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[SPARK-10575][Spark Core]Wrapped RDD.takeSample with Scope #8730

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vinodkc wants to merge 8 commits into from
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[SPARK-10575][Spark Core]Wrapped RDD.takeSample with Scope #8730

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cf2c466
wrapped in scope
vinodkc Sep 12, 2015
c82b4f9
Added assert instead of IAE
vinodkc Sep 13, 2015
afe9396
fixed condition
vinodkc Sep 13, 2015
c06c6e5
Removed space
vinodkc Sep 13, 2015
7fa497d
Update RDD.scala
vinodkc Sep 15, 2015
b37778e
Fixed Review Comment
vinodkc Sep 15, 2015
4e6ce62
Update RDD.scala
vinodkc Sep 15, 2015
70de2b4
Handled review comments
Sep 15, 2015
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69 changes: 32 additions & 37 deletions core/src/main/scala/org/apache/spark/rdd/RDD.scala
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Original file line number Diff line number Diff line change
Expand Up @@ -469,50 +469,45 @@ abstract class RDD[T: ClassTag](
* @param seed seed for the random number generator
* @return sample of specified size in an array
*/
// TODO: rewrite this without return statements so we can wrap it in a scope
def takeSample(
withReplacement: Boolean,
num: Int,
seed: Long = Utils.random.nextLong): Array[T] = {
seed: Long = Utils.random.nextLong): Array[T] = withScope {
val numStDev = 10.0

if (num < 0) {
throw new IllegalArgumentException("Negative number of elements requested")
} else if (num == 0) {
return new Array[T](0)
}

val initialCount = this.count()
if (initialCount == 0) {
return new Array[T](0)
}

val maxSampleSize = Int.MaxValue - (numStDev * math.sqrt(Int.MaxValue)).toInt
if (num > maxSampleSize) {
throw new IllegalArgumentException("Cannot support a sample size > Int.MaxValue - " +
s"$numStDev * math.sqrt(Int.MaxValue)")
}

val rand = new Random(seed)
if (!withReplacement && num >= initialCount) {
return Utils.randomizeInPlace(this.collect(), rand)
}

val fraction = SamplingUtils.computeFractionForSampleSize(num, initialCount,
withReplacement)

var samples = this.sample(withReplacement, fraction, rand.nextInt()).collect()
require(num >= 0, "Negative number of elements requested")
require(num <= (Int.MaxValue - (numStDev * math.sqrt(Int.MaxValue)).toInt),
"Cannot support a sample size > Int.MaxValue - " +
s"$numStDev * math.sqrt(Int.MaxValue)")

// If the first sample didn't turn out large enough, keep trying to take samples;
// this shouldn't happen often because we use a big multiplier for the initial size
var numIters = 0
while (samples.length < num) {
logWarning(s"Needed to re-sample due to insufficient sample size. Repeat #$numIters")
samples = this.sample(withReplacement, fraction, rand.nextInt()).collect()
numIters += 1
if (num == 0) {
new Array[T](0)
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@andrewor14 andrewor14 Sep 14, 2015

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Hm, the only difference here is that if num == 0 we still do a count(), whereas before we just return quickly. I think we should preserve the old behavior even though it adds another layer of nesting and unfortunately makes the code harder to read.

} else {
val initialCount = this.count()
if(initialCount ==0)
{
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@andrewor14 andrewor14 Sep 15, 2015

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these two lines have a lot of style errors... they should be

if (initialCount == 0) {
  new Array[T](0)
} else {
  ...
}

new Array[T](0)
} else {
val rand = new Random(seed)
if (!withReplacement && num >= initialCount) {
Utils.randomizeInPlace(this.collect(), rand)
} else {
val fraction = SamplingUtils.computeFractionForSampleSize(num, initialCount,
withReplacement)
var samples = this.sample(withReplacement, fraction, rand.nextInt()).collect()

// If the first sample didn't turn out large enough, keep trying to take samples;
// this shouldn't happen often because we use a big multiplier for the initial size
var numIters = 0
while (samples.length < num) {
logWarning(s"Needed to re-sample due to insufficient sample size. Repeat #$numIters")
samples = this.sample(withReplacement, fraction, rand.nextInt()).collect()
numIters += 1
}
Utils.randomizeInPlace(samples, rand).take(num)
}
}
}

Utils.randomizeInPlace(samples, rand).take(num)
}

/**
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