SPARK-3278 changes after PR comments apache#3519. Change to IsotonicRegression api. Isotonic parameter now follows api of other mllib algorithms

Author: zapletal-martin

mllib/src/main/scala/org/apache/spark/mllib/regression/IsotonicRegression.scala

@@ -18,6 +18,7 @@
 package org.apache.spark.mllib.regression
 
 import java.io.Serializable
+import java.lang.{Double => JDouble}
 import java.util.Arrays.binarySearch
 
 import org.apache.spark.api.java.{JavaDoubleRDD, JavaRDD}
@@ -53,8 +54,9 @@ class IsotonicRegressionModel (
    * @param testData Features to be labeled.
    * @return Predicted labels.
    */
-  def predict(testData: RDD[Double]): RDD[Double] =
+  def predict(testData: RDD[Double]): RDD[Double] = {
     testData.map(predict)
+  }
 
   /**
    * Predict labels for provided features.
@@ -63,8 +65,9 @@ class IsotonicRegressionModel (
    * @param testData Features to be labeled.
    * @return Predicted labels.
    */
-  def predict(testData: JavaDoubleRDD): JavaDoubleRDD =
+  def predict(testData: JavaDoubleRDD): JavaDoubleRDD = {
     JavaDoubleRDD.fromRDD(predict(testData.rdd.asInstanceOf[RDD[Double]]))
+  }
 
   /**
    * Predict a single label.
@@ -75,8 +78,8 @@ class IsotonicRegressionModel (
    *         If testData exactly matches a boundary then associated prediction is directly returned
    *         If testData is lower or higher than all boundaries
    *           then first or last prediction is returned respectively
-   *         If testData falls between two values in boundary then predictions is treated as piecewise
-   *           linear function and interpolated value is returned
+   *         If testData falls between two values in boundary then predictions is treated
+   *         as piecewise linear function and interpolated value is returned
    */
   def predict(testData: Double): Double = {
 
@@ -88,8 +91,8 @@ class IsotonicRegressionModel (
 
     val normalisedInsertIndex = -insertIndex - 1
 
-    //Find if the index was lower than all values,
-    //higher than all values, inbetween two values or exact match.
+    // Find if the index was lower than all values,
+    // higher than all values, inbetween two values or exact match.
     if (insertIndex == -1) {
       predictions.head
     } else if (normalisedInsertIndex == boundaries.length){
@@ -121,37 +124,50 @@ class IsotonicRegressionModel (
  *   "An approach to parallelizing isotonic regression."
  *   Applied Mathematics and Parallel Computing. Physica-Verlag HD, 1996. 141-147.
  */
-class IsotonicRegression extends Serializable {
+class IsotonicRegression private (private var isotonic: Boolean) extends Serializable {
 
   /**
-   * Run pool adjacent violators algorithm to obtain isotonic regression model.
+   * Constructs IsotonicRegression instance with default parameter isotonic = true
+   * @return New instance of IsotonicRegression
+   */
+  def this() = this(true)
+
+  /**
+   * Sets the isotonic parameter
+   * @param isotonic Isotonic (increasing) or antitonic (decreasing) sequence.
+   * @return The instance of IsotonicRegression
+   */
+  def setIsotonic(isotonic: Boolean): this.type = {
+    this.isotonic = isotonic
+    this
+  }
+
+  /**
+   * Run IsotonicRegression algorithm to obtain isotonic regression model.
    *
    * @param input RDD of tuples (label, feature, weight) where label is dependent variable
    *              for which we calculate isotonic regression, feature is independent variable
    *              and weight represents number of measures with default 1.
    *
-   * @param isotonic Isotonic (increasing) or antitonic (decreasing) sequence.
    * @return Isotonic regression model.
    */
-  def run(
-      input: RDD[(Double, Double, Double)],
-      isotonic: Boolean): IsotonicRegressionModel =
+  def run(input: RDD[(Double, Double, Double)]): IsotonicRegressionModel = {
     createModel(parallelPoolAdjacentViolators(input, isotonic), isotonic)
+  }
 
-/**
+  /**
    * Run pool adjacent violators algorithm to obtain isotonic regression model.
    *
    * @param input JavaRDD of tuples (label, feature, weight) where label is dependent variable
    *              for which we calculate isotonic regression, feature is independent variable
    *              and weight represents number of measures with default 1.
    *
-   * @param isotonic Isotonic (increasing) or antitonic (decreasing) sequence.
    * @return Isotonic regression model.
    */
   def run(
-       input: JavaRDD[(java.lang.Double, java.lang.Double, java.lang.Double)],
-       isotonic: Boolean): IsotonicRegressionModel =
-    run(input.rdd.asInstanceOf[RDD[(Double, Double, Double)]], isotonic)
+      input: JavaRDD[(JDouble, JDouble, JDouble)]): IsotonicRegressionModel = {
+    run(input.rdd.asInstanceOf[RDD[(Double, Double, Double)]])
+  }
 
   /**
    * Creates isotonic regression model with given parameters.
@@ -164,11 +180,7 @@ class IsotonicRegression extends Serializable {
   protected def createModel(
       predictions: Array[(Double, Double, Double)],
       isotonic: Boolean): IsotonicRegressionModel = {
-
-    val labels = predictions.map(_._1)
-    val features = predictions.map(_._2)
-
-    new IsotonicRegressionModel(features, labels)
+    new IsotonicRegressionModel(predictions.map(_._2), predictions.map(_._1))
   }
 
   /**
@@ -249,4 +261,4 @@ class IsotonicRegression extends Serializable {
 
     poolAdjacentViolators(parallelStepResult.collect(), isotonic)
   }
-}
+}

mllib/src/test/java/org/apache/spark/mllib/regression/JavaIsotonicRegressionSuite.java

@@ -61,7 +61,7 @@ private IsotonicRegressionModel runIsotonicRegression(double[] labels) {
     JavaRDD<Tuple3<Double, Double, Double>> trainRDD =
       sc.parallelize(generateIsotonicInput(labels)).cache();
 
-    return new IsotonicRegression().run(trainRDD, true);
+    return new IsotonicRegression().run(trainRDD);
   }
 
   @Before

mllib/src/test/scala/org/apache/spark/mllib/regression/IsotonicRegressionSuite.scala

@@ -23,31 +23,35 @@ import org.apache.spark.mllib.util.MLlibTestSparkContext
 
 class IsotonicRegressionSuite extends FunSuite with MLlibTestSparkContext with Matchers {
 
-  private def round(d: Double) =
+  private def round(d: Double) = {
     Math.round(d * 100).toDouble / 100
+  }
 
-  private def generateIsotonicInput(labels: Seq[Double]): Seq[(Double, Double, Double)] =
+  private def generateIsotonicInput(labels: Seq[Double]): Seq[(Double, Double, Double)] = {
     labels.zip(1 to labels.size).map(point => (point._1, point._2.toDouble, 1d))
+  }
 
   private def generateIsotonicInput(
       labels: Seq[Double],
-      weights: Seq[Double]): Seq[(Double, Double, Double)] =
+      weights: Seq[Double]): Seq[(Double, Double, Double)] = {
     labels.zip(1 to labels.size)
       .zip(weights)
       .map(point => (point._1._1, point._1._2.toDouble, point._2))
+  }
 
   private def runIsotonicRegression(
       labels: Seq[Double],
       weights: Seq[Double],
       isotonic: Boolean): IsotonicRegressionModel = {
     val trainRDD = sc.parallelize(generateIsotonicInput(labels, weights)).cache()
-    new IsotonicRegression().run(trainRDD, isotonic)
+    new IsotonicRegression().setIsotonic(isotonic).run(trainRDD)
   }
 
   private def runIsotonicRegression(
       labels: Seq[Double],
-      isotonic: Boolean): IsotonicRegressionModel =
+      isotonic: Boolean): IsotonicRegressionModel = {
     runIsotonicRegression(labels, Array.fill(labels.size)(1d), isotonic)
+  }
 
   test("increasing isotonic regression") {
     val model = runIsotonicRegression(Seq(1, 2, 3, 3, 1, 6, 17, 16, 17, 18), true)
@@ -99,7 +103,7 @@ class IsotonicRegressionSuite extends FunSuite with MLlibTestSparkContext with M
 
   test("isotonic regression with unordered input") {
     val trainRDD = sc.parallelize(generateIsotonicInput(Seq(1, 2, 3, 4, 5)).reverse).cache()
-    val model = new IsotonicRegression().run(trainRDD, true)
+    val model = new IsotonicRegression().run(trainRDD)
 
     assert(model.predictions === Array(1, 2, 3, 4, 5))
   }