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MueLu_AggregationPhase3Algorithm_kokkos_def.hpp
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46 #ifndef MUELU_AGGREGATIONPHASE3ALGORITHM_KOKKOS_DEF_HPP
47 #define MUELU_AGGREGATIONPHASE3ALGORITHM_KOKKOS_DEF_HPP
48 
49 #ifdef HAVE_MUELU_KOKKOS_REFACTOR
50 
51 #include <Teuchos_Comm.hpp>
52 #include <Teuchos_CommHelpers.hpp>
53 
54 #include <Xpetra_Vector.hpp>
55 
57 
58 #include "MueLu_Aggregates_kokkos.hpp"
59 #include "MueLu_Exceptions.hpp"
60 #include "MueLu_LWGraph_kokkos.hpp"
61 #include "MueLu_Monitor.hpp"
62 
63 namespace MueLu {
64 
65  // Try to stick unaggregated nodes into a neighboring aggregate if they are
66  // not already too big. Otherwise, make a new aggregate
67  template <class LocalOrdinal, class GlobalOrdinal, class Node>
68  void AggregationPhase3Algorithm_kokkos<LocalOrdinal, GlobalOrdinal, Node>::BuildAggregates(const ParameterList& params, const LWGraph_kokkos& graph, Aggregates_kokkos& aggregates, std::vector<unsigned>& aggStat, LO& numNonAggregatedNodes) const {
69  Monitor m(*this, "BuildAggregates");
70 
71  const LO numRows = graph.GetNodeNumVertices();
72  const int myRank = graph.GetComm()->getRank();
73 
74  ArrayRCP<LO> vertex2AggId = aggregates.GetVertex2AggId()->getDataNonConst(0);
75  ArrayRCP<LO> procWinner = aggregates.GetProcWinner() ->getDataNonConst(0);
76 
77  LO numLocalAggregates = aggregates.GetNumAggregates();
78 
79  for (LO i = 0; i < numRows; i++) {
80  if (aggStat[i] == AGGREGATED || aggStat[i] == IGNORED)
81  continue;
82 
83  typename LWGraph_kokkos::row_type neighOfINode = graph.getNeighborVertices(i);
84 
85  // We don't want a singleton. So lets see if there is an unaggregated
86  // neighbor that we can also put with this point.
87  bool isNewAggregate = false;
88  for (int j = 0; j < neighOfINode.size(); j++) {
89  LO neigh = neighOfINode(j);
90 
91  if (neigh != i && graph.isLocalNeighborVertex(neigh) && aggStat[neigh] == READY) {
92  isNewAggregate = true;
93 
94  aggStat [neigh] = AGGREGATED;
95  vertex2AggId[neigh] = numLocalAggregates;
96  procWinner [neigh] = myRank;
97 
98  numNonAggregatedNodes--;
99  }
100  }
101 
102  if (isNewAggregate) {
103  // Create new aggregate (not singleton)
104  aggregates.SetIsRoot(i);
105  vertex2AggId[i] = numLocalAggregates++;
106 
107  } else {
108  // We do not want a singleton, but there are no non-aggregated
109  // neighbors. Lets see if we can connect to any other aggregates
110  // NOTE: This is very similar to phase 2b, but simplier: we stop with
111  // the first found aggregate
112  int j = 0;
113  for (; j < neighOfINode.size(); j++) {
114  LO neigh = neighOfINode(j);
115 
116  // We don't check (neigh != rootCandidate), as it is covered by checking (aggStat[neigh] == AGGREGATED)
117  if (graph.isLocalNeighborVertex(neigh) && aggStat[neigh] == AGGREGATED)
118  break;
119  }
120 
121  if (j < neighOfINode.size()) {
122  // Assign to an adjacent aggregate
123  vertex2AggId[i] = vertex2AggId[neighOfINode(j)];
124 
125  } else {
126  // Create new aggregate (singleton)
127  this->GetOStream(Warnings1) << "Found singleton: " << i << std::endl;
128 
129  aggregates.SetIsRoot(i);
130  vertex2AggId[i] = numLocalAggregates++;
131  }
132  }
133 
134  // One way or another, the node is aggregated (possibly into a singleton)
135  aggStat [i] = AGGREGATED;
136  procWinner[i] = myRank;
137  numNonAggregatedNodes--;
138 
139  }
140 
141  // update aggregate object
142  aggregates.SetNumAggregates(numLocalAggregates);
143  }
144 
145 } // end namespace
146 
147 #endif // HAVE_MUELU_KOKKOS_REFACTOR
148 #endif // MUELU_AGGREGATIONPHASE3ALGORITHM_KOKKOS_DEF_HPP
LocalOrdinal LO
Namespace for MueLu classes and methods.
Additional warnings.