[GitHub] spark pull request: [SPARK-11432][GraphX] Personalized PageRank sh...

[dbtsai <gi...@git.apache.org>]

Github user dbtsai commented on a diff in the pull request:

    https://github.com/apache/spark/pull/9386#discussion_r43599996
  
    --- Diff: graphx/src/main/scala/org/apache/spark/graphx/lib/PageRank.scala ---
    @@ -104,17 +104,25 @@ object PageRank extends Logging {
           graph: Graph[VD, ED], numIter: Int, resetProb: Double = 0.15,
           srcId: Option[VertexId] = None): Graph[Double, Double] =
       {
    +    val personalized = srcId isDefined
         // Initialize the PageRank graph with each edge attribute having
    -    // weight 1/outDegree and each vertex with attribute 1.0.
    +    // weight 1/outDegree and each vertex with attribute resetProb.
    +    // When running personalized pagerank, only the source vertex
    +    // has an attribute resetProb. All others are set to 0.
         var rankGraph: Graph[Double, Double] = graph
           // Associate the degree with each vertex
           .outerJoinVertices(graph.outDegrees) { (vid, vdata, deg) => deg.getOrElse(0) }
           // Set the weight on the edges based on the degree
           .mapTriplets( e => 1.0 / e.srcAttr, TripletFields.Src )
           // Set the vertex attributes to the initial pagerank values
    -      .mapVertices( (id, attr) => resetProb )
    +      .mapVertices( (id, attr) => {
    +        if (personalized) {
    +          if (id == srcId.get) resetProb else 0.0
    +        } else {
    +          resetProb
    +        }
    +      })
     
    -    val personalized = srcId isDefined
         val src: VertexId = srcId.getOrElse(-1L)
    --- End diff --
    
    Move up `val src: VertexId = srcId.getOrElse(-1L) ` to `val personalized = srcId isDefined`


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