Added partly written DTStatsAggregator

Author: jkbradley

mllib/src/main/scala/org/apache/spark/mllib/tree/impl/DTStatsAggregator.scala

@@ -0,0 +1,52 @@
+/*
+ * 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.mllib.tree.impl
+
+import scala.collection.mutable
+
+
+/**
+ * :: Experimental ::
+ * DecisionTree statistics aggregator.
+ * This holds a flat array of statistics for a set of (nodes, features, bins)
+ * and helps with indexing.
+ * TODO: Allow views of Vector types to replace some of the code in here.
+ */
+private[tree] class DTStatsAggregator(
+    val numNodes: Int,
+    val numFeatures: Int,
+    val numBins: Array[Int],
+    val statsSize: Int) {
+
+  require(numBins.size == numFeatures, s"DTStatsAggregator was given numBins" +
+    s" (of size ${numBins.size}) which did not match numFeatures = $numFeatures.")
+
+  val featureOffsets: Array[Int] = numBins.scanLeft(0)(_ + _).map(statsSize * _)
+
+  val allStatsSize: Int = numNodes * featureOffsets.last * statsSize
+
+  val allStats: Array[Double] = new Array[Double](allStatsSize)
+
+// TODO: Make views
+  /*
+  Uses:
+  point access
+
+   */
+
+}

mllib/src/main/scala/org/apache/spark/mllib/tree/impurity/Gini.scala

@@ -89,9 +89,6 @@ private[tree] class GiniAggregator(numClasses: Int)
       throw new IllegalArgumentException(s"GiniAggregator given label $label" +
         s" but requires label < numClasses (= ${counts.size}).")
     }
-    if (label.toInt >= counts.size) {
-      throw new RuntimeException(s"label = $label, counts = $counts")
-    }
     counts(label.toInt) += 1
   }
 

mllib/src/main/scala/org/apache/spark/mllib/tree/impurity/Impurity.scala

@@ -113,6 +113,7 @@ private[tree] abstract class ImpurityAggregator(statsSize: Int) extends Serializ
   /**
    * Return the index of the largest element in this array.
    * If there are ties, the first maximal element is chosen.
+   * TODO: Move this elsewhere in Spark?
    */
   protected def indexOfLargestArrayElement(array: Array[Double]): Int = {
     val result = array.foldLeft(-1, Double.MinValue, 0) {