Github user manishamde commented on a diff in the pull request: https://github.com/apache/spark/pull/2435#discussion_r17889650 --- Diff: mllib/src/main/scala/org/apache/spark/mllib/tree/RandomForest.scala --- @@ -0,0 +1,430 @@ +/* + * 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 + +import scala.collection.JavaConverters._ +import scala.collection.mutable + +import org.apache.spark.Logging +import org.apache.spark.annotation.Experimental +import org.apache.spark.api.java.JavaRDD +import org.apache.spark.mllib.regression.LabeledPoint +import org.apache.spark.mllib.tree.configuration.Algo._ +import org.apache.spark.mllib.tree.configuration.QuantileStrategy._ +import org.apache.spark.mllib.tree.configuration.Strategy +import org.apache.spark.mllib.tree.impl.{BaggedPoint, TreePoint, DecisionTreeMetadata, TimeTracker} +import org.apache.spark.mllib.tree.impurity.Impurities +import org.apache.spark.mllib.tree.model._ +import org.apache.spark.rdd.RDD +import org.apache.spark.storage.StorageLevel +import org.apache.spark.util.Utils + +/** + * :: Experimental :: + * A class which implements a random forest learning algorithm for classification and regression. + * It supports both continuous and categorical features. + * + * @param strategy The configuration parameters for the random forest algorithm which specify + * the type of algorithm (classification, regression, etc.), feature type + * (continuous, categorical), depth of the tree, quantile calculation strategy, + * etc. + * @param numTrees If 1, then no bootstrapping is used. If > 1, then bootstrapping is done. + * @param featureSubsetStrategy Number of features to consider for splits at each node. + * Supported: "auto" (default), "all", "sqrt", "log2", "onethird". + * If "auto" is set, this parameter is set based on numTrees: + * if numTrees == 1, then featureSubsetStrategy = "all"; + * if numTrees > 1, then featureSubsetStrategy = "sqrt". + * @param seed Random seed for bootstrapping and choosing feature subsets. + */ +@Experimental +private class RandomForest ( + private val strategy: Strategy, + private val numTrees: Int, + featureSubsetStrategy: String, + private val seed: Int) + extends Serializable with Logging { + + strategy.assertValid() + require(numTrees > 0, s"RandomForest requires numTrees > 0, but was given numTrees = $numTrees.") + require(RandomForest.supportedFeatureSubsetStrategies.contains(featureSubsetStrategy), + s"RandomForest given invalid featureSubsetStrategy: $featureSubsetStrategy." + + s" Supported values: ${RandomForest.supportedFeatureSubsetStrategies.mkString(", ")}.") + + /** + * Method to train a decision tree model over an RDD + * @param input Training data: RDD of [[org.apache.spark.mllib.regression.LabeledPoint]] + * @return RandomForestModel that can be used for prediction + */ + def train(input: RDD[LabeledPoint]): RandomForestModel = { + + val timer = new TimeTracker() + + timer.start("total") + + timer.start("init") + + val retaggedInput = input.retag(classOf[LabeledPoint]) + val metadata = + DecisionTreeMetadata.buildMetadata(retaggedInput, strategy, numTrees, featureSubsetStrategy) + logDebug("algo = " + strategy.algo) + logDebug("numTrees = " + numTrees) + logDebug("seed = " + seed) + logDebug("maxBins = " + metadata.maxBins) + logDebug("featureSubsetStrategy = " + featureSubsetStrategy) + logDebug("numFeaturesPerNode = " + metadata.numFeaturesPerNode) + + // Find the splits and the corresponding bins (interval between the splits) using a sample + // of the input data. + timer.start("findSplitsBins") + val (splits, bins) = DecisionTree.findSplitsBins(retaggedInput, metadata) + timer.stop("findSplitsBins") + logDebug("numBins: feature: number of bins") + logDebug(Range(0, metadata.numFeatures).map { featureIndex => + s"\t$featureIndex\t${metadata.numBins(featureIndex)}" + }.mkString("\n")) + + // Bin feature values (TreePoint representation). + // Cache input RDD for speedup during multiple passes. + val treeInput = TreePoint.convertToTreeRDD(retaggedInput, bins, metadata) + val baggedInput = if (numTrees > 1) { + BaggedPoint.convertToBaggedRDD(treeInput, numTrees, seed) + } else { + BaggedPoint.convertToBaggedRDDWithoutSampling(treeInput) + }.persist(StorageLevel.MEMORY_AND_DISK) + + // depth of the decision tree + val maxDepth = strategy.maxDepth + require(maxDepth <= 30, + s"DecisionTree currently only supports maxDepth <= 30, but was given maxDepth = $maxDepth.") + + // Max memory usage for aggregates + val maxMemoryUsage: Long = strategy.maxMemoryInMB * 1024L * 1024L + logDebug("max memory usage for aggregates = " + maxMemoryUsage + " bytes.") + val maxMemoryPerNode = { + val featureSubset: Option[Array[Int]] = if (metadata.subsamplingFeatures) { + // Find numFeaturesPerNode largest bins to get an upper bound on memory usage. --- End diff -- Ok, I see the TODO a few lines below. Maybe, we should move it here. :-)
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