LabelPropagation: Fix compile errors and style; rename from LPA

graphx/src/main/scala/org/apache/spark/graphx/lib/LPA.scala → graphx/src/main/scala/org/apache/spark/graphx/lib/LabelPropagation.scala

@@ -20,43 +20,44 @@ package org.apache.spark.graphx.lib
 import scala.reflect.ClassTag
 import org.apache.spark.graphx._
 
-/** LPA algorithm. */
-object LPA {
+/** Label Propagation algorithm. */
+object LabelPropagation {
   /**
-   * Run LPA (label propogation algorithm) for detecting communities in networks using the pregel framework.
-   * 
-   * Each node in the network is initially assigned to its own community.  At every super step 
-   * nodes send their community affiliation to all neighbors and update their state to the mode 
-   * community affiliation of incomming messages.  
+   * Run static Label Propagation for detecting communities in networks.
    *
-   * LPA is a standard community detection algorithm for graphs.  It is very inexpensive 
+   * Each node in the network is initially assigned to its own community. At every superstep, nodes
+   * send their community affiliation to all neighbors and update their state to the mode community
+   * affiliation of incoming messages.
+   *
+   * LPA is a standard community detection algorithm for graphs. It is very inexpensive
    * computationally, although (1) convergence is not guaranteed and (2) one can end up with
    * trivial solutions (all nodes are identified into a single community).
    *
-   * @tparam VD the vertex attribute type (discarded in the computation)
    * @tparam ED the edge attribute type (not used in the computation)
    *
    * @param graph the graph for which to compute the community affiliation
-   * @param maxSteps the number of supersteps of LPA to be performed
+   * @param maxSteps the number of supersteps of LPA to be performed. Because this is a static
+   * implementation, the algorithm will run for exactly this many supersteps.
    *
    * @return a graph with vertex attributes containing the label of community affiliation
    */
-  def run[VD: ClassTag, ED: ClassTag](graph: Graph[VD, ED], maxSteps: Int): Graph[VertexId, Long]{
+  def run[ED: ClassTag](graph: Graph[_, ED], maxSteps: Int): Graph[VertexId, ED] = {
     val lpaGraph = graph.mapVertices { case (vid, _) => vid }
-    def sendMessage(edge: EdgeTriplet[VertexId, ED]) = {
-      Iterator((e.srcId, Map(e.dstAttr -> 1L)),(e.dstId, Map(e.srcAttr -> 1L)))
+    def sendMessage(e: EdgeTriplet[VertexId, ED]) = {
+      Iterator((e.srcId, Map(e.dstAttr -> 1L)), (e.dstId, Map(e.srcAttr -> 1L)))
     }
-    def mergeMessage(count1: Map[VertexId, Long], count2: Map[VertexId, Long]): Map[VertexId, Long] = {
+    def mergeMessage(count1: Map[VertexId, Long], count2: Map[VertexId, Long])
+      : Map[VertexId, Long] = {
       (count1.keySet ++ count2.keySet).map { i =>
-        val count1Val = count1.getOrElse(i,0L)
-        val count2Val = count2.getOrElse(i,0L)
-	i -> (count1Val +count2Val)
-	}.toMap
+        val count1Val = count1.getOrElse(i, 0L)
+        val count2Val = count2.getOrElse(i, 0L)
+	    i -> (count1Val + count2Val)
+	  }.toMap
     }
-    def vertexProgram(vid: VertexId, attr: Long, message: Map[VertexId, Long])={
-      if (message.isEmpty) attr else message.maxBy{_._2}._1),
+    def vertexProgram(vid: VertexId, attr: Long, message: Map[VertexId, Long]) = {
+      if (message.isEmpty) attr else message.maxBy(_._2)._1
     }
-    val initialMessage = Map[VertexId,Long]()
+    val initialMessage = Map[VertexId, Long]()
     Pregel(lpaGraph, initialMessage, maxIterations = maxSteps)(
       vprog = vertexProgram,
       sendMsg = sendMessage,