MueLu Phase2a: Include root node in aggregate

trilinos · Apr 24, 2020 · e9cb5cc · e9cb5cc
1 parent f3005a4
commit e9cb5cc
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Showing 2 changed files with 15 additions and 12 deletions.
diff --git a/packages/muelu/src/Graph/UncoupledAggregation/MueLu_AggregationPhase2aAlgorithm_def.hpp b/packages/muelu/src/Graph/UncoupledAggregation/MueLu_AggregationPhase2aAlgorithm_def.hpp
@@ -106,7 +106,7 @@ namespace MueLu {
             //       to count all aggregated neighbour nodes for the aggregation criteria
             // NOTE: We check here for the maximum aggregation size. If we would do it below
             //       with all the other check too big aggregates would not be accepted at all.
-            if (aggSize < as<size_t>(maxNodesPerAggregate))
+            if (aggSize < as<size_t>(maxNodesPerAggregate-1))
               aggList[aggSize++] = neigh;
           }
 
@@ -122,13 +122,17 @@ namespace MueLu {
         aggregates.SetIsRoot(rootCandidate);
         aggIndex = numLocalAggregates++;
 
+        // Add the root.
+        aggStat     [rootCandidate] = AGGREGATED;
+        vertex2AggId[rootCandidate] = aggIndex;
+        procWinner  [rootCandidate] = myRank;
         for (size_t k = 0; k < aggSize; k++) {
           aggStat     [aggList[k]] = AGGREGATED;
           vertex2AggId[aggList[k]] = aggIndex;
           procWinner  [aggList[k]] = myRank;
         }
 
-        numNonAggregatedNodes -= aggSize;
+        numNonAggregatedNodes -= aggSize+1;
       }
     }
 

diff --git a/...ges/muelu/src/Graph/UncoupledAggregation/MueLu_AggregationPhase2aAlgorithm_kokkos_def.hpp b/...ges/muelu/src/Graph/UncoupledAggregation/MueLu_AggregationPhase2aAlgorithm_kokkos_def.hpp
@@ -133,20 +133,13 @@ namespace MueLu {
 
                                   // Loop over neighbors to count how many nodes could join
                                   // the new aggregate
-                                  // Note on 2019-11-22, LBV:
-                                  // The rootCandidate is not taken into account and in fact
-                                  // not aggregatesd later on. To change that we want to
-                                  // modify:
-                                  // if(aggSize < maxNodesPerAggregate)
-                                  // to:
-                                  // if(aggSize < maxNodesPerAggregate - 1)
                                   LO numNeighbors = 0;
                                   for(int j = 0; j < neighbors.length; ++j) {
                                     LO neigh = neighbors(j);
                                     if(neigh != rootCandidate) {
                                       if(graph.isLocalNeighborVertex(neigh) &&
                                          (aggStat(neigh) == READY) &&
-                                         (aggSize < maxNodesPerAggregate)) {
+                                         (aggSize < maxNodesPerAggregate-1)) {
                                         ++aggSize;
                                       }
                                       ++numNeighbors;
@@ -155,8 +148,6 @@ namespace MueLu {
 
                                   // If a sufficient number of nodes can join the new aggregate
                                   // then we actually create the aggregate.
-                                  // Note on 2019-11-22, LBV:
-                                  // Same changes as described in the note above could be applied
                                   if(aggSize > minNodesPerAggregate &&
                                      aggSize > factor*numNeighbors) {
 
@@ -165,6 +156,14 @@ namespace MueLu {
                                       atomic_fetch_add(&numLocalAggregates(), 1);
 
                                     LO numAggregated = 0;
+
+                                    // Add the root.
+                                    aggStat(rootCandidate)         = AGGREGATED;
+                                    vertex2AggId(rootCandidate, 0) = aggIndex;
+                                    procWinner(rootCandidate, 0)   = myRank;
+                                    ++numAggregated;
+                                    --lNumNonAggregatedNodes;
+
                                     for(int neighIdx = 0; neighIdx < neighbors.length; ++neighIdx) {
                                       LO neigh = neighbors(neighIdx);
                                       if(neigh != rootCandidate) {