srowen commented on a change in pull request #31588:
URL: https://github.com/apache/spark/pull/31588#discussion_r582891889
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File path: mllib/src/main/scala/org/apache/spark/ml/feature/VectorSlicer.scala
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@@ -110,22 +110,21 @@ final class VectorSlicer @Since("1.5.0") (@Since("1.5.0")
override val uid: Stri
}
// Prepare output attributes
- val inds = getSelectedFeatureIndices(dataset.schema)
- val selectedAttrs = inputAttr.attributes.map { attrs =>
- inds.map(index => attrs(index))
- }
+ val selectedIndices = getSelectedFeatureIndices(dataset.schema)
+ val selectedAttrs = inputAttr.attributes.map { attrs =>
selectedIndices.map(attrs.apply) }
val outputAttr = selectedAttrs match {
case Some(attrs) => new AttributeGroup($(outputCol), attrs)
- case None => new AttributeGroup($(outputCol), inds.length)
+ case None => new AttributeGroup($(outputCol), selectedIndices.length)
}
- // Select features
+ val sorted = selectedIndices.length > 1 &&
selectedIndices.sliding(2).forall(t => t(1) > t(0))
Review comment:
That would be the drawback, yeah, another boolean and a check every time
one is created. The upside is all calls to slice are potentially optimized, and
maybe, that sortedness can be used elsewhere?
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