Avoid using MapRetrievalCache unless node lookup is expensive. The cl…

…ass constructs "CacheEntry" objects when adding to the cache, which if the cache is not used makes us slower, and even if the cache is used is roughly a wash speed-wise if map lookup is fast (e.g. a HashMap or ImmutableMap, and an object with a reasonable hashCode()).

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Created by MOE: https://github.com/google/moe
MOE_MIGRATED_REVID=126874176

guava/src/com/google/common/graph/AbstractConfigurableGraph.java

@@ -25,6 +25,7 @@
 
 import java.util.Map;
 import java.util.Set;
+import java.util.TreeMap;
 
 import javax.annotation.Nullable;
 
@@ -90,7 +91,10 @@ private static <N> Map<N, NodeAdjacencies<N>> getNodeMapforBuilder(
     this.isDirected = builder.directed;
     this.allowsSelfLoops = builder.allowsSelfLoops;
     this.nodeOrder = builder.nodeOrder;
-    this.nodeConnections = new MapRetrievalCache<N, NodeAdjacencies<N>>(nodeConnections);
+    // Prefer the heavier "MapRetrievalCache" for nodes if lookup is expensive.
+    this.nodeConnections = (nodeConnections instanceof TreeMap)
+        ? new MapRetrievalCache<N, NodeAdjacencies<N>>(nodeConnections)
+        : new MapIteratorCache<N, NodeAdjacencies<N>>(nodeConnections);
   }
 
   /**

guava/src/com/google/common/graph/AbstractConfigurableNetwork.java

@@ -29,6 +29,7 @@
 
 import java.util.Map;
 import java.util.Set;
+import java.util.TreeMap;
 
 import javax.annotation.Nullable;
 
@@ -124,9 +125,11 @@ private static <N, E> Map<E, N> getEdgeMapForBuilder(
     this.allowsSelfLoops = builder.allowsSelfLoops;
     this.nodeOrder = builder.nodeOrder;
     this.edgeOrder = builder.edgeOrder;
-    // Prefer the heavier "MapRetrievalCache" for nodes to optimize for the case where methods
-    // accessing the same node(s) are called repeatedly, such as in Graphs.removeEdgesConnecting().
-    this.nodeConnections = new MapRetrievalCache<N, NodeConnections<N, E>>(nodeConnections);
+    // Prefer the heavier "MapRetrievalCache" for nodes if lookup is expensive. This optimizes
+    // methods that access the same node(s) repeatedly, such as Graphs.removeEdgesConnecting().
+    this.nodeConnections = (nodeConnections instanceof TreeMap)
+        ? new MapRetrievalCache<N, NodeConnections<N, E>>(nodeConnections)
+        : new MapIteratorCache<N, NodeConnections<N, E>>(nodeConnections);
     this.edgeToReferenceNode = new MapIteratorCache<E, N>(edgeToReferenceNode);
   }