Github user srowen commented on a diff in the pull request:
https://github.com/apache/spark/pull/9020#discussion_r41539167
--- Diff: mllib/src/main/scala/org/apache/spark/mllib/linalg/Vectors.scala
---
@@ -512,6 +513,92 @@ object Vectors {
squaredDistance
}
+ private def dot(a : DenseVector, b : DenseVector) : Double = {
+ (a.toArray zip b.toArray).map(x => (x._1 * x._2)).sum
+ }
+
+ private def dot(a : SparseVector, b : DenseVector) : Double = {
+ (a.indices zip a.values).map(x => { b(x._1)*x._2 }).sum
--- End diff --
What I mean is that you can already just call Breeze for this without any
code change in Spark, using `toBreeze`. It's easy; I get that it sometimes
involves a copy. Do we have a compelling case for needing this enough and
needing it to be fast in Spark that it should be added to `Vector`? I ask just
because I don't see anything changed to call it.
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