org.apache.flink.api.java.functions.SampleWithFraction Maven / Gradle / Ivy
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* to you under the Apache License, Version 2.0 (the
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* http://www.apache.org/licenses/LICENSE-2.0
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package org.apache.flink.api.java.functions;
import org.apache.flink.annotation.Internal;
import org.apache.flink.api.common.functions.RichMapPartitionFunction;
import org.apache.flink.api.java.sampling.BernoulliSampler;
import org.apache.flink.api.java.sampling.PoissonSampler;
import org.apache.flink.api.java.sampling.RandomSampler;
import org.apache.flink.util.Collector;
import java.util.Iterator;
/**
* A map partition function wrapper for sampling algorithms with fraction, the sample algorithm
* takes the partition iterator as input.
*
* @param
*/
@Internal
public class SampleWithFraction extends RichMapPartitionFunction {
private boolean withReplacement;
private double fraction;
private long seed;
/**
* Create a function instance of SampleWithFraction.
*
* @param withReplacement Whether element can be selected more than once.
* @param fraction Probability that each element is selected.
* @param seed random number generator seed.
*/
public SampleWithFraction(boolean withReplacement, double fraction, long seed) {
this.withReplacement = withReplacement;
this.fraction = fraction;
this.seed = seed;
}
@Override
public void mapPartition(Iterable values, Collector out) throws Exception {
RandomSampler sampler;
long seedAndIndex = seed + getRuntimeContext().getIndexOfThisSubtask();
if (withReplacement) {
sampler = new PoissonSampler<>(fraction, seedAndIndex);
} else {
sampler = new BernoulliSampler<>(fraction, seedAndIndex);
}
Iterator sampled = sampler.sample(values.iterator());
while (sampled.hasNext()) {
out.collect(sampled.next());
}
}
}