Github user srowen commented on a diff in the pull request:
https://github.com/apache/spark/pull/17090#discussion_r103349590
--- Diff: mllib/src/main/scala/org/apache/spark/ml/recommendation/ALS.scala
---
@@ -248,18 +248,18 @@ class ALSModel private[ml] (
@Since("1.3.0")
def setPredictionCol(value: String): this.type = set(predictionCol,
value)
+ private val predict = udf { (userFeatures: Seq[Float], itemFeatures:
Seq[Float]) =>
+ if (userFeatures != null && itemFeatures != null) {
+ blas.sdot(rank, userFeatures.toArray, 1, itemFeatures.toArray, 1)
--- End diff --
I wonder how the overhead of converting to an array compares with the
efficiency of calling sdot -- could be faster to just do the Seqs by hand? is
it possible to operate on something besides Seq?
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