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TINKERPOP-2376 Improved probability distribution on global sample() #1301

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Merged
spmallette merged 1 commit into from
Jul 16, 2020
Merged

TINKERPOP-2376 Improved probability distribution on global sample() #1301

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1 change: 1 addition & 0 deletions CHANGELOG.asciidoc
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Expand Up @@ -26,6 +26,7 @@ image::https://raw.githubusercontent.com/apache/tinkerpop/master/docs/static/ima
* Fixed bug in `has(T,Traversal)` where results were not being returned.
* Fixed bug in `select(Traversal)` where side-effects were getting lost if accessed from the child traversal.
* Fixed authorization bug when using `WsAndHttpChannelizerHandler` with keep-alive enabled.
* Improved sampling distribution for global scope `sample()` operations.

[[release-3-4-7]]
=== TinkerPop 3.4.7 (Release Date: June 1, 2020)
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9 changes: 4 additions & 5 deletions ...ain/java/org/apache/tinkerpop/gremlin/process/traversal/step/filter/SampleGlobalStep.java
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Expand Up @@ -86,22 +86,21 @@ public void barrierConsumer(final TraverserSet<S> traverserSet) {
int runningAmountToSample = 0;
while (runningAmountToSample < this.amountToSample) {
boolean reSample = false;
double runningWeight = 0.0d;
double runningTotalWeight = totalWeight;
for (final Traverser.Admin<S> s : traverserSet) {
long sampleBulk = sampledSet.contains(s) ? sampledSet.get(s).bulk() : 0;
if (sampleBulk < s.bulk()) {
final double currentWeight = ((ProjectedTraverser<S, Number>) s).getProjections().get(0).doubleValue();
for (int i = 0; i < (s.bulk() - sampleBulk); i++) {
runningWeight = runningWeight + currentWeight;
if (RANDOM.nextDouble() <= ((runningWeight / totalWeight))) {
if (RANDOM.nextDouble() <= ((currentWeight / runningTotalWeight))) {
final Traverser.Admin<S> split = s.split();
split.setBulk(1L);
sampledSet.add(split);
runningAmountToSample++;
totalWeight = totalWeight - currentWeight;
reSample = true;
break;
}
runningTotalWeight = runningTotalWeight - currentWeight;
}
if (reSample || (runningAmountToSample >= this.amountToSample))
break;
Expand Down Expand Up @@ -139,4 +138,4 @@ public void setTraversal(final Traversal.Admin<?, ?> parentTraversal) {
public int hashCode() {
return super.hashCode() ^ this.amountToSample ^ this.probabilityTraversal.hashCode();
}
}
}