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[SPARK-31436][ML] MinHash keyDistance optimization #28206

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[SPARK-31436][ML] MinHash keyDistance optimization #28206

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a35d739
init
zhengruifeng Apr 13, 2020
a77225e
empty -> 1.0
zhengruifeng Apr 13, 2020
7725d09
use iter.size for remaining elements
zhengruifeng Apr 14, 2020
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41 changes: 34 additions & 7 deletions mllib/src/main/scala/org/apache/spark/ml/feature/MinHashLSH.scala
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Expand Up @@ -70,19 +70,46 @@ class MinHashLSHModel private[ml](

@Since("2.1.0")
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@zhengruifeng zhengruifeng Apr 14, 2020

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keyDistance was not exposed to the end users, is this since annotation needed?

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@srowen srowen Apr 14, 2020

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I suppose it's protected so a little more visible to callers. I wouldn't remove it just for its own sake.

override protected[ml] def keyDistance(x: Vector, y: Vector): Double = {
val xSet = x.nonZeroIterator.map(_._1).toSet
val ySet = y.nonZeroIterator.map(_._1).toSet
val intersectionSize = xSet.intersect(ySet).size.toDouble
val unionSize = xSet.size + ySet.size - intersectionSize
assert(unionSize > 0, "The union of two input sets must have at least 1 elements")
1 - intersectionSize / unionSize
val xIter = x.nonZeroIterator.map(_._1)
val yIter = y.nonZeroIterator.map(_._1)
if (xIter.isEmpty) {
require(yIter.hasNext, "The union of two input sets must have at least 1 elements")
return 1.0
} else if (yIter.isEmpty) {
return 1.0
}

var xIndex = xIter.next
var yIndex = yIter.next
var xSize = 1
var ySize = 1
var intersectionSize = 0

while (xIndex != -1 && yIndex != -1) {
if (xIndex == yIndex) {
intersectionSize += 1
xIndex = if (xIter.hasNext) { xSize += 1; xIter.next } else -1
yIndex = if (yIter.hasNext) { ySize += 1; yIter.next } else -1
} else if (xIndex > yIndex) {
yIndex = if (yIter.hasNext) { ySize += 1; yIter.next } else -1
} else {
xIndex = if (xIter.hasNext) { xSize += 1; xIter.next } else -1
}
}

xSize += xIter.size
ySize += yIter.size

val unionSize = xSize + ySize - intersectionSize
require(unionSize > 0, "The union of two input sets must have at least 1 elements")
1 - intersectionSize.toDouble / unionSize
}

@Since("2.1.0")
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@zhengruifeng zhengruifeng Apr 14, 2020

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ditto

override protected[ml] def hashDistance(x: Seq[Vector], y: Seq[Vector]): Double = {
// Since it's generated by hashing, it will be a pair of dense vectors.
// TODO: This hashDistance function requires more discussion in SPARK-18454
x.zip(y).map(vectorPair =>
x.iterator.zip(y.iterator).map(vectorPair =>
vectorPair._1.toArray.zip(vectorPair._2.toArray).count(pair => pair._1 != pair._2)
).min
}
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