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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
61namespace 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 makeNonAdjAggs = false;
70 bool error_on_isolated = false;
71 if(params.isParameter("aggregation: error on nodes with no on-rank neighbors"))
72 error_on_isolated = params.get<bool>("aggregation: error on nodes with no on-rank neighbors");
73 if(params.isParameter("aggregation: phase3 avoid singletons"))
74 makeNonAdjAggs = params.get<bool>("aggregation: phase3 avoid singletons");
75
76 size_t numSingletons=0;
77
78 const LO numRows = graph.GetNodeNumVertices();
79 const int myRank = graph.GetComm()->getRank();
80
81 ArrayRCP<LO> vertex2AggId = aggregates.GetVertex2AggId()->getDataNonConst(0);
82 ArrayRCP<LO> procWinner = aggregates.GetProcWinner() ->getDataNonConst(0);
83
84 LO numLocalAggregates = aggregates.GetNumAggregates();
85
86 for (LO i = 0; i < numRows; i++) {
87 if (aggStat[i] == AGGREGATED || aggStat[i] == IGNORED)
88 continue;
89
90 ArrayView<const LocalOrdinal> neighOfINode = graph.getNeighborVertices(i);
91
92 // We don't want a singleton. So lets see if there is an unaggregated
93 // neighbor that we can also put with this point.
94 bool isNewAggregate = false;
95 bool failedToAggregate = true;
96 for (int j = 0; j < neighOfINode.size(); j++) {
97 LO neigh = neighOfINode[j];
98
99 if (neigh != i && graph.isLocalNeighborVertex(neigh) && aggStat[neigh] == READY) {
100 isNewAggregate = true;
101
102 aggStat [neigh] = AGGREGATED;
103 vertex2AggId[neigh] = numLocalAggregates;
104 procWinner [neigh] = myRank;
105
106 numNonAggregatedNodes--;
107 }
108 }
109
110 if (isNewAggregate) {
111 // Create new aggregate (not singleton)
112 aggStat [i] = AGGREGATED;
113 procWinner [i] = myRank;
114 numNonAggregatedNodes--;
115 aggregates.SetIsRoot(i);
116 vertex2AggId[i] = numLocalAggregates++;
117
118 failedToAggregate = false;
119 } else {
120 // We do not want a singleton, but there are no non-aggregated
121 // neighbors. Lets see if we can connect to any other aggregates
122 // NOTE: This is very similar to phase 2b, but simplier: we stop with
123 // the first found aggregate
124 int j = 0;
125 for (; j < neighOfINode.size(); j++) {
126 LO neigh = neighOfINode[j];
127
128 // We don't check (neigh != rootCandidate), as it is covered by checking (aggStat[neigh] == AGGREGATED)
129 if (graph.isLocalNeighborVertex(neigh) && aggStat[neigh] == AGGREGATED)
130 break;
131 }
132
133 if (j < neighOfINode.size()) {
134 // Assign to an adjacent aggregate
135 vertex2AggId[i] = vertex2AggId[neighOfINode[j]];
136 numNonAggregatedNodes--;
137 failedToAggregate = false;
138 }
139 }
140
141 if (failedToAggregate && makeNonAdjAggs) {
142 // it we are still didn't find an aggregate home for i (i.e., we have
143 // a potential singleton), we are desperate. Basically, we seek to
144 // group i with any other local point to form an aggregate (even if
145 // it is not a neighbor of i. Either we find a vertex that is already
146 // aggregated or not aggregated.
147 // 1) if found vertex is aggregated, then assign i to this aggregate
148 // 2) if found vertex is not aggregated, create new aggregate
149
150
151 for (LO ii = 0; ii < numRows; ii++) { // look for anyone else
152 if ( (ii != i) && (aggStat[ii] != IGNORED) ) {
153 failedToAggregate = false; // found someone so start
154 aggStat[i] = AGGREGATED; // marking i as aggregated
155 procWinner[i]= myRank;
156
157 if (aggStat[ii] == AGGREGATED)
158 vertex2AggId[i] = vertex2AggId[ii];
159 else {
160 vertex2AggId[i] = numLocalAggregates;
161 vertex2AggId[ii] = numLocalAggregates;
162 aggStat [ii] = AGGREGATED;
163 procWinner [ii] = myRank;
164 numNonAggregatedNodes--; // acounts for ii now being aggregated
165 aggregates.SetIsRoot(i);
166 numLocalAggregates++;
167 }
168 numNonAggregatedNodes--; // accounts for i now being aggregated
169 break;
170 } //if ( (ii != i) && (aggStat[ii] != IGNORED ...
171 } //for (LO ii = 0; ...
172 }
173 if (failedToAggregate) {
174 if (error_on_isolated) {
175 // Error on this isolated node, as the user has requested
176 std::ostringstream oss;
177 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;
178 oss<<"If this error is being generated at level 0, this is due to an initial partitioning problem in your matrix."<<std::endl;
179 oss<<"If this error is being generated at any other level, try turning on repartitioning, which may fix this problem."<<std::endl;
180 throw Exceptions::RuntimeError(oss.str());
181 } else {
182 // Create new aggregate (singleton)
183 // this->GetOStream(Warnings1) << "Found singleton: " << i << std::endl;
184 numSingletons++;
185
186 aggregates.SetIsRoot(i);
187 vertex2AggId[i] = numLocalAggregates++;
188 numNonAggregatedNodes--;
189 }
190 }
191
192 // One way or another, the node is aggregated (possibly into a singleton)
193 aggStat [i] = AGGREGATED;
194 procWinner[i] = myRank;
195
196 } // loop over numRows
197
198
199 if(numSingletons > 0)
200 this->GetOStream(Runtime0)<<" WARNING Rank "<<myRank<<" singletons :"<<numSingletons<<" (phase)"<<std::endl;
201
202
203 // update aggregate object
204 aggregates.SetNumAggregates(numLocalAggregates);
205 }
206
207} // end namespace
208
209#endif /* MUELU_AGGREGATIONPHASE3ALGORITHM_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.
Exception throws to report errors in the internal logical of the program.
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.
@ Runtime0
One-liner description of what is happening.