Github user jegonzal commented on a diff in the pull request:
https://github.com/apache/spark/pull/10#discussion_r11915905
--- Diff:
graphx/src/main/scala/org/apache/spark/graphx/lib/ShortestPaths.scala ---
@@ -0,0 +1,76 @@
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one or more
+ * contributor license agreements. See the NOTICE file distributed with
+ * this work for additional information regarding copyright ownership.
+ * The ASF licenses this file to You under the Apache License, Version 2.0
+ * (the "License"); you may not use this file except in compliance with
+ * the License. You may obtain a copy of the License at
+ *
+ * http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
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+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
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+ */
+
+package org.apache.spark.graphx.lib
+
+import org.apache.spark.graphx._
+
+object ShortestPaths {
+ type SPMap = Map[VertexId, Int] // map of landmarks -> minimum distance
to landmark
--- End diff --
The scala map data-structures can be pretty costly and inefficient.
Instead you could use an array containing the distances and then maintain a
global map (shared by broadcast variable) with the mapping from vertex id to
index in the array. This should also reduce the memory overhead substantially
since each vertex will not need to maintain its own locally Map data structure.
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