Github user smurching commented on a diff in the pull request:
https://github.com/apache/spark/pull/19433#discussion_r146731070
--- Diff:
mllib/src/main/scala/org/apache/spark/ml/tree/impl/AggUpdateUtils.scala ---
@@ -0,0 +1,85 @@
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one or more
+ * contributor license agreements. See the NOTICE file distributed with
+ * this work for additional information regarding copyright ownership.
+ * The ASF licenses this file to You under the Apache License, Version 2.0
+ * (the "License"); you may not use this file except in compliance with
+ * the License. You may obtain a copy of the License at
+ *
+ * http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package org.apache.spark.ml.tree.impl
+
+import org.apache.spark.ml.tree.Split
+
+/**
+ * Helpers for updating DTStatsAggregators during collection of sufficient
stats for tree training.
+ */
+private[impl] object AggUpdateUtils {
+
+ /**
+ * Updates the parent node stats of the passed-in impurity aggregator
with the labels
+ * corresponding to the feature values at indices [from, to).
+ */
+ private[impl] def updateParentImpurity(
+ statsAggregator: DTStatsAggregator,
+ col: FeatureVector,
+ from: Int,
+ to: Int,
+ instanceWeights: Array[Double],
+ labels: Array[Double]): Unit = {
+ from.until(to).foreach { idx =>
+ val rowIndex = col.indices(idx)
+ val label = labels(rowIndex)
+ statsAggregator.updateParent(label, instanceWeights(rowIndex))
+ }
+ }
+
+ /**
+ * Update aggregator for an (unordered feature, label) pair
+ * @param splits Array of arrays of splits for each feature; splits(i) =
splits for feature i.
+ */
+ private[impl] def updateUnorderedFeature(
+ agg: DTStatsAggregator,
+ featureValue: Int,
+ label: Double,
+ featureIndex: Int,
+ featureIndexIdx: Int,
+ splits: Array[Array[Split]],
--- End diff --
Good call, I'll make this change.
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