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From jkbradley <...@git.apache.org>
Subject [GitHub] spark pull request: [SPARK-3161][MLLIB] Adding a node Id caching m...
Date Tue, 21 Oct 2014 20:30:38 GMT
Github user jkbradley commented on a diff in the pull request:

    https://github.com/apache/spark/pull/2868#discussion_r19176858
  
    --- Diff: mllib/src/main/scala/org/apache/spark/mllib/tree/impl/NodeIdCache.scala ---
    @@ -0,0 +1,171 @@
    +/*
    + * 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
    +
    +import org.apache.spark.rdd.RDD
    +import org.apache.spark.annotation.DeveloperApi
    +import org.apache.spark.mllib.tree.configuration.FeatureType._
    +import spire.implicits._
    +import org.apache.spark.storage.StorageLevel
    +import org.apache.spark.mllib.tree.model.{Bin, Split}
    +
    +/**
    + * :: DeveloperApi ::
    + * This is used by the node id cache to find the child id that a data point would belong
to.
    + * @param split Split information.
    + * @param leftChildIndex Left child index.
    + * @param rightChildIndex Right child index.
    + */
    +@DeveloperApi
    +private[tree] case class NodeIndexUpdater(
    +    split: Split,
    +    leftChildIndex: Int,
    +    rightChildIndex: Int) {
    +  /**
    +   * Determine a child node index based on the feature value and the split.
    +   * @param binnedFeatures Binned feature values.
    +   * @param bins Bin information to convert the bin indices to approximate feature values.
    +   * @return Child node index to update to.
    +   */
    +  def updateNodeIndex(binnedFeatures: Array[Int], bins: Array[Array[Bin]]): Int = {
    +    if (split.featureType == Continuous) {
    +      val featureIndex = split.feature
    +      val binIndex = binnedFeatures(featureIndex)
    +      val featureValueUpperBound = bins(featureIndex)(binIndex).highSplit.threshold
    +      if (featureValueUpperBound <= split.threshold) {
    +        leftChildIndex
    +      } else {
    +        rightChildIndex
    +      }
    +    } else {
    +      if (split.categories.contains(binnedFeatures(split.feature).toDouble)) {
    +        leftChildIndex
    +      } else {
    +        rightChildIndex
    +      }
    +    }
    +  }
    +}
    +
    +/**
    + * A given TreePoint would belong to a particular node per tree.
    + * This is used to keep track of which node for a particular tree that a TreePoint belongs
to.
    + * A separate RDD of Array[Int] needs to be maintained and updated at each iteration.
    + * @param data The RDD of training rows.
    + * @param cur The initial values in the cache
    + *            (should be an Array of all 1's (meaning the root nodes)).
    + * @param checkpointDir The checkpoint directory where
    + *                      the checkpointed files will be stored.
    + * @param checkpointInterval The checkpointing interval
    + *                           (how often should the cache be checkpointed.).
    + */
    +@DeveloperApi
    +private[tree] class NodeIdCache(
    +  val data: RDD[BaggedPoint[TreePoint]],
    +  var cur: RDD[Array[Int]],
    +  val checkpointDir: Option[String],
    +  val checkpointInterval: Int) {
    +
    +  // To keep track of the past checkpointed RDDs.
    +  val checkpointQueue = mutable.Queue[RDD[Array[Int]]]()
    +  var rddUpdateCount = 0
    +  if (checkpointDir != None) {
    +    cur.sparkContext.setCheckpointDir(checkpointDir.get)
    +  }
    +
    +  /**
    +   * Update the node index values in the cache.
    +   * This updates the RDD and its lineage.
    +   * TODO: Passing bin information to executors seems unnecessary and costly.
    +   * @param nodeIdUpdaters A map of node index updaters.
    +   *                       The key is the indices of nodes that we want to update.
    +   * @param bins Bin information needed to find child node indices.
    +   */
    +  def updateNodeIndices(
    +      nodeIdUpdaters: Array[Map[Int, NodeIndexUpdater]],
    +      bins: Array[Array[Bin]]): Unit = {
    +    val updatedRDD = data.zip(cur).map {
    +      dataPoint => {
    +        cfor(0)(_ < nodeIdUpdaters.length, _ + 1)(
    +          treeId => {
    +            val nodeIdUpdater = nodeIdUpdaters(treeId).getOrElse(dataPoint._2(treeId),
null)
    +            if (nodeIdUpdater != null) {
    +              val newNodeIndex = nodeIdUpdater.updateNodeIndex(
    +                binnedFeatures = dataPoint._1.datum.binnedFeatures,
    +                bins = bins)
    +              dataPoint._2(treeId) = newNodeIndex
    +            }
    +          }
    +        )
    +
    +        dataPoint._2
    +      }
    +    }
    +
    +    cur = updatedRDD
    +    rddUpdateCount += 1
    +
    +    // Handle checkpointing if the directory is not None.
    +    if (checkpointDir != None && (rddUpdateCount % checkpointInterval) == 0)
{
    +      // Let's see if we can unpersist previous checkpoints.
    +      var canUnpersist = true
    +      while (checkpointQueue.size > 1 && canUnpersist) {
    +        // We can unpersist the oldest checkpoint iff
    +        // the next checkpoint actually exists in the file system.
    +        if (checkpointQueue.get(1).get.getCheckpointFile != None) {
    +          val old = checkpointQueue.dequeue()
    +          old.unpersist()
    +        } else {
    +          canUnpersist = false
    +        }
    +      }
    +
    +      cur.persist(StorageLevel.MEMORY_AND_DISK)
    +      cur.checkpoint()
    +      checkpointQueue.enqueue(cur)
    +    }
    +  }
    +}
    +
    +@DeveloperApi
    +private[tree] object NodeIdCache {
    +  /**
    +   * Initialize the node Id cache with initial node Id values.
    +   * @param data The RDD of training rows.
    +   * @param numTrees The number of trees that we want to create cache for.
    +   * @param checkpointDir The checkpoint directory where the checkpointed files will
be stored.
    +   * @param checkpointInterval The checkpointing interval
    +   *                           (how often should the cache be checkpointed.).
    +   * @param initVal The inital values in the cache.
    --- End diff --
    
    "inital" ---> "initial"


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