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MueLu_AggregationPhase3Algorithm_def.hpp
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46 #ifndef MUELU_AGGREGATIONPHASE3ALGORITHM_DEF_HPP_
47 #define MUELU_AGGREGATIONPHASE3ALGORITHM_DEF_HPP_
48 
49 #include <Teuchos_Comm.hpp>
50 #include <Teuchos_CommHelpers.hpp>
51 
52 #include <Xpetra_Vector.hpp>
53 
55 
56 #include "MueLu_Aggregates.hpp"
57 #include "MueLu_Exceptions.hpp"
58 #include "MueLu_GraphBase.hpp"
59 #include "MueLu_Monitor.hpp"
60 
61 namespace MueLu {
62 
63  // Try to stick unaggregated nodes into a neighboring aggregate if they are
64  // not already too big. Otherwise, make a new aggregate
65  template <class LocalOrdinal, class GlobalOrdinal, class Node>
66  void AggregationPhase3Algorithm<LocalOrdinal, GlobalOrdinal, Node>::BuildAggregates(const ParameterList& params, const GraphBase& graph, Aggregates& aggregates, std::vector<unsigned>& aggStat, LO& numNonAggregatedNodes) const {
67  Monitor m(*this, "BuildAggregates");
68 
69  const LO numRows = graph.GetNodeNumVertices();
70  const int myRank = graph.GetComm()->getRank();
71 
72  ArrayRCP<LO> vertex2AggId = aggregates.GetVertex2AggId()->getDataNonConst(0);
73  ArrayRCP<LO> procWinner = aggregates.GetProcWinner() ->getDataNonConst(0);
74 
75  LO numLocalAggregates = aggregates.GetNumAggregates();
76 
77  for (LO i = 0; i < numRows; i++) {
78  if (aggStat[i] == AGGREGATED || aggStat[i] == IGNORED)
79  continue;
80 
81  ArrayView<const LocalOrdinal> neighOfINode = graph.getNeighborVertices(i);
82 
83  // We don't want a singleton. So lets see if there is an unaggregated
84  // neighbor that we can also put with this point.
85  bool isNewAggregate = false;
86  for (int j = 0; j < neighOfINode.size(); j++) {
87  LO neigh = neighOfINode[j];
88 
89  if (neigh != i && graph.isLocalNeighborVertex(neigh) && aggStat[neigh] == READY) {
90  isNewAggregate = true;
91 
92  aggStat [neigh] = AGGREGATED;
93  vertex2AggId[neigh] = numLocalAggregates;
94  procWinner [neigh] = myRank;
95 
96  numNonAggregatedNodes--;
97  }
98  }
99 
100  if (isNewAggregate) {
101  // Create new aggregate (not singleton)
102  aggregates.SetIsRoot(i);
103  vertex2AggId[i] = numLocalAggregates++;
104 
105  } else {
106  // We do not want a singleton, but there are no non-aggregated
107  // neighbors. Lets see if we can connect to any other aggregates
108  // NOTE: This is very similar to phase 2b, but simplier: we stop with
109  // the first found aggregate
110  int j = 0;
111  for (; j < neighOfINode.size(); j++) {
112  LO neigh = neighOfINode[j];
113 
114  // We don't check (neigh != rootCandidate), as it is covered by checking (aggStat[neigh] == AGGREGATED)
115  if (graph.isLocalNeighborVertex(neigh) && aggStat[neigh] == AGGREGATED)
116  break;
117  }
118 
119  if (j < neighOfINode.size()) {
120  // Assign to an adjacent aggregate
121  vertex2AggId[i] = vertex2AggId[neighOfINode[j]];
122 
123  } else {
124  // Create new aggregate (singleton)
125  this->GetOStream(Warnings1) << "Found singleton: " << i << std::endl;
126 
127  aggregates.SetIsRoot(i);
128  vertex2AggId[i] = numLocalAggregates++;
129  }
130  }
131 
132  // One way or another, the node is aggregated (possibly into a singleton)
133  aggStat [i] = AGGREGATED;
134  procWinner[i] = myRank;
135  numNonAggregatedNodes--;
136 
137  }
138 
139  // update aggregate object
140  aggregates.SetNumAggregates(numLocalAggregates);
141  }
142 
143 } // end namespace
144 
145 #endif /* MUELU_AGGREGATIONPHASE3ALGORITHM_DEF_HPP_ */
Container class for aggregation information.
void BuildAggregates(const ParameterList &params, const GraphBase &graph, Aggregates &aggregates, std::vector< unsigned > &aggStat, LO &numNonAggregatedNodes) const
Local aggregation.
virtual size_t GetNodeNumVertices() const =0
Return number of vertices owned by the calling node.
LocalOrdinal LO
Namespace for MueLu classes and methods.
void SetIsRoot(LO i, bool value=true)
Set root node information.
Additional warnings.
const RCP< LOVector > & GetVertex2AggId() const
Returns constant vector that maps local node IDs to local aggregates IDs.
virtual bool isLocalNeighborVertex(LocalOrdinal v) const =0
Return true if vertex with local id &#39;v&#39; is on current process.
virtual const RCP< const Teuchos::Comm< int > > GetComm() const =0
MueLu representation of a graph.
Timer to be used in non-factories.
LO GetNumAggregates() const
returns the number of aggregates of the current processor. Note: could/should be renamed to GetNumLoc...
const RCP< LOVector > & GetProcWinner() const
Returns constant vector that maps local node IDs to owning processor IDs.
virtual Teuchos::ArrayView< const LocalOrdinal > getNeighborVertices(LocalOrdinal v) const =0
Return the list of vertices adjacent to the vertex &#39;v&#39;.
void SetNumAggregates(LO nAggregates)
Set number of local aggregates on current processor.