Github user shenh062326 commented on a diff in the pull request:
https://github.com/apache/spark/pull/5608#discussion_r29107048
--- Diff: core/src/main/scala/org/apache/spark/util/SizeEstimator.scala ---
@@ -204,25 +204,36 @@ private[spark] object SizeEstimator extends Logging {
}
} else {
// Estimate the size of a large array by sampling elements without
replacement.
- var size = 0.0
+ // To exclude the shared objects that the array elements may link,
sample twice
+ // and use the min one to caculate array size.
val rand = new Random(42)
- val drawn = new OpenHashSet[Int](ARRAY_SAMPLE_SIZE)
- var numElementsDrawn = 0
- while (numElementsDrawn < ARRAY_SAMPLE_SIZE) {
- var index = 0
- do {
- index = rand.nextInt(length)
- } while (drawn.contains(index))
- drawn.add(index)
- val elem = ScalaRunTime.array_apply(array,
index).asInstanceOf[AnyRef]
- size += SizeEstimator.estimate(elem, state.visited)
- numElementsDrawn += 1
- }
- state.size += ((length / (ARRAY_SAMPLE_SIZE * 1.0)) * size).toLong
+ val drawn = new OpenHashSet[Int](2 * ARRAY_SAMPLE_SIZE)
+ val s1 = sampleArray(array, state, rand, drawn, length)
+ val s2 = sampleArray(array, state, rand, drawn, length)
+ val size = math.min(s1, s2)
+ state.size += math.max(s1, s2) +
+ (size * ((length - ARRAY_SAMPLE_SIZE) /
(ARRAY_SAMPLE_SIZE))).toLong
}
}
}
+ private def sampleArray(array: AnyRef, state: SearchState,
--- End diff --
OK, thanks for review.
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