[dKaMinPar:Coarsening] Fix crash when a PE does not get any vertices

KaHIP · Jan 9, 2024 · 0c7127a · 0c7127a
1 parent b0cdb01
commit 0c7127a
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Showing 2 changed files with 5 additions and 2 deletions.
diff --git a/kaminpar-dist/coarsening/coarsener.cc b/kaminpar-dist/coarsening/coarsener.cc
@@ -67,7 +67,10 @@ const DistributedGraph *Coarsener::coarsen_once_global(const GlobalNodeWeight ma
   _global_clusterer->initialize(*graph);
   auto &clustering =
       _global_clusterer->cluster(*graph, static_cast<NodeWeight>(max_cluster_weight));
-  if (clustering.empty()) { // Empty --> converged
+
+  bool empty = clustering.empty();
+  MPI_Allreduce(MPI_IN_PLACE, &empty, 1, MPI_CXX_BOOL, MPI_LAND, graph->communicator());
+  if (empty) { // Empty --> converged
     DBG << "... converged with empty clustering";
     return graph;
   }

diff --git a/kaminpar-dist/coarsening/contraction/cluster_contraction.cc b/kaminpar-dist/coarsening/contraction/cluster_contraction.cc
@@ -900,7 +900,7 @@ ContractionResult contract_clustering(
   auto nonlocal_nodes = find_nonlocal_nodes(graph, lnode_to_gcluster);
 
   IF_STATS {
-    const GlobalNodeID total_num_nonlocal_nodes =
+    const auto total_num_nonlocal_nodes =
         mpi::allreduce<GlobalNodeID>(nonlocal_nodes.size(), MPI_SUM, graph.communicator());
     STATS << "Total number of nonlocal nodes: " << total_num_nonlocal_nodes;
   }