the number of distinct capacities of $N$ \cite{ROS}. In
this paper, we present algorithms for general, sparse
and planar networks that have significantly lower
running times. For general networks, we show that the
time complexity can be reduced to $O(r^{\ast}
m+r^{\ast} n \log n)$, where $r^{\ast}$ is at most the
number of capacities greater than the capacity of the
shortest (with respect to lead time) path in $N$. For
sparse networks, we present an algorithm with time
complexity $O(n \log n + r^{\ast} n + r^{\ast}
\tilde{\gamma} \log \tilde{\gamma})$, where
$\tilde{\gamma}$ is a topological measure of $N$. Since
for sparse networks $\tilde{\gamma}$ ranges from $1$ up
to $\Theta(n)$, this constitutes an improvement over
the previously known bound of $O(r n \log n)$ in all
cases that $\tilde{\gamma}=o(n)$. For planar networks,
the complexity becomes $O(n \log n + n\log^3
\tilde{\gamma}+ r^{\ast} \tilde{\gamma})$. Similar
improvements are obtained for the all--pairs quickest
path problem. We also give the first algorithm for
solving the dynamic quickest path problem.",
}
@TechReport{Dartmouth:TR94-206,
author = "Dimitrios Kavvadias and Grammati E. Pantziou and Paul
G. Spirakis and Christos D. Zaroliagis",
title = "{Efficient Sequential and Parallel Algorithms for the
Negative Cycle Problem}",
institution = "Dartmouth College, Computer Science",
address = "Hanover, NH",
number = "PCS-TR94-206",
year = "1994",
abstract = "We present here an algorithm for detecting (and
outputting, if exists) a negative cycle in an
$n$-vertex planar digraph $G$ with real edge weights.
Its running time ranges from $O(n)$ up to
$O(n^{1.5}\log n)$ as a certain topological measure of
$G$ varies from $1$ up to $\Theta(n)$. Moreover, an
efficient CREW PRAM implementation is given. Our
algorithm applies also to digraphs whose genus $\gamma$
is $o(n)$.",
}
@TechReport{Dartmouth:TR94-207,
author = "Fillia Makedon and Samuel A. Rebelsky and Matthew
Cheyney and Charles B. Owen and Peter A. Gloor",
title = "{Issues and Obstacles with Multimedia Authoring}",
institution = "Dartmouth College, Computer Science",
address = "Hanover, NH",
number = "PCS-TR94-207",
year = "1995",
month = may,
URL = "http://www.cs.dartmouth.edu/reports/TR94-207.ps.Z",
comment = "Invited Presentation, EdMedia '94 Vancouver, Canada.
Also published in the EdMedia'94 conference
proceedings. This Technical Report has occasionally
been listed (accidentally) as TR95-256. TR94-207 is the
correct number.",
abstract = "Unlike traditional authoring, multimedia authoring
involves making hard choices, forecasting technological
evolution and adapting to software and hardware
technology changes. It is, perhaps, an unstable field
of endeavor for an academic to be in. Yet, it is
important that academics are, in fact, part of this
process. This paper discusses some of the common
threads shared by three dissimilar cases of multimedia
authoring which we have experimented with, that of
multimedia conference proceedings, multimedia
courseware development and multimedia information
kiosks. We consider these applications from an academic
point of view and review the benefits and pitfalls of
academic development while sharing points of
hard-learned wisdom. We draw on experiences from some
of the projects run at the Dartmouth Experimental
Visualization Laboratory (DEVlab), where we have been
developing different types of multimedia
applications.",
}
@TechReport{Dartmouth:TR94-208,
author = "M. Cheyney and P. Gloor and D. B. Johnson and F.
Makedon and J. Matthews and P. Metaxas",
title = "{Conference on a Disk: A Successful Experiment in
Hypermedia Publishing (Extended Abstract)}",
institution = "Dartmouth College, Computer Science",
address = "Hanover, NH",
number = "PCS-TR94-208",
year = "1994",
month = mar,
URL = "http://www.cs.dartmouth.edu/reports/TR94-208.pdf",
abstract = "Academic conferences are a long-standing and effective
form of multimedia communication. Conference
participants can transmit and recieve information
through sight, speech, gesture, text, and touch. This
same-time, same-place communication is sufficiently
valuable to justify large investments in time and
travel funds. Printed conference proceedings are
attempts to recapture the value of a life conference,
but they are limited by a fragmented and inefficient
approach to the problem. We addressed this problem in
the multimedia proceedings of the DAGS'92 conference.
The recently published CD-ROM delibers text, graphic,
audio, and video information as an integrated whole,
with extensive provisions for random access and
hypermedia linking. We belive that this project
provides a model for future conference publications and
highlights some of the research issues that must be
resolved before similar publications can be quickly and
inexpensively produced.",
}
@TechReport{Dartmouth:TR94-209,
author = "J. Matthews and F. Makedon and P. Gloor",
title = "{Videoscheme: A Research, Authoring, and Teaching Tool
for Multimedia}",
institution = "Dartmouth College, Computer Science",
address = "Hanover, NH",
number = "PCS-TR94-209",
year = "1994",
month = mar,
URL = "http://www.cs.dartmouth.edu/reports/TR94-209.pdf",
abstract = "The availability of digital multimedia technology
poses new challenges to researchers, authors, and
educators, even as it creates new opportunities for
rich communication. This paper suggests interactive
computer programming as a fruitful approach to these
challenges. VideoScheme, a prototype video programming
environment, is described along with promising
applications.",
}
@TechReport{Dartmouth:TR94-211,
author = "David Kotz and Nils Nieuwejaar",
title = "{Dynamic File-Access Characteristics of a Production
Parallel Scientific Workload}",
institution = "Dartmouth College, Computer Science",
address = "Hanover, NH",
number = "PCS-TR94-211",
year = "1994",
URL = "http://www.cs.dartmouth.edu/reports/TR94-211.ps.Z",
comment = "TR94-230 is related.",
abstract = "Multiprocessors have permitted astounding increases in
computational performance, but many cannot meet the
intense I/O requirements of some scientific
applications. An important component of any solution to
this I/O bottleneck is a parallel file system that can
provide high-bandwidth access to tremendous amounts of
data in parallel to hundreds or thousands of
processors. Most successful systems are based on a
solid understanding of the characteristics of the
expected workload, but until now there have been no
comprehensive workload characterizations of
multiprocessor file systems. We began the CHARISMA
project in an attempt to fill that gap. We instrumented
the common node library on the iPSC/860 at NASA Ames to
record all file-related activity over a two-week
period. Our instrumentation is different from previous
efforts in that it collects information about every
read and write request and about the mix of jobs
running in the machine (rather than from selected
applications). The trace analysis in this paper leads
to many recommendations for designers of multiprocessor
file systems. First, the file system should support
simultaneous access to many different files by many
jobs. Second, it should expect to see many small
requests, predominantly sequential and regular access
patterns (although of a different form than in
uniprocessors), little or no concurrent file-sharing
between jobs, significant byte- and block-sharing
between processes within jobs, and strong interprocess
locality. Third, our trace-driven simulations showed
that these characteristics led to great success in
caching, both at the compute nodes and at the I/O
nodes. Finally, we recommend supporting strided I/O
requests in the file-system interface, to reduce
overhead and allow more performance optimization by the
file system.",
}
@TechReport{Dartmouth:TR94-213,
author = "Perry Fizzano and Clifford Stein and David R. Karger
and Joel Wein",
title = "{Job Scheduling in Rings}",
institution = "Dartmouth College, Computer Science",
address = "Hanover, NH",
number = "PCS-TR94-213",
year = "1994",
URL = "http://www.cs.dartmouth.edu/reports/TR94-213.ps.Z",
abstract = "We give distributed approximation algorithms for job
scheduling in a ring architecture. In contrast to
almost all other parallel scheduling models, the model
we consider captures the influence of the underlying
communications network by specifying that task
migration from one processor to another takes time
proportional to the distance between those two
processors in the network. As a result, our algorithms
must balance both computational load and communication
time. The algorithms are simple, require no global
control, and work in a variety of settings. All come
with small constant-factor approximation guarantees;
the basic algorithm yields schedules of length at most
4.22 times optimal. We also give a lower bound on the
performance of any distributed algorithm some results
for a simple capacitated case, and the results of
simulation experiments, which give better results than
our worst-case analysis.",
}
@TechReport{Dartmouth:TR94-214,
author = "Chris Armen and Clifford Stein",
title = "{A 2-3/4-Approximation Algorithm for the Shortest
Superstring Problem}",
institution = "Dartmouth College, Computer Science",
address = "Hanover, NH",
number = "PCS-TR94-214",
year = "1994",
abstract = "Given a collection of strings S={s_1,...,s_n} over an
alphabet Sigma, a superstring alpha of S is a string
containing each s_i as a substring, that is, for each
i, 1<=i<=n, alpha contains a block of |s_i| consecutive
characters that match s_i exactly. The shortest
superstring problem is the problem of finding a
superstring alpha of minimum length. The shortest
superstring problem has applications in both
computational biology and data compression. The problem
is NP-hard [GallantMS80]; in fact, it was recently
shown to be MAX SNP-hard [BlumJLTY91]. Given the
importance of the applications, several heuristics and
approximation algorithms have been proposed. Constant
factor approximation algorithms have been given in
[BlumJLTY91] (factor of 3), [TengY93] (factor of
2-8/9), [CzumajGPR94] (factor of 2-5/6) and
[KosarajuPS94] (factor of 2-50/63). Informally, the key
to any algorithm for the shortest superstring problem
is to identify sets of strings with large amounts of
similarity, or overlap. While the previous algorithms
and their analyses have grown increasingly
sophisticated, they reveal remarkably little about the
structure of strings with large amounts of overlap. In
this sense, they are solving a more general problem
than the one at hand. In this paper, we study the
structure of strings with large amounts of overlap and
use our understanding to give an algorithm that finds a
superstring whose length is no more than 2-3/4 times
that of the optimal superstring. We prove several
interesting properties about short periodic strings,
allowing us to answer questions of the following form:
given a string with some periodic structure,
characterize all the possible periodic strings that can
have a large amount of overlap with the first string.",
}
@TechReport{Dartmouth:TR94-215,
author = "Matthew T. Dickerson and Robert L. Scot Drysdale and
Scott A. McElfresh and Emo Welzl",
title = "{Fast Greedy Triangulation Algorithms}",
institution = "Dartmouth College, Computer Science",
address = "Hanover, NH",
number = "PCS-TR94-215",
year = "1994",
URL = "http://www.cs.dartmouth.edu/reports/TR94-215.ps.Z",
abstract = "The greedy triangulation of a set $S$ of $n$ points in
the plane is the triangulation obtained by starting
with the empty set and at each step adding the shortest
compatible edge between two of the points, where a
compatible edge is defined to be an edge that crosses
none of the previously added edges. In this paper we
present a simple, practical algorithm that computes the
greedy triangulation in expected time $O(n \log n)$ and
space $O(n)$ for points uniformly distributed over any
convex shape. A variant of this algorithm should be
fast for some other distributions. As part of this
algorithm we give an edge compatiblity test that
requires $O(n)$ time for both tests and updates to the
underlying data structure. We also prove properties
about the expected lengths of edges in greedy and
Delaunay triangulations of uniformly distributed
points.",
}
@TechReport{Dartmouth:TR94-216,
author = "Perry Fizzano and Clifford Stein",
title = "{Scheduling in a Ring with Unit Capacity Links}",
institution = "Dartmouth College, Computer Science",
address = "Hanover, NH",
number = "PCS-TR94-216",
year = "1994",
URL = "http://www.cs.dartmouth.edu/reports/TR94-216.ps.Z",
abstract = "We consider the problem of scheduling unit-sized jobs
on a ring of processors with the objective of
minimizing the completion time of the last job. Unlike
much previous work we place restrictions on the
capacity of the network links connecting processors. We
give a polynomial time centralized algorithm that
produces optimal length schedules. We also give a
simple distributed 2-approximation algorithm.",
}
@TechReport{Dartmouth:TR94-217,
author = "James Gochee",
title = "{SPEDE: A Simple Programming Environment for
Distributed Execution (Users' Manual)}",
institution = "Dartmouth College, Computer Science",
address = "Hanover, NH",
number = "PCS-TR94-217",
year = "1994",
URL = "http://www.cs.dartmouth.edu/reports/TR94-217.ps.Z",
comment = "A Senior Thesis in the Department of Math and Computer
Science, Dartmouth College, 1992. See also Technical
Report PCS-TR94-218 for a technical description of
SPEDE.",
abstract = "Traditional single processor computers are quickly
reaching their full computational potentials. The quest
for faster and faster chips have brought technology to
the point where the laws of physics are hampering
future gains. Significant gains in speed must therefore
come from using multiple processors instead of a single
processor. This technology usually represents itself in
the form of a parallel computer, such as the Connection
Machine Model 5. Recently however, much interest has
been focused on software that organizes single
processor computers to behave like a parallel computer.
This is desirable for sites which have large
installations of workstations, since the cost of new
parallel systems are prohibitive. SPEDE, a Simple
Programming Environment for Distributed Execution, was
designed for this purpose. It allows UNIX based
machines of varying hardware types to be organized and
utilized by a programmer of parallel applications.
SPEDE is a user level system in that it requires no
special privileges to run. Every user keeps a separate
copy of the system so that security issues are covered
by the normal UNIX operating environment. SPEDE is
characterized as a large grained distributed
environment. This means that applications which have a
large processing to I/O ratio will be much more
effective than those with a small ratio. SPEDE allows
users to coordinate the use of many computers through a
straightforward interface. Machines are organized by
classes, which are terms that can be used to label and
group them into more manageable units. For example,
users might want to create a class based on the byte
ordering of machines, or by their location. Users can
then specify more completely which machines they want
to use for a particular session. Sessions are
essentially the interaction between objects in the
SPEDE environment. A user creates an object to perform
a certain task, such as constructing part of a fractal
image. Objects can send and receive messages from other
objects using a simple interface provided with SPEDE.
Objects are machine independent, which means that the
same object can be run simultaneously on different
platforms. This is achieved by translating all messages
into standard network byte ordering. However, if user
data is being passed between objects, it is the user's
responsibility to make sure byte ordering is correct.
The SPEDE system involves several major components.
These components help control and manage object
interactions. Figure 1 shows a running session running
with three machines (each surrounded by an oval
rectangle). There are also three objects running, two
named MandComp and one named Mand. Each object is on a
different machine, although it is possible to have
multiple objects on a single machine. In the figure,
the lines connecting the various entities represent
socket connections. UNIX sockets are the transport
mechanism used in SPEDE, although one could implement a
lower level protocol for more efficient communication.
Sockets can also be a problem because some machines
have strict limits on the number of connections a user
can have open at any given time.",
}
@TechReport{Dartmouth:TR94-218,
author = "James Gochee",
title = "{SPEDE: Simple Programming Environment for Distributed
Execution}",
institution = "Dartmouth College, Computer Science",
address = "Hanover, NH",
number = "PCS-TR94-218",
year = "1994",
URL = "http://www.cs.dartmouth.edu/reports/TR94-218.ps.Z",
comment = "A Senior Thesis in the Department of Math and Computer
Science, Dartmouth College, 1992.
See also Technical
Report PCS-TR94-217 for a user's manual for SPEDE.",
abstract = "One of the main goals for people who use computer
systems, particularly computational scientists, is
speed. In the quest for ways to make applications run
faster, engineers have developed parallel computers,
which use more than one CPU to solve a task. However,
many institutions already posses significant
computational power in networks of workstations.
Through software, it is possible to glue together
clusters of machines to simulate a parallel
environment. SPEDE is one such system, designed to
place the potential of local machines at the fingertips
of the programmer. Through a simple interface, users
design computational objects that can be linked and run
in parallel. The goal of the project is to have a small
portable environment that allows various types of
computer systems to interact. SPEDE requires no
altering of the kernel and does not require system
privileges to use. Using SPEDE, programmers can get
significant speedup for computationally intensive
problems. As an example, a Mandelbrot image generator
was implemented, that attained a five-fold speedup with
eight processors.",
}
@TechReport{Dartmouth:TR94-219,
author = "James R. Driscoll and Dennis M. Healy and Daniel N.
Rockmore",
title = "{Fast Spherical Transforms on Distance Transitive
Graphs}",
institution = "Dartmouth College, Computer Science",
address = "Hanover, NH",
number = "PCS-TR94-219",
year = "1994",
}
@TechReport{Dartmouth:TR94-220,
author = "David Kotz and Song Bac Toh and Sriram Radhakrishnan",
title = "{A Detailed Simulation Model of the HP 97560 Disk
Drive}",
institution = "Dartmouth College, Computer Science",
address = "Hanover, NH",
number = "PCS-TR94-220",
year = "1994",
URL = "http://www.cs.dartmouth.edu/reports/TR94-220.ps.Z",
comment = "The software is
available.",
abstract = "We implemented a detailed model of the HP 97560 disk
drive, to replicate a model devised by Ruemmler and
Wilkes (both of Hewlett-Packard, HP). Our model
simulates one or more disk drives attached to one or
more SCSI buses. The design is broken into three
components: a test driver, the disk model itself, and
the discrete-event simulation support. Thus, the disk
model can be easily extracted and used in other
simulation environments. We validated our model using
traces obtained from HP, using the same {"}demerit{"}
measure as Ruemmler and Wilkes. We obtained a demerit
percentage of 3.9%, indicating that our model was
extremely accurate. This paper describes our
implementation, and is meant for those wishing to use
our model, see our validation, or understand our
code.",
}
@TechReport{Dartmouth:TR94-222,
author = "Dennis M. Healy and Sean S. B. Moore and Daniel N.
Rockmore",
title = "{Efficiency and Stability Issues in the Numerical
Computation of Fourier Transforms and Convolutions on
the 2-Sphere}",
institution = "Dartmouth College, Computer Science",
address = "Hanover, NH",
number = "PCS-TR94-222",
year = "1994",
}
@TechReport{Dartmouth:TR94-223,
author = "Thomas H. Cormen and Thomas Sundquist and Leonard F.
Wisniewski",
title = "{Asymptotically Tight Bounds for Performing BMMC
Permutations on Parallel Disk Systems}",
institution = "Dartmouth College, Computer Science",
address = "Hanover, NH",
number = "PCS-TR94-223",
year = "1994",
URL = "http://www.cs.dartmouth.edu/reports/TR94-223.ps.Z",
abstract = "We give asymptotically equal lower and upper bounds
for the number of parallel I/O operations required to
perform bit-matrix-multiply/complement (BMMC)
permutations on parallel disk systems. In a BMMC
permutation on N records, where N is a power of 2, each
(lg N)-bit source address x maps to a corresponding (lg
N)-bit target address y by the matrix equation y = Ax
XOR c, where matrix multiplication is performed over
GF(2). The characteristic matrix A is (lg N) x (lg N)
and nonsingular over GF(2). Under the Vitter-Shriver
parallel-disk model with N records, D disks, B records
per block, and M records of memory, we show a universal
lower bound of $\Omega \left( \frac{N}{BD} \left( 1 +
\frac{\rank{\gamma}}{\lg (M/B)} \right) \right)$
parallel I/Os for performing a BMMC permutation, where
gamma is the lower left (lg (N/B)) x (lg B) submatrix
of the characteristic matrix. We adapt this lower bound
to show that the algorithm for bit-permute/complement
(BPC) permutations in Cormen93a is asymptotically
optimal. We also present an algorithm that uses at most
$\frac{2N}{BD} \left( 4 \ceil{\frac{\rank{\gamma}}{\lg
(M/B)}} + 4 \right)$ parallel I/Os, which
asymptotically matches the lower bound and improves
upon the BMMC algorithm in Cormen93a. When rank (gamma)
is low, this method is an improvement over the
general-permutation bound of $\Theta \left(
\frac{N}{BD} \frac{\lg (N/B)}{\lg (M/B)} \right)$. We
introduce a new subclass of BMMC permutations, called
memory-load-dispersal (MLD) permutations, which can be
performed in one pass. This subclass, which is used in
the BMMC algorithm, extends the catalog of one-pass
permutations appearing in Cormen93a. Although many BMMC
permutations of practical interest fall into subclasses
that might be explicitly invoked within the source
code, we show how to detect in at most $N/BD +
\ceil{\frac{\lg (N/B) + 1}{D}}$ parallel I/Os whether a
given vector of target addresses specifies a BMMC
permutation. Thus, one can determine efficiently at run
time whether a permutation to be performed is BMMC and
then avoid the general-permutation algorithm and save
parallel I/Os by using our algorithm.",
}
@TechReport{Dartmouth:TR94-224,
author = "Kristin Bruhl",
title = "{BMMC Permutations on a DECmpp 12000/sx 2000}",
institution = "Dartmouth College, Computer Science",
address = "Hanover, NH",
number = "PCS-TR94-224",
year = "1994",
URL = "http://www.cs.dartmouth.edu/reports/TR94-224.ps.Z",
comment = "A Senior Honors Thesis in Computer Science. Advisor:
Thomas Cormen.",
abstract = "Increasingly, modern computing problems, including
many scientific and business applications, require huge
amounts of data to be examined, modified, and stored.
Parallel computers can be used to decrease the time
needed to operate on such large data sets, by allowing
computations to be performed on many pieces of data at
once. For example, on the DECmpp machine used in our
research, there are 2048 processors in the parallel
processor array. The DECmpp can read data into each of
these processors, perform a computation in parallel on
all of it, and write the data out again, theoretically
decreasing the execution time by a factor of 2048 over
the time required by one of its processors. Often, the
computations that occur after the data is in the
processors involve rearranging, or permuting, the data
within the array of parallel processors. Information
moves between processors by means of a network
connecting them. Communication through the network can
be very expensive, especially if there are many
collisions--simultaneous contentions for the same
network resource--between items of data moving from one
processor to another. When a program performs hundreds
or even thousands of these permutations during its
execution, a bottleneck can occur, impeding the overall
performance of the program. Effective algorithms that
decrease the time required to permute the data within a
parallel computer can yield a significant speed
increase in running programs with large data sets.
Cormen has designed algorithms to improve performance
when the data movement is defined by certain classes of
permutations. This thesis will examine the performance
of one of these classes, the
bit-matrix-multiply/complement (BMMC) permutation, when
implemented on the DECmpp. Although Cormen's algorithm
was designed for parallel disk systems, this thesis
adapts it to permutations of data residing in the
memory of the parallel processors. The DECmpp network
follows the model of an Extended Delta Network (EDN).
One characteristic of an EDN is that it has a set of
input and output ports to the network, each of which
can carry only one item of data at a time. If more than
one item needs to travel over a given port, a collision
occurs. The data must access the port serially, which
slows down the entire operation. Cormen's algorithm
reduces these collisions by computing a schedule for
sending the data over the network. For small data sets,
it is not worthwhile to perform the extra operations to
generate such a schedule, because the overhead
associated with computing the schedule outweighs the
time gained by preventing collisions at the network
ports. As the size of the data set increases,
eliminating collisions becomes more and more valuable.
On the DECmpp, when the data permutation involves more
than 128 elements per processor, our algorithm beats
the more naive and obvious method for permuting in the
parallel processor array.",
}
@TechReport{Dartmouth:TR94-225,
author = "Christine McGavran",
title = "{Human Creativity Through Computer Gaming}",
institution = "Dartmouth College, Computer Science",
address = "Hanover, NH",
number = "PCS-TR94-225",
year = "1994",
comment = "A Senior Honors Thesis in Computer Science.",
}
@TechReport{Dartmouth:TR94-226,
author = "David Kotz",
title = "{Disk-directed I/O for MIMD Multiprocessors}",
institution = "Dartmouth College, Computer Science",
address = "Hanover, NH",
number = "PCS-TR94-226",
year = "1994",
URL = "http://www.cs.dartmouth.edu/reports/TR94-226.ps.Z",
comment = "A shorter version of this paper appeared in OSDI,
although this TR has more recent numbers. The OSDI
version is available here. A more
complete journal version is here. The simulator software is
also available..",
abstract = "Many scientific applications that run on today's
multiprocessors are bottlenecked by their file I/O
needs. Even if the multiprocessor is configured with
sufficient I/O hardware, the file-system software often
fails to provide the available bandwidth to the
application. Although libraries and improved
file-system interfaces can make a significant
improvement, we believe that fundamental changes are
needed in the file-server software. We propose a new
technique, disk-directed I/O, that flips the usual
relationship between server and client to allow the
disks (actually, disk servers) to determine the flow of
data for maximum performance. Our simulations show that
tremendous performance gains are possible. Indeed,
disk-directed I/O provided consistent high performance
that was largely independent of data distribution, and
close to the maximum disk bandwidth.",
}
@TechReport{Dartmouth:TR94-227,
author = "Robert Beals and Daniel N. Rockmore and Ki-Seng Tan",
title = "{Deciding Finiteness for Matrix Groups Over Function
Fields}",
institution = "Dartmouth College, Computer Science",
address = "Hanover, NH",
number = "PCS-TR94-227",
year = "1995",
month = jun,
URL = "http://www.cs.dartmouth.edu/reports/TR94-227.pdf",
abstract = "Let S be any finite subset GLn(F(t)) where F is a
field. In this paper we give algorithms to decide if
the group generated by S is finite. In the case of
characteristic zero, slight modifications of earlier
work of Babai, Beals and Rockmore [1] give polynomial
time deterministic algorithms to solve this problem.
The case of positive characteristic turns out to be
more subtle and our algorithms depend on a structure
theorem proved here, generalizing a theorem of Weil. We
also present a fairly detailed analysis of the size of
finite subgroups in this case and give bounds which
depend upon the number of generators. To this end we
also introduce the notion of the diameter of a finitely
generated algebra and derive some upper bounds related
to this quantity. In positive characteristic the
deterministic algorithms we present are exponential. A
randomized algorithm based on ideas of the Meat-Axe is
also given. While not provably efficient, the success
of the Meat-Axe suggests the randomized algorithm will
be useful.",
}
@TechReport{Dartmouth:TR94-229,
author = "David R. Karger and Clifford Stein",
title = "{A New Approach to the Minumum Cut Problem}",
institution = "Dartmouth College, Computer Science",
address = "Hanover, NH",
number = "PCS-TR94-229",
year = "1994",
}
@TechReport{Dartmouth:TR94-230,
author = "Nils Nieuwejaar and David Kotz",
title = "{A Multiprocessor Extension to the Conventional File
System Interface}",
institution = "Dartmouth College, Computer Science",
address = "Hanover, NH",
number = "PCS-TR94-230",
year = "1994",
URL = "http://www.cs.dartmouth.edu/reports/TR94-230.ps.Z",
comment = "A result of the CHARISMA project.
This report has been superceded by report
PCS-TR95-253.",
abstract = "As the I/O needs of parallel scientific applications
increase, file systems for multiprocessors are being
designed to provide applications with parallel access
to multiple disks. Many parallel file systems present
applications with a conventional Unix-like interface
that allows the application to access multiple disks
transparently. By tracing all the activity of a
parallel file system in a production, scientific
computing environment, we show that many applications
exhibit highly regular, but non-consecutive I/O access
patterns. Since the conventional interface does not
provide an efficient method of describing these
patterns, we present an extension which supports
strided and nested-strided I/O requests.",
}
@TechReport{Dartmouth:TR94-231,
author = "Fillia Makedon and James Matthews and Charles B. Owen
and Samuel A. Rebelsky",
title = "{Multimedia authoring, development environments, and
digital video editing.}",
institution = "Dartmouth College, Computer Science",
address = "Hanover, NH",
number = "PCS-TR94-231",
year = "1,",
month = nov,
URL = "http://www.cs.dartmouth.edu/reports/TR94-231.ps.Z",
comment = "Appeared in: Proc. of SPIE Defining the Global
Information Infrastructure: Systems and Services
(Critical Review), Boston, MA, 11/2/94.",
abstract = "Multimedia systems integrate text, audio, video,
graphics, and other media and allow them to be utilized
in a combined and interactive manner. Using this
exciting and rapidly developing technology, multimedia
applications can provide extensive benefits in a
variety of arenas, including research, education,
medicine, and commerce. While there are many commercial
multimedia development packages, the easy and fast
creation of a useful, full-featured multimedia document
is not yet a straightforward task. This paper addresses
issues in the development of multimedia documents,
ranging from user-interface tools that manipulate
multimedia documents to multimedia communication
technologies such as compression, digital video editing
and information retrieval. It outlines the basic steps
in the multimedia authoring process and some of the
requirements that need to be met by multimedia
development environments. It also presents the role of
video, an essential component of multimedia systems and
the role of programming in digital video editing. A
model is described for remote access of distributed
video. The paper concludes with a discussion of future
research directions and new uses of multimedia
documents.",
}
@TechReport{Dartmouth:TR94-232,
author = "David Kotz and Ting Cai",
title = "{Exploring the Use of I/O Nodes for Computation in a
MIMD Multiprocessor}",
institution = "Dartmouth College, Computer Science",
address = "Hanover, NH",
number = "PCS-TR94-232",
year = "1994",
URL = "http://www.cs.dartmouth.edu/reports/TR94-232.ps.Z",
comment = "Revised version appeared in IOPADS '95 at IPPS
'95, pages 78-89.",
abstract = "As parallel systems move into the production
scientific computing world, the emphasis will be on
cost-effective solutions that provide high throughput
for a mix of applications. Cost-effective solutions
demand that a system make effective use of all of its
resources. Many MIMD multiprocessors today, however,
distinguish between ``compute'' and ``I/O'' nodes, the
latter having attached disks and being dedicated to
running the file-system server. This static division of
responsibilities simplifies system management but does
not necessarily lead to the best performance in
workloads that need a different balance of computation
and I/O. Of course, computational processes sharing a
node with a file-system service may receive less CPU
time, network bandwidth, and memory bandwidth than they
would on a computation-only node. In this paper we
examine this issue experimentally. We found that
high-performance I/O does not necessarily require
substantial CPU time, leaving plenty of time for
application computation. There were some complex
file-system requests, however, which left little CPU
time available to the application. (The impact on
network and memory bandwidth still needs to be
determined.) For applications (or users) that cannot
tolerate an occasional interruption, we recommend that
they continue to use only compute nodes. For tolerant
applications needing more cycles than those provided by
the compute nodes, we recommend that they take full
advantage of both compute and I/O nodes for
computation, and that operating systems should make
this possible.",
}
@TechReport{Dartmouth:TR94-233,
author = "Tom Leighton and Fillia Makedon and Spyros Tragoudas",
title = "{Hypergraph Partitioning Algorithms}",
institution = "Dartmouth College, Computer Science",
address = "Hanover, NH",
number = "PCS-TR94-233",
year = "1994",
month = oct # ",",
abstract = "We present the first polynomial time approximation
algorithms for the balanced hypergraph partitioning
problem. The approximations are within polylogarithmic
factors of the optimal solutions. The choice of
algorithm involves a time complexity/approximation
bound tradeoff. We employ a two step methodology. First
we approximate the flux of the input hypergraph. This
involves an approximate solution to a concurrent flow
problem on the hypergraph. In the second step we use
the approximate flux to obtain approximations for the
balanced bipartitioning problem. Our results extend the
approximation algorithms by Leighton-Rao on graphs to
hypergraphs. We also give the first polylogarithmic
times optimal approximation algorithms for multiway
(graph and hypergraph) partitioning problems into
bounded size sets. A better approximation algorithm for
the latter problem is finally presented for the special
case of bounded sets of size at most O(log n) on planar
graphs and hypergraphs, where n is the number of nodes
of the input instance.",
}
@TechReport{Dartmouth:TR94-235,
author = "David Kotz",
title = "{A DAta-Parallel Programming Library for Education
(DAPPLE)}",
institution = "Dartmouth College, Computer Science",
address = "Hanover, NH",
number = "PCS-TR94-235",
year = "1994",
URL = "http://www.cs.dartmouth.edu/reports/TR94-235.ps.Z",
comment = "A revision
of this report appeared in SIGCSE '95.",
abstract = "In the context of our overall goal to bring the
concepts of parallel computing into the undergraduate
curriculum, we set out to find a parallel-programming
language for student use. To make it accessible to
students at all levels, and to be independent of any
particular hardware platform, we chose to design our
own language, based on a data-parallel model and on
C++. The result, DAPPLE, is a C++ class library
designed to provide the illusion of a data-parallel
programming language on conventional hardware and with
conventional compilers. DAPPLE defines Vectors and
Matrices as basic classes, with all the usual C++
operators overloaded to provide elementwise arithmetic.
In addition, DAPPLE provides typical data-parallel
operations like scans, permutations, and reductions.
Finally, DAPPLE provides a parallel if-then-else
statement to restrict the scope of the above operations
to partial vectors or matrices.",
}
@TechReport{Dartmouth:TR94-236,
author = "Perry Fizzano and Clifford Stein",
title = "{Distributed Scheduling in Finite Capacity Networks
}",
institution = "Dartmouth College, Computer Science",
address = "Hanover, NH",
number = "PCS-TR94-236",
year = "1994",
month = nov # ",",
URL = "http://www.cs.dartmouth.edu/reports/TR94-236.ps.Z",
abstract = "We consider the problem of scheduling unit-sized jobs
in a distributed network of processors. Each processor
only knows the number of jobs it and its neighbors
have. We give an analysis of intuitive algorithm and
prove that the algorithm produces schedules that are
within a logarithmic factor of the length of the
optimal schedule given that the optimal schedule is
sufficiently long.",
}
@TechReport{Dartmouth:TR94-238,
author = "Peter Su",
title = "{Efficient Parallel Algorithms for Closest Point
Problems}",
institution = "Dartmouth College, Computer Science",
address = "Hanover, NH",
number = "PCS-TR94-238",
year = "1994",
month = nov,
URL = "http://www.cs.dartmouth.edu/reports/TR94-238.pdf",
comment = "Advisor: Scot Drysdale",
abstract = "This dissertation develops and studies fast algorithms
for solving closest point problems. Algorithms for such
problems have applications in many areas including
statistical classification, crystallography, data
compression, and finite element analysis. In addition
to a comprehensive empirical study of known sequential
methods, I introduce new parallel algorithms for these
problems that are both efficient and practical. I
present a simple and flexible programming model for
designing and analyzing parallel algorithms. Also, I
describe fast parallel algorithms for nearest-neighbor
searching and constructing Voronoi diagrams. Finally, I
demonstrate that my algorithms actually obtain good
performance on a wide variety of machine architectures.
The key algorithmic ideas that I examine are exploiting
spatial locality, and random sampling. Spatial
decomposition provides allows many concurrent threads
to work independently of one another in local areas of
a shared data structure. Random sampling provides a
simple way to adaptively decompose irregular problems,
and to balance workload among many threads. Used
together, these techniques result in effective
algorithms for a wide range of geometric problems. The
key experimental ideas used in my thesis are simulation
and animation. I use algorithm animation to validate
algorithms and gain intuition about their behavior. I
model the expected performance of algorithms using
simulation experiences, and some knowledge as to how
much critical primitive operations will cost on a given
machine. In addition, I do this without the burden of
esoteric computational models that attempt to cover
every possible variable in the design of a computer
system. An iterative process of design, validation, and
simulation delays the actual implementation until as
many details as possible are accounted for. Then,
further experiments are used to turn the
implementations for better performance.",
}
@TechReport{Dartmouth:TR94-239,
author = "Samuel A. Rebelsky and James Ford and Kenneth Harker
and Fillia Makedon and Panagiotis Metaxas and Charles
B. Owen",
title = "{The Design and Development of Interactive Multimedia
Conference Proceedings}",
institution = "Dartmouth College, Computer Science",
address = "Hanover, NH",
number = "PCS-TR94-239",
year = "1994",
}
@TechReport{Dartmouth:TR94-240,
author = "Samuel A. Rebelsky",
title = "{Incremental Equational Programming}",
institution = "Dartmouth College, Computer Science",
address = "Hanover, NH",
number = "PCS-TR94-240",
year = "1994",
}
@TechReport{Dartmouth:TR94-241,
author = "Samuel A. Rebelsky and Fillia Makedon and James
Matthews and Charles B. Owen and Laura Bright and
Kenneth Harker and Nancy Toth and Panagiotis Metaxas",
title = "{Building Multimedia Proceedings: The Roles of Video
in Interactive Electronic Conference Proceedings}",
institution = "Dartmouth College, Computer Science",
address = "Hanover, NH",
number = "PCS-TR94-241",
year = "1994",
}
@TechReport{Dartmouth:TR94-243,
author = "Thomas H. Cormen and Alex Colvin",
title = "{ViC*: A Preprocessor for Virtual-Memory C*}",
institution = "Dartmouth College, Computer Science",
address = "Hanover, NH",
number = "PCS-TR94-243",
year = "1994",
URL = "http://www.cs.dartmouth.edu/reports/TR94-243.ps.Z",
abstract = "This paper describes the functionality of ViC*, a
compiler-like preprocessor for out-of-core C*. The
input to ViC* is a C* program but with certain shapes
declared \verb`outofcore`, which means that all
parallel variables of these shapes reside on disk. The
output is a standard C* program with the appropriate
I/O and library calls added for efficient access to
out-of-core parallel variables.",
}
@TechReport{Dartmouth:TR95-250,
author = "Thomas H. Cormen and Sumit Chawla and Preston Crow and
Melissa Hirschl and Roberto Hoyle and Keith D. Kotay
and Rolf H. Nelson and Nils Nieuwejaar and Scott M.
Silver and Michael B. Taylor and Rajiv Wickremesinghe",
title = "{DartCVL: The Dartmouth C Vector Library}",
institution = "Dartmouth College, Computer Science",
address = "Hanover, NH",
number = "PCS-TR95-250",
year = "1995",
URL = "http://www.cs.dartmouth.edu/reports/TR95-250.ps.Z",
abstract = "As a class project, we implemented a version of CVL,
the C Vector Library, on a DECmpp 12000/Sx 2000, which
is equivalent to the MasPar MP-2 massively parallel
computer. We compare our implementation, DartCVL, to
the University of North Carolina implementation, UnCvl.
DartCVL was designed for the MP-2 architecture and
UnCvl was designed for the MP-1. Because the MasPar
MP-1 and MP-2 are functionally equivalent, both DartCVL
and UnCvl will run on either. Differences in the
designs of the two machines, however, may lead to
different software design decisions. DartCVL differs
from UnCvl in two key ways. First, DartCVL uses
hierarchical virtualization, whereas UnCvl uses
cut-and-stack. Second, DartCVL runs as much serial code
as possible on the console, whereas UnCvl runs all
serial code on the Array Control Unit (ACU). The
console (a DECstation 5000/240 at Dartmouth) has a
significantly faster serial processor than the ACU.
DartCVL is optimized for the MP-2, and our timing
results indicate that it usually runs faster than UnCvl
on the 2048-processor machine at Dartmouth.",
}
@TechReport{Dartmouth:TR95-251,
author = "David Kotz",
title = "{Disk-directed I/O for an Out-of-Core Computation}",
institution = "Dartmouth College, Computer Science",
address = "Hanover, NH",
number = "PCS-TR95-251",
year = "1995",
URL = "http://www.cs.dartmouth.edu/reports/TR95-251.ps.Z",
comment = "A revised
version of this report appeared in HPDC '95.",
abstract = "New file systems are critical to obtain good I/O
performance on large multiprocessors. Several
researchers have suggested the use of collective
file-system operations, in which all processes in an
application cooperate in each I/O request. Others have
suggested that the traditional low-level interface
(read, write, seek) be augmented with various
higher-level requests (e.g., read matrix), allowing the
programmer to express a complex transfer in a single
(perhaps collective) request. Collective, high-level
requests permit techniques like two-phase I/O and
disk-directed I/O to significantly improve performance
over traditional file systems and interfaces. Neither
of these techniques have been tested on anything other
than simple benchmarks that read or write matrices.
Many applications, however, intersperse computation and
I/O to work with data sets that cannot fit in main
memory. In this paper, we present the results of
experiments with an ``out-of-core'' LU-decomposition
program, comparing a traditional interface and file
system with a system that has a high-level, collective
interface and disk-directed I/O. We found that a
collective interface was awkward in some places, and
forced additional synchronization. Nonetheless,
disk-directed I/O was able to obtain much better
performance than the traditional system.",
}
@TechReport{Dartmouth:TR95-252,
author = "Robert S. Gray",
title = "{Content-based image retrieval: color and edges }",
institution = "Dartmouth College, Computer Science",
address = "Hanover, NH",
number = "PCS-TR95-252",
year = "1995",
month = mar,
URL = "http://www.cs.dartmouth.edu/reports/TR95-252.ps.Z",
abstract = "One of the tools that will be essential for future
electronic publishing is a powerful image retrieval
system. The author should be able to search an image
database for images that convey the desired information
or mood; a reader should be able to search a corpus of
published work for images that are relevant to his or
her needs. Most commercial image retrieval systems
associate keywords or text with each image and require
the user to enter a keyword or textual description of
the desired image. This text-based approach has
numerous drawbacks -- associating keywords or text with
each image is a tedious task; some image features may
not be mentioned in the textual description; some
features are ``nearly impossible to describe with
text''; and some features can be described in widely
different ways [Niblack, 1993]. In an effort to
overcome these problems and improve retrieval
performance, researchers have focused more and more on
content-based image retrieval in which retrieval is
accomplished by comparing image features directly
rather than textual descriptions of the image features.
Features that are commonly used in content-based
retrieval include color, shape, texture and edges. In
this report we describe a simple content-based system
that retrieves color images on the basis of their color
distributions and edge characteristics. The system uses
two retrieval techniques that have been described in
the literature -- i.e. histogram intersection to
compare color distributions and sketch comparison to
compare edge characteristics. The performance of the
system is evaluated and various extensions to the
existing techniques are proposed.",
}
@TechReport{Dartmouth:TR95-253,
author = "Nils Nieuwejaar and David Kotz",
title = "{Low-level Interfaces for High-level Parallel I/O}",
institution = "Dartmouth College, Computer Science",
address = "Hanover, NH",
number = "PCS-TR95-253",
year = "1995",
month = mar,
URL = "http://www.cs.dartmouth.edu/reports/TR95-253.ps.Z",
comment = "This TR supercedes PCS-TR94-230. A result of the CHARISMA project.
Appeared in IOPADS
'95 at IPPS '95.",
abstract = "As the I/O needs of parallel scientific applications
increase, file systems for multiprocessors are being
designed to provide applications with parallel access
to multiple disks. Many parallel file systems present
applications with a conventional Unix-like interface
that allows the application to access multiple disks
transparently. By tracing all the activity of a
parallel file system in a production, scientific
computing environment, we show that many applications
exhibit highly regular, but non-consecutive I/O access
patterns. Since the conventional interface does not
provide an efficient method of describing these
patterns, we present three extensions to the interface
that support strided, nested-strided, and
nested-batched I/O requests. We show how these
extensions can be used to express common access
patterns.",
}
@TechReport{Dartmouth:TR95-254,
author = "David Kotz",
title = "{Expanding the Potential for Disk-Directed I/O}",
institution = "Dartmouth College, Computer Science",
address = "Hanover, NH",
number = "PCS-TR95-254",
year = "1995",
month = mar,
URL = "http://www.cs.dartmouth.edu/reports/TR95-254.ps.Z",
comment = "Revised version
appeared in SPDP'95.",
abstract = "As parallel computers are increasingly used to run
scientific applications with large data sets, and as
processor speeds continue to increase, it becomes more
important to provide fast, effective parallel file
systems for data storage and for temporary files. In an
earlier work we demonstrated that a technique we call
disk-directed I/O has the potential to provide
consistent high performance for large, collective,
structured I/O requests. In this paper we expand on
this potential by demonstrating the ability of a
disk-directed I/O system to read irregular subsets of
data from a file, and to filter and distribute incoming
data according to data-dependent functions.",
}
@TechReport{Dartmouth:TR95-256,
author = "Fillia Makedon and Samuel A. Rebelsky and Matthew
Cheyney and Charles B. Owen and Peter A. Gloor",
title = "{Issues and Obstacles with Multimedia Authoring
(renumbered)}",
institution = "Dartmouth College, Computer Science",
address = "Hanover, NH",
number = "PCS-TR95-256",
year = "1995",
month = may,
comment = "This Technical Report report has occasionally been
cited (incorrectly) as TR95-256. TR94-207 is the
correct number. On the web, see TR94-207.",
}
@TechReport{Dartmouth:TR95-258,
author = "Kenneth Harker",
title = "{TIAS: A Transportable Intelligent Agent System}",
institution = "Dartmouth College, Computer Science",
address = "Hanover, NH",
number = "PCS-TR95-258",
year = "1995",
month = jun,
URL = "http://www.cs.dartmouth.edu/reports/TR95-258.ps.Z",
comment = "A Senior Honors Thesis in Computer Science.",
abstract = "In recent years, there has been an explosive growth in
the amount of information available to our society. In
particular, the amount of information available on-line
through vast networks like the global Internet has been
growing at a staggering rate. This growth rate has by
far exceeded the rate of growth in network speeds, as
has the number of individuals and organizations seeking
access to this information. There is thus a motivation
to find abstract methods of manipulating this on-line
data in ways that both serve the needs of end users
efficiently and use network resources intelligently. In
lieu of a traditional client-server model of
information processing, which is both inflexible and
potentially very inefficient, a Transportable
Intelligent Agent system has the potential to achieve a
more efficient and flexible network system. An
intelligent agent is a program that models the
information space for a user, and allows the user to
specify how the information is to be processed. A
transportable agent can suspend its execution,
transport itself to a new location on a network, and
resume execution at the new location. This is a
particularly attractive model for both wireless and
dialup networks where a user might not be able to
maintain a permanent network connection, as well as for
situations where the amount of information to be
processed is large relative to the network bandwidth.
Preliminary work in the field has shown that such agent
systems are possible and deserve further study. This
thesis describes a prototype transportable intelligent
agent system that extends work already done in the
field. Agents are written in a modified version of the
Tcl programming language and transported using TCP/IP
connections. Several simple examples demonstrate the
properties of the system.",
}
@TechReport{Dartmouth:TR95-259,
author = "Scott R. Cushman",
title = "{A Multiple Discrete Pass Algorithm on a DEC Alpha
2100}",
institution = "Dartmouth College, Computer Science",
address = "Hanover, NH",
number = "PCS-TR95-259",
year = "1995",
month = jun,
URL = "http://www.cs.dartmouth.edu/reports/TR95-259.ps.Z",
comment = "Senior Honors Thesis. No abstract. This thesis
presents the results of an I/O-intensive algorithm on a
DEC Alpha 2100 with an eight-disk array.",
}
@TechReport{Dartmouth:TR95-260,
author = "Song Bac Toh",
title = "{Simulation of a Video-on-Demand System}",
institution = "Dartmouth College, Computer Science",
address = "Hanover, NH",
number = "PCS-TR95-260",
year = "1995",
month = jun,
URL = "http://www.cs.dartmouth.edu/reports/TR95-260.ps.Z",
comment = "A Senior Honors Thesis in Computer Science.",
abstract = "This paper presents a simulation study of a
video-on-demand system. The focus of the study is the
effectiveness of different caching strategies on a
video-on-demand system with two levels of cache, RAM
and disks, in front of a tape library. Using an
event-driven simulator, I show that caching was helpful
in increasing the service capacity of the system.
On-demand caching showed its advantages especially when
the requests were clustered around a few popular titles
(in other words, there was temporal locality).",
}
@TechReport{Dartmouth:TR95-261,
author = "Robert S. Gray",
title = "{Ph.D. Thesis Proprosal: Transportable Agents}",
institution = "Dartmouth College, Computer Science",
address = "Hanover, NH",
number = "PCS-TR95-261",
year = "1995",
month = may,
URL = "http://www.cs.dartmouth.edu/reports/TR95-261.ps.Z",
abstract = "One of the paradigms that has been suggested for
allowing efficient access to remote resources is
transportable agents. A transportable agent is a named
program that can migrate from machine to machine in a
heterogeneous network. The program chooses when and
where to migrate. It can suspend its execution at an
arbitrary point, transport to another machine and
resume execution on the new machine. Transportable
agents have several advantages over the traditional
client/server model. Transportable agents consume less
network bandwidth and do not require a connection
between communicating machines -- this is attractive in
all networks and particularly attractive in wireless
networks. Transportable agents are a convenient
paradigm for distributed computing since they hide the
communication channels but not the location of the
computation. Transportable agents allow clients and
servers to program each other. However transportable
agents pose numerous challenges such as security,
privacy and efficiency. Existing transportable agent
systems do not meet all of these challenges. In
addition there has been no formal characterization of
the performance of transportable agents. This thesis
addresses these weakness. The thesis has two parts --
(1) formally characterize the performance of
transportable agents through mathematical analysis and
network simulation and (2) implement a complete
transportable agent system.",
}
@TechReport{Dartmouth:TR95-262,
author = "Chris Armen and Clifford Stein",
title = "{A 2-2/3 Approximation for the Shortest Superstring
Problem}",
institution = "Dartmouth College, Computer Science",
address = "Hanover, NH",
number = "PCS-TR95-262",
year = "1995",
month = jun,
URL = "http://www.cs.dartmouth.edu/reports/TR95-262.ps.Z",
abstract = "Given a collection of strings S={s_1, ..., s_n} over
an alphabet \Sigma, a superstring \alpha of S is a
string containing each s_i as a substring; that is, for
each i, 1<=i<=n, \alpha contains a block of |s_i|
consecutive characters that match s_i exactly. The
shortest superstring problem is the problem of finding
a superstring \alpha of minimum length. The shortest
superstring problem has applications in both data
compression and computational biology. In data
compression, the problem is a part of a general model
of string compression proposed by Gallant, Maier and
Storer (JCSS '80). Much of the recent interest in the
problem is due to its application to DNA sequence
assembly. The problem has been shown to be NP-hard; in
fact, it was shown by Blum et al.(JACM '94) to be MAX
SNP-hard. The first O(1)-approximation was also due to
Blum et al., who gave an algorithm that always returns
a superstring no more than 3 times the length of an
optimal solution. Several researchers have published
results that improve on the approximation ratio; of
these, the best previous result is our algorithm
ShortString, which achieves a 2 3/4-approximation (WADS
'95). We present our new algorithm, G-ShortString,
which achieves a ratio of 2 2/3. It generalizes the
ShortString algorithm, but the analysis differs
substantially from that of ShortString. Our previous
work identified classes of strings that have a nested
periodic structure, and which must be present in the
worst case for our algorithms. We introduced machinery
to descibe these strings and proved strong structural
properties about them. In this paper we extend this
study to strings that exhibit a more relaxed form of
the same structure, and we use this understanding to
obtain our improved result.",
}
@TechReport{Dartmouth:TR95-263,
author = "Nils Nieuwejaar and David Kotz and Apratim
Purakayastha and Carla Schlatter Ellis and Michael
Best",
title = "{File-Access Characteristics of Parallel Scientific
Workloads}",
institution = "Dartmouth College, Computer Science",
address = "Hanover, NH",
number = "PCS-TR95-263",
year = "1995",
month = aug,
URL = "http://www.cs.dartmouth.edu/reports/TR95-263.ps.Z",
comment = "See also the related papers from Supercomputing
'94, IEEE
Parallel and Distributed Technology, and IPPS '95",
abstract = "Phenomenal improvements in the computational
performance of multiprocessors have not been matched by
comparable gains in I/O system performance. This
imbalance has resulted in I/O becoming a significant
bottleneck for many scientific applications. One key to
overcoming this bottleneck is improving the performance
of parallel file systems. The design of a
high-performance parallel file system requires a
comprehensive understanding of the expected workload.
Unfortunately, until recently, no general workload
studies of parallel file systems have been conducted.
The goal of the CHARISMA project was to remedy this
problem by characterizing the behavior of several
production workloads, on different machines, at the
level of individual reads and writes. The first set of
results from the CHARISMA project describe the
workloads observed on an Intel iPSC/860 and a Thinking
Machines CM-5. This paper is intended to compare and
contrast these two workloads for an understanding of
their essential similarities and differences, isolating
common trends and platform-dependent variances. Using
this comparison, we are able to gain more insight into
the general principles that should guide parallel
file-system design.",
}
@TechReport{Dartmouth:TR95-264,
author = "Matt Bishop and Mark Valence and Leonard F.
Wisniewski",
title = "{Process Migration for Heterogeneous Distributed
Systems}",
institution = "Dartmouth College, Computer Science",
address = "Hanover, NH",
number = "PCS-TR95-264",
year = "1995",
month = aug,
URL = "http://www.cs.dartmouth.edu/reports/TR95-264.ps.Z",
abstract = "The policies and mechanisms for migrating processes in
a distributed system become more complicated in a
heterogeneous environment, where the hosts may differ
in their architecture and operating systems. These
distributed systems include a large quantity and great
diversity of resources which may not be fully utilized
without the means to migrate processes to the idle
resources. In this paper, we present a graph model for
single process migration which can be used for load
balancing as well as other non-traditional scenarios
such as migration during the graceful degradation of a
host. The graph model provides the basis for a layered
approach to implementing the mechanisms for process
migration in a Heterogeneous Migration Facility (HMF).
HMF provides the user with a library to automatically
migrate processes and checkpoint data.",
}
@TechReport{Dartmouth:TR95-265,
author = "Leonard F. Wisniewski",
title = "{Structured Permuting in Place on Parallel Disk
Systems}",
institution = "Dartmouth College, Computer Science",
address = "Hanover, NH",
number = "PCS-TR95-265",
year = "1995",
month = sep,
URL = "http://www.cs.dartmouth.edu/reports/TR95-265.ps.Z",
abstract = "The ability to perform permutations of large data sets
in place reduces the amount of necessary available disk
storage. The simplest way to perform a permutation
often is to read the records of a data set from a
source portion of data storage, permute them in memory,
and write them to a separate target portion of the same
size. It can be quite expensive, however, to provide
disk storage that is twice the size of very large data
sets. Permuting in place reduces the expense by using
only a small amount of extra disk storage beyond the
size of the data set. This paper features in-place
algorithms for commonly used structured permutations.
We have developed an asymptotically optimal algorithm
for performing BMMC (bit-matrix-multiply/complement)
permutations in place that requires at most
$\frac{2N}{BD}\left( 2\ceil{\frac{\rank{\gamma}}{\lg
(M/B)}} + \frac{7}{2}\right)$ parallel disk accesses,
as long as $M \geq 2BD$, where $N$ is the number of
records in the data set, $M$ is the number of records
that can fit in memory, $D$ is the number of disks, $B$
is the number of records in a block, and $\gamma$ is
the lower left $\lg (N/B) \times \lg B$ submatrix of
the characteristic matrix for the permutation. This
algorithm uses $N+M$ records of disk storage and
requires only a constant factor more parallel disk
accesses and insignificant additional computation than
a previously published asymptotically optimal algorithm
that uses $2N$ records of disk storage. We also give
algorithms to perform mesh and torus permutations on a
$d$-dimensional mesh. The in-place algorithm for mesh
permutations requires at most $3\ceil{N/BD}$ parallel
I/Os and the in-place algorithm for torus permutations
uses at most $4dN/BD$ parallel I/Os. The algorithms for
mesh and torus permutations require no extra disk space
as long as the memory size~$M$ is at least~$3BD$. The
torus algorithm improves upon the previous best
algorithm in terms of both time and space.",
}
@TechReport{Dartmouth:TR95-266,
author = "Sean S. B. Moore and Leonard F. Wisniewski",
title = "{Complexity Analysis of Two Permutations Used by Fast
Cosine Transform Algorithms }",
institution = "Dartmouth College, Computer Science",
address = "Hanover, NH",
number = "PCS-TR95-266",
year = "1995",
month = oct,
URL = "http://www.cs.dartmouth.edu/reports/TR95-266.ps.Z",
abstract = "Recently developed fast cosine transform (FCT)
algorithms require fewer operations than any other
known general algorithm. Similar to related fast
transform algorithms (e.g., the FFT), these algorithms
permute the data before, during, or after the
computation of the transform. The choice of this
permutation may be an important consideration in
reducing the complexity of the permutation algorithm.
In this paper, we derive the complexity to generate the
permutation mappings used in these FCT algorithms for
power-of-2 data sets by representing them as linear
index transformations and translating them into
combinational circuits. Moreover, we show that one of
these permutations not only allows efficient
implementation, but is also self-invertible, i.e., we
can use the same circuit to generate the permutation
mapping for both the fast cosine transform and its
inverse, like the bit-reversal permutation used by FFT
algorithms. These results may be useful to designers of
low-level algorithms for implementing fast cosine
transforms.",
}
@TechReport{Dartmouth:TR95-267,
author = "Elizabeth A. M. Shriver and Leonard F. Wisniewski",
title = "{An API for Choreographing Data Accesses }",
institution = "Dartmouth College, Computer Science",
address = "Hanover, NH",
number = "PCS-TR95-267",
year = "1995",
month = nov,
URL = "http://www.cs.dartmouth.edu/reports/TR95-267.ps.Z",
comment = "Also published as Courant Institute Tech Report 708.",
abstract = "Current APIs for multiprocessor multi-disk file
systems are not easy to use in developing out-of-core
algorithms that choreograph parallel data accesses.
Consequently, the efficiency of these algorithms is
hard to achieve in practice. We address this deficiency
by specifying an API that includes data-access
primitives for data choreography. With our API, the
programmer can easily access specific blocks from each
disk in a single operation, thereby fully utilizing the
parallelism of the underlying storage system. Our API
supports the development of libraries of commonly-used
higher-level routines such as matrix-matrix addition,
matrix-matrix multiplication, and BMMC
(bit-matrix-multiply/complement) permutations. We
illustrate our API in implementations of these three
high-level routines to demonstrate how easy it is to
use.",
}
@TechReport{Dartmouth:TR95-270,
author = "David Kotz",
title = "{Interfaces for Disk-Directed I/O}",
institution = "Dartmouth College, Computer Science",
address = "Hanover, NH",
number = "PCS-TR95-270",
year = "1995",
month = sep,
URL = "http://www.cs.dartmouth.edu/reports/TR95-270.ps.Z",
abstract = "In other papers I propose the idea of disk-directed
I/O for multiprocessor file systems. Those papers focus
on the performance advantages and capabilities of
disk-directed I/O, but say little about the
application-programmer's interface or about the
interface between the compute processors and I/O
processors. In this short note I discuss the
requirements for these interfaces, and look at many
existing interfaces for parallel file systems. I
conclude that many of the existing interfaces could be
adapted for use in a disk-directed I/O system.",
}
@TechReport{Dartmouth:TR95-271,
author = "Sumit Chawla and Dennis M. Healy",
title = "{A Fast Parallel Implementation of the Wavelet Packet
Best Basis Algorithm on the MP-2 for Real-Time MRI}",
institution = "Dartmouth College, Computer Science",
address = "Hanover, NH",
number = "PCS-TR95-271",
year = "1996",
month = oct,
comment = "See report PCS-TR96-271.",
abstract = "This technical report is equivalent to technical
report PCS-TR96-271, issued in October 1996.",
}
@TechReport{Dartmouth:TR95-272,
author = "Stavros G. Kolliopoulos and Clifford Stein",
title = "{Finding Real-Valued Single-Source Shortest Paths in
o(n^3) Expected Time}",
institution = "Dartmouth College, Computer Science",
address = "Hanover, NH",
number = "PCS-TR95-272",
year = "1995",
month = oct,
abstract = "Given an $n$-vertex directed network $G$ with real
costs on the edges and a designated source vertex $s$,
we give a new algorithm to compute shortest paths from
$s$. Our algorithm is a simple deterministic one with
$O(n^2 \log n)$ expected running time over a large
class of input distributions. The shortest path problem
is an old and fundamental problem with a host of
applications. Our algorithm is the first
strongly-polynomial algorithm in over 35 years to
improve upon some aspect of the running time of the
celebrated Bellman-Ford algorithm for arbitrary
networks, with any type of cost assignments.",
}
@TechReport{Dartmouth:TR95-273,
author = "Saurab Nog and David Kotz",
title = "{A Performance Comparison of TCP/IP and MPI on FDDI,
Fast Ethernet, and Ethernet}",
institution = "Dartmouth College, Computer Science",
address = "Hanover, NH",
number = "PCS-TR95-273",
year = "1996",
month = jan,
URL = "http://www.cs.dartmouth.edu/reports/TR95-273.ps.Z",
abstract = "Communication is a very important factor affecting
distributed applications. Getting a close handle on
network performance (both bandwidth and latency) is
thus crucial to understanding overall application
performance. We benchmarked some of the metrics of
network performance using two sets of experiments,
namely roundtrip and datahose. The tests were designed
to measure a combination of network latency, bandwidth,
and contention. We repeated the tests for two protocols
(TCP/IP and MPI) and three networks (100 Mbit FDDI
(Fiber Distributed Data Interface), 100 Mbit Fast
Ethernet, and 10 Mbit Ethernet). The performance
results provided interesting insights into the
behaviour of these networks under different load
conditions and the software overheads associated with
an MPI implementation (MPICH). This document presents
details about the experiments, their results, and our
analysis of the performance. Revised on 1/8/96 to
emphasize our use of a particular MPI implementation,
MPICH.",
}
@TechReport{Dartmouth:TR96-255,
author = "Daniela Rus and Devika Subramanian",
title = "{Information retrieval, information structure, and
information agents}",
institution = "Dartmouth College, Computer Science",
address = "Hanover, NH",
number = "PCS-TR96-255",
year = "1996",
month = jan,
abstract = "This paper presents a customizable architecture for
software agents that capture and access information in
large, heterogeneous, distributed electronic
repositories. The key idea is to exploit underlying
structure at various levels of granularity to build
high-level indices with task-specific interpretations.
Information agents construct such indices and are
configured as a network of reusable modules called
structure detectors and segmenters. We illustrate our
architecture with the design and implementation of
smart information filters in two contexts: retrieving
stock market data from Internet newsgroups, and
retrieving technical reports from Internet ftp sites.",
}
@TechReport{Dartmouth:TR96-257,
author = "Saurab Nog and Carl J. Beckmann",
title = "{A Queuing Analysis of Bandwidth Allocation Schemes
for Compressed Video}",
institution = "Dartmouth College, Computer Science",
address = "Hanover, NH",
number = "PCS-TR96-257",
year = "1996",
month = mar,
URL = "http://www.cs.dartmouth.edu/reports/TR96-257.ps.Z",
comment = "Revised on 3/25/96 to include discrete event
simulation results.",
abstract = "Video and audio compression techniques allow
continuous media streams to be transmitted at bit rates
that are a function of the delivered quality of
service. Digital networks will be increasingly used for
the transmission of such continuous media streams. This
paper describes an admission control policy in which
the quality of service is negotiated at stream
initiation, and is a function of both the desired
quality of service and the available bandwidth
resources. The advantage of this approach is the
ability to robustly service large numbers of users,
while providing increased quality of service during low
usage periods. Several simple algorithms for
implementing this policy are described and evaluated
using queuing model analysis applied to
video-on-demand. The queuing model results are compared
with simulation results to validate their accuracy.",
}
@TechReport{Dartmouth:TR96-271,
author = "Sumit Chawla and Dennis M. Healy",
title = "{A Fast Parallel Implementation of the Wavelet Packet
Best Basis Algorithm on the MP-2 for Real-Time MRI}",
institution = "Dartmouth College, Computer Science",
address = "Hanover, NH",
number = "PCS-TR96-271",
year = "1996",
month = oct,
URL = "http://www.cs.dartmouth.edu/reports/TR96-271.ps.Z",
abstract = "Adaptive signal representations such as those
determined by best-basis type algorithms have found
extensive application in image processing, although
their use in real-time applications may be limited by
the complexity of the algorithm. In contrast to the
wavelet transform which can be computed in O(n) time,
the full wavelet packet expansion required for the
standard best basis search takes O(n log n) time to
compute. In the parallel world, however, both
transforms take O(log n) to compute when the number of
processors equal the number of data elements, making
the wavelet packet expansion attractive to implement.
This note describes near real-time performance obtained
with a parallel implementation of best basis algorithms
for Wavelet Packet bases. The platform for our
implementation is a DECmpp 12000/Sx 2000, a parallel
machine identical to the MasPar MP-2. The DECmpp is a
single instruction, multiple data (SIMD) system; such
systems support a data parallel programming model, a
model well suited to the task at hand. We have
implemented the 1D and the 2D WPT on this machine and
our results show a significant speedup over the
sequential counterparts. In the 1D case we almost
attain the theoretical speedup, while in the 2D case we
increase execution speed by about two orders of
magnitude. The current implementation of the 1D
transform is limited to signals of length 2048, and the
2D transform is limited to images of size: 32x32,
64x64, and 128x128. We are currently working on
extending our transform to handle signals and images of
larger size.",
}
@TechReport{Dartmouth:TR96-277,
author = "Prasad Jayanti",
title = "{Compositional Reasoning is not possible in
Determining the Solvability of Consensus}",
institution = "Dartmouth College, Computer Science",
address = "Hanover, NH",
number = "PCS-TR96-277",
year = "1996",
month = jan,
abstract = "Consensus, which requires processes with different
input values to eventually agree on one of these
values, is a fundamental problem in fault-tolerant
computing. We study this problem in the context of
asynchronous shared-memory systems. In our model,
shared-memory consists of a sequence of cells and
supports a specific set of operations. Prior research
on consensus focussed on its solvability in
shared-memories supporting specific operations. In this
paper, we investigate the following general question:
Let OP1 and OP2 be any two sets of operations such that
each set includes read and write operations. Suppose
there is no consensus protocol for N processes in a
shared-memory that supports only operations in OP1 and
in a shared-memory that supports only operations in
OP2. Does it follow that there is no consensus protocol
for N processes in a shared-memory that supports all
operations in OP1 and all operations in OP_2? This
question is in the same spirit as the robustness
question, but there are significant differences, both
conceptually and in the models of shared-memory for
which the two questions are studied. For deterministic
types, the robustness question has been known to have a
positive answer, In contrast, we prove that the answer
to the question posed above is negative even if
operations are deterministic.",
}
@TechReport{Dartmouth:TR96-278,
author = "Robert S. Gray and Daniela Rus and David Kotz",
title = "{Transportable Information Agents}",
institution = "Dartmouth College, Computer Science",
address = "Hanover, NH",
number = "PCS-TR96-278",
year = "1996",
month = feb,
URL = "http://www.cs.dartmouth.edu/reports/TR96-278.ps.Z",
comment = "Revised version to appear in AAAI '96 Workshop on
Intelligent Adaptive Agents.",
abstract = "We have designed and implemented autonomous software
agents. Autonomous software agents navigate
independently through a heterogeneous network. They are
capable of sensing the network configuration,
monitoring software conditions, and interacting with
other agents. Autonomous agents are implemented as
transportable programs, e.g., programs that are capable
of suspending execution, moving to a different machine,
and starting from where they left off. We illustrate
the intelligent behavior of autonomous agents in the
context of distributed information-gathering tasks.",
}
@TechReport{Dartmouth:TR96-279,
author = "Robert S. Gray",
title = "{Fast compression of transportable Tcl scripts}",
institution = "Dartmouth College, Computer Science",
address = "Hanover, NH",
number = "PCS-TR96-279",
year = "1996",
month = feb,
URL = "http://www.cs.dartmouth.edu/reports/TR96-279.ps.Z",
abstract = "An information agent is charged with the task of
searching a collection of electronic resources for
information that is relevant to the user's current
needs. These resources are often distributed across a
network and can contain tremendous quantities of data.
One of the paradigms that has been suggested for
allowing efficient access to such resources is
transportable agents -- the agent is sent to the
machine that maintains the information resource; the
agent executes on this remote machine and then returns
its results to the local machine. We have implemented a
transportable agent system that uses the Tool Command
Language (Tcl) as the agent language. Each Tcl script
can suspend its execution at an arbitrary point,
transport itself to another machine and resume
execution on the new machine. The execution state of
the script -- which includes the commands that have not
been executed -- must be transmitted to the new
machine. Although the execution state tends to be
small, there will be a large number of agents moving
across the network in a large-scale system. Thus it is
desirable to compress the execution state as much as
possible. Furthermore any compression scheme must be
fast so that it does not become a bottleneck between
the transportable agent system and the network
routines. In this paper we explore several fast
compression methods.",
}
@TechReport{Dartmouth:TR96-280,
author = "Saurab Nog and Sumit Chawla and David Kotz",
title = "{An RPC Mechanism for Transportable Agents}",
institution = "Dartmouth College, Computer Science",
address = "Hanover, NH",
number = "PCS-TR96-280",
year = "1996",
month = mar,
URL = "http://www.cs.dartmouth.edu/reports/TR96-280.ps.Z",
abstract = "Transportable agents are autonomous programs that
migrate from machine to machine, performing complex
processing at each step to satisfy client requests. As
part of their duties agents often need to communicate
with other agents. We propose to use remote procedure
call (RPC) along with a flexible interface definition
language (IDL), to add structure to inter-agent
communication. The real power of our Agent RPC comes
from a client-server binding mechanism based on
flexible IDL matching and from support for multiple
simultaneous bindings. Our agents are programmed in
Agent Tcl; we describe how the Tcl implementation made
RPC particularly easy to implement. Finally, although
our RPC is designed for Agent Tcl programs, the
concepts would also work for standard Tcl programs.",
}
@TechReport{Dartmouth:TR96-281,
author = "David K. Maslen and Daniel N. Rockmore",
title = "{Generalized FFTS - A Survey of Some Recent Results}",
institution = "Dartmouth College, Computer Science",
address = "Hanover, NH",
number = "PCS-TR96-281",
year = "1996",
month = apr,
URL = "http://www.cs.dartmouth.edu/reports/TR96-281.ps.Z",
comment = "This will appear as part of the Proceedings for the
1994 Workshop in Groups and Computation, DIMACS Series
of the AMS, edited by Larry Finkelstein and William
Kantor.",
abstract = "In this paper we survey some recent work directed
towards generalizing the fast Fourier transform (FFT).
We work primarily from the point of view of group
representation theory. In this setting the classical
FFT can be viewed as a family of efficient algorithms
for computing the Fourier transform of either a
function defined on a finite abelian group, or a
bandlimited function on a compact abelian group. We
discuss generalizations of the FFT to arbitrary finite
groups and compact Lie groups.",
}
@TechReport{Dartmouth:TR96-282,
author = "Daniel N. Rockmore",
title = "{Some Applications of Generalized FFTs}",
institution = "Dartmouth College, Computer Science",
address = "Hanover, NH",
number = "PCS-TR96-282",
year = "1996",
month = jul,
URL = "http://www.cs.dartmouth.edu/reports/TR96-282.pdf",
abstract = "Generalized FFTs are efficient algorithms for
computing a Fourier transform of a function defined on
finite group, or a bandlimited function defined on a
compact group. The development of such algorithms has
been accompanied and motivated by a growing number of
both potential and realized applications. This paper
will attempt to survey some of these applications.
Appendices include some more detailed examples.",
}
@TechReport{Dartmouth:TR96-283,
author = "Ting Cai and Peter A. Gloor and Saurab Nog",
title = "{DartFlow: A Workflow Management System on the Web
using Transportable Agents}",
institution = "Dartmouth College, Computer Science",
address = "Hanover, NH",
number = "PCS-TR96-283",
year = "1996",
month = may,
URL = "http://www.cs.dartmouth.edu/reports/TR96-283.ps.Z",
abstract = "Workflow management systems help streamline business
processes and increase productivity. This paper
describes the design and implementation of the DartFlow
workflow management system. DartFlow uses Web-browser
embedded Java applets as its front end and
transportable agents as the backbone. While Java
applets provide a safe and platform independent GUI,
the use of transportable agents makes DartFlow highly
flexible and scalable. This paper describes the design
and implementation of DartFlow, as well as a workflow
application that exploits DartFlow's agent-based
design.",
}
@TechReport{Dartmouth:TR96-285,
author = "Robert S. Gray and David Kotz and Saurab Nog and
Daniela Rus and George Cybenko",
title = "{Mobile agents for mobile computing}",
institution = "Dartmouth College, Computer Science",
address = "Hanover, NH",
number = "PCS-TR96-285",
year = "1996",
month = may,
URL = "http://www.cs.dartmouth.edu/reports/TR96-285.ps.Z",
abstract = "Mobile agents are programs that can move through a
network under their own control, migrating from host to
host and interacting with other agents and resources on
each. We argue that these mobile, autonomous agents
have the potential to provide a convenient, efficient
and robust programming paradigm for distributed
applications, particularly when partially connected
computers are involved. Partially connected computers
include mobile computers such as laptops and personal
digital assistants as well as modem-connected home
computers, all of which are often disconnected from the
network. In this paper, we describe the design and
implementation of our mobile-agent system, Agent Tcl,
and the specific features that support mobile computers
and disconnected operation. These features include
network-sensing tools and a docking system that allows
an agent to transparently move between mobile
computers, regardless of when the computers connect to
the network.",
}
@TechReport{Dartmouth:TR96-286,
author = "Nils Nieuwejaar and David Kotz",
title = "{The Galley Parallel File System}",
institution = "Dartmouth College, Computer Science",
address = "Hanover, NH",
number = "PCS-TR96-286",
year = "1996",
month = may,
URL = "http://www.cs.dartmouth.edu/reports/TR96-286.ps.Z",
comment = "Revised version appeared in the journal Parallel
Computing. This paper is a combination of two
papers, from ICS
'96 and a IOPADS
'96.",
abstract = "Most current multiprocessor file systems are designed
to use multiple disks in parallel, using the high
aggregate bandwidth to meet the growing I/O
requirements of parallel scientific applications. Many
multiprocessor file systems provide applications with a
conventional Unix-like interface, allowing the
application to access multiple disks transparently.
This interface conceals the parallelism within the file
system, increasing the ease of programmability, but
making it difficult or impossible for sophisticated
programmers and libraries to use knowledge about their
I/O needs to exploit that parallelism. In addition to
providing an insufficient interface, most current
multiprocessor file systems are optimized for a
different workload than they are being asked to
support. We introduce Galley, a new parallel file
system that is intended to efficiently support
realistic scientific multiprocessor workloads. We
discuss Galley's file structure and application
interface, as well as the performance advantages
offered by that interface.",
}
@TechReport{Dartmouth:TR96-287,
author = "Scott M. Silver",
title = "{Implementation and Analysis of Software Based Fault
Isolation}",
institution = "Dartmouth College, Computer Science",
address = "Hanover, NH",
number = "PCS-TR96-287",
year = "1996",
month = jun,
URL = "http://www.cs.dartmouth.edu/reports/TR96-287.ps.Z",
comment = "A Senior Undergraduate Honors Thesis in Computer
Science.",
abstract = "Extensible applications rely upon user-supplied,
untrusted modules to extend their functionality. To
remain reliable, applications must isolate themselves
from user modules. One method places each user module
in a separate address space (process), which uses
hardware virtual memory support to isolate the user
process. Costly inter-process communication, however,
prohibits frequent communication between the
application and the untrusted module. We implemented
and analyzed a software method for isolating an
application from user modules. The technique uses a
single address space. We provide a logical address
space and per-module access to system resources for
each module. Our software technique is a two-step
process. First, we augment a module's code so that it
cannot access any address outside of an assigned range.
Second, we prevent the module from using system calls
to access resources outside of its fault domain. This
method for software isolation has two particular
advantages over processes. First, for frequently
communicating modules, we significantly reduce context
switch time. Thus, we demonstrate near-optimal
inter-module communication using software fault
isolation. Second, our software-based techniques
provide an efficient and expedient solution in
situations where only one address space is available
(e.g., kernel, or a single-address-space operating
system).",
}
@TechReport{Dartmouth:TR96-288,
author = "Joel T. Thomas",
title = "{The Panda Array I/O Library on the Galley Parallel
File System}",
institution = "Dartmouth College, Computer Science",
address = "Hanover, NH",
number = "PCS-TR96-288",
year = "1996",
month = jun,
URL = "http://www.cs.dartmouth.edu/reports/TR96-288.ps.Z",
comment = "A Senior Undergraduate Honors Thesis.",
abstract = "The Panda Array I/O library, created at the University
of Illinois, Urbana-Champaign, was built especially to
address the needs of high-performance scientific
applications. I/O has been one of the most frustrating
bottlenecks to high performance for quite some time,
and the Panda project is an attempt to ameliorate this
problem while still providing the user with a simple,
high-level interface. The Galley File System, with its
hierarchical structure of files and strided requests,
is another attempt at addressing the performance
problem. My project was to redesign the Panda Array
library for use on the Galley file system. This project
involved porting Panda's three main functions: a
checkpoint function for writing a large array
periodically for 'safekeeping,' a restart function that
would allow a checkpointed file to be read back in, and
finally a timestep function that would allow the user
to write a group of large arrays several times in a
sequence. Panda supports several different
distributions in both the compute-node memories and
I/O-node disks. We have found that the Galley File
System provides a good environment on which to build
high-performance libraries, and that the mesh of Panda
and Galley was a successful combination.",
}
@TechReport{Dartmouth:TR96-289,
author = "Denis M. Serenyi",
title = "{Segmenting Workstation Screen Images}",
institution = "Dartmouth College, Computer Science",
address = "Hanover, NH",
number = "PCS-TR96-289",
year = "1996",
month = jun,
URL = "http://www.cs.dartmouth.edu/reports/TR96-289.ps.Z",
comment = "A Senior Undergraduate Honors Thesis in Computer
Science.",
abstract = "None.",
}
@TechReport{Dartmouth:TR96-290,
author = "Y. Joy Ko and Michael B. Taylor",
title = "{MRI On the Fly: Accelerating MRI Imaging Using LDA
Classification with LDB Feature Extraction}",
institution = "Dartmouth College, Computer Science",
address = "Hanover, NH",
number = "PCS-TR96-290",
year = "1996",
month = jun,
URL = "http://www.cs.dartmouth.edu/reports/TR96-290.ps.Z",
comment = "A Senior Undergraduate Honors Thesis in Computer
Science.
Postscript is 10 MB uncompressed!
You
can also retrieve this file in two pieces: A,
B",
abstract = "To improve MRI acquisition time, we explored the uses
of linear discriminant analysis (LDA), and local
discriminant bases (LDB) for the task of classifying
MRI images using a minimal set of signal acquisitions.
Our algorithm has both off-line and on-line components.
The off-line component uses the k-basis algorithm to
partition a set of training images (all from a
particular region of a patient) into classes. For each
class, we find a basis by applying the best basis
algorithm on the images in that class. We keep these
bases to be used by the on-line process. We then apply
LDB to the training set with the class assignments,
determining the best discriminant basis for the set. We
rank the basis coordinates according to discriminating
power, and retain the top M coordinates for the on-line
algorithm. We keep the top M coordinates, which index
the basis functions with the most discriminating
capability, for on-line purposes. Finally, we train LDA
on these transformed coordinates, producing a
classifier for the images. With the off-line
requirements complete, we can take advantage of the
simplicity and speed of the on-line mechanism to
acquire an image in a similar region of the patient. We
need acquire only the M important coordinates of the
image in the discriminant basis to create a ``scout
image.'' This image, which can be acquired quickly
since M is much much smaller than the number of
measurements needed to fill in the values of the 256 by
256 pixels, is then sent through the map furnished by
LDA which in turn assigns a class to the image.
Returning to the list of bases that we kept from the
k-bases algorithm, we find the optimal basis for the
particular class at hand. We then acquire the image
using that optimal basis, omitting the coefficients
with the least truncation error. The complete image can
then be quickly reconstructed using the inverse wavelet
packet transform. The power of our algorithm is that
the on-line task is fast and simple, while the
computational complexity lies mostly in the off-line
task that needs to be done only once for images in a
certain region. In addition, our algorithm only makes
use of the flexibility of MRI hardware, so no
modifications in hardware design are needed.",
}
@TechReport{Dartmouth:TR96-291,
author = "Jonathan A. Moore",
title = "{Object Oriented Scenes for Virtual Light}",
institution = "Dartmouth College, Computer Science",
address = "Hanover, NH",
number = "PCS-TR96-291",
year = "1995",
month = jun,
URL = "http://www.cs.dartmouth.edu/reports/TR96-291.ps.Z",
comment = "A Senior Undergraduate Honors Thesis in Computer
Science.
Please see the TIFF
images.",
abstract = "Ray tracing is one of many way to use a computer to
generate an image. Ray tracers produce images by
simulating light. Eliminating the details that might
distract one from the interesting parts of ray tracing
algorithms was purpose of my thesis project. The
software I have written can be divide into three parts:
the virtual frame buffer, the support classes and the
ray tracing abstract base classes. The virtual frame
buffer class, vfb, provides a simple means of rendering
and studying the final image produced by a graphical
algorithm. The support classes provide an elegant
notation for the equations involved in ray tracing. The
ray tracing base classes and associated classes provide
a object oriented structure for defining the objects
that make up a scene.",
}
@TechReport{Dartmouth:TR96-292,
author = "Dennis M. Healy and Daniel N. Rockmore and Sean S. B.
Moore",
title = "{FFTs for the 2-Sphere-Improvements and Variations}",
institution = "Dartmouth College, Computer Science",
address = "Hanover, NH",
number = "PCS-TR96-292",
year = "1996",
month = jun,
}
@TechReport{Dartmouth:TR96-293,
author = "Thomas H. Cormen and Melissa Hirschl",
title = "{Early Experiences in Evaluating the Parallel Disk
Model with the ViC* Implementation}",
institution = "Dartmouth College, Computer Science",
address = "Hanover, NH",
number = "PCS-TR96-293",
year = "1996",
month = sep,
URL = "http://www.cs.dartmouth.edu/reports/TR96-293.ps.Z",
comment = "Revised version appeared in Parallel Computing 23(4),
June 1997. Original version August 7, 1996; revised
version September 6, 1996.",
abstract = "Although several algorithms have been developed for
the Parallel Disk Model (PDM), few have been
implemented. Consequently, little has been known about
the accuracy of the PDM in measuring I/O time and total
time to perform an out-of-core computation. This paper
analyzes timing results on a uniprocessor with several
disks for two PDM algorithms, out-of-core radix sort
and BMMC permutations, to determine the strengths and
weaknesses of the PDM. The results indicate the
following. First, good PDM algorithms are usually not
I/O bound. Second, of the four PDM parameters, two
(problem size and memory size) are good indicators of
I/O time and running time, but the other two (block
size and number of disks) are not. Third, because PDM
algorithms tend not to be I/O bound, asynchronous I/O
effectively hides I/O times. The software interface to
the PDM is part of the ViC* run-time library. The
interface is a set of wrappers that are designed to be
both efficient and portable across several parallel
file systems and target machines.",
}
@TechReport{Dartmouth:TR96-294,
author = "Thomas H. Cormen and David M. Nicol",
title = "{Performing Out-of-Core FFTs on Parallel Disk
Systems}",
institution = "Dartmouth College, Computer Science",
address = "Hanover, NH",
number = "PCS-TR96-294",
year = "1997",
month = aug,
URL = "http://www.cs.dartmouth.edu/reports/TR96-294.ps.Z",
comment = "Similar paper to appear in Parallel Computing.
Original version August 7, 1996; revised September 6,
1996 and August 14, 1997. (Compressed
Postscript for September 1996 version.)",
abstract = "The Fast Fourier Transform (FFT) plays a key role in
many areas of computational science and engineering.
Although most one-dimensional FFT problems can be
solved entirely in main memory, some important classes
of applications require out-of-core techniques. For
these, use of parallel I/O systems can improve
performance considerably. This paper shows how to
perform one-dimensional FFTs using a parallel disk
system with independent disk accesses. We present both
analytical and experimental results for performing
out-of-core FFTs in two ways: using traditional virtual
memory with demand paging, and using a provably
asymptotically optimal algorithm for the Parallel Disk
Model (PDM) of Vitter and Shriver. When run on a DEC
2100 server with a large memory and eight parallel
disks, the optimal algorithm for the PDM runs up to
144.7 times faster than in-core methods under demand
paging. Moreover, even including I/O costs, the
normalized times for the optimal PDM algorithm are
competitive, or better than, those for in-core methods
even when they run entirely in memory.",
}
@TechReport{Dartmouth:TR96-295,
author = "Clifford Stein and Joel Wein",
title = "{On the Existence of Schedules that are Near-Optimal
for both Makespan and Total Weighted Completion time}",
institution = "Dartmouth College, Computer Science",
address = "Hanover, NH",
number = "PCS-TR96-295",
year = "1996",
month = jul,
URL = "http://www.cs.dartmouth.edu/reports/TR96-295.ps.Z",
abstract = "We give a simple proof that, for any instance of a
very general class of scheduling problems, there exists
a schedule of makespan at most twice that of the
optimal possible and of total weighted completion time
at most twice that of the optimal possible. We then
refine the analysis, yielding variants of this theorem
with improved constants, and give some algorithmic
consequences of the technique.",
}
@TechReport{Dartmouth:TR96-296,
author = "David Kotz",
title = "{Tuning STARFISH}",
institution = "Dartmouth College, Computer Science",
address = "Hanover, NH",
number = "PCS-TR96-296",
year = "1996",
month = oct,
URL = "http://www.cs.dartmouth.edu/reports/TR96-296.ps.Z",
abstract = "STARFISH is a parallel file-system simulator we built
for our research into the concept of disk-directed I/O.
In this report, we detail steps taken to tune the file
systems supported by STARFISH, which include a
traditional parallel file system (with caching) and a
disk-directed I/O system. In particular, we now support
two-phase I/O, use smarter disk scheduling, increased
the maximum number of outstanding requests that a
compute processor may make to each disk, and added
gather/scatter block transfer. We also present results
of the experiments driving the tuning effort.",
}
@TechReport{Dartmouth:TR96-297,
author = "David Kotz",
title = "{Applications of Parallel I/O}",
institution = "Dartmouth College, Computer Science",
address = "Hanover, NH",
number = "PCS-TR96-297",
year = "1996",
month = oct,
URL = "http://www.cs.dartmouth.edu/reports/TR96-297.ps.Z",
comment = "A supplement of this report appeared as TR98-337. The bibliography
for this technical report is also available in BibTeX
and HTML,
with links to many of the cited papers.",
abstract = "Scientific applications are increasingly being
implemented on massively parallel supercomputers. Many
of these applications have intense I/O demands, as well
as massive computational requirements. This paper is
essentially an annotated bibliography of papers and
other sources of information about scientific
applications using parallel I/O. It will be updated
periodically.",
}
@TechReport{Dartmouth:TR96-298,
author = "David M. Nicol and Xiaowen Liu",
title = "{The Dark Side of Risk (What your mother never told
you about Time Warp) }",
institution = "Dartmouth College, Computer Science",
address = "Hanover, NH",
number = "PCS-TR96-298",
year = "1996",
month = nov,
URL = "http://www.cs.dartmouth.edu/reports/TR96-298.ps.Z",
abstract = "This paper is a reminder of the danger of allowing
``risk'' when synchronizing a parallel discrete-event
simulation: a simulation code that runs correctly on a
serial machine may, when run in parallel, fail
catastrophically. This can happen when Time Warp
presents an ``inconsistent'' message to an LP, a
message that makes absolutely no sense given the LP's
state. Failure may result if the simulation modeler did
not anticipate the possibility of this inconsistency.
While the problem is not new, there has been little
discussion of how to deal with it; furthermore the
problem may not be evident to new users or potential
users of parallel simulation. This paper shows how the
problem may occur, and the damage it may cause. We show
how one may eliminate inconsistencies due to lagging
rollbacks and stale state, but then show that so long
as risk is allowed it is still possible for an LP to be
placed in a state that is inconsistent with model
semantics, again making it vulnerable to failure. We
finally show how simulation code can be tested to
ensure safe execution under a risk-free protocol.
Whether risky or risk-free, we conclude that under
current practice the development of correct and safe
parallel simulation code is not transparent to the
modeler; certain protections must be included in model
code or model testing that are not rigorously necessary
if the simulation were executed only serially.",
}
@TechReport{Dartmouth:TR96-299,
author = "Brian J. Premore and David M. Nicol and Xiaowen Liu",
title = "{A Critique of the Telecommunications Description
Language (TeD)}",
institution = "Dartmouth College, Computer Science",
address = "Hanover, NH",
number = "PCS-TR96-299",
year = "1996",
month = nov,
URL = "http://www.cs.dartmouth.edu/reports/TR96-299.ps.Z",
abstract = "TeD is an object-oriented description language
designed to facilitate the modeling of large scale
telecommunication networks, with simulation on parallel
and distributed platforms. TeD models are mapped to the
Georgia Tech Time Warp engine (GTW) for execution. In
this paper we outline the features of TeD, pointing out
its strengths and identifying characteristics that gave
us trouble as we used TeD to model detailed networks.
Our issues are motivated specifically by a model of TCP
and a model of multicast resource allocation. Our
intention is to illustrate by example what TeD can do,
and characteristics that a potential TeD user should be
aware of.",
}
@TechReport{Dartmouth:TR96-300,
author = "Nils Nieuwejaar",
title = "{Galley: A New Parallel File System for Parallel
Applications}",
institution = "Dartmouth College, Computer Science",
address = "Hanover, NH",
number = "PCS-TR96-300",
year = "1996",
month = nov # ",",
URL = "http://www.cs.dartmouth.edu/reports/TR96-300.ps.Z",
abstract = "Most current multiprocessor file systems are designed
to use multiple disks in parallel, using the high
aggregate bandwidth to meet the growing I/O
requirements of parallel scientific applications. Most
multiprocessor file systems provide applications with a
conventional Unix-like interface, allowing the
application to access those multiple disks
transparently. This interface conceals the parallelism
within the file system, increasing the ease of
programmability, but making it difficult or impossible
for sophisticated application and library programmers
to use knowledge about their I/O to exploit that
parallelism. In addition to providing an insufficient
interface, most current multiprocessor file systems are
optimized for a different workload than they are being
asked to support. In this work we examine current
multiprocessor file systems, as well as how those file
systems are used by scientific applications. Contrary
to the expectations of the designers of current
parallel file systems, the workloads on those systems
are dominated by requests to read and write small
pieces of data. Furthermore, rather than being accessed
sequentially and contiguously, as in uniprocessor and
supercomputer workloads, files in multiprocessor file
systems are accessed in regular, structured, but
non-contiguous patterns. Based on our observations of
multiprocessor workloads, we have designed Galley, a
new parallel file system that is intended to
efficiently support realistic scientific multiprocessor
workloads. In this work, we introduce Galley and
discuss its design and implementation. We describe
Galley's new three-dimensional file structure and
discuss how that structure can be used by parallel
applications to achieve higher performance. We
introduce several new data-access interfaces, which
allow applications to explicitly describe the regular
access patterns we found to be common in parallel file
system workloads. We show how these new interfaces
allow parallel applications to achieve tremendous
increases in I/O performance. Finally, we discuss how
Galley's new file structure and data-access interfaces
can be useful in practice.",
}
@TechReport{Dartmouth:TR96-301,
author = "Charles B. Owen and Fillia Makedon",
title = "{High Quality Alias Free Image Rotation}",
institution = "Dartmouth College, Computer Science",
address = "Hanover, NH",
number = "PCS-TR96-301",
year = "1996",
month = nov # ",",
URL = "http://www.cs.dartmouth.edu/reports/TR96-301.ps.Z",
comment = "Appears in Proceedings of 30th Asilomar Conference on
Signals, Systems and Computers, Pacific Grove, CA,
November 2-6, 1996.",
abstract = "This paper presents new algorithms for the rotation of
images. The primary design criteria for these
algorithms is very high quality. Common methods for
image rotation, including convolutional and separable
approaches, are examined and shown to exhibit
significant high frequency aliasing problems. A new
resampling filter design methodology is presented which
minimizes the problem for conventional
convolution-based image rotation. The paper also
presents a new separable image rotation algorithm which
exhibits improved performance in term of reduction in
artifacts and an efficient $O(N^{2} log N)$ running
time.",
}
@TechReport{Dartmouth:TR96-302,
author = "Neal E. Young",
title = "{Cross-input Amortization Captures the Diffuse
Adversary}",
institution = "Dartmouth College, Computer Science",
address = "Hanover, NH",
number = "PCS-TR96-302",
year = "1996",
month = dec,
URL = "http://www.cs.dartmouth.edu/reports/TR96-302.ps.Z",
abstract = "Koutsoupias and Papadimitriou recently raised the
question of how well deterministic on-line paging
algorithms can do against a certain class of
adversarially biased random inputs. Such an input is
given in an on-line fashion; the adversary determines
the next request probabilistically, subject to the
constraint that no page may be requested with
probability more than a fixed $\epsilon>0$. In this
paper, we answer their question by estimating, within a
factor of two, the optimal competitive ratio of any
deterministic on-line strategy against this adversary.
We further analyze randomized on-line strategies,
obtaining upper and lower bounds within a factor of
two. These estimates reveal the qualitative changes as
$\epsilon$ ranges continuously from 1 (the standard
model) towards 0 (a severely handicapped adversary).
The key to our upper bounds is a novel charging scheme
that is appropriate for adversarially biased random
inputs. The scheme adjusts the costs of each input so
that the expected cost of a random input is unchanged,
but working with adjusted costs, we can obtain
worst-case bounds on a per-input basis. This lets us
use worst-case analysis techniques while still thinking
of some of the costs as expected costs.",
}
@TechReport{Dartmouth:TR97-303,
author = "Thomas H. Cormen and Jake Wegmann and David M. Nicol",
title = "{Multiprocessor Out-of-Core FFTs with Distributed
Memory and Parallel Disks}",
institution = "Dartmouth College, Computer Science",
address = "Hanover, NH",
number = "PCS-TR97-303",
year = "1997",
month = jan,
URL = "http://www.cs.dartmouth.edu/reports/TR97-303.ps.Z",
comment = "Revised version appeared in IOPADS '97.",
abstract = "This paper extends an earlier out-of-core Fast Fourier
Transform (FFT) method for a uniprocessor with the
Parallel Disk Model (PDM) to use multiple processors.
Four out-of-core multiprocessor methods are examined.
Operationally, these methods differ in the size of
{"}mini-butterfly{"} computed in memory and how the
data are organized on the disks and in the distributed
memory of the multiprocessor. The methods also perform
differing amounts of I/O and communication. Two of them
have the remarkable property that even though they are
computing the FFT on a multiprocessor, all
interprocessor communication occurs outside the
mini-butterfly computations. Performance results on a
small workstation cluster indicate that except for
unusual combinations of problem size and memory size,
the methods that do not perform interprocessor
communication during the mini-butterfly computations
require approximately 86% of the time of those that do.
Moreover, the faster methods are much easier to
implement.",
}
@TechReport{Dartmouth:TR97-304,
author = "David M. Nicol and Gianfranco F. Ciardo",
title = "{Automated Parallelization of Discrete State-space
Generation}",
institution = "Dartmouth College, Computer Science",
address = "Hanover, NH",
number = "PCS-TR97-304",
year = "1997",
month = jan,
URL = "http://www.cs.dartmouth.edu/reports/TR97-304.ps.Z",
comment = "Submitted to Journal of Parallel and Distributed
Computing.",
abstract = "We consider the problem of generating a large
state-space in a distributed fashion. Unlike previously
proposed solutions that partition the set of reachable
states according to a hashing function provided by the
user, we explore heuristic methods that completely
automate the process. The first step is an initial
random walk through the state space to initialize a
search tree, duplicated in each processor. Then, the
reachability graph is built in a distributed way, using
the search tree to assign each newly found state to
classes assigned to the available processors.
Furthermore, we explore two remapping criteria that
attempt to balance memory usage or future workload,
respectively. We show how the cost of computing the
global snapshot required for remapping will scale up
for system sizes in the foreseeable future. An
extensive set of results is presented to support our
conclusions that remapping is extremely beneficial.",
}
@TechReport{Dartmouth:TR97-305,
author = "Daniela Rus and P. deSantis",
title = "{The Self-Organizing Desk}",
institution = "Dartmouth College, Computer Science",
address = "Hanover, NH",
number = "PCS-TR97-305",
year = "1997",
month = jan,
URL = "http://www.cs.dartmouth.edu/reports/TR97-305.ps.Z",
comment = "In Proceedings of the 1997 International Joint
Conference on Artificial Intelligence, Nagoya, Japan,
August 1997.",
abstract = "The self-organizing desk is a system that enhances a
physical desk-top with electronic information. It can
remember, organize, update, and manipulate the
information contained in the documents on a desk. The
system consists of a simple robot eye that can survey
the desk, a module for smart extraction of information
from the images taken by the robot, a module for
representing this information in multiple views, and a
module that allows a user to interact with this
information.",
}
@TechReport{Dartmouth:TR97-306,
author = "Melissa Hirschl and David Kotz",
title = "{AGDB: A Debugger for Agent Tcl}",
institution = "Dartmouth College, Computer Science",
address = "Hanover, NH",
number = "PCS-TR97-306",
year = "1997",
month = feb,
URL = "http://www.cs.dartmouth.edu/reports/TR97-306.ps.Z",
abstract = "The Agent Tcl language is an extension of Tcl/Tk that
supports distributed programming in the form of
transportable agents. AGDB is a debugger for the Agent
Tcl language. AGDB mixes of traditional and distributed
debugging facilities. Traditional debugging features
include breakpoints (line-specific, conditional, and
once-only), watch conditions and variables, and
interrupts. Distributed-debugging features address
issues inherent in distributed programming such as
migration and communication. These capabilities make
debugging distributed programs difficult because they
add complexities like race conditions to the set of
problems a program can encounter. This paper discusses
how AGDB uses distributed debugging features to debug
agents.",
}
@TechReport{Dartmouth:TR97-307,
author = "Xiaowen Liu and Charles B. Owen and Fillia Makedon",
title = "{Automatic Video Pause Detection Filter}",
institution = "Dartmouth College, Computer Science",
address = "Hanover, NH",
number = "PCS-TR97-307",
year = "1997",
month = feb,
URL = "http://www.cs.dartmouth.edu/reports/TR97-307.ps.Z",
abstract = "Increasing interest in multimedia research has been
drawn upon the development of video indexing and
content-based image retrieval techniques. In this
report, we proposed several pause detection algorithms,
which instead of searching for significant visual
transitions, the algorithms detect significant pauses
in video streams. A realization of the algorithms was
implemented using ImageTcl toolkit developed at
Dartmouth Experimental Visualization Laboratory. In
addition to proposing and studying the effectiveness of
the pause detection algorithms, another major goal will
be to incorporate our algorithms into ImageTcl and test
the stability and applicability of the ImageTcl
environment. Priliminary experiments showed relatively
good results of our pause detection algorithms.",
}
@TechReport{Dartmouth:TR97-308,
author = "Fillia Makedon and James Matthews and Charles B. Owen
and Samuel A. Rebelsky",
title = "{An Efficient Scheme for a Distributed Video Retrieval
System for Remote Users}",
institution = "Dartmouth College, Computer Science",
address = "Hanover, NH",
number = "PCS-TR97-308",
year = "1997",
month = feb # ",",
URL = "http://www.cs.dartmouth.edu/reports/TR97-308.ps.Z",
abstract = "The new era of digital video and multimedia
technologies has created the potential for large
libraries of digital video. With this new technology
come the challenges of creating usable means by which
such large and diverse depositories of digital
information (digital libraries) can be efficiently
queried and accessed so that (a) the response is fast,
(b) the communication over the Internet is minimal and
(c) the retrieval is characterized by high precision
and recall. In this paper we discuss how existing
digital video editing tools, together with data
compression techniques, can be combined to create a
fast, accurate and cost effective video retrieval
system for remote users. The traditional approaches
employed in text databases, such as keyword searching
and volume browsing, are inadequate mechanisms for a
video retrieval system for remote users because, (a)
they don't apply to video at all, or (b) they are not
practical due to the amounts of data involved, or (c)
they have insufficient resolution to be useful in a
video archive. New techniques must be developed that
facilitate the query and selection of digital video.
This paper presents one such scheme.",
}
@TechReport{Dartmouth:TR97-309,
author = "Charles B. Owen and Fillia Makedon and Glen Frank and
Michael Kenyon",
title = "{ASML: Automatic Site Markup Language 1.03}",
institution = "Dartmouth College, Computer Science",
address = "Hanover, NH",
number = "PCS-TR97-309",
year = "1997",
month = feb,
URL = "http://www.cs.dartmouth.edu/reports/TR97-309.ps.Z",
abstract = "Creation of large and complex World Wide Web sites is
hampered by the {"}page at a time{"} approach of many
tools and the programming knowledge and custom software
development required for automated solutions. This
report describes the development of the Automatic Site
Markup Language (ASML). ASML is a new markup language
designed to produce large, complicated web sites which
can include dynamic content. ASML extends HTML with
new, high-level features while still preserving
complete compatibility with common browser and server
technologies. It has powerful indexing and searching
facilities, and enables the automatic translation of
document formats. Most importantly, ASML provides
HTML-like features at the site level rather than just
the page level",
}
@TechReport{Dartmouth:TR97-310,
author = "Charles B. Owen and Fillia Makedon",
title = "{Multimedia Data Analysis using ImageTcl (Extended
version)}",
institution = "Dartmouth College, Computer Science",
address = "Hanover, NH",
number = "PCS-TR97-310",
year = "10,",
month = jul,
URL = "http://www.cs.dartmouth.edu/reports/TR97-310.ps.Z",
comment = "A shorter version of this paper appears in the
Proceedings of Gesellschaft fur Klassifikation e.V.,
University of Potsdam, Potsdam, Germany, March 12-14,
1997",
abstract = "ImageTcl is an new system which provides powerful
Tcl/Tk based media scripting capabilities similar to
those of the ViewSystem and Rivl in a unique
environment that allows rapid prototyping and
development of new components in the C++ language.
Powerful user tools automate the creation of new
components as well as the addition of new data types
and file formats. Applications using ImageTcl at the
Dartmouth Experimental Visualization Laboratory
(DEVLAB) include multiple stream media data analysis,
automatic image annotation, and image sequence motion
analysis. ImageTcl combines the high speed of compiled
languages with the testing and parameterization
advantages of scripting languages.",
}
@TechReport{Dartmouth:TR97-311,
author = "Prasad Jayanti and Sanjay Khanna",
title = "{On the Power of Multi-Objects}",
institution = "Dartmouth College, Computer Science",
address = "Hanover, NH",
number = "PCS-TR97-311",
year = "1997",
month = mar,
comment = "Appeared in WDAG 1997, Lecture Notes in Computer
Science #1320.",
abstract = "In the standard ``single-object'' model of
shared-memory computing, it is assumed that a process
accesses at most one shared object in each of its
steps. In this paper, we consider a more powerful
variant---the ``multi-object'' model---in which each
process may access *any* finite number of shared
objects atomically in each of its steps. We present
results that relate the synchronization power of a type
in the multi-object model to its synchronization power
in the single-object model. Although the types
fetch&add and swap have the same synchronization power
in the single-object model, Afek, Merritt, and
Taubenfeld showed that their synchronization powers
differ in the multi-object model. We prove that this
divergence phenomenon is exhibited {\em only\/} by
types at levels 1 and 2; all higher level types have
the same unbounded synchronization power in the
multi-object model stated above. This paper identifies
all possible relationships between a type's
synchronization power in the single-object model and
its synchronization power in the multi-object model.",
}
@TechReport{Dartmouth:TR97-312,
author = "Sanjay Khanna and David Kotz",
title = "{A Split-Phase Interface for Parallel File Systems}",
institution = "Dartmouth College, Computer Science",
address = "Hanover, NH",
number = "PCS-TR97-312",
year = "1997",
month = mar,
URL = "http://www.cs.dartmouth.edu/reports/TR97-312.ps.Z",
abstract = "We describe the effects of a new user-level library
for the Galley Parallel File System. This library
allows some pre-existing sequential programs to make
use of the Galley Parallel File System with minimal
modification. It permits programs to efficiently use
the parallel file system because the user-level library
groups accesses together. We examine the performance of
our library, and we show how code needs to be modified
to use the library.",
}
@TechReport{Dartmouth:TR97-313,
author = "Dawn Lawrie",
title = "{Self-Organizing File Cabinet}",
institution = "Dartmouth College, Computer Science",
address = "Hanover, NH",
number = "PCS-TR97-313",
year = "1997",
month = may,
URL = "http://www.cs.dartmouth.edu/reports/TR97-313.ps.Z",
comment = "Senior Honors Thesis. Advisor: Daniela Rus.
The
figures are included in a separate appendix
(1285KB uncompressed, 167KB compressed).",
abstract = "This thesis presents a self-organized file cabinet.
This file cabinet uses electronic information to
augment the physical world. By using a scanner to
transform documents into electronic files, the
self-organized file cabinet can index the documents on
visual and textual information. The self-organized file
cabinet helps the user find the documents at a later
date. The focus of this thesis is on the design and
evaluation of the self-organized file cabinet. User
studies show that this tool is natural to use.",
}
@TechReport{Dartmouth:TR97-314,
author = "Ka-Tak Lo",
title = "{KLZ: A Prototype X Protocol Compression System}",
institution = "Dartmouth College, Computer Science",
address = "Hanover, NH",
number = "PCS-TR97-314",
year = "1997",
month = may,
URL = "http://www.cs.dartmouth.edu/reports/TR97-314.ps.Z",
comment = "Senior Honors Thesis. Advisor: John M. Danskin.",
abstract = "One of the most commonly used graphics protocol is the
X Protocol, enabling programs to display graphics
images. When running the X Protocol over the network, a
lot of structured data (messages with fields) need to
be transmitted. Delays can be detected by human users
when connected through a low-bandwidth network. The
solution is to compress the X protocol. XRemote, a
network version of the X Protocol, uses
Dictionary-based compression. In XRemote, strings are
recorded in the dictionary. When a string repeats, its
index in the dictionary is transmitted. Higher
Bandwidth X (HBX) uses statistical modeling techniques
instead. A context model, which depends on the nature
of the field in a particular type of message and the
frequencies of the values of the field, is associated
with each field. XRemote is much faster than HBX, but
HBX achieves better compression than XRemote. The KLZ
system is developed to take advantage of our knowledge
about the fields in the XMotionNotify packet (what X
sends when the mouse moves) and fast Dictionary (LZW)
compression. In essence, KLZ reorders and rewrites
fields in the XMotionNotify packet so that the fields
will be more easily compressed by the fast LZ coder. My
experiments show that KLZ compresses this packet nearly
as well as HBX, and 5 times better than pure LZ. KLZ is
slightly faster than pure LZ, and and 10 times faster
than HBX. Since many modems already implement LZ
compression, KLZ could also be used to reorder data
before passing them to the modem with LZ compression
for transmission. This reordering would lead to vastly
improved compression almost for free.",
}
@TechReport{Dartmouth:TR97-315,
author = "Simon Holmes a Court",
title = "{Admission Control Policies for Internet File Transfer
Protocols}",
institution = "Dartmouth College, Computer Science",
address = "Hanover, NH",
number = "PCS-TR97-315",
year = "1997",
month = may,
URL = "http://www.cs.dartmouth.edu/reports/TR97-315.ps.Z",
comment = "Senior Honors Thesis. Advisor: John M. Danskin.",
abstract = "Server congestion is a major cause of frustration with
the Internet. It is not uncommon for a server with a
new release of popular software to be swamped by many
times more clients than it can possibly handle. Current
Internet file transfer protocols, namely FTP and HTTP,
do not have any policy to regulate client admission. In
this thesis we are concerned with server admission
policies that will improve clients' experience with
servers under heavy load. Using a purpose-built network
simulator, we compare the prevalent protocols with two
new protocols that include policies taken from
processor scheduling. By applying more intelligent
client admission policies it is hoped that the quality
of service on the Internet can be improved.",
}
@TechReport{Dartmouth:TR97-316,
author = "Jon Feldman",
title = "{The Complexity Of Clerkship Scheduling}",
institution = "Dartmouth College, Computer Science",
address = "Hanover, NH",
number = "PCS-TR97-316",
year = "1997",
month = may,
URL = "http://www.cs.dartmouth.edu/reports/TR97-316.ps.Z",
comment = "Senior Honors Thesis. Advisor: Cliff Stein.",
abstract = "Medical students must complete a clerkship program in
their fourth year. Individual students have preferences
for the clerkships to which they are assigned. However,
individual hospitals also have capacities on how many
students may be assigned to each clerkship. The problem
of scheduling medical students to clerkships is
formalized. The problem is then placed in a theoretical
framework, and the most general case of Clerkship
Scheduling is proven NP-hard. A detailed approximation
algorithm is given, and an implementation of this
algorithm is discussed and tested.",
}
@TechReport{Dartmouth:TR97-317,
author = "Thomas H. Cormen",
title = "{Performing BMMC Permutations Efficiently on
Distributed-Memory Multiprocessors with MPI}",
institution = "Dartmouth College, Computer Science",
address = "Hanover, NH",
number = "PCS-TR97-317",
year = "1997",
month = may,
URL = "http://www.cs.dartmouth.edu/reports/TR97-317.ps.Z",
comment = "Revised version appeared in Algorithmica volume 24,
number 3/4, July and August 1999, pages 349-370.",
abstract = "This paper presents an architecture-independent method
for performing BMMC permutations on multiprocessors
with distributed memory. All interprocessor
communication uses the MPI function
MPI_Sendrecv_replace(). The number of elements and
number of processors must be powers of 2, with at least
one element per processor, and there is no inherent
upper bound on the ratio of elements per processor. Our
method transmits only data without transmitting any
source or target indices, which conserves network
bandwidth. When data is transmitted, the source and
target processors implicitly agree on each other's
identity and the indices of the elements being
transmitted. A C-callable implementation of our method
is available from Netlib. The implementation allows
preprocessing (which incurs a modest cost) to be
factored out for multiple runs of the same permutation,
even if on different data. Data may be laid out in any
one of several ways: processor-major, processor-minor,
or anything in between.",
}
@TechReport{Dartmouth:TR97-318,
author = "Eric Hagen",
title = "{An Information Retrieval System for Performing
Hierarchical Document Clustering }",
institution = "Dartmouth College, Computer Science",
address = "Hanover, NH",
number = "PCS-TR97-318",
year = "1997",
month = may,
URL = "http://www.cs.dartmouth.edu/reports/TR97-318.ps.Z",
comment = "Senior Honors Thesis. Advisor: Javed Aslam.",
abstract = "This thesis presents a system for web-based
information retrieval that supports precise and
informative post-query organization (automated document
clustering by topic) to decrease real search time on
the part of the user. Most existing Information
Retrieval systems depend on the user to perform
intelligent, specific queries with Boolean operators in
order to minimize the set of returned documents. The
user essentially must guess the appropriate keywords
before performing the query. Other systems use a vector
space model which is more suitable to performing the
document similarity operations which permit
hierarchical clustering of returned documents by topic.
This allows {"}post query{"} refinement by the user.
The system we propose is a hybrid beween these two
systems, compatibile with the former, while providing
the enhanced document organization permissable by the
latter.",
}
@TechReport{Dartmouth:TR97-319,
author = "J. Aslam and K. Pelekhov and Daniela Rus",
title = "{Generating, Visualizing and Evaluating High Quality
Clusters for Information Organization}",
institution = "Dartmouth College, Computer Science",
address = "Hanover, NH",
number = "PCS-TR97-319",
year = "1997",
month = aug,
URL = "http://www.cs.dartmouth.edu/reports/TR97-319.ps.Z",
comment = "Submitted to the 1998 SIGIR Conference.",
abstract = "We present and analyze the star clustering algorithm.
We discuss an implementation of this algorithm that
supports browsing and document retrieval through
information organization. We define three parameters
for evaluating a clustering algorithm to measure the
topic separation and topic aggregation achieved by the
algorithm. In the absence of benchmarks, we present a
method for randomly generating clustering data. Data
from our user study shows evidence that the star
algorithm is effective for organizing information.",
}
@TechReport{Dartmouth:TR97-320,
author = "Neal E. Young",
title = "{On-Line File Caching}",
institution = "Dartmouth College, Computer Science",
address = "Hanover, NH",
number = "PCS-TR97-320",
year = "1997",
month = jul,
URL = "http://www.cs.dartmouth.edu/reports/TR97-320.ps.Z",
abstract = "Consider the following file caching problem: in
response to a sequence of requests for files, where
each file has a specified size and retrieval cost,
maintain a cache of files of total size at most some
specified k so as to minimize the total retrieval cost.
Specifically, when a requested file is not in the
cache, bring it into the cache, pay the retrieval cost,
and choose files to remove from the cache so that the
total size of files in the cache is at most k. This
problem generalizes previous paging and caching
problems by allowing objects of arbitrary size and
cost, both important attributes when caching files for
world-wide-web browsers, servers, and proxies. We give
a simple deterministic on-line algorithm that
generalizes many well-known paging and weighted-caching
strategies, including least-recently-used,
first-in-first-out, flush-when-full, and the balance
algorithm. On any request sequence, the total cost
incurred by the algorithm is at most k/(k-h+1) times
the minimum possible using a cache of size h <= k. For
any algorithm satisfying the latter bound, we show it
is also the case that for most choices of k, the
retrieval cost is either insignificant or the
competitive ratio is constant. This helps explain why
competitive ratios of many on-line paging algorithms
have been typically observed to be constant in
practice.",
}
@TechReport{Dartmouth:TR97-321,
author = "Charles B. Owen and Fillia Makedon",
title = "{Multiple Media Stream Data Analysis: Theory and
Applications (Extended version)}",
institution = "Dartmouth College, Computer Science",
address = "Hanover, NH",
number = "PCS-TR97-321",
year = "10,",
month = jul,
URL = "http://www.cs.dartmouth.edu/reports/TR97-321.ps.Z",
comment = "A shorter version of this paper appears in the
Proceedings of Gesellschaft fur Klassifikation e.V.,
University of Potsdam, Potsdam, Germany, March 12-14,
1997",
abstract = "This paper presents a new model for multiple media
stream data analysis as well as descriptions of some
applications of this model in development at Dartmouth
College. This model formalizes the exploitation of
correlations between multiple, potentially
heterogeneous, media streams in support of numerous
application areas. The goal of the technique is to
determine temporal and spatial alignments which
optimize a correlation function and indicate
commonality and synchronization between media streams.
It also provides a framework for comparison of media in
unrelated domains. Applications such as text-to-speech
alignment, functional magnetic resonance imaging,
speaker localization, and degraded media realignment
are described.",
}
@TechReport{Dartmouth:TR97-322,
author = "Thomas H. Cormen",
title = "{Determining an Out-of-Core FFT Decomposition Strategy
for Parallel Disks by Dynamic Programming}",
institution = "Dartmouth College, Computer Science",
address = "Hanover, NH",
number = "PCS-TR97-322",
year = "1997",
month = jul,
URL = "http://www.cs.dartmouth.edu/reports/TR97-322.ps.Z",
comment = "Also appeared in Proceedings of the Workshop on
Algorithms for Parallel Machines, 1996-97 Special Year
on Mathematics of High Performance Computing, Institute
for Mathematics and Its Applications, University of
Minnesota, Minneapolis, September 1996.",
abstract = "We present an out-of-core FFT algorithm based on the
in-core FFT method developed by Swarztrauber. Our
algorithm uses a recursive divide-and-conquer strategy,
and each stage in the recursion presents several
possibilities for how to split the problem into
subproblems. We give a recurrence for the algorithm's
I/O complexity on the Parallel Disk Model and show how
to use dynamic programming to determine optimal splits
at each recursive stage. The algorithm to determine the
optimal splits takes only Theta(lg^2 N) time for an
N-point FFT, and it is practical. The out-of-core FFT
algorithm itself takes considerably longer.",
}
@TechReport{Dartmouth:TR97-323,
author = "Alex Colvin and Thomas H. Cormen",
title = "{ViC*: A Compiler for Virtual-Memory C*}",
institution = "Dartmouth College, Computer Science",
address = "Hanover, NH",
number = "PCS-TR97-323",
year = "1997",
month = nov,
URL = "http://www.cs.dartmouth.edu/reports/TR97-323.ps.Z",
comment = "Revised version appeared in the Proceedings of the
Third International Workshop on High-Level Parallel
Programming Models and Supportive Environments (HIPS
'98), March 1998, pages 23-33.",
abstract = "This paper describes the functionality of ViC*, a
compiler for a variant of the data-parallel language C*
with support for out-of-core data. The compiler
translates C* programs with shapes declared outofcore,
which describe parallel data stored on disk. The
compiler output is a SPMD-style program in standard C
with I/O and library calls added to efficiently access
out-of-core parallel data. The ViC* compiler also
applies several program transformations to improve
out-of-core data layout and access.",
}
@TechReport{Dartmouth:TR97-324,
author = "J. Aslam and K. Pelekhov and Daniela Rus",
title = "{Computing Dense Clusters On-line for Information
Organization}",
institution = "Dartmouth College, Computer Science",
address = "Hanover, NH",
number = "PCS-TR97-324",
year = "1997",
month = oct,
URL = "http://www.cs.dartmouth.edu/reports/TR97-324.ps.Z",
comment = "Submitted to the 1998 SIGIR Conference.",
abstract = "We present and analyze the off-line star algorithm for
clustering static information systems and the on-line
star algorithm for clustering dynamic information
systems. These algorithms partition a document
collection into a number of clusters that is naturally
induced by the collection. We show a lower bound on the
accuracy of the clusters produced by these algorithms.
We use the random graph model to show that both star
algorithms produce correct clusters in time Theta(V +
E). Finally, we provide data from extensive
experiments.",
}
@TechReport{Dartmouth:TR97-325,
author = "Stavros G. Kolliopoulos and Clifford Stein",
title = "{Approximating Disjoint-Path Problems Using Greedy
Algorithms and Packing Integer Programs }",
institution = "Dartmouth College, Computer Science",
address = "Hanover, NH",
number = "PCS-TR97-325",
year = "1997",
month = oct,
comment = "Revised November 1997.",
abstract = "In the edge(vertex)-disjoint path problem we are given
a graph $G$ and a set ${\cal T}$ of connection
requests. Every connection request in ${\cal T}$ is a
vertex pair $(s_i,t_i),$ $1 \leq i \leq K.$ The
objective is to connect a maximum number of the pairs
via edge(vertex)-disjoint paths. The edge-disjoint path
problem can be generalized to the multiple-source
unsplittable flow problem where connection request $i$
has a demand $\rho_i$ and every edge $e$ a capacity
$u_e.$ All these problems are NP-hard and have a
multitude of applications in areas such as routing,
scheduling and bin packing. Given the hardness of the
problem, we study polynomial-time approximation
algorithms. In this context, a $\rho$-approximation
algorithm is able to route at least a $1/\rho$ fraction
of the connection requests. Although the edge- and
vertex-disjoint path problems, and more recently the
unsplittable flow generalization, have been extensively
studied, they remain notoriously hard to approximate
with a bounded performance guarantee. For example, even
for the simple edge-disjoint path problem, no
$o(\sqrt{|E|})$-approximation algorithm is known.
Moreover some of the best existing approximation ratios
are obtained through sophisticated and non-standard
randomized rounding schemes. In this paper we introduce
techniques which yield algorithms for a wide range of
disjoint-path and unsplittable flow problems. For the
general unsplittable flow problem, even with weights on
the commodities, our techniques lead to the first
approximation algorithm and obtain an approximation
ratio that matches, to within logarithmic factors, the
$O(\sqrt{|E|})$ approximation ratio for the simple
edge-disjoint path problem. In addition to this result
and to improved bounds for several disjoint-path
problems, our techniques simplify and unify the
derivation of many existing approximation results. We
use two basic techniques. First, we propose simple
greedy algorithms for edge- and vertex-disjoint paths
and second, we propose the use of a framework based on
packing integer programs for more general problems such
as unsplittable flow. A packing integer program is of
the form maximize $c^{T}\cdot x,$ subject to $Ax \leq
b,$ $A,b,c \geq 0.$ As part of our tools we develop
improved approximation algorithms for a class of
packing integer programs, a result that we believe is
of independent interest.",
}
@TechReport{Dartmouth:TR97-326,
author = "Jonathan Bredin and David Kotz and Daniela Rus",
title = "{Market-based Resource Control for Mobile Agents}",
institution = "Dartmouth College, Computer Science",
address = "Hanover, NH",
number = "PCS-TR97-326",
year = "1997",
month = nov,
URL = "http://www.cs.dartmouth.edu/reports/TR97-326.ps.Z",
comment = "A revised version appeared in the conference
Autonomous Agents '98. See here.
See related
papers.",
abstract = "Mobile agents are programs that can migrate from
machine to machine in a heterogeneous, partially
disconnected network. As mobile agents move across a
network, they consume resources. We discuss a system
for controlling the activities of mobile agents that
uses electronic cash, a banking system, and a set of
resource managers. We describe protocols for
transactions between agents. We present fixed-pricing
and dynamic-pricing policies for resources. We focus on
and analyze the sealed-bid second-price auction as a
mechanism for dynamic pricing.",
}
@TechReport{Dartmouth:TR98-311,
author = "Jonathan Bredin and David Kotz and Daniela Rus",
title = "{Utility Driven Mobile-Agent Scheduling}",
institution = "Dartmouth College, Computer Science",
address = "Hanover, NH",
number = "PCS-TR98-311",
year = "5,",
month = may,
comment = "This technical report number is incorrect. The correct
number for this report is TR98-331.
TR98-331 web page. See related
papers.",
}
@TechReport{Dartmouth:TR98-327,
author = "Robert S. Gray",
title = "{Agent Tcl: A flexible and secure mobile-agent
system}",
institution = "Dartmouth College, Computer Science",
address = "Hanover, NH",
number = "PCS-TR98-327",
year = "1998",
month = jan,
URL = "http://www.cs.dartmouth.edu/reports/TR98-327.ps.Z",
comment = "Ph.D. Thesis.
Related
papers.",
abstract = "A mobile agent is an autonomous program that can
migrate under its own control from machine to machine
in a heterogeneous network. In other words, the program
can suspend its execution at an arbitrary point,
transport itself to another machine, and then resume
execution from the point of suspension. Mobile agents
have the potential to provide a {\em single, general
framework} in which a wide range of distributed
applications can be implemented efficiently and easily.
Several challenges must be faced, however, most notably
reducing migration overhead, protecting a machine from
malicious agents (and an agent from malicious
machines), and insulating the agent against network and
machine failures. Agent Tcl is a mobile-agent system
under development at Dartmouth College that has evolved
from a Tcl-only system into a multiple-language system
that currently supports Tcl, Java, and Scheme. In this
thesis, we examine the motivation behind mobile agents,
describe the base Agent Tcl system and its security
mechanisms for protecting a machine against malicious
agents, and analyze the system's current performance.
Finally, we discuss the security, fault-tolerance and
performance enhancements that will be necessary for
Agent Tcl and mobile agents in general to realize their
full potential.",
}
@TechReport{Dartmouth:TR98-328,
author = "Cem Paya",
title = "{A framework for World Wide Web client-authentication
protocols}",
institution = "Dartmouth College, Computer Science",
address = "Hanover, NH",
number = "PCS-TR98-328",
year = "1998",
month = mar,
URL = "http://www.cs.dartmouth.edu/reports/TR98-328.ps.Z",
comment = "Senior Honors Thesis. Advisor: Robert H. Morris, Sr.",
abstract = "Existing client-authentication protocols deployed on
the World Wide Web today are based on conventional
distributed systems and fail to address the problems
specific to the application domain. Some of the
protocols restrict the mobility of the client by
equating user identity to a machine or network address,
others depend on sound password management strategies,
and yet others compromise the privacy of the user by
transmitting personal information for authentication.
We introduce a new framework for client-authentication
by separating two goals that current protocols achieve
simultaneously: 1. Maintain persistent sense of
identity across different sessions. 2. Prove facts
about the user to the site. These problems are
independent, in the sense that any protocol for solving
the first problem can be combined with any protocol for
solving the second. Separation of the two purposes
opens up the possibility of designing systems which
balance two conflicting goals, authentication and
anonymity. We propose a solution to the first problem,
based on the Digital Signature Standard. The
implications of this framework from the point of view
of user privacy are examined. The paper is concluded
with suggestions for integrating the proposed scheme
into the existing WWW architecture.",
}
@TechReport{Dartmouth:TR98-329,
author = "Matthew P. Carter and David Kotz",
title = "{An Implementation of the Vesta Parallel File System
API on the Galley Parallel File System}",
institution = "Dartmouth College, Computer Science",
address = "Hanover, NH",
number = "PCS-TR98-329",
year = "1998",
month = apr,
URL = "http://www.cs.dartmouth.edu/reports/TR98-329.ps.Z",
abstract = "To demonstrate the flexibility of the Galley parallel
file system and to analyze the efficiency and
flexibility of the Vesta parallel file system
interface, we implemented Vesta's
application-programming interface on top of Galley. We
implemented the Vesta interface using Galley's
file-access methods, whose design arose from extensive
testing and characterization of the I/O requirements of
scientific applications for high-performance
multiprocessors. We used a parallel CPU, parallel I/O,
out-of-core matrix-multiplication application to test
the Vesta interface in both its ability to specify data
access patterns and in its run-time efficiency. In
spite of its powerful ability to specify the
distribution of regular, non-overlapping data access
patterns across disks, we found that the Vesta
interface has some significant limitations. We discuss
these limitations in detail in the paper, along with
the performance results.",
}
@TechReport{Dartmouth:TR98-330,
author = "Jon Howell",
title = "{Straightforward Java Persistence Through
Checkpointing}",
institution = "Dartmouth College, Computer Science",
address = "Hanover, NH",
number = "PCS-TR98-330",
year = "1998",
month = apr,
URL = "http://www.cs.dartmouth.edu/reports/TR98-330.ps.Z",
comment = "Superceded by a conference paper available at
http://www.cs.dartmouth.edu/~jonh/research/",
abstract = "Several techniques have been proposed for adding
persistence to the Java language environment. This
paper describes a scheme based on checkpointing the
Java Virtual Machine, and compares the scheme to other
techniques. Checkpointing offers two unique advantages:
first, the implementation is independent of the JVM
implementation, and therefore survives JVM updates;
second, because checkpointing saves and restores
execution state, even threads become persistent
entities.",
}
@TechReport{Dartmouth:TR98-331,
author = "Jonathan Bredin and David Kotz and Daniela Rus",
title = "{Utility Driven Mobile-Agent Scheduling}",
institution = "Dartmouth College, Computer Science",
address = "Hanover, NH",
number = "PCS-TR98-331",
year = "1998",
month = oct,
URL = "http://www.cs.dartmouth.edu/reports/TR98-331.ps.Z",
comment = "Original version in May 1998; revised October 3, 1998.
See related
papers.",
abstract = "We investigate the possibility of using markets to
regulate mobile agents, computer programs that are
capable of migrating from one machine to another.
Market participation requires quantitative information
about resource consumption to define demand and
calculate utility. We create a formal utility model to
derive user-demand functions, allowing agents to
efficiently plan expenditure and deal with price
fluctuations. By quantifying demand and utility,
resource owners can precisely set a value for a good.
We simulate our model in a mobile agent scheduling
environment and show how prices fluctuate, compounding
uncertainty in an agent's plans. To solve this problem,
we propose that resource owners sell options to allow
agents to trade away their risk.",
}
@TechReport{Dartmouth:TR98-332,
author = "Michael G. Ross",
title = "{Multiscouting: Guiding distributed manipulation with
multiple mobile sensors}",
institution = "Dartmouth College, Computer Science",
address = "Hanover, NH",
number = "PCS-TR98-332",
year = "1998",
month = jun,
URL = "http://www.cs.dartmouth.edu/reports/TR98-332.ps.Z",
comment = "Senior Honors Thesis. Advisor: Daniela Rus. Source
code available by
ftp",
abstract = "This thesis investigates the use of multiple mobile
sensors to guide the motion of a distributed
manipulation system. In our system, multiple robots
cooperatively place a large object at a goal in a
dynamic, unstructured, unmapped environment. We take
the system developed in [Rus, Kabir, Kotay, Soutter
1996], which employs a single mobile sensor for
navigational tasks, and extend it to allow the use of
multiple mobile sensors. This allows the system to
perform successful manipulations in a larger class of
spaces than was possible in the single scout model. We
focus on the development of a negotiation protocol that
enables multiple scouts to cooperatively plan system
motion. This algorithm enhances the previous' system's
scalability and adds greater fault-tolerance. Two
alternate algorithms for cooperation: a modification of
negotiation and a bidding protocol, are also discussed.
Finally, an implementation of the negotiation protocol
is described and experimental data produced by the
implementation is analyzed.",
}
@TechReport{Dartmouth:TR98-333,
author = "Christopher S. Leon",
title = "{An Implementation of External-Memory Depth-First
Search}",
institution = "Dartmouth College, Computer Science",
address = "Hanover, NH",
number = "PCS-TR98-333",
year = "1998",
month = jun,
URL = "http://www.cs.dartmouth.edu/reports/TR98-333.ps.Z",
comment = "Senior Honors Thesis. Advisor: Tom Cormen",
abstract = "In many different areas of computing, problems can
arise which are too large to fit in main memory. For
these problems, the I/O cost of moving data between
main memory and secondary storage (for example, disks)
becomes a significant bottleneck affecting the
performance of the program. Since most algorithms do
not take into account the size of main memory, new
algorithms have been developed to optimize the number
of I/O's performed. This paper details the
implementation of one such algorithm, for
external-memory depth-first search. Depth-first search
is a basic tool for solving many problems in graph
theory, and since graph theory is applicable for many
large computational problems, it is important to make
sure that such a basic tool is designed to avoid the
bottleneck of main memory to secondary storage I/O's.
The algorithm whose implementation is described in this
paper is sketched out in an extended abstract by Chiang
et al. We attempt to improve the given algorithm by
minimizing I/O's performed, and to extend the algorithm
by finding disjoint trees, and by classifying all the
edges in the problem.",
}
@TechReport{Dartmouth:TR98-334,
author = "Jack Pien",
title = "{C Compiler Targeting the Java Virtual Machine}",
institution = "Dartmouth College, Computer Science",
address = "Hanover, NH",
number = "PCS-TR98-334",
year = "1998",
month = jun,
URL = "http://www.cs.dartmouth.edu/reports/TR98-334.ps.Z",
comment = "Senior Honors Thesis. Advisor: Jay Aslam.",
abstract = "One of the major drawbacks in the field of computer
software development has been the inability for
applications to compile once and execute across many
different platforms. With the emergence of the Internet
and the networking of many different platforms, the
Java programming language and the Java Platform was
created by Sun Microsystems to address this {"}Write
Once, Run Anywhere{"} problem. What sets a compiled
Java program apart from programs compiled from other
high level languages is the ability of a Java Virtual
Machine to execute the compiled Java program on any
platform, as long as the Java Virtual Machine is
running on top of that platform. Java's cross platform
capabilities can be extended to other high level
languages such as C. The main objective of our project
is to implement a compiler targeting the Java Platform
for a subset of the C language. This will allow code
written in that subset of C to be compiled into Java
Virtual Machine instructions, also known as JVM
bytecode, which can then be executed on a Java Virtual
Machine running on any platform. The reader is assumed
to be intimately familiar with compiler construction,
the use of the flex scanner generator, the use of the
GNU bison parser generator, and the structure and
implementation of the Java Virtual Machine.",
}
@TechReport{Dartmouth:TR98-335,
author = "Charles B. Owen",
title = "{Multiple Media Correlation: Theory and
Applications}",
institution = "Dartmouth College, Computer Science",
address = "Hanover, NH",
number = "PCS-TR98-335",
year = "1998",
month = jun,
URL = "http://www.cs.dartmouth.edu/reports/TR98-335.ps.Z",
comment = "Ph.D dissertation.",
abstract = "This thesis introduces multiple media correlation, a
new technology for the automatic alignment of multiple
media objects such as text, audio, and video. This
research began with the question: what can be learned
when multiple multimedia components are analyzed
simultaneously? Most ongoing research in computational
multimedia has focused on queries, indexing, and
retrieval within a single media type. Video is
compressed and searched independently of audio, text is
indexed without regard to temporal relationships it may
have to other media data. Multiple media correlation
provides a framework for locating and exploiting
correlations between multiple, potentially
heterogeneous, media streams. The goal is computed
synchronization, the determination of temporal and
spatial alignments that optimize a correlation function
and indicate commonality and synchronization between
media objects. The model also provides a basis for
comparison of media in unrelated domains. There are
many real-world applications for this technology,
including speaker localization, musical score
alignment, and degraded media realignment. Two
applications, text-to-speech alignment and parallel
text alignment, are described in detail with
experimental validation. Text-to-speech alignment
computes the alignment between a textual transcript and
speech-based audio. The presented solutions are
effective for a wide variety of content and are useful
not only for retrieval of content, but in support of
automatic captioning of movies and video. Parallel text
alignment provides a tool for the comparison of
alternative translations of the same document that is
particularly useful to the classics scholar interested
in comparing translation techniques or styles. The
results presented in this thesis include (a) new media
models more useful in analysis applications, (b) a
theoretical model for multiple media correlation, (c)
two practical application solutions that have
wide-spread applicability, and (d) Xtrieve, a
multimedia database retrieval system that demonstrates
this new technology and demonstrates application of
multiple media correlation to information retrieval.
This thesis demonstrates that computed alignment of
media objects is practical and can provide immediate
solutions to many information retrieval and content
presentation problems. It also introduces a new area
for research in media data analysis.",
}
@TechReport{Dartmouth:TR98-336,
author = "Christine J. Alvarado",
title = "{Distributed Route Planning Using Partial Map
Building}",
institution = "Dartmouth College, Computer Science",
address = "Hanover, NH",
number = "PCS-TR98-336",
year = "1998",
month = jun,
URL = "http://www.cs.dartmouth.edu/reports/TR98-336.ps.Z",
comment = "Senior Honors Thesis. Advisor: Daniela Rus. Source
code available by
ftp.",
abstract = "Our goal is to manipulate and guide an object across
an unknown environment toward a goal in a known
location in space. Our tools include a system of
manipulation robots, which are {"}blind{"} and one
mobile scout robot who relies on a series of sonar
sensors for information about the environment. Previous
solutions to this problem have taken a simultaneous
guiding and manipulating approach, moving the whole
system under the scout's guidance. My approach,
however, presents a separate scouting algorithm that
can return a series of coordinates through which the
manipulation system can safely pass to reach the goal
in a static environment. This new approach produces
more optimal paths to the goal, as well as evading the
concern of what actions to take should the entire
system reach a dead end. In this paper I will present
both the algorithm and the experimental results I
obtained when I built the scouting system.",
}
@TechReport{Dartmouth:TR98-337,
author = "Ron Oldfield and David Kotz",
title = "{Applications of Parallel I/O}",
institution = "Dartmouth College, Computer Science",
address = "Hanover, NH",
number = "PCS-TR98-337",
year = "1998",
month = aug,
URL = "http://www.cs.dartmouth.edu/reports/TR98-337.ps.Z",
comment = "Supplement to PCS-TR96-297.",
abstract = "Scientific applications are increasingly being
implemented on massively parallel supercomputers. Many
of these applications have intense I/O demands, as well
as massive computational requirements. This paper is
essentially an annotated bibliography of papers and
other sources of information about scientific
applications using parallel I/O. It will be updated
periodically.",
}
@TechReport{Dartmouth:TR98-338,
author = "Michael H. Pryor",
title = "{The Effects of Singular Value Decomposition on
Collaborative Filtering}",
institution = "Dartmouth College, Computer Science",
address = "Hanover, NH",
number = "PCS-TR98-338",
year = "1998",
month = jun,
URL = "http://www.cs.dartmouth.edu/reports/TR98-338.ps.Z",
comment = "Senior Honors Thesis. Advisor: Jay Aslam and Geoff
Davis.",
abstract = "As the information on the web increases exponentially,
so do the efforts to automatically filter out useless
content and to search for interesting content. Through
both explicit and implicit actions, users define where
their interests lie. Recent efforts have tried to group
similar users together in order to better use this data
to provide the best overall filtering capabilities to
everyone. This thesis discusses ways in which linear
algebra, specifically the singular value decomposition,
can be used to augment these filtering capabilities to
provide better user feedback. The goal is to modify the
way users are compared with one another, so that we can
more efficiently predict similar users. Using data
collected from the PhDs.org website, we tested our
hypothesis on both explicit web page ratings and
implicit visits data.",
}
@TechReport{Dartmouth:TR98-339,
author = "Peter N. DeSantis",
title = "{Avoiding Conflicts Dynamically in Direct Mapped
Caches with Minimal Hardware Support}",
institution = "Dartmouth College, Computer Science",
address = "Hanover, NH",
number = "PCS-TR98-339",
year = "1998",
month = jun,
URL = "http://www.cs.dartmouth.edu/reports/TR98-339.ps.Z",
comment = "Senior Honors Thesis. Advisor: Tom Cormen.",
abstract = "The memory system is often the weakest link in the
performance of today's computers. Cache design has
received increasing attention in recent years as
increases in CPU performance continues to outpace
decreases in memory latency. Bershad et al. proposed a
hardware modification called the Cache Miss Lookaside
buffer which attempts to dynamically identify data
which is conflicting in the cache and remap pages to
avoid future conflicts. In a follow-up paper, Bershad
et al. tried to modify this idea to work with standard
hardware but had less success than with their dedicated
hardware. In this thesis, we focus on a modification of
these ideas, using less complicated hardware and
focusing more on sampling policies. The hardware
support is reduced to a buffer of recent cache misses
and a cache miss counter. Because determination of
remapping candidates is moved to software, sampling
policies are studied to reduce overhead which will most
likely fall on the OS. Our results show that sampling
can be highly effective in identifying conflicts that
should be remapped. Finally, we show that the
theoretical performance of such a system can compare
favorably with more costly higher associativity
caches.",
}
@TechReport{Dartmouth:TR98-340,
author = "Jon Howell and Mark Montague",
title = "{Hey, You Got Your Language In My Operating System!}",
institution = "Dartmouth College, Computer Science",
address = "Hanover, NH",
number = "PCS-TR98-340",
year = "1998",
month = dec,
URL = "http://www.cs.dartmouth.edu/reports/TR98-340.ps.Z",
abstract = "Several projects in the operating systems research
community suggest a trend of convergence among features
once divided between operating systems and languages.
We describe how partial evaluation and transformational
programming systems apply to this trend by providing a
general framework for application support, from
compilation to run-time services. We contend that the
community will no longer think of implementing a static
collection of services and calling it an operating
system; instead, this general framework will allow
applications to be flexibly configured, and the
``operating system'' will simply be the application
support that is supplied at run-time.",
}
@TechReport{Dartmouth:TR98-341,
author = "Matthew P. Carter",
title = "{Boosting a Simple Weak Learner For Classifying
Handwritten Digits}",
institution = "Dartmouth College, Computer Science",
address = "Hanover, NH",
number = "PCS-TR98-341",
year = "1998",
month = jun,
URL = "http://www.cs.dartmouth.edu/reports/TR98-341.ps.Z",
comment = "Senior Honors Thesis. Advisor: Jay Aslam.",
abstract = "A weak PAC learner is one which takes labeled training
examples and produces a classifier which can label test
examples more accurately than random guessing. A strong
learner (also known as a PAC learner), on the other
hand, is one which takes labeled training examples and
produces a classifier which can label test examples
arbitrarily accurately. Schapire has constructively
proved that a strong PAC learner can be derived from a
weak PAC learner. A performance boosting algorithm
takes a set of training examples and a weak PAC
learning algorithm and generates a strong PAC learner.
Our research attempts to solve the problem of learning
a multi-valued function and then boosting the
performance of this learner. We implemented the
AdaBoost.M2 boosting algorithm. We developed a
problem-general weak learning algorithm, capable of
running under AdaBoost.M2, for learning a multi-valued
function of uniform length bit sequences. We applied
our learning algorithms to the problem of classifying
handwritten digits. For training and testing data, we
used the MNIST dataset. Our experiments demonstrate the
underlying weak learner's ability to achieve a fairly
low error rate on the testing data, as well as the
boosting algorithm's ability to reduce the error rate
of the weak learner.",
}
@TechReport{Dartmouth:TR98-342,
author = "Craig McGray and Daniela Rus",
title = "{Abstractions for Simplifying Planning in
Self-Reconfigurable Robotic Systems}",
institution = "Dartmouth College, Computer Science",
address = "Hanover, NH",
number = "PCS-TR98-342",
year = "1998",
month = oct,
URL = "http://www.cs.dartmouth.edu/reports/TR98-342.pdf",
abstract = "In [KVRM], we described a three-dimensional
self-reconfiguring robot module called the Molecule
Robot. In this paper, we provide a system of
abstractions for modules in self-reconfigurable robotic
systems, and show how this system can be used to
simplify the motion planning of the Molecule Robot
system.",
}
@TechReport{Dartmouth:TR98-343,
author = "Jon Howell and David Kotz",
title = "{Snowflake: Spanning administrative domains}",
institution = "Dartmouth College, Computer Science",
address = "Hanover, NH",
number = "PCS-TR98-343",
year = "1998",
month = dec,
URL = "http://www.cs.dartmouth.edu/reports/TR98-343.ps.Z",
abstract = "Many distributed systems provide a ``single-system
image'' to their users, so the user has the illusion
that they are using a single system when in fact they
are using many distributed resources. It is a powerful
abstraction that helps users to manage the complexity
of using distributed resources. The goal of the
Snowflake project is to discover how single-system
images can be made to span administrative domains. Our
current prototype organizes resources in namespaces and
distributes them using Java Remote Method Invocation.
Challenging issues include how much flexibility should
be built into the namespace interface, and how
transparent the network and persistent storage should
be. We outline future work on making Snowflake
administrator-friendly.",
}
@TechReport{Dartmouth:TR99-344,
author = "Neal E. Young",
title = "{Greedy Approximation Algorithms for K-Medians by
Randomized Rounding}",
institution = "Dartmouth College, Computer Science",
address = "Hanover, NH",
number = "PCS-TR99-344",
year = "1999",
month = mar,
URL = "http://www.cs.dartmouth.edu/reports/TR99-344.ps.Z",
abstract = "We give an improved approximation algorithm for the
general k-medians problem. Given any \epsilon>0, the
algorithm finds a solution of total distance at most
D(1+\epsilon) using at most k ln(n+n/\epsilon) medians
(a.k.a. sites), provided some solution of total
distance D using k medians exists. This improves over
the best previous bound (w.r.t. the number of medians)
by a factor of \Omega(1/\epsilon) provided
1/\epsilon=n^O(1). The algorithm is a greedy algorithm,
derived using the method of oblivious randomized
rounding. It requires at most k ln(n+n/\epsilon)
linear-time iterations. We also derive algorithms for
fractional and weighted variants of the problem.",
}
@TechReport{Dartmouth:TR99-345,
author = "Jonathan Bredin and David Kotz and Daniela Rus",
title = "{Mobile-Agent Planning in a Market-Oriented
Environment}",
institution = "Dartmouth College, Computer Science",
address = "Hanover, NH",
number = "PCS-TR99-345",
year = "1999",
month = may,
URL = "http://www.cs.dartmouth.edu/reports/TR99-345.ps.Z",
comment = "See related
papers.",
abstract = "We propose a method for increasing incentives for
sites to host arbitrary mobile agents in which mobile
agents purchase their computing needs from host sites.
We present a scalable market-based CPU allocation
policy and an on-line algorithm that plans a mobile
agent's expenditure over a multihop ordered itinerary.
The algorithm chooses a set of sites at which to
execute and computational priorities at each site to
minimize execution time while preserving a prespecified
budget constraint. We present simulation results of our
algorithm to show that our allocation policy and
planning algorithm scale well as more agents are added
to the system.",
}
@TechReport{Dartmouth:TR99-346,
author = "James D. Chalfant",
title = "{Parallel DaSSF Discrete-Event Simulation without
Shared Memory}",
institution = "Dartmouth College, Computer Science",
address = "Hanover, NH",
number = "PCS-TR99-346",
year = "1999",
month = jun,
URL = "http://www.cs.dartmouth.edu/reports/TR99-346.ps.Z",
comment = "Undergraduate Honors Thesis. Advisor: David Nicol.",
abstract = "The Dartmouth implementation of the Scalable
Simulation Framework (DaSSF) is a discrete-event
simulator used primarily in the simulation of networks.
It achieves high performance through parallel
processing. DaSSF 1.22 requires shared memory between
all processors in order to operate. This limits the
number of processors available and the hardware
platforms that can exploit parallelism. We are
interested in extending parallel DaSSF operation to
architectures without shared memory. We explore the
requirements of this by implementing parallel DaSSF
using MPI as the sole form of interaction between
processors. The approaches used to achieve this can be
abstracted and applied to the current version of DaSSF.
This would allow parallel simulation using shared
memory by processors within a single machine, and also
at a higher level between separate machines using
distributed memory.",
}
@TechReport{Dartmouth:TR99-347,
author = "April M. Rasala",
title = "{Existence Theorems for Scheduling to Meet Two
Objectives}",
institution = "Dartmouth College, Computer Science",
address = "Hanover, NH",
number = "PCS-TR99-347",
year = "1999",
month = jun,
URL = "http://www.cs.dartmouth.edu/reports/TR99-347.ps.Z",
comment = "Undergraduate Honors Thesis. Advisor: Cliff Stein.",
abstract = "We will look at the existence of schedules which are
simultaneously near-optimal for two criteria. First, we
will present some techniques for proving existence
theorems, in a very general setting, for bicriterion
scheduling problems. We will then use these techniques
to prove existence theorems for a large class of
problems. We will consider the relationship between
objective functions based on completion time, flow
time, lateness and the number of on-time jobs. We will
also present negative results first for the problem of
simultaneously minimizing the maximum flow time and
average weighted flow time and second for minimizing
the maximum flow time and simultaneously maximizing the
number of on-time jobs. In some cases we will also
present lower bounds and algorithms that approach our
bicriterion existence theorems. Finally we will improve
upon our general existence results in one more specific
environment.",
}
@TechReport{Dartmouth:TR99-348,
author = "Marsette A. Vona",
title = "{A Two Dimensional Crystalline Atomic Unit Modular
Self-reconfigurable Robot}",
institution = "Dartmouth College, Computer Science",
address = "Hanover, NH",
number = "PCS-TR99-348",
year = "1999",
month = jun,
URL = "http://www.cs.dartmouth.edu/reports/TR99-348.ps.Z",
comment = "Undergraduate Honors Thesis. Advisor: Daniela Rus.",
abstract = "Self-reconfigurable robots are designed so that they
can change their external shape without human
intervention. One general way to achieve such
functionality is to build a robot composed of multiple,
identical unit modules. If the modules are designed so
that they can be assembled into rigid structures, and
so that individual units within such structures can be
relocated within and about the structure, then
self-reconfiguration is possible. We propose the
Crystalline Atomic unit modular self-reconfigurable
robot, where each unit is called an Atom. In two
dimensions, an Atom is square. Connectors at the faces
of each Atom support structure formation (such
structures are called Crystals). Centrally placed
prismatic degrees of freedom give Atoms the ability to
contract their outer side-length by a constant factor.
By contracting and expanding groups of Atoms in a
coordinated way, Atoms can relocate within and about
Crystals. Thus Atoms are shown to satisfy the two
properties necessary to function as modules of a
self-reconfigurable robot. A powerful software
simulator for Crystalline Atomic robots in two and
three dimensions, called xtalsim, is presented. Xtalsim
includes a high-level language interface for specifying
reconfigurations, an engine which expands implicit
reconfiguration plans into explicit Crystal state
sequences, and an interactive animator which displays
the results in a virtual environment. An automated
planning algorithm for generating reconfigurations,
called the Melt-Grow planner, is described. The
Melt-Grow planner is fast (O(n2) for Crystals of n
Atoms) and complete for a fully general subset of
Crystals. The Melt-Grow planner is implemented and
interfaced to xtalsim, and an automatically planned
reconfiguration is simulated. Finally, the mechanics,
electronics, and software for an Atom implementation
are developed. Two Atoms are constructed and
experiments are performed which indicate that, with
some hardware improvements, an interesting
self-reconfiguration could be demonstrated by a group
of Atoms.",
}
@TechReport{Dartmouth:TR99-349,
author = "David H. Kung",
title = "{Improved Computer Detection and Mapping of Cerebral
Oxygenation}",
institution = "Dartmouth College, Computer Science",
address = "Hanover, NH",
number = "PCS-TR99-349",
year = "1999",
month = jun # ",",
URL = "http://www.cs.dartmouth.edu/reports/TR99-349.ps.Z",
comment = "Undergraduate Honors Thesis. Advisors: George Cybenko
and Keith Paulsen.",
abstract = "Near-infrared (NIR) optical image reconstruction that
incorporates blood oxygen level dependant (BOLD)
magnetic resonance imaging has the potential to improve
both quantifiable measurement of oxygenation and the
spatial resolution involved in such mapping. My thesis
continues some preliminary work in this area through
development of an analytic diffusion parameter
estimation algorithm for use with a NIR imaging array
and development of a finite element mesh utility to
read a priori BOLD images and tag them with property
elements for NIR image resolution improvement.",
}
@TechReport{Dartmouth:TR99-350,
author = "Lauren M. Baptist",
title = "{Two Algorithms for Performing Multidimensional,
Multiprocessor, Out-of-Core FFTs}",
institution = "Dartmouth College, Computer Science",
address = "Hanover, NH",
number = "PCS-TR99-350",
year = "1999",
month = jun,
URL = "http://www.cs.dartmouth.edu/reports/TR99-350.ps.Z",
comment = "Undergraduate Honors Thesis. Advisor: Tom Cormen.",
abstract = "We show two algorithms for computing multidimensional
Fast Fourier Transforms (FFTs) on a multiprocessor
system with distributed memory when problem sizes are
so large that the data do not fit in the memory of the
entire system. Instead, data reside on a parallel disk
system and are brought into memory in sections. We use
the Parallel Disk Model for implementation and
analysis. The first method is a straightforward
out-of-core variant of a well-known method for in-core,
multidimensional FFTs. It performs 1-dimensional FFT
computations on each dimension in turn. This method is
easy to generalize to any number of dimensions, and it
also readily permits the individual dimensions to be of
any sizes that are integer powers of~2. The key step is
an out-of-core transpose operation that places the data
along each dimension into contiguous positions on the
parallel disk system so that the data for the
1-dimensional FFTs are contiguous. The second method is
an adaptation of another well-known method for in-core,
multidimensional FFTs. This method computes all
dimensions simultaneously. It is more difficult to
generalize to arbitrary radices and number of
dimensions in this method than in the first method. Our
present implementation is therefore limited to two
dimensions of equal size, that are again integer powers
of~2. We present I/O complexity analyses for both
methods as well as empirical results for a DEC~2100
server and an SGI Origin~2000, each of which has a
parallel disk system. Our results indicate that the
methods are comparable in speed in two-dimensions.",
}
@TechReport{Dartmouth:TR99-351,
author = "Matthew D. Pearson",
title = "{Fast Out-of-Core Sorting on Parallel Disk Systems}",
institution = "Dartmouth College, Computer Science",
address = "Hanover, NH",
number = "PCS-TR99-351",
year = "1999",
month = jun,
URL = "http://www.cs.dartmouth.edu/reports/TR99-351.ps.Z",
comment = "Undergraduate Honors Thesis. Advisor: Tom Cormen.",
abstract = "This paper discusses our implementation of
Rajasekaran's (l,m)-mergesort algorithm (LMM) for
sorting on parallel disks. LMM is asymptotically
optimal for large problems and has the additional
advantage of a low constant in its I/O complexity. Our
implementation is written in C using the ViC* I/O API
for parallel disk systems. We compare the performance
of LMM to that of the C library function qsort on a DEC
Alpha server. qsort makes a good benchmark because it
is fast and performs comparatively well under demand
paging. Since qsort fails when the swap disk fills up,
we can only compare these algorithms on a limited range
of inputs. Still, on most out-of-core problems, our
implementation of LMM runs between 1.5 and 1.9 times
faster than qsort, with the gap widening with
increasing problem size.",
}
@TechReport{Dartmouth:TR99-352,
author = "Jason M. Whaley",
title = "{An Application of Word Sense Disambiguation to
Information Retrieval}",
institution = "Dartmouth College, Computer Science",
address = "Hanover, NH",
number = "PCS-TR99-352",
year = "1999",
month = jun,
URL = "http://www.cs.dartmouth.edu/reports/TR99-352.ps.Z",
comment = "Undergraduate Honors Thesis. Advisor: Jay Aslam.",
abstract = "The problems of word sense disambiguation and document
indexing for information retrieval have been
extensively studied. It has been observed that indexing
using disambiguated meanings, rather than word stems,
should improve information retrieval results. We
present a new corpus-based algorithm for performing
word sense disambiguation. The algorithm does not need
to train on many senses of each word; it uses instead
the probability that certain concepts will occur
together. That algorithm is then used to index several
corpa of documents. Our indexing algorithm does not
generally outperform the traditional stem-based tf.idf
model.",
}
@TechReport{Dartmouth:TR99-353,
author = "Bruce Randall Donald and Frederick Henle",
title = "{Using Haptic Vector Fields for Animation Motion
Control}",
institution = "Dartmouth College, Computer Science",
address = "Hanover, NH",
number = "PCS-TR99-353",
year = "1999",
month = may,
URL = "http://www.cs.dartmouth.edu/reports/TR99-353.ps.Z",
abstract = "We are exploring techniques for animation authoring
and editing using a haptic force-feedback device. In
our system, a family of animations is encoded by a
bundle of trajectories. This bundle in turn defines a
time-varying, higher-order vector field on a
configuration space for the animation. A haptic input
device provides a low-dimensional parameterization of
the resulting dynamical system, and the haptic force
feedback permits browsing and editing of the space of
animations, by allowing the user to experience the
vector field as physical forces.",
}
@TechReport{Dartmouth:TR99-354,
author = "Marisa E. Kolodny",
title = "{Computers, Art and Smart Rooms: A Smart Picture Frame
that Senses the Weather and Genetically Evolves
Images}",
institution = "Dartmouth College, Computer Science",
address = "Hanover, NH",
number = "PCS-TR99-354",
year = "1999",
month = jun,
URL = "http://www.cs.dartmouth.edu/reports/TR99-354.ps.Z",
comment = "Undergraduate Honors Thesis. Advisor: Daniela Rus.",
abstract = "By using sensors to sense the environment and genetic
programming to evolve images, this thesis explores two
methods for developing smart pictures that can be
integrated with a living space. The system presented
senses the weather and indoor conditions, displays
current weather and forecast information retrieved from
the web, and displays genetically evolved images.
Sensing the weather not only provides the user with
information they might find useful, but also allows the
computer to gain a better understanding of the user
which in turn allows the computer to respond more
accurately. Genetic programming allows the computer to
better respond to its environment by evolving fitter
programs.",
}
@TechReport{Dartmouth:TR99-355,
author = "Hongxia Quan",
title = "{The Implementation of DaSSF OTcl APIs}",
institution = "Dartmouth College, Computer Science",
address = "Hanover, NH",
number = "PCS-TR99-355",
year = "1999",
month = jun # ",",
URL = "http://www.cs.dartmouth.edu/reports/TR99-355.pdf",
comment = "Thesis Advisor: David M. Nicol",
abstract = "As an extension of Tcl, Otcl provides basic
functionality for object-oriented programming in
scripting language Tcl. We implemented the Otcl APIs
for DaSSF (a parallel simulator software written in C++
at Dartmouth College) using Tclcl software package
written in University of California at Berkeley. This
document discussed the issues involved in the
implementation, especially the communications between
C++ objects and Otcl objects required by DaSSF and the
naming problems.",
}
@TechReport{Dartmouth:TR99-356,
author = "Artem Lifschitz",
title = "{An Environment for the Facilitation of Robotic
Programming}",
institution = "Dartmouth College, Computer Science",
address = "Hanover, NH",
number = "PCS-TR99-356",
year = "1999",
month = jun,
URL = "http://www.cs.dartmouth.edu/reports/TR99-356.ps.Z",
comment = "The postscript {"}paper{"} is actually a source code
listing. The author chose not to release his written
thesis as a Technical Report. The work represents an
Undergraduate Honors Thesis; Advisor: Daniela Rus.",
abstract = "I have developed, tested, and evaluated a robot
programming environment organized as a library of
flexible data structures to facilitate the creation of
robotics programs. Abstractions are the basis of all of
the achievements of Computer Science, and if it were
possible to create a truly flexible, generic
abstraction for the programming of robots -- the
science of robotics could advance at a faster pace. For
this reason, I have attempted to implement the
abstraction of low-level commands, and the assembling
of them into hierarchies of higher-level actions. My
libraries provide mechanisms for the manipulation and
queuing of actions, as well as for the timing of
low-level sensing and actuation. I have tested these
libraries by implementing a cooperative multi-agent
formation algorithm in the SoccerServer environment.
Often, when a new level of abstraction is introduced --
significant overhead is added. However, I have
conducted experiments to show that there is no
significant overhead in using this system by comparing
the performance of SoccerServer agents that have been
programmed using it against the performance of other
agents.",
}
@TechReport{Dartmouth:TR99-357,
author = "Jeffrey D. Isaacs and Javed A. Aslam",
title = "{Investigating Measures for Pairwise Document
Similarity}",
institution = "Dartmouth College, Computer Science",
address = "Hanover, NH",
number = "PCS-TR99-357",
year = "1999",
month = jun,
URL = "http://www.cs.dartmouth.edu/reports/TR99-357.ps.Z",
comment = "Undergraduate Honors Thesis. Advisor: Jay Aslam.",
abstract = "The need for a more effective similarity measure is
growing as a result of the astonishing amount of
information being placed online. Most existing
similarity measures are defined by empirically derived
formulas and cannot easily be extended to new
applications. We present a pairwise document similarity
measure based on Information Theory, and present corpus
dependent and independent applications of this measure.
When ranked with existing similarity measures over TREC
FBIS data, our corpus dependent information theoretic
similarity measure ranked first.",
}
@TechReport{Dartmouth:TR99-358,
author = "Chris Bailey-Kellogg and Alik Widge and John J. Kelley
and Marcelo J. Berardi and John H. Bushweller and Bruce
Randall Donald",
title = "{The NOESY Jigsaw: Automated Protein Secondary
Structure and Main-Chain Assignment from Sparse,
Unassigned NMR Data}",
institution = "Dartmouth College, Computer Science",
address = "Hanover, NH",
number = "PCS-TR99-358",
year = "1999",
month = oct,
URL = "http://www.cs.dartmouth.edu/reports/TR99-358.ps.Z",
comment = "To appear in
The Fourth Annual International Conference on
Computational Molecular Biology (RECOMB'2000),
Tokyo, Japan, April 8-11, 2000.",
abstract = "High-throughput, data-directed computational protocols
for Structural Genomics (or Proteomics) are required in
order to evaluate the protein products of genes for
structure and function at rates comparable to current
gene-sequencing technology. This paper presents the
Jigsaw algorithm, a novel high-throughput, automated
approach to protein structure characterization with
nuclear magnetic resonance (NMR). Jigsaw consists of
two main components: (1) graph-based secondary
structure pattern identification in unassigned
heteronuclear NMR data, and (2) assignment of spectral
peaks by probabilistic alignment of identified
secondary structure elements against the primary
sequence. Jigsaw's deferment of assignment until after
secondary structure identification differs greatly from
traditional approaches, which begin by correlating
peaks among dozens of experiments. By deferring
assignment, Jigsaw not only eliminates this bottleneck,
it also allows the number of experiments to be reduced
from dozens to four, none of which requires 13C-labeled
protein. This in turn dramatically reduces the amount
and expense of wet lab molecular biology for protein
expression and purification, as well as the total
spectrometer time to collect data. Our results for
three test proteins demonstrate that we are able to
identify and align approximately 80 percent of
alpha-helical and 60 percent of beta-sheet structure.
Jigsaw is extremely fast, running in minutes on a
Pentium-class Linux workstation. This approach yields
quick and reasonably accurate (as opposed to the
traditional slow and extremely accurate) structure
calculations, utilizing a suite of graph analysis
algorithms to compensate for the data sparseness.
Jigsaw could be used for quick structural assays to
speed data to the biologist early in the process of
investigation, and could in principle be applied in an
automation-like fashion to a large fraction of the
proteome.",
}
@TechReport{Dartmouth:TR99-359,
author = "Bruce Randall Donald and Chris Bailey-Kellogg and John
J. Kelley and Clifford Stein",
title = "{SAR by MS for Functional Genomics (Structure-Activity
Relation by Mass Spectrometry)}",
institution = "Dartmouth College, Computer Science",
address = "Hanover, NH",
number = "PCS-TR99-359",
year = "1999",
month = oct,
URL = "http://www.cs.dartmouth.edu/reports/TR99-359.ps.Z",
comment = "This report is superceded by
TR2000-362 .",
abstract = "Large-scale functional genomics will require fast,
high-throughput experimental techniques, coupled with
sophisticated computer algorithms for data analysis and
experiment planning. In this paper, we introduce a
combined experimental-computational protocol called
Structure-Activity Relation by Mass Spectrometry
(SAR by MS), which can be used to elucidate the
function of protein-DNA or protein-protein complexes.
We present algorithms for SAR by MS and analyze their
complexity. Carefully-designed Matrix-Assisted Laser
Desorption/Ionization Time-Of-Flight (MALDI TOF) and
Electrospray Ionization (ESI) assays require only
femtomolar samples, take only microseconds per spectrum
to record, enjoy a resolution of up to one dalton in
$10^6$, and (in the case of MALDI) can operate on
protein complexes up to a megadalton in mass. Hence,
the technique is attractive for high-throughput
functional genomics. In SAR by MS, selected residues or
nucleosides are 2H-, 13C-, and/or 15N-labeled. Second,
the complex is crosslinked. Third, the complex is
cleaved with proteases and/or endonucleases. Depending
on the binding mode, some cleavage sites will be
shielded by the crosslinking. Finally, a mass spectrum
of the resulting fragments is obtained and analyzed.
The last step is the Data Analysis phase, in
which the mass signatures are interpreted to obtain
constraints on the functional binding mode.
Experiment Planning entails deciding what
labeling strategy and cleaving agents to employ, so as
to minimize mass degeneracy and spectral overlap, in
order that the constraints derived in data analysis
yield a small number of binding hypotheses. A number of
combinatorial and algorithmic questions arise in
deriving algorithms for both Experiment Planning and
Data Analysis. We explore the complexity of these
problems, obtaining upper and lower bounds.
Experimental results are reported from an
implementation of our algorithms.",
}
@TechReport{Dartmouth:TR99-360,
author = "Jonathan Bredin and Rajiv T. Maheswaran and Cagri Imer
and Tamer Basar and David Kotz and Daniela Rus",
title = "{A Game-Theoretic Formulation of Multi-Agent Resource
Allocation}",
institution = "Dartmouth College, Computer Science",
address = "Hanover, NH",
number = "PCS-TR99-360",
year = "1999",
month = oct,
URL = "http://www.cs.dartmouth.edu/reports/TR99-360.ps.Z",
comment = "Submitted to {"}Autonomous Agents 2000{"}. See related
papers.",
abstract = "This paper considers resource allocation in a network
with mobile agents competing for computational
priority. We formulate this problem as a multi-agent
game with the players being agents purchasing service
from a common server. We show that there exists a
computable Nash equilibrium when agents have perfect
information into the future. We simulate a network of
hosts and agents using our strategy to show that our
resource-allocation mechanism effectively prioritizes
agents according to their endowments.",
}
@TechReport{Dartmouth:TR99-361,
author = "Jon Howell and David Kotz",
title = "{An Access-Control Calculus for Spanning
Administrative Domains}",
institution = "Dartmouth College, Computer Science",
address = "Hanover, NH",
number = "PCS-TR99-361",
year = "1999",
month = nov,
URL = "http://www.cs.dartmouth.edu/reports/TR99-361.ps.Z",
comment = "Superceded by TR2000-363.",
abstract = "In our quest to give users uniform access to resources
unimpeded by administrative boundaries, we discovered
that we needed transitive sharing among users, with the
possibility of restricted access along each sharing
link. To achieve that goal, we extend Lampson et al.'s
calculus for access control to support restricted
delegations. We discuss the advantages of our
extension, including the simplification of constructs
like ACLs and statement expiration. We also apply our
extension to model the Simple Public Key Infrastructure
and make suggestions about its future development. Our
extended calculus exposes some surprising consequences
in such systems that use restricted delegation.",
}