VecScatterBegin#
Begins a generalized scatter from one vector to another. Complete the scattering phase with VecScatterEnd().
Synopsis#
#include "petscsf.h"
PetscErrorCode VecScatterBegin(VecScatter sf, Vec x, Vec y, InsertMode addv, ScatterMode mode)
Neighbor-wise Collective
Input Parameters#
sf - scatter context generated by
VecScatterCreate()x - the vector from which we scatter
y - the vector to which we scatter
addv - either
ADD_VALUES,MAX_VALUES,MIN_VALUESorINSERT_VALUES, withINSERT_VALUESmode any location not scattered to retains its old value; i.e. the vector is NOT first zeroed.mode - the scattering mode, usually
SCATTER_FORWARD. The available modes are:SCATTER_FORWARDorSCATTER_REVERSE
Notes#
The vectors x and y need not be the same vectors used in the call
to VecScatterCreate(), but x must have the same parallel data layout
as that passed in as the x to VecScatterCreate(), similarly for the y.
Most likely they have been obtained from VecDuplicate().
You cannot change the values in the input vector between the calls to VecScatterBegin()
and VecScatterEnd().
If you use SCATTER_REVERSE the two arguments x and y should be reversed, from
the SCATTER_FORWARD.
y[iy[i]] = x[ix[i]], for i=0,…,ni-1
This scatter is far more general than the conventional
scatter, since it can be a gather or a scatter or a combination,
depending on the indices ix and iy. If x is a parallel vector and y
is sequential, VecScatterBegin() can serve to gather values to a
single processor. Similarly, if y is parallel and x sequential, the
routine can scatter from one processor to many processors.
See Also#
Low-level Vector Communication, VecScatter, VecScatterCreate(), VecScatterEnd()
Level#
intermediate
Location#
Examples#
src/tao/pde_constrained/tutorials/hyperbolic.c
src/ksp/ksp/tutorials/ex49.c
src/ksp/ksp/tutorials/ex43.c
src/tao/pde_constrained/tutorials/elliptic.c
src/dm/tutorials/ex22.c
src/dm/tutorials/ex6.c
src/tao/constrained/tutorials/ex1.c
src/dm/tutorials/ex25.c
src/ksp/ksp/tutorials/ex73.c
src/dm/tutorials/ex14.c
Index of all PetscSF routines
Table of Contents for all manual pages
Index of all manual pages