Github user mengxr commented on a diff in the pull request:
https://github.com/apache/spark/pull/1975#discussion_r16322130
--- Diff:
mllib/src/main/scala/org/apache/spark/mllib/tree/DecisionTree.scala ---
@@ -198,29 +214,22 @@ class DecisionTree (private val strategy: Strategy)
extends Serializable with Lo
index: Int,
maxDepth: Int,
nodeSplitStats: (Split, InformationGainStats),
- parentImpurities: Array[Double],
- filters: Array[List[Filter]]): Unit = {
+ parentImpurities: Array[Double]): Unit = {
+ if (level >= maxDepth)
+ return
// 0 corresponds to the left child node and 1 corresponds to the right
child node.
var i = 0
while (i <= 1) {
- // Calculate the index of the node from the node level and the index
at the current level.
+ // Calculate the index of the node from the node level and the index
at the current level.
val nodeIndex = math.pow(2, level + 1).toInt - 1 + 2 * index + i
- if (level < maxDepth) {
- val impurity = if (i == 0) {
- nodeSplitStats._2.leftImpurity
- } else {
- nodeSplitStats._2.rightImpurity
- }
- logDebug("nodeIndex = " + nodeIndex + ", impurity = " + impurity)
- // noting the parent impurities
- parentImpurities(nodeIndex) = impurity
- // noting the parents filters for the child nodes
- val childFilter = new Filter(nodeSplitStats._1, if (i == 0) -1
else 1)
- filters(nodeIndex) = childFilter :: filters((nodeIndex - 1) / 2)
- for (filter <- filters(nodeIndex)) {
- logDebug("Filter = " + filter)
- }
+ val impurity = if (i == 0) {
+ nodeSplitStats._2.leftImpurity
+ } else {
+ nodeSplitStats._2.rightImpurity
}
+ logDebug("nodeIndex = " + nodeIndex + ", impurity = " + impurity)
+ // noting the parent impurities
+ parentImpurities(nodeIndex) = impurity
--- End diff --
Since most of the code is removed, maybe we can unfold the while loop:
~~~
val leftNodeIndex = math.pow(2, level + 1).toInt - 1 + 2 * index
parentImpurities(leftNodeIndex) = nodeSplitStats._2.leftImpurity
val rightNodeIndex = leftNodeIndex + 1
parentImpurities(rightNodeIndex) = nodeSplitStats._2.rightImpurity
~~~
Btw, could the code be simplified if we don't use `leftNode` and
`rightNode` but `childNodes: Array[Node]`?
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