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MueLu_AggregationPhase2bAlgorithm_def.hpp
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46#ifndef MUELU_AGGREGATIONPHASE2BALGORITHM_DEF_HPP_
47#define MUELU_AGGREGATIONPHASE2BALGORITHM_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
61namespace MueLu {
62
63 // Try to stick unaggregated nodes into a neighboring aggregate if they are
64 // not already too big
65 template <class LocalOrdinal, class GlobalOrdinal, class Node>
66 void AggregationPhase2bAlgorithm<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 const int defaultConnectWeight = 100;
78 const int penaltyConnectWeight = 10;
79
80 std::vector<int> aggWeight (numLocalAggregates, 0);
81 std::vector<int> connectWeight(numRows, defaultConnectWeight);
82 std::vector<int> aggPenalties (numRows, 0);
83
84 // We do this cycle twice.
85 // I don't know why, but ML does it too
86 // taw: by running the aggregation routine more than once there is a chance that also
87 // non-aggregated nodes with a node distance of two are added to existing aggregates.
88 // Assuming that the aggregate size is 3 in each direction running the algorithm only twice
89 // should be sufficient.
90 for (int k = 0; k < 2; k++) {
91 for (LO i = 0; i < numRows; i++) {
92 if (aggStat[i] != READY)
93 continue;
94
95 ArrayView<const LocalOrdinal> neighOfINode = graph.getNeighborVertices(i);
96
97 for (int j = 0; j < neighOfINode.size(); j++) {
98 LO neigh = neighOfINode[j];
99
100 // We don't check (neigh != i), as it is covered by checking (aggStat[neigh] == AGGREGATED)
101 if (graph.isLocalNeighborVertex(neigh) && aggStat[neigh] == AGGREGATED)
102 aggWeight[vertex2AggId[neigh]] += connectWeight[neigh];
103 }
104
105 int bestScore = -100000;
106 int bestAggId = -1;
107 int bestConnect = -1;
108
109 for (int j = 0; j < neighOfINode.size(); j++) {
110 LO neigh = neighOfINode[j];
111
112 if (graph.isLocalNeighborVertex(neigh) && aggStat[neigh] == AGGREGATED) {
113 int aggId = vertex2AggId[neigh];
114 int score = aggWeight[aggId] - aggPenalties[aggId];
115
116 if (score > bestScore) {
117 bestAggId = aggId;
118 bestScore = score;
119 bestConnect = connectWeight[neigh];
120
121 } else if (aggId == bestAggId && connectWeight[neigh] > bestConnect) {
122 bestConnect = connectWeight[neigh];
123 }
124
125 // Reset the weights for the next loop
126 aggWeight[aggId] = 0;
127 }
128 }
129
130 if (bestScore >= 0) {
131 aggStat [i] = AGGREGATED;
132 vertex2AggId[i] = bestAggId;
133 procWinner [i] = myRank;
134
135 numNonAggregatedNodes--;
136
137 aggPenalties[bestAggId]++;
138 connectWeight[i] = bestConnect - penaltyConnectWeight;
139 }
140 }
141 }
142 }
143
144} // end namespace
145
146#endif /* MUELU_AGGREGATIONPHASE2BALGORITHM_DEF_HPP_ */
Container class for aggregation information.
const RCP< LOMultiVector > & GetVertex2AggId() const
Returns constant vector that maps local node IDs to local aggregates IDs.
const RCP< LOVector > & GetProcWinner() const
Returns constant vector that maps local node IDs to owning processor IDs.
LO GetNumAggregates() const
returns the number of aggregates of the current processor. Note: could/should be renamed to GetNumLoc...
void BuildAggregates(const ParameterList &params, const GraphBase &graph, Aggregates &aggregates, std::vector< unsigned > &aggStat, LO &numNonAggregatedNodes) const
Local aggregation.
MueLu representation of a graph.
virtual const RCP< const Teuchos::Comm< int > > GetComm() const =0
virtual bool isLocalNeighborVertex(LocalOrdinal v) const =0
Return true if vertex with local id 'v' is on current process.
virtual Teuchos::ArrayView< const LocalOrdinal > getNeighborVertices(LocalOrdinal v) const =0
Return the list of vertices adjacent to the vertex 'v'.
virtual size_t GetNodeNumVertices() const =0
Return number of vertices owned by the calling node.
Timer to be used in non-factories.
Namespace for MueLu classes and methods.