Github user jkbradley commented on a diff in the pull request:
https://github.com/apache/spark/pull/2435#discussion_r18008890
--- Diff:
mllib/src/main/scala/org/apache/spark/mllib/tree/impl/DecisionTreeMetadata.scala
---
@@ -128,13 +139,34 @@ private[tree] object DecisionTreeMetadata {
}
}
+ // Set number of features to use per node (for random forests).
+ val _featureSubsetStrategy = featureSubsetStrategy match {
+ case "auto" => if (numTrees == 1) "all" else "sqrt"
+ case _ => featureSubsetStrategy
+ }
+ val numFeaturesPerNode: Int = _featureSubsetStrategy match {
+ case "all" => numFeatures
+ case "sqrt" => math.sqrt(numFeatures).ceil.toInt
+ case "log2" => math.max(1, (math.log(numFeatures) /
math.log(2)).ceil.toInt)
--- End diff --
sqrt and log2 are used in scikit-learn. I have not seen onethird. I'd be
OK with removing it. (Can you also please check out the comments above about
this? It would be good to know if I should go ahead and include more options
for this parameter, and also if I should rename the parameter to match another
library. Thanks!)
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