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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  bool error_on_isolated = false;
70  if(params.isParameter("aggregation: error on nodes with no on-rank neighbors"))
71  params.get<bool>("aggregation: error on nodes with no on-rank neighbors");
72 
73  const LO numRows = graph.GetNodeNumVertices();
74  const int myRank = graph.GetComm()->getRank();
75 
76  ArrayRCP<LO> vertex2AggId = aggregates.GetVertex2AggId()->getDataNonConst(0);
77  ArrayRCP<LO> procWinner = aggregates.GetProcWinner() ->getDataNonConst(0);
78 
79  LO numLocalAggregates = aggregates.GetNumAggregates();
80 
81  for (LO i = 0; i < numRows; i++) {
82  if (aggStat[i] == AGGREGATED || aggStat[i] == IGNORED)
83  continue;
84 
85  ArrayView<const LocalOrdinal> neighOfINode = graph.getNeighborVertices(i);
86 
87  // We don't want a singleton. So lets see if there is an unaggregated
88  // neighbor that we can also put with this point.
89  bool isNewAggregate = false;
90  for (int j = 0; j < neighOfINode.size(); j++) {
91  LO neigh = neighOfINode[j];
92 
93  if (neigh != i && graph.isLocalNeighborVertex(neigh) && aggStat[neigh] == READY) {
94  isNewAggregate = true;
95 
96  aggStat [neigh] = AGGREGATED;
97  vertex2AggId[neigh] = numLocalAggregates;
98  procWinner [neigh] = myRank;
99 
100  numNonAggregatedNodes--;
101  }
102  }
103 
104  if (isNewAggregate) {
105  // Create new aggregate (not singleton)
106  aggregates.SetIsRoot(i);
107  vertex2AggId[i] = numLocalAggregates++;
108 
109  } else {
110  // We do not want a singleton, but there are no non-aggregated
111  // neighbors. Lets see if we can connect to any other aggregates
112  // NOTE: This is very similar to phase 2b, but simplier: we stop with
113  // the first found aggregate
114  int j = 0;
115  for (; j < neighOfINode.size(); j++) {
116  LO neigh = neighOfINode[j];
117 
118  // We don't check (neigh != rootCandidate), as it is covered by checking (aggStat[neigh] == AGGREGATED)
119  if (graph.isLocalNeighborVertex(neigh) && aggStat[neigh] == AGGREGATED)
120  break;
121  }
122 
123  if (j < neighOfINode.size()) {
124  // Assign to an adjacent aggregate
125  vertex2AggId[i] = vertex2AggId[neighOfINode[j]];
126  } else if (error_on_isolated) {
127  // Error on this isolated node, as the user has requested
128  std::ostringstream oss;
129  oss<<"MueLu::AggregationPhase3Algorithm::BuildAggregates: MueLu has detected a non-Dirichlet node that has no on-rank neighbors and is terminating (by user request). "<<std::endl;
130  oss<<"If this error is being generated at level 0, this is due to an initial partitioning problem in your matrix."<<std::endl;
131  oss<<"If this error is being generated at any other level, try turning on repartitioning, which may fix this problem."<<std::endl;
132  throw Exceptions::RuntimeError(oss.str());
133  } else {
134  // Create new aggregate (singleton)
135  this->GetOStream(Warnings1) << "Found singleton: " << i << std::endl;
136 
137  aggregates.SetIsRoot(i);
138  vertex2AggId[i] = numLocalAggregates++;
139  }
140  }
141 
142  // One way or another, the node is aggregated (possibly into a singleton)
143  aggStat [i] = AGGREGATED;
144  procWinner[i] = myRank;
145  numNonAggregatedNodes--;
146 
147  }
148 
149  // update aggregate object
150  aggregates.SetNumAggregates(numLocalAggregates);
151  }
152 
153 } // end namespace
154 
155 #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.
T & get(const std::string &name, T def_value)
virtual size_t GetNodeNumVertices() const =0
Return number of vertices owned by the calling node.
LocalOrdinal LO
size_type size() const
Namespace for MueLu classes and methods.
void SetIsRoot(LO i, bool value=true)
Set root node information.
Additional warnings.
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...
bool isParameter(const std::string &name) const
const RCP< LOMultiVector > & GetVertex2AggId() const
Returns constant vector that maps local node IDs to local aggregates IDs.
Exception throws to report errors in the internal logical of the program.
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.