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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 
61 namespace 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_ */
const RCP< LOVector > & GetProcWinner() const
Returns constant vector that maps local node IDs to owning processor IDs.
Container class for aggregation information.
virtual size_t GetNodeNumVertices() const =0
Return number of vertices owned by the calling node.
size_type size() const
LocalOrdinal LO
LO GetNumAggregates() const
returns the number of aggregates of the current processor. Note: could/should be renamed to GetNumLoc...
virtual bool isLocalNeighborVertex(LocalOrdinal v) const =0
Return true if vertex with local id &#39;v&#39; is on current process.
const RCP< LOMultiVector > & GetVertex2AggId() const
Returns constant vector that maps local node IDs to local aggregates IDs.
virtual const RCP< const Teuchos::Comm< int > > GetComm() const =0
MueLu representation of a graph.
Timer to be used in non-factories.
void BuildAggregates(const ParameterList &params, const GraphBase &graph, Aggregates &aggregates, std::vector< unsigned > &aggStat, LO &numNonAggregatedNodes) const
Local aggregation.
virtual Teuchos::ArrayView< const LocalOrdinal > getNeighborVertices(LocalOrdinal v) const =0
Return the list of vertices adjacent to the vertex &#39;v&#39;.