updated based on similar previous PR comments

mllib/src/main/scala/org/apache/spark/ml/evaluation/RegressionEvaluator.scala

@@ -71,7 +71,7 @@ final class RegressionEvaluator @Since("1.4.0") (@Since("1.4.0") override val ui
   def setLabelCol(value: String): this.type = set(labelCol, value)
 
   /** @group setParam */
-  @Since("2.2.0")
+  @Since("3.0.0")
   def setWeightCol(value: String): this.type = set(weightCol, value)
 
   setDefault(metricName -> "rmse")
@@ -88,7 +88,7 @@ final class RegressionEvaluator @Since("1.4.0") (@Since("1.4.0") override val ui
       .rdd
       .map { case Row(prediction: Double, label: Double, weight: Double) =>
         (prediction, label, weight) }
-    val metrics = new RegressionMetrics(false, predictionAndLabelsWithWeights)
+    val metrics = new RegressionMetrics(predictionAndLabelsWithWeights)
     val metric = $(metricName) match {
       case "rmse" => metrics.rootMeanSquaredError
       case "mse" => metrics.meanSquaredError

mllib/src/main/scala/org/apache/spark/mllib/evaluation/RegressionMetrics.scala

@@ -34,31 +34,20 @@ import org.apache.spark.sql.DataFrame
  */
 @Since("1.2.0")
 class RegressionMetrics @Since("2.0.0") (
-    throughOrigin: Boolean, predAndObsWithOptWeight: RDD[_])
+    predAndObsWithOptWeight: RDD[_ <: Product], throughOrigin: Boolean)
     extends Logging {
 
   @Since("1.2.0")
-  def this(predictionAndObservations: RDD[(Double, Double)]) =
-    this(false, predictionAndObservations)
-
-  /**
-   * Evaluator for regression.
-   *
-   * @param predictionAndObservations an RDD of (prediction, observation) pairs
-   * @param throughOrigin True if the regression is through the origin. For example, in linear
-   *                      regression, it will be true without fitting intercept.
-   */
-  @Since("2.0.0")
-  def this(predictionAndObservations: RDD[(Double, Double)], throughOrigin: Boolean) =
-  this(throughOrigin, predictionAndObservations)
+  def this(predictionAndObservations: RDD[_ <: Product]) =
+    this(predictionAndObservations, false)
 
   /**
    * An auxiliary constructor taking a DataFrame.
    * @param predictionAndObservations a DataFrame with two double columns:
    *                                  prediction and observation
    */
   private[mllib] def this(predictionAndObservations: DataFrame) =
-    this(false, predictionAndObservations.rdd.map(r => (r.getDouble(0), r.getDouble(1))))
+    this(predictionAndObservations.rdd.map(r => (r.getDouble(0), r.getDouble(1))))
 
   /**
    * Use MultivariateOnlineSummarizer to calculate summary statistics of observations and errors.

mllib/src/main/scala/org/apache/spark/mllib/stat/MultivariateOnlineSummarizer.scala

@@ -52,7 +52,7 @@ class MultivariateOnlineSummarizer extends MultivariateStatisticalSummary with S
   private var totalCnt: Long = 0
   private var totalWeightSum: Double = 0.0
   private var weightSquareSum: Double = 0.0
-  private var currWeightSum: Array[Double] = _
+  private var weightSum: Array[Double] = _
   private var nnz: Array[Long] = _
   private var currMax: Array[Double] = _
   private var currMin: Array[Double] = _
@@ -78,7 +78,7 @@ class MultivariateOnlineSummarizer extends MultivariateStatisticalSummary with S
       currM2n = Array.ofDim[Double](n)
       currM2 = Array.ofDim[Double](n)
       currL1 = Array.ofDim[Double](n)
-      currWeightSum = Array.ofDim[Double](n)
+      weightSum = Array.ofDim[Double](n)
       nnz = Array.ofDim[Long](n)
       currMax = Array.fill[Double](n)(Double.MinValue)
       currMin = Array.fill[Double](n)(Double.MaxValue)
@@ -91,7 +91,7 @@ class MultivariateOnlineSummarizer extends MultivariateStatisticalSummary with S
     val localCurrM2n = currM2n
     val localCurrM2 = currM2
     val localCurrL1 = currL1
-    val localWeightSum = currWeightSum
+    val localWeightSum = weightSum
     val localNumNonzeros = nnz
     val localCurrMax = currMax
     val localCurrMin = currMin
@@ -139,8 +139,8 @@ class MultivariateOnlineSummarizer extends MultivariateStatisticalSummary with S
       weightSquareSum += other.weightSquareSum
       var i = 0
       while (i < n) {
-        val thisNnz = currWeightSum(i)
-        val otherNnz = other.currWeightSum(i)
+        val thisNnz = weightSum(i)
+        val otherNnz = other.weightSum(i)
         val totalNnz = thisNnz + otherNnz
         val totalCnnz = nnz(i) + other.nnz(i)
         if (totalNnz != 0.0) {
@@ -157,7 +157,7 @@ class MultivariateOnlineSummarizer extends MultivariateStatisticalSummary with S
           currMax(i) = math.max(currMax(i), other.currMax(i))
           currMin(i) = math.min(currMin(i), other.currMin(i))
         }
-        currWeightSum(i) = totalNnz
+        weightSum(i) = totalNnz
         nnz(i) = totalCnnz
         i += 1
       }
@@ -170,7 +170,7 @@ class MultivariateOnlineSummarizer extends MultivariateStatisticalSummary with S
       this.totalCnt = other.totalCnt
       this.totalWeightSum = other.totalWeightSum
       this.weightSquareSum = other.weightSquareSum
-      this.currWeightSum = other.currWeightSum.clone()
+      this.weightSum = other.weightSum.clone()
       this.nnz = other.nnz.clone()
       this.currMax = other.currMax.clone()
       this.currMin = other.currMin.clone()
@@ -189,7 +189,7 @@ class MultivariateOnlineSummarizer extends MultivariateStatisticalSummary with S
     val realMean = Array.ofDim[Double](n)
     var i = 0
     while (i < n) {
-      realMean(i) = currMean(i) * (currWeightSum(i) / totalWeightSum)
+      realMean(i) = currMean(i) * (weightSum(i) / totalWeightSum)
       i += 1
     }
     Vectors.dense(realMean)
@@ -214,8 +214,8 @@ class MultivariateOnlineSummarizer extends MultivariateStatisticalSummary with S
       val len = currM2n.length
       while (i < len) {
         // We prevent variance from negative value caused by numerical error.
-        realVariance(i) = math.max((currM2n(i) + deltaMean(i) * deltaMean(i) * currWeightSum(i) *
-          (totalWeightSum - currWeightSum(i)) / totalWeightSum) / denominator, 0.0)
+        realVariance(i) = math.max((currM2n(i) + deltaMean(i) * deltaMean(i) * weightSum(i) *
+          (totalWeightSum - weightSum(i)) / totalWeightSum) / denominator, 0.0)
         i += 1
       }
     }

mllib/src/main/scala/org/apache/spark/mllib/stat/MultivariateStatisticalSummary.scala

@@ -47,7 +47,7 @@ trait MultivariateStatisticalSummary {
   /**
    * Sum of weights.
    */
-  @Since("2.2.0")
+  @Since("3.0.0")
   def weightSum: Double
 
   /**

mllib/src/test/scala/org/apache/spark/mllib/evaluation/RegressionMetricsSuite.scala

@@ -137,7 +137,7 @@ class RegressionMetricsSuite extends SparkFunSuite with MLlibTestSparkContext {
   test("regression metrics with same (1.0) weight samples") {
     val predictionAndObservationWithWeight = sc.parallelize(
       Seq((2.25, 3.0, 1.0), (-0.25, -0.5, 1.0), (1.75, 2.0, 1.0), (7.75, 7.0, 1.0)), 2)
-    val metrics = new RegressionMetrics(false, predictionAndObservationWithWeight)
+    val metrics = new RegressionMetrics(predictionAndObservationWithWeight, false)
     assert(metrics.explainedVariance ~== 8.79687 absTol eps,
       "explained variance regression score mismatch")
     assert(metrics.meanAbsoluteError ~== 0.5 absTol eps, "mean absolute error mismatch")
@@ -174,7 +174,7 @@ class RegressionMetricsSuite extends SparkFunSuite with MLlibTestSparkContext {
   test("regression metrics with weighted samples") {
     val predictionAndObservationWithWeight = sc.parallelize(
       Seq((2.25, 3.0, 0.1), (-0.25, -0.5, 0.2), (1.75, 2.0, 0.15), (7.75, 7.0, 0.05)), 2)
-    val metrics = new RegressionMetrics(false, predictionAndObservationWithWeight)
+    val metrics = new RegressionMetrics(predictionAndObservationWithWeight, false)
     assert(metrics.explainedVariance ~== 5.2425 absTol eps,
       "explained variance regression score mismatch")
     assert(metrics.meanAbsoluteError ~== 0.4 absTol eps, "mean absolute error mismatch")