Github user srowen commented on a diff in the pull request:
https://github.com/apache/spark/pull/14140#discussion_r70819198
--- Diff:
mllib/src/main/scala/org/apache/spark/mllib/regression/IsotonicRegression.scala
---
@@ -408,9 +409,11 @@ class IsotonicRegression private (private var
isotonic: Boolean) extends Seriali
*/
private def parallelPoolAdjacentViolators(
input: RDD[(Double, Double, Double)]): Array[(Double, Double,
Double)] = {
- val parallelStepResult = input
- .sortBy(x => (x._2, x._1))
- .glom()
+ val keyedInput = input.keyBy(_._2)
+ val parallelStepResult = keyedInput
+ .partitionBy(new RangePartitioner(keyedInput.getNumPartitions,
keyedInput))
+ .values
+ .mapPartitions( p => Iterator(p.toSeq.sortBy(x => (x._2,
x._1)).toArray))
--- End diff --
Ah I'm reading badly this morning. Of course right about `keyedInput` and
yes the `Iterator` wraps the array, right. But I think that your last change is
spot on, at least one conversion could be avoided. LGTM
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