Github user etrain commented on a diff in the pull request: https://github.com/apache/spark/pull/886#discussion_r14836561 --- Diff: mllib/src/main/scala/org/apache/spark/mllib/tree/DecisionTree.scala --- @@ -768,104 +973,157 @@ object DecisionTree extends Serializable with Logging { /** * Extracts left and right split aggregates. * @param binData Array[Double] of size 2*numFeatures*numSplits - * @return (leftNodeAgg, rightNodeAgg) tuple of type (Array[Double], - * Array[Double]) where each array is of size(numFeature,2*(numSplits-1)) + * @return (leftNodeAgg, rightNodeAgg) tuple of type (Array[Array[Array[Double\]\]\], + * Array[Array[Array[Double\]\]\]) where each array is of size(numFeature, + * (numBins - 1), numClasses) */ def extractLeftRightNodeAggregates( - binData: Array[Double]): (Array[Array[Double]], Array[Array[Double]]) = { + binData: Array[Double]): (Array[Array[Array[Double]]], Array[Array[Array[Double]]]) = { + + + def findAggForOrderedFeatureClassification( + leftNodeAgg: Array[Array[Array[Double]]], + rightNodeAgg: Array[Array[Array[Double]]], + featureIndex: Int) { + + // shift for this featureIndex + val shift = numClasses * featureIndex * numBins + + var classIndex = 0 + while (classIndex < numClasses) { + // left node aggregate for the lowest split + leftNodeAgg(featureIndex)(0)(classIndex) = binData(shift + classIndex) + // right node aggregate for the highest split + rightNodeAgg(featureIndex)(numBins - 2)(classIndex) + = binData(shift + (numClasses * (numBins - 1)) + classIndex) + classIndex += 1 + } + + // Iterate over all splits. + var splitIndex = 1 + while (splitIndex < numBins - 1) { + // calculating left node aggregate for a split as a sum of left node aggregate of a + // lower split and the left bin aggregate of a bin where the split is a high split + var innerClassIndex = 0 + while (innerClassIndex < numClasses) { + leftNodeAgg(featureIndex)(splitIndex)(innerClassIndex) + = binData(shift + numClasses * splitIndex + innerClassIndex) + + leftNodeAgg(featureIndex)(splitIndex - 1)(innerClassIndex) + rightNodeAgg(featureIndex)(numBins - 2 - splitIndex)(innerClassIndex) = + binData(shift + (numClasses * (numBins - 1 - splitIndex) + innerClassIndex)) + + rightNodeAgg(featureIndex)(numBins - 1 - splitIndex)(innerClassIndex) + innerClassIndex += 1 + } + splitIndex += 1 + } + } + + def findAggForUnorderedFeatureClassification( + leftNodeAgg: Array[Array[Array[Double]]], + rightNodeAgg: Array[Array[Array[Double]]], + featureIndex: Int) { + + val rightChildShift = numClasses * numBins * numFeatures + var splitIndex = 0 + while (splitIndex < numBins - 1) { + var classIndex = 0 + while (classIndex < numClasses) { + // shift for this featureIndex + val shift = numClasses * featureIndex * numBins + splitIndex * numClasses + val leftBinValue = binData(shift + classIndex) + val rightBinValue = binData(rightChildShift + shift + classIndex) + leftNodeAgg(featureIndex)(splitIndex)(classIndex) = leftBinValue + rightNodeAgg(featureIndex)(splitIndex)(classIndex) = rightBinValue + classIndex += 1 + } + splitIndex += 1 + } + } + + def findAggForRegression( + leftNodeAgg: Array[Array[Array[Double]]], + rightNodeAgg: Array[Array[Array[Double]]], + featureIndex: Int) { + + // shift for this featureIndex + val shift = 3 * featureIndex * numBins + // left node aggregate for the lowest split + leftNodeAgg(featureIndex)(0)(0) = binData(shift + 0) + leftNodeAgg(featureIndex)(0)(1) = binData(shift + 1) + leftNodeAgg(featureIndex)(0)(2) = binData(shift + 2) + + // right node aggregate for the highest split + rightNodeAgg(featureIndex)(numBins - 2)(0) = + binData(shift + (3 * (numBins - 1))) + rightNodeAgg(featureIndex)(numBins - 2)(1) = + binData(shift + (3 * (numBins - 1)) + 1) + rightNodeAgg(featureIndex)(numBins - 2)(2) = + binData(shift + (3 * (numBins - 1)) + 2) + + // Iterate over all splits. + var splitIndex = 1 + while (splitIndex < numBins - 1) { + // calculating left node aggregate for a split as a sum of left node aggregate of a + // lower split and the left bin aggregate of a bin where the split is a high split + leftNodeAgg(featureIndex)(splitIndex)(0) = binData(shift + 3 * splitIndex) + --- End diff -- This is kind of annoying, I'm sure, but the repeated use of 0,1,2 offsets here here is starting to look like a code smell. A while loop here over the range 0,1,2 would tighten things up.
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