Github user sethah commented on a diff in the pull request: https://github.com/apache/spark/pull/11989#discussion_r57978546 --- Diff: mllib/src/main/scala/org/apache/spark/mllib/tree/impl/DecisionTreeMetadata.scala --- @@ -183,11 +183,40 @@ private[spark] object DecisionTreeMetadata extends Logging { } case _ => featureSubsetStrategy } + + object featureSubsetNumber { + def unapply(strategy: String): Option[Int] = try { + val number = strategy.toInt + if (0 < number) { + Some(number) + } else { + None + } + } catch { + case _ : java.lang.NumberFormatException => None + } + } + + object featureSubsetFraction { + def unapply(strategy: String): Option[Double] = try { + val fraction = strategy.toDouble + if (0.0 < fraction && fraction <= 1.0) { + Some(fraction) + } else { + None + } + } catch { + case _ : java.lang.NumberFormatException => None + } + } + 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) case "onethird" => (numFeatures / 3.0).ceil.toInt + case featureSubsetNumber(number) => if (number > numFeatures) numFeatures else number + case featureSubsetFraction(fraction) => (fraction * numFeatures).ceil.toInt --- End diff -- Again, I think regex can simplify things a bit here. I haven't tried the following, but it should work. ```scala val isIntRegex = "(\\d+)".r val isFractionRegex = "(0?\\.\\d+|1.0+)".r 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) case "onethird" => (numFeatures / 3.0).ceil.toInt case isIntRegex(number) => if (number > numFeatures) numFeatures else number case isFractionRegex(fraction) => (fraction * numFeatures).ceil.toInt } ``` Then we could avoid adding the `featureSubset*` objects.
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