[GitHub] srowen closed pull request #23048: transform DenseVector x DenseVector sqdist from imperativ to function…

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srowen closed pull request #23048: transform DenseVector x DenseVector sqdist from imperativ to function…
URL: https://github.com/apache/spark/pull/23048
 
 
   

This is a PR merged from a forked repository.
As GitHub hides the original diff on merge, it is displayed below for
the sake of provenance:

As this is a foreign pull request (from a fork), the diff is supplied
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diff --git a/mllib-local/src/main/scala/org/apache/spark/ml/linalg/Vectors.scala b/mllib-local/src/main/scala/org/apache/spark/ml/linalg/Vectors.scala
index 6e950f968a65d..42364fe132dd5 100644
--- a/mllib-local/src/main/scala/org/apache/spark/ml/linalg/Vectors.scala
+++ b/mllib-local/src/main/scala/org/apache/spark/ml/linalg/Vectors.scala
@@ -370,14 +370,19 @@ object Vectors {
       case (v1: DenseVector, v2: SparseVector) =>
         squaredDistance = sqdist(v2, v1)
 
-      case (DenseVector(vv1), DenseVector(vv2)) =>
-        var kv = 0
+      case (DenseVector(vv1), DenseVector(vv2)) => {
         val sz = vv1.length
-        while (kv < sz) {
-          val score = vv1(kv) - vv2(kv)
-          squaredDistance += score * score
-          kv += 1
+        @annotation.tailrec
+        def go(d: Double, kv: Int): Double = {
+          if (kv < sz) {
+            val score = vv1(kv) - vv2(kv)
+            go(d + score * score, kv + 1)
+          }
+          else d
         }
+        go(0D, 0)
+      }
+
       case _ =>
         throw new IllegalArgumentException("Do not support vector type " + v1.getClass +
           " and " + v2.getClass)


 

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