Github user mengxr commented on a diff in the pull request:
https://github.com/apache/spark/pull/2595#discussion_r18235836
--- Diff:
mllib/src/main/scala/org/apache/spark/mllib/tree/DecisionTree.scala ---
@@ -518,30 +516,58 @@ object DecisionTree extends Serializable with Logging
{
agg
}
- // Calculate bin aggregates.
- timer.start("aggregation")
- val binAggregates: DTStatsAggregator = {
- val initAgg = if (metadata.subsamplingFeatures) {
- new DTStatsAggregatorSubsampledFeatures(metadata,
treeToNodeToIndexInfo)
- } else {
- new DTStatsAggregatorFixedFeatures(metadata, numNodes)
- }
- input.treeAggregate(initAgg)(binSeqOp, DTStatsAggregator.binCombOp)
- }
- timer.stop("aggregation")
-
// Calculate best splits for all nodes in the group
timer.start("chooseSplits")
+ // In each parition, iterate all instances and compute aggregate stats
for each node,
+ // yield an (nodeIndex, nodeAggregateStats) pair for each node.
+ // After a `reduceByKey` operation,
+ // stats of a node will be shuffled to a particular partition and be
combined together,
+ // then best splits for nodes are found there.
+ // Finally, only best Splits for nodes are collected to driver to
construct decision tree.
+ val nodeToBestSplits: Map[Int, (Split, InformationGainStats, Predict)]
=
+ input.mapPartitions(points => {
--- End diff --
~~~
input.mapPartitions { points =>
...
}
~~~
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