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MueLu_AggregationPhase2aAlgorithm_def.hpp
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46#ifndef MUELU_AGGREGATIONPHASE2AALGORITHM_DEF_HPP_
47#define MUELU_AGGREGATIONPHASE2AALGORITHM_DEF_HPP_
48
49
50#include <Teuchos_Comm.hpp>
51#include <Teuchos_CommHelpers.hpp>
52
53#include <Xpetra_Vector.hpp>
54
56
57#include "MueLu_GraphBase.hpp"
58#include "MueLu_Aggregates.hpp"
59#include "MueLu_Exceptions.hpp"
60#include "MueLu_Monitor.hpp"
61
62namespace MueLu {
63
64 template <class LocalOrdinal, class GlobalOrdinal, class Node>
65 void AggregationPhase2aAlgorithm<LocalOrdinal, GlobalOrdinal, Node>::BuildAggregates(const ParameterList& params, const GraphBase& graph, Aggregates& aggregates, std::vector<unsigned>& aggStat, LO& numNonAggregatedNodes) const {
66 Monitor m(*this, "BuildAggregates");
67
68 int minNodesPerAggregate = params.get<int>("aggregation: min agg size");
69 int maxNodesPerAggregate = params.get<int>("aggregation: max agg size");
70 bool matchMLbehavior = params.get<bool>("aggregation: match ML phase2a");
71
72 const LO numRows = graph.GetNodeNumVertices();
73 const int myRank = graph.GetComm()->getRank();
74
75 ArrayRCP<LO> vertex2AggId = aggregates.GetVertex2AggId()->getDataNonConst(0);
76 ArrayRCP<LO> procWinner = aggregates.GetProcWinner() ->getDataNonConst(0);
77
78 LO numLocalAggregates = aggregates.GetNumAggregates();
79
80 LO numLocalNodes = procWinner.size();
81 LO numLocalAggregated = numLocalNodes - numNonAggregatedNodes;
82
83 const double aggFactor = params.get<double>("aggregation: phase2a agg factor");
84 double factor = as<double>(numLocalAggregated)/(numLocalNodes+1);
85 factor = pow(factor, aggFactor);
86
87 int aggIndex = -1;
88 size_t aggSize = 0;
89 std::vector<int> aggList(graph.getLocalMaxNumRowEntries());
90
91 for (LO rootCandidate = 0; rootCandidate < numRows; rootCandidate++) {
92 if (aggStat[rootCandidate] != READY)
93 continue;
94
95 LO numNeighbors = 0;
96 aggSize = 0;
97 if (matchMLbehavior) {
98 aggList[aggSize++] = rootCandidate;
99 numNeighbors++;
100 }
101
102 ArrayView<const LocalOrdinal> neighOfINode = graph.getNeighborVertices(rootCandidate);
103
104
105 for (int j = 0; j < neighOfINode.size(); j++) {
106 LO neigh = neighOfINode[j];
107
108 if (neigh != rootCandidate) {
109 if (graph.isLocalNeighborVertex(neigh) && aggStat[neigh] == READY) {
110 // If aggregate size does not exceed max size, add node to the tentative aggregate
111 // NOTE: We do not exit the loop over all neighbours since we have still
112 // to count all aggregated neighbour nodes for the aggregation criteria
113 // NOTE: We check here for the maximum aggregation size. If we would do it below
114 // with all the other check too big aggregates would not be accepted at all.
115 if (aggSize < as<size_t>(maxNodesPerAggregate))
116 aggList[aggSize++] = neigh;
117 }
118
119 numNeighbors++;
120 }
121 }
122
123 // NOTE: ML uses a hardcoded value 3 instead of MinNodesPerAggregate
124 if (aggSize > as<size_t>(minNodesPerAggregate) &&
125 (aggSize > factor*numNeighbors)) {
126 // Accept new aggregate
127 // rootCandidate becomes the root of the newly formed aggregate
128 aggregates.SetIsRoot(rootCandidate);
129 aggIndex = numLocalAggregates++;
130
131 for (size_t k = 0; k < aggSize; k++) {
132 aggStat [aggList[k]] = AGGREGATED;
133 vertex2AggId[aggList[k]] = aggIndex;
134 procWinner [aggList[k]] = myRank;
135 }
136
137 numNonAggregatedNodes -= aggSize;
138 }
139 }
140
141 // update aggregate object
142 aggregates.SetNumAggregates(numLocalAggregates);
143 }
144
145} // end namespace
146
147#endif /* MUELU_AGGREGATIONPHASE2AALGORITHM_DEF_HPP_ */
Container class for aggregation information.
void SetIsRoot(LO i, bool value=true)
Set root node 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 SetNumAggregates(LO nAggregates)
Set number of local aggregates on current processor.
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 getLocalMaxNumRowEntries() const =0
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.