def iterate()

in cassovary-core/src/main/scala/com/twitter/cassovary/algorithms/linkanalysis/PageRank.scala [85:113]

• 25 lines of code
• 4 McCabe index (conditional complexity)

  def iterate(prevIteration: PageRankIterationState): PageRankIterationState = {
    val beforePR = prevIteration.pageRank
    val afterPR  = new Array[Double](graph.maxNodeId + 1)

    log.debug("Calculating new PageRank values based on previous iteration...")
    val prog = Progress("pagerank_calc", 65536, Some(graph.nodeCount))

    //must correct for nodes with no outgoing connections
    val dangleSum = dampingFactor * zeroOutgoing.foldLeft(0.0){ (partialSum, n) => partialSum + beforePR(n) } / nodeCount

    graph foreach { node =>
      val neighbors = efficientNeighbors(node)
      if (isInStored) {
        var newNodePR = 0.0
        neighbors.foreach {
          nbr => newNodePR += dampingFactor * beforePR(nbr) / outboundCount(nbr)
        }
        afterPR(node.id) = newNodePR + dampingAmount + dangleSum
      }
      else {
        neighbors foreach { nbr =>
          afterPR(nbr) += dampingFactor * beforePR(node.id) / node .outboundCount
        }
        afterPR(node.id) += dangleSum + dampingAmount
      }
      prog.inc
    }
    PageRankIterationState(afterPR, deltaOfArrays(prevIteration.pageRank, afterPR), prevIteration.iteration + 1)
  }