change OnlineLDA to class

Author: hhbyyh

mllib/src/main/scala/org/apache/spark/mllib/clustering/OnlineLDA.scala

@@ -24,7 +24,6 @@ import org.apache.spark.annotation.Experimental
 import org.apache.spark.mllib.linalg._
 import org.apache.spark.rdd.RDD
 
-
 /**
  * :: Experimental ::
  * Latent Dirichlet Allocation (LDA), a topic model designed for text documents.
@@ -37,7 +36,58 @@ import org.apache.spark.rdd.RDD
  *   Hoffman, Blei and Bach, "Online Learning for Latent Dirichlet Allocation." NIPS, 2010.
  */
 @Experimental
-object OnlineLDA{
+class OnlineLDA(
+    private var k: Int,
+    private var numIterations: Int,
+    private var miniBatchFraction: Double,
+    private var tau_0: Double,
+    private var kappa: Double) {
+
+  def this() = this(k = 10, numIterations = 100, miniBatchFraction = 0.01,
+    tau_0 = 1024, kappa = 0.5)
+
+  /**
+   * Number of topics to infer.  I.e., the number of soft cluster centers.
+   * (default = 10)
+   */
+  def setK(k: Int): this.type = {
+    require(k > 0, s"OnlineLDA k (number of clusters) must be > 0, but was set to $k")
+    this.k = k
+    this
+  }
+
+  /**
+   * Set the number of iterations for OnlineLDA. Default 100.
+   */
+  def setNumIterations(iters: Int): this.type = {
+    this.numIterations = iters
+    this
+  }
+
+  /**
+   * Set fraction of data to be used for each iteration. Default 0.01.
+   */
+  def setMiniBatchFraction(fraction: Double): this.type = {
+    this.miniBatchFraction = fraction
+    this
+  }
+
+  /**
+   * A (positive) learning parameter that downweights early iterations. Default 1024.
+   */
+  def setTau_0(t: Double): this.type = {
+    this.tau_0 = t
+    this
+  }
+
+  /**
+   * Learning rate: exponential decay rate. Default 0.5.
+   */
+  def setKappa(kappa: Double): this.type = {
+    this.kappa = kappa
+    this
+  }
+
 
   /**
    * Learns an LDA model from the given data set, using online variational Bayes (VB) algorithm.
@@ -49,33 +99,18 @@ object OnlineLDA{
    *                   The term count vectors are "bags of words" with a fixed-size vocabulary
    *                   (where the vocabulary size is the length of the vector).
    *                   Document IDs must be unique and >= 0.
-   * @param k Number of topics to infer.
-   * @param batchNumber Number of batches to split input corpus. For each batch, recommendation
-   *                    size is [4, 16384]. -1 for automatic batchNumber.
    * @return  Inferred LDA model
    */
-  def run(documents: RDD[(Long, Vector)], k: Int, batchNumber: Int = -1): LDAModel = {
-    require(batchNumber > 0 || batchNumber == -1,
-      s"batchNumber must be greater or -1, but was set to $batchNumber")
-    require(k > 0, s"LDA k (number of clusters) must be > 0, but was set to $k")
-
+  def run(documents: RDD[(Long, Vector)]): LDAModel = {
     val vocabSize = documents.first._2.size
     val D = documents.count().toInt // total documents count
-    val batchSize =
-      if (batchNumber == -1) { // auto mode
-        if (D / 100 > 16384) 16384
-        else if (D / 100 < 4) 4
-        else D / 100
-      }
-      else {
-        D / batchNumber
-      }
-
-    val onlineLDA = new OnlineLDAOptimizer(k, D, vocabSize)
-    val actualBatchNumber = Math.ceil(D.toDouble / batchSize).toInt
-    for(i <- 1 to actualBatchNumber){
-      val batch = documents.sample(true, batchSize.toDouble / D)
-      onlineLDA.submitMiniBatch(batch)
+    val onlineLDA = new OnlineLDAOptimizer(k, D, vocabSize, tau_0, kappa)
+
+    val arr = Array.fill(math.ceil(1.0 / miniBatchFraction).toInt)(miniBatchFraction)
+    for(i <- 0 until numIterations){
+      val splits = documents.randomSplit(arr)
+      val index = i % splits.size
+      onlineLDA.submitMiniBatch(splits(index))
     }
     onlineLDA.getTopicDistribution()
   }
@@ -93,10 +128,12 @@ object OnlineLDA{
  *   Hoffman, Blei and Bach, "Online Learning for Latent Dirichlet Allocation." NIPS, 2010.
  */
 @Experimental
-class OnlineLDAOptimizer (
+private[clustering] class OnlineLDAOptimizer (
     private var k: Int,
     private var D: Int,
-    private val vocabSize:Int) extends Serializable {
+    private val vocabSize: Int,
+    private val tau_0: Double,
+    private val kappa: Double) extends Serializable {
 
   // Initialize the variational distribution q(beta|lambda)
   private var lambda = getGammaMatrix(k, vocabSize)       // K * V
@@ -115,7 +152,11 @@ class OnlineLDAOptimizer (
    *                   Document IDs must be unique and >= 0.
    * @return  Inferred LDA model
    */
-  def submitMiniBatch(documents: RDD[(Long, Vector)]): Unit = {
+  private[clustering] def submitMiniBatch(documents: RDD[(Long, Vector)]): Unit = {
+    if(documents.isEmpty()){
+      return
+    }
+
     var stat = BDM.zeros[Double](k, vocabSize)
     stat = documents.treeAggregate(stat)(gradient, _ += _)
     update(stat, i, documents.count().toInt)
@@ -125,13 +166,13 @@ class OnlineLDAOptimizer (
   /**
    * get the topic-term distribution
    */
-  def getTopicDistribution(): LDAModel ={
+  private[clustering] def getTopicDistribution(): LDAModel ={
     new LocalLDAModel(Matrices.fromBreeze(lambda).transpose)
   }
 
   private def update(raw: BDM[Double], iter:Int, batchSize: Int): Unit ={
-    // weight of the mini-batch. 1024 helps down weights early iterations
-    val weight = math.pow(1024 + iter, -0.5)
+    // weight of the mini-batch.
+    val weight = math.pow(tau_0 + iter, -kappa)
 
     // This step finishes computing the sufficient statistics for the M step
     val stat = raw :* expElogbeta