[jira] [Created] (SPARK-36420) Use `isEmpty` to improve performance in Pregel's superstep

["xiepengjie (Jira)" <ji...@apache.org>]

xiepengjie created SPARK-36420:
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             Summary: Use `isEmpty` to improve performance in Pregel's superstep
                 Key: SPARK-36420
                 URL: https://issues.apache.org/jira/browse/SPARK-36420
             Project: Spark
          Issue Type: Improvement
          Components: GraphX
    Affects Versions: 2.4.7
            Reporter: xiepengjie
             Fix For: 3.3.0


When I was running `Graphx.connectedComponents` with 20+ billion vertices and edges, I found that count is very slow.
{code:java}
object Pregel extends Logging {
  ...
  def apply[VD: ClassTag, ED: ClassTag, A: ClassTag] (...): Graph[VD, ED] = {
    ...
    // Maybe messages.isEmpty() is better than messages.count()
    var activeMessages = messages.count()

    // Loop
    var prevG: Graph[VD, ED] = null
    var i = 0
    while (activeMessages > 0 && i < maxIterations) {
      ...
      activeMessages = messages.count()
      ...
    }
    ...
    g
  } // end of apply

} // end of class Pregel
{code}
Maybe we only need an action operator here and active-messages are not empty, so we don’t need to use count, it’s better to use isEmpty. I verified it and it worked very well.

 



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