Peng Meng created SPARK-21624:
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Summary: Optimize communication cost of RF/GBT/DT
Key: SPARK-21624
URL: https://issues.apache.org/jira/browse/SPARK-21624
Project: Spark
Issue Type: Improvement
Components: ML, MLlib
Affects Versions: 2.3.0
Reporter: Peng Meng
{quote}The implementation of RF is bound by either the cost of statistics
computation on workers or by communicating the sufficient statistics.{quote}
The statistics are stored in allStats:
{code:java}
/**
* Flat array of elements.
* Index for start of stats for a (feature, bin) is:
* index = featureOffsets(featureIndex) + binIndex * statsSize
*/
private var allStats: Array[Double] = new Array[Double](allStatsSize)
{code}
The size of allStats maybe very large, and it can be very spare, especially on
the nodes that near the leave of the tree.
I have changed allStats from Array to SparseVector, my tests show the
communication is down by about 50%.
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