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MueLu_AggregationPhase1Algorithm_def.hpp
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46#ifndef MUELU_AGGREGATIONPHASE1ALGORITHM_DEF_HPP_
47#define MUELU_AGGREGATIONPHASE1ALGORITHM_DEF_HPP_
48
49#include <queue>
50
51#include <Teuchos_Comm.hpp>
52#include <Teuchos_CommHelpers.hpp>
53
54#include <Xpetra_Vector.hpp>
55
57
58#include "MueLu_GraphBase.hpp"
59#include "MueLu_Aggregates.hpp"
60#include "MueLu_Exceptions.hpp"
61#include "MueLu_Monitor.hpp"
62
63namespace MueLu {
64
65 template <class LocalOrdinal, class GlobalOrdinal, class Node>
67 BuildAggregates(const ParameterList& params, const GraphBase& graph, Aggregates& aggregates, std::vector<unsigned>& aggStat,
68 LO& numNonAggregatedNodes) const {
69 Monitor m(*this, "BuildAggregates");
70
71 std::string orderingStr = params.get<std::string>("aggregation: ordering");
72 int maxNeighAlreadySelected = params.get<int> ("aggregation: max selected neighbors");
73 int minNodesPerAggregate = params.get<int> ("aggregation: min agg size");
74 int maxNodesPerAggregate = params.get<int> ("aggregation: max agg size");
75
76 TEUCHOS_TEST_FOR_EXCEPTION(maxNodesPerAggregate < minNodesPerAggregate, Exceptions::RuntimeError,
77 "MueLu::UncoupledAggregationAlgorithm::BuildAggregates: minNodesPerAggregate must be smaller or equal to MaxNodePerAggregate!");
78
79 enum {
80 O_NATURAL,
81 O_RANDOM,
82 O_GRAPH
83 } ordering;
84 ordering = O_NATURAL; // initialize variable (fix CID 143665)
85 if (orderingStr == "natural") ordering = O_NATURAL;
86 if (orderingStr == "random" ) ordering = O_RANDOM;
87 if (orderingStr == "graph" ) ordering = O_GRAPH;
88
89 const LO numRows = graph.GetNodeNumVertices();
90 const int myRank = graph.GetComm()->getRank();
91
92 ArrayRCP<LO> vertex2AggId = aggregates.GetVertex2AggId()->getDataNonConst(0);
93 ArrayRCP<LO> procWinner = aggregates.GetProcWinner() ->getDataNonConst(0);
94
95 LO numLocalAggregates = aggregates.GetNumAggregates();
96
97 ArrayRCP<LO> randomVector;
98 if (ordering == O_RANDOM) {
99 randomVector = arcp<LO>(numRows);
100 for (LO i = 0; i < numRows; i++)
101 randomVector[i] = i;
102 RandomReorder(randomVector);
103 }
104
105 int aggIndex = -1;
106 size_t aggSize = 0;
107 std::vector<int> aggList(graph.getLocalMaxNumRowEntries());
108
109 std::queue<LO> graphOrderQueue;
110
111 // Main loop over all local rows of graph(A)
112 for (LO i = 0; i < numRows; i++) {
113 // Step 1: pick the next node to aggregate
114 LO rootCandidate = 0;
115 if (ordering == O_NATURAL) rootCandidate = i;
116 else if (ordering == O_RANDOM) rootCandidate = randomVector[i];
117 else if (ordering == O_GRAPH) {
118
119 if (graphOrderQueue.size() == 0) {
120 // Current queue is empty for "graph" ordering, populate with one READY node
121 for (LO jnode = 0; jnode < numRows; jnode++)
122 if (aggStat[jnode] == READY) {
123 graphOrderQueue.push(jnode);
124 break;
125 }
126 }
127 if (graphOrderQueue.size() == 0) {
128 // There are no more ready nodes, end the phase
129 break;
130 }
131 rootCandidate = graphOrderQueue.front(); // take next node from graph ordering queue
132 graphOrderQueue.pop(); // delete this node in list
133 }
134
135 if (aggStat[rootCandidate] != READY)
136 continue;
137
138 // Step 2: build tentative aggregate
139 aggSize = 0;
140 aggList[aggSize++] = rootCandidate;
141
142 ArrayView<const LO> neighOfINode = graph.getNeighborVertices(rootCandidate);
143
144 // If the number of neighbors is less than the minimum number of nodes
145 // per aggregate, we know this is not going to be a valid root, and we
146 // may skip it, but only for "natural" and "random" (for "graph" we still
147 // need to fetch the list of local neighbors to continue)
148 if ((ordering == O_NATURAL || ordering == O_RANDOM) &&
149 neighOfINode.size() < minNodesPerAggregate) {
150 continue;
151 }
152
153 LO numAggregatedNeighbours = 0;
154
155 for (int j = 0; j < neighOfINode.size(); j++) {
156 LO neigh = neighOfINode[j];
157
158 if (neigh != rootCandidate && graph.isLocalNeighborVertex(neigh)) {
159
160 if (aggStat[neigh] == READY || aggStat[neigh] == NOTSEL) {
161 // If aggregate size does not exceed max size, add node to the
162 // tentative aggregate
163 // NOTE: We do not exit the loop over all neighbours since we have
164 // still to count all aggregated neighbour nodes for the
165 // aggregation criteria
166 // NOTE: We check here for the maximum aggregation size. If we
167 // would do it below with all the other check too big aggregates
168 // would not be accepted at all.
169 if (aggSize < as<size_t>(maxNodesPerAggregate))
170 aggList[aggSize++] = neigh;
171
172 } else {
173 numAggregatedNeighbours++;
174 }
175 }
176 }
177
178 // Step 3: check if tentative aggregate is acceptable
179 if ((numAggregatedNeighbours <= maxNeighAlreadySelected) && // too many connections to other aggregates
180 (aggSize >= as<size_t>(minNodesPerAggregate))) { // too few nodes in the tentative aggregate
181 // Accept new aggregate
182 // rootCandidate becomes the root of the newly formed aggregate
183 aggregates.SetIsRoot(rootCandidate);
184 aggIndex = numLocalAggregates++;
185
186 for (size_t k = 0; k < aggSize; k++) {
187 aggStat [aggList[k]] = AGGREGATED;
188 vertex2AggId[aggList[k]] = aggIndex;
189 procWinner [aggList[k]] = myRank;
190 }
191
192 numNonAggregatedNodes -= aggSize;
193
194 } else {
195 // Aggregate is not accepted
196 aggStat[rootCandidate] = NOTSEL;
197
198 // Need this for the "graph" ordering below
199 // The original candidate is always aggList[0]
200 aggSize = 1;
201 }
202
203 if (ordering == O_GRAPH) {
204 // Add candidates to the list of nodes
205 // NOTE: the code have slightly different meanings depending on context:
206 // - if aggregate was accepted, we add neighbors of neighbors of the original candidate
207 // - if aggregate was not accepted, we add neighbors of the original candidate
208 for (size_t k = 0; k < aggSize; k++) {
209 ArrayView<const LO> neighOfJNode = graph.getNeighborVertices(aggList[k]);
210
211 for (int j = 0; j < neighOfJNode.size(); j++) {
212 LO neigh = neighOfJNode[j];
213
214 if (graph.isLocalNeighborVertex(neigh) && aggStat[neigh] == READY)
215 graphOrderQueue.push(neigh);
216 }
217 }
218 }
219 }
220
221 // Reset all NOTSEL vertices to READY
222 // This simplifies other algorithms
223 for (LO i = 0; i < numRows; i++)
224 if (aggStat[i] == NOTSEL)
225 aggStat[i] = READY;
226
227 // update aggregate object
228 aggregates.SetNumAggregates(numLocalAggregates);
229 }
230
231 template <class LocalOrdinal, class GlobalOrdinal, class Node>
233 //TODO: replace int
234 int n = list.size();
235 for(int i = 0; i < n-1; i++)
236 std::swap(list[i], list[RandomOrdinal(i,n-1)]);
237 }
238
239 template <class LocalOrdinal, class GlobalOrdinal, class Node>
241 return min + as<int>((max-min+1) * (static_cast<double>(std::rand()) / (RAND_MAX + 1.0)));
242 }
243
244} // end namespace
245
246
247#endif /* MUELU_AGGREGATIONPHASE1ALGORITHM_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 RandomReorder(ArrayRCP< LO > list) const
Utility to take a list of integers and reorder them randomly (by using a local permutation).
void BuildAggregates(const ParameterList &params, const GraphBase &graph, Aggregates &aggregates, std::vector< unsigned > &aggStat, LO &numNonAggregatedNodes) const
Local aggregation.
int RandomOrdinal(int min, int max) const
Generate a random number in the range [min, max].
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 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.