[GitHub] spark pull request #14068: [SPARK-16469] enhanced simulate multiply

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

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

    https://github.com/apache/spark/pull/14068#discussion_r70181291
  
    --- Diff: mllib/src/main/scala/org/apache/spark/mllib/linalg/distributed/BlockMatrix.scala ---
    @@ -426,16 +426,19 @@ class BlockMatrix @Since("1.3.0") (
           partitioner: GridPartitioner): (BlockDestinations, BlockDestinations) = {
         val leftMatrix = blockInfo.keys.collect() // blockInfo should already be cached
         val rightMatrix = other.blocks.keys.collect()
    +
    +    val rightCounterpartsHelper = rightMatrix.groupBy(_._1).mapValues(_.map(_._2))
         val leftDestinations = leftMatrix.map { case (rowIndex, colIndex) =>
    -      val rightCounterparts = rightMatrix.filter(_._1 == colIndex)
    -      val partitions = rightCounterparts.map(b => partitioner.getPartition((rowIndex, b._2)))
    -      ((rowIndex, colIndex), partitions.toSet)
    +      ((rowIndex, colIndex), rightCounterpartsHelper.getOrElse(colIndex, Array()).map(b =>
    --- End diff --
    
    nit: for readability could you assign this to a variable instead of inlining it?
    In addition, for multi-line expressions
    ```scala
    .map { b =>
      blah
    }
    ```
    is more preferred


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