new community handling

kahypar · Sep 12, 2024 · e888028 · e888028
1 parent 0e6d505
commit e888028
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Showing 2 changed files with 39 additions and 20 deletions.
diff --git a/mt-kahypar/partition/coarsening/multilevel/multilevel_vertex_pair_rater.h b/mt-kahypar/partition/coarsening/multilevel/multilevel_vertex_pair_rater.h
@@ -176,26 +176,9 @@ class MultilevelVertexPairRater {
       fillRatingMap<ScorePolicy>(hypergraph, u, tmp_ratings, cluster_ids);
     }
 
+    int cpu_id = THREAD_ID;
     const HypernodeWeight weight_u = cluster_weight[u];
     const PartitionID community_u_id = hypergraph.communityID(u);
-    bool ignore_communities = false;
-    if (may_ignore_communities) {
-      ignore_communities = true;
-      // ignore communities if no contraction within the community is possible
-      for (const auto& entry: tmp_ratings) {
-        const HypernodeID tmp_target = entry.key;
-        const HypernodeWeight target_weight = cluster_weight[entry.key];
-          if ( tmp_target != u && weight_u + target_weight <= max_allowed_node_weight
-               && similarity_policy.acceptContraction(hypergraph, _context, u, tmp_target)
-               && community_u_id == hypergraph.communityID(tmp_target) ) {
-            // TODO: fixed vertices?!
-            ignore_communities = false;
-            break;
-          }
-      }
-    }
-
-    int cpu_id = THREAD_ID;
     RatingType max_rating = std::numeric_limits<RatingType>::min();
     HypernodeID target = std::numeric_limits<HypernodeID>::max();
     HypernodeID target_id = std::numeric_limits<HypernodeID>::max();
@@ -219,7 +202,7 @@ class MultilevelVertexPairRater {
 
         DBG << "r(" << u << "," << tmp_target << ")=" << tmp_rating;
         if ( accept_fixed_vertex_contraction &&
-             (ignore_communities || community_u_id == hypergraph.communityID(tmp_target)) &&
+             (may_ignore_communities || community_u_id == hypergraph.communityID(tmp_target)) &&
              AcceptancePolicy::acceptRating( tmp_rating, max_rating,
                target_id, tmp_target_id, cpu_id, _already_matched) ) {
           max_rating = tmp_rating;

diff --git a/mt-kahypar/partition/coarsening/multilevel/three_phase_coarsener.h b/mt-kahypar/partition/coarsening/multilevel/three_phase_coarsener.h
@@ -91,6 +91,7 @@ class ThreePhaseCoarsener : public ICoarsener,
     _clustering_data(_hg.initialNumNodes(), context),
     _num_nodes_tracker(),
     _initial_num_nodes(_hg.initialNumNodes()),
+    _num_communities(kInvalidPartition),
     _current_vertices(),
     _pass_nr(0),
     _progress_bar(_hg.initialNumNodes(), 0, false),
@@ -153,6 +154,10 @@ class ThreePhaseCoarsener : public ICoarsener,
     bool did_second_lp = false;
     bool did_second_two_hop = false;
 
+    if (shouldIgnoreCommunities(hierarchy_contraction_limit)) {
+      cc.may_ignore_communities = true;
+    }
+
     // TODO: degree zero nodes?!
     // Phase 1: LP coarsening, but forbid contraction of low degree nodes onto high degree nodes
     coarseningRound("first_lp_round", "First LP round",
@@ -171,10 +176,15 @@ class ThreePhaseCoarsener : public ICoarsener,
     }
 
     // Phase 3: LP and two-hop coarsening with all contractions allowed (as well as contracting size 1 communities)
-    cc.may_ignore_communities = true;  // TODO: test/disable this
     cc.contract_aggressively = true;
     cc.hierarchy_contraction_limit = target_contraction_size;
     if (current_num_nodes > target_contraction_size) {
+      // lazy initialization of community count, since it requires scanning all nodes
+      initializeCommunityCount(current_hg);
+      if (shouldIgnoreCommunities(target_contraction_size)) {
+        cc.may_ignore_communities = true;
+      }
+
       DBG << "Start Second LP round: " << V(_num_nodes_tracker.currentNumNodes()) << V(target_contraction_size);
       coarseningRound("second_lp_round", "Second LP round",
                       current_hg, _lp_clustering, _always_accept_policy, cc);
@@ -281,6 +291,31 @@ class ThreePhaseCoarsener : public ICoarsener,
       _context.coarsening.contraction_limit );
   }
 
+  void initializeCommunityCount(const Hypergraph& hypergraph) {
+    if (_num_communities == kInvalidPartition) {
+      _num_communities =
+          tbb::parallel_reduce(
+                  tbb::blocked_range<HypernodeID>(ID(0), hypergraph.initialNumNodes()),
+                  0, [&](const tbb::blocked_range<HypernodeID>& range, PartitionID init) {
+            PartitionID my_range_num_communities = init;
+            for (HypernodeID hn = range.begin(); hn < range.end(); ++hn) {
+              if ( hypergraph.nodeIsEnabled(hn) ) {
+                my_range_num_communities = std::max(my_range_num_communities, hypergraph.communityID(hn) + 1);
+              }
+            }
+            return my_range_num_communities;
+          },
+          [](const PartitionID lhs, const PartitionID rhs) {
+            return std::max(lhs, rhs);
+          });
+      _num_communities = std::max(_num_communities, 1);
+    }
+  }
+
+  bool shouldIgnoreCommunities(HypernodeID hierarchy_contraction_limit) {
+    return _num_communities != kInvalidPartition && UL(_num_communities) > hierarchy_contraction_limit;
+  }
+
   LPClustering _lp_clustering;
   TwoHopClustering _two_hop_clustering;
   SimilarityPolicy _similarity_policy;
@@ -289,6 +324,7 @@ class ThreePhaseCoarsener : public ICoarsener,
   ConcurrentClusteringData _clustering_data;
   NumNodesTracker _num_nodes_tracker;
   HypernodeID _initial_num_nodes;
+  PartitionID _num_communities;
   parallel::scalable_vector<HypernodeID> _current_vertices;
   int _pass_nr;
   utils::ProgressBar _progress_bar;