Github user freeman-lab commented on a diff in the pull request:
https://github.com/apache/spark/pull/5267#discussion_r29121114
--- Diff:
mllib/src/main/scala/org/apache/spark/mllib/clustering/HierarchicalClustering.scala
---
@@ -0,0 +1,574 @@
+/*
+ * 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.clustering
+
+import breeze.linalg.{DenseVector => BDV, SparseVector => BSV, Vector =>
BV, norm => breezeNorm}
+import org.apache.spark.mllib.linalg.{Vector, Vectors}
+import org.apache.spark.rdd.RDD
+import org.apache.spark.util.random.XORShiftRandom
+import org.apache.spark.{Logging, SparkException}
+
+import scala.collection.{Map, mutable}
+
+
+object HierarchicalClustering extends Logging {
+
+ private[clustering] val ROOT_INDEX_KEY: Long = 1
+
+ /**
+ * Finds the closes cluster's center
+ *
+ * @param metric a distance metric
+ * @param centers centers of the clusters
+ * @param point a target point
+ * @return an index of the array of clusters
+ */
+ private[mllib]
+ def findClosestCenter(metric: Function2[BV[Double], BV[Double], Double])
+ (centers: Seq[BV[Double]])(point: BV[Double]): Int = {
+ val (closestCenter, closestIndex) =
+ centers.zipWithIndex.map { case (center, idx) => (metric(center,
point), idx)}.minBy(_._1)
+ closestIndex
+ }
+}
+
+/**
+ * This is a divisive hierarchical clustering algorithm based on bi-sect
k-means algorithm.
+ *
+ * The main idea of this algorithm is based on "A comparison of document
clustering techniques",
+ * M. Steinbach, G. Karypis and V. Kumar. Workshop on Text Mining, KDD,
2000.
+ * http://cs.fit.edu/~pkc/classes/ml-internet/papers/steinbach00tr.pdf
+ *
+ * @param numClusters tne number of clusters you want
+ * @param clusterMap the pairs of cluster and its index as Map
+ * @param maxIterations the number of maximal iterations
+ * @param maxRetries the number of maximum retries
+ * @param seed a random seed
+ */
+class HierarchicalClustering private (
+ private var numClusters: Int,
+ private var clusterMap: Map[Long, ClusterTree],
+ private var maxIterations: Int,
+ private var maxRetries: Int,
+ private var seed: Long) extends Logging {
+
+ /**
+ * Constructs with the default configuration
+ */
+ def this() = this(20, mutable.ListMap.empty[Long, ClusterTree], 20, 10,
1)
+
+ /**
+ * Sets the number of clusters you want
+ */
+ def setNumClusters(numClusters: Int): this.type = {
+ this.numClusters = numClusters
+ this
+ }
+
+ def getNumClusters: Int = this.numClusters
+
+ /**
+ * Sets the number of maximal iterations in each clustering step
+ */
+ def setMaxIterations(maxIterations: Int): this.type = {
+ this.maxIterations = maxIterations
+ this
+ }
+
+ def getSubIterations: Int = this.maxIterations
+
+ /**
+ * Sets the number of maximum retries of each clustering step
+ */
+ def setMaxRetries(maxRetries: Int): this.type = {
+ this.maxRetries = maxRetries
+ this
+ }
+
+ def getMaxRetries: Int = this.maxRetries
+
+ /**
+ * Sets the random seed
+ */
+ def setSeed(seed: Long): this.type = {
+ this.seed = seed
+ this
+ }
+
+ def getSeed: Long = this.seed
+
+ /**
+ * Runs the hierarchical clustering algorithm
+ * @param input RDD of vectors
+ * @return model for the hierarchical clustering
+ */
+ def run(input: RDD[Vector]): HierarchicalClusteringModel = {
+ val sc = input.sparkContext
+ log.info(s"${sc.appName} starts a hierarchical clustering algorithm")
+
+ var data = initData(input).cache()
+ val startTime = System.currentTimeMillis()
+
+ // `clusters` is described as binary tree structure
+ // `clusters(1)` means the root of a binary tree
+ var clusters = summarizeAsClusters(data)
+ var leafClusters = clusters
+ var step = 1
+ var numDividedClusters = 0
+ var noMoreDividable = false
+ var rddArray = Array.empty[RDD[(Long, BV[Double])]]
+ // the number of maximum nodes of a binary tree by given parameter
+ val multiplier = math.ceil(math.log10(this.numClusters) /
math.log10(2.0)) + 1
+ val maxAllNodesInTree = math.pow(2, multiplier).toInt
+
+ while (clusters.size < maxAllNodesInTree && noMoreDividable == false) {
+ log.info(s"${sc.appName} starts step ${step}")
+
+ // enough to be clustered if the number of divided clusters is equal
to 0
+ val divided = getDividedClusters(data, leafClusters)
+ if (divided.size == 0) {
+ noMoreDividable = true
+ }
+ else {
+ // update each index
+ val newData = updateClusterIndex(data, divided).cache()
+ rddArray = rddArray ++ Array(data)
+ data = newData
+
+ // keep recent 2 cached RDDs in order to run more quickly
+ if (rddArray.size > 1) {
+ val head = rddArray.head
+ head.unpersist()
+ rddArray = rddArray.filterNot(_.hashCode() == head.hashCode())
+ }
+
+ // merge the divided clusters with the map as the cluster tree
+ clusters = clusters ++ divided
+ numDividedClusters = data.map(_._1).distinct().count().toInt
+ leafClusters = divided
+ step += 1
+
+ log.info(s"${sc.appName} adding ${divided.size} new clusters at
step:${step}")
+ }
+ }
+ // unpersist kept RDDs
+ rddArray.foreach(_.unpersist())
+
+ // build a cluster tree by Map class which is expressed
+ log.info(s"Building the cluster tree is started in ${sc.appName}")
+ val root = buildTree(clusters, HierarchicalClustering.ROOT_INDEX_KEY,
this.numClusters)
+ if (root == None) {
+ new SparkException("Failed to build a cluster tree from a Map type
of clusters")
+ }
+
+ // set the elapsed time for training
+ val finishTime = (System.currentTimeMillis() - startTime) / 1000.0
+ log.info(s"Elapsed Time for Hierarchical Clustering Training:
${finishTime} [sec]")
+
+ // make a hierarchical clustering model
+ val model = new HierarchicalClusteringModel(root.get)
+ val leavesNodes = model.getClusters()
+ if (leavesNodes.size < this.numClusters) {
+ log.warn(s"# clusters is less than you have expected:
${leavesNodes.size} / ${numClusters}. ")
+ }
+ model
+ }
+
+ /**
+ * Assigns the initial cluster index id to all data
+ */
+ private[clustering]
+ def initData(data: RDD[Vector]): RDD[(Long, BV[Double])] = {
+ data.map { v: Vector => (HierarchicalClustering.ROOT_INDEX_KEY,
v.toBreeze)}.cache
+ }
+
+ /**
+ * Summarizes data by each cluster as ClusterTree2 classes
+ */
+ private[clustering]
+ def summarizeAsClusters(data: RDD[(Long, BV[Double])]): Map[Long,
ClusterTree] = {
+ // summarize input data
+ val stats = summarize(data)
+
+ // convert statistics to ClusterTree class
+ stats.map { case (i, (sum, n, sumOfSquares)) =>
+ val center = Vectors.fromBreeze(sum :/ n)
+ val variances = n match {
+ case n if n > 1 => Vectors.fromBreeze(sumOfSquares.:*(n) - (sum :*
sum) :/ (n * (n - 1.0)))
+ case _ => Vectors.zeros(sum.size)
+ }
+ (i, new ClusterTree(center, n.toLong, variances))
+ }.toMap
+ }
+
+ /**
+ * Summarizes data by each cluster as Map
+ */
+ private[clustering]
+ def summarize(data: RDD[(Long, BV[Double])]): Map[Long, (BV[Double],
Double, BV[Double])] = {
+ data.mapPartitions { iter =>
+ // calculate the accumulation of the all point in a partition and
count the rows
+ val map = mutable.Map.empty[Long, (BV[Double], Double, BV[Double])]
+ iter.foreach { case (idx: Long, point: BV[Double]) =>
+ // get a map value or else get a sparse vector
+ val (sumBV, n, sumOfSquares) = map.get(idx)
+ .getOrElse(BSV.zeros[Double](point.size), 0.0,
BSV.zeros[Double](point.size))
+ map(idx) = (sumBV + point, n + 1.0, sumOfSquares + (point :*
point))
+ }
+ map.toIterator
+ }.reduceByKey { case ((sum1, n1, sumOfSquares1), (sum2, n2,
sumOfSquares2)) =>
+ // sum the accumulation and the count in the all partition
+ (sum1 + sum2, n1 + n2, sumOfSquares1 + sumOfSquares2)
+ }.collect().toMap
+ }
+
+ /**
+ * Gets the initial centers for bi-sect k-means
+ */
+ private[clustering]
+ def initChildrenCenter(clusters: Map[Long, BV[Double]]): Map[Long,
BV[Double]] = {
+ val rand = new XORShiftRandom()
+ rand.setSeed(this.seed)
+
+ clusters.flatMap { case (idx, center) =>
+ val childrenIndexes = Array(2 * idx, 2 * idx + 1)
+ val relativeErrorCoefficient = 0.001
+ Array(
+ (2 * idx, center.map(elm => elm - (elm * relativeErrorCoefficient
* rand.nextDouble()))),
+ (2 * idx + 1, center.map(elm => elm + (elm *
relativeErrorCoefficient * rand.nextDouble())))
+ )
+ }.toMap
+ }
+
+ /**
+ * Gets the new divided centers
+ */
+ private[clustering]
+ def getDividedClusters(data: RDD[(Long, BV[Double])],
+ dividedClusters: Map[Long, ClusterTree]): Map[Long, ClusterTree] = {
+ val sc = data.sparkContext
+ val appName = sc.appName
+
+ // get keys of dividable clusters
+ val dividableKeys = dividedClusters.filter { case (idx, cluster) =>
+ cluster.variances.toArray.sum > 0.0 && cluster.records >= 2
+ }.keySet
+ if (dividableKeys.size == 0) {
+ log.info(s"There is no dividable clusters in ${appName}.")
+ return Map.empty[Long, ClusterTree]
+ }
+
+ // divide input data
+ var dividableData = data.filter { case (idx, point) =>
dividableKeys.contains(idx)}
+ var dividableClusters = dividedClusters.filter { case (k, v) =>
dividableKeys.contains(k)}
+ val idealIndexes = dividableKeys.flatMap(idx => Array(2 * idx, 2 * idx
+ 1).toIterator)
+ var stats = divide(data, dividableClusters)
+
+ // if there is clusters which is failed to be divided,
+ // retry to divide only failed clusters again and again
+ var tryTimes = 1
+ while (stats.size < dividableKeys.size * 2 && tryTimes <=
this.maxRetries) {
+ // get the indexes of clusters which is failed to be divided
+ val failedIndexes =
idealIndexes.filterNot(stats.keySet.contains).map(idx => (idx / 2).toLong)
+ val failedCenters = dividedClusters.filter { case (idx, clstr) =>
failedIndexes.contains(idx)}
+ log.info(s"# failed clusters is ${failedCenters.size} of
${dividableKeys.size}" +
+ s"at ${tryTimes} times in ${appName}")
+
+ // divide the failed clusters again
+ sc.broadcast(failedIndexes)
+ dividableData = data.filter { case (idx, point) =>
failedIndexes.contains(idx)}
+ val missingStats = divide(dividableData, failedCenters)
+ stats = stats ++ missingStats
+ tryTimes += 1
+ }
+
+ // make children clusters
+ stats.filter { case (i, (sum, n, sumOfSquares)) => n > 0}
+ .map { case (i, (sum, n, sumOfSquares)) =>
+ val center = Vectors.fromBreeze(sum :/ n)
+ val variances = n match {
+ case 1 => Vectors.sparse(sum.size, Array(), Array())
+ case _ => Vectors.fromBreeze(sumOfSquares.:*(n) - (sum :* sum) :/
(n * (n - 1.0)))
+ }
+ val child = new ClusterTree(center, n.toLong, variances)
+ (i, child)
+ }.toMap
+ }
+
+ /**
+ * Builds a cluster tree from a Map of clusters
+ *
+ * @param treeMap divided clusters as a Map class
+ * @param rootIndex index you want to start
+ * @param numClusters the number of clusters you want
+ * @return a built cluster tree
+ */
+ private[clustering]
+ def buildTree(treeMap: Map[Long, ClusterTree],
+ rootIndex: Long,
+ numClusters: Int): Option[ClusterTree] = {
+
+ // if there is no index in the Map
+ if (!treeMap.contains(rootIndex)) return None
+
+ // build a cluster tree if the queue is empty or until the number of
leaves clusters is enough
+ var numLeavesClusters = 1
+ val root = treeMap(rootIndex)
+ var leavesQueue = Map(rootIndex -> root)
+ while (leavesQueue.size > 0 && numLeavesClusters < numClusters) {
+ // pick up the cluster whose variance is the maximum in the queue
+ val mostScattered = leavesQueue.maxBy(_._2.variancesNorm)
+ val mostScatteredKey = mostScattered._1
+ val mostScatteredCluster = mostScattered._2
+
+ // relate the most scattered cluster to its children clusters
+ val childrenIndexes = Array(2 * mostScatteredKey, 2 *
mostScatteredKey + 1)
+ if (childrenIndexes.forall(i => treeMap.contains(i))) {
+ // insert children to the most scattered cluster
+ val children = childrenIndexes.map(i => treeMap(i))
+ mostScatteredCluster.insert(children)
+
+ // calculate the local dendrogram height
+ // TODO Supports distance metrics other Euclidean distance metric
+ val metric = (bv1: BV[Double], bv2: BV[Double]) => breezeNorm(bv1
- bv2, 2.0)
+ val localHeight = children
+ .map(child => metric(child.center.toBreeze,
mostScatteredCluster.center.toBreeze)).max
+ mostScatteredCluster.setLocalHeight(localHeight)
+
+ // update the queue
+ leavesQueue = leavesQueue ++ childrenIndexes.map(i => (i ->
treeMap(i))).toMap
+ numLeavesClusters += 1
+ }
+
+ // remove the cluster which is involved to the cluster tree
+ leavesQueue = leavesQueue.filterNot(_ == mostScattered)
+
+ log.info(s"Total Leaves Clusters: ${numLeavesClusters} /
${numClusters}. " +
+ s"Cluster ${childrenIndexes.mkString(",")} are merged.")
+ }
+ Some(root)
+ }
+
+ /**
+ * Divides the input data
+ *
+ * @param data the pairs of cluster index and point which you want to
divide
+ * @param clusters the clusters you want to divide AS a Map class
+ * @return divided clusters as Map
+ */
+ private[clustering]
+ def divide(data: RDD[(Long, BV[Double])],
+ clusters: Map[Long, ClusterTree]): Map[Long, (BV[Double], Double,
BV[Double])] = {
+
+ val sc = data.sparkContext
+ val centers = clusters.map { case (idx, cluster) => (idx,
cluster.center.toBreeze)}
+ var newCenters = initChildrenCenter(centers)
+ if (newCenters.size == 0) {
+ return Map.empty[Long, (BV[Double], Double, BV[Double])]
+ }
+ sc.broadcast(newCenters)
--- End diff --
This use of `sc.broadcast` has no effect because the output isn't assigned
or used. Instead, you want something like val `bcNewCenters =
sc.broadcast(newCenters)` and then access within the map as bcCenters.value.
This appears in a few other places as well.
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