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@amaembo
Last active Oct 12, 2021
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JMH benchmark for different solutions of http://stackoverflow.com/q/30089761/4856258
package org.sample;
import java.util.concurrent.TimeUnit;
import javax.util.streamex.*;
import java.util.stream.*;
import java.util.*;
import org.openjdk.jmh.infra.Blackhole;
import org.openjdk.jmh.annotations.*;
@Warmup(iterations = 5, time = 1, timeUnit = TimeUnit.SECONDS)
@Measurement(iterations = 10, time = 1, timeUnit = TimeUnit.SECONDS)
@BenchmarkMode(Mode.AverageTime)
@OutputTimeUnit(TimeUnit.MICROSECONDS)
@Fork(2)
@State(Scope.Benchmark)
public class PairTest {
@Param({ "10000", "100000", "1000000" })
private int n;
private List<Integer> input;
@Setup
public void setUp() {
input = IntStreamEx.of(new Random(1), n, 1, 10000).boxed().toList();
}
@Benchmark
public void naiveIterator(Blackhole bh) {
List<Integer> result = new ArrayList<>();
Integer last = null;
for (Integer cur : input) {
if (last != null && last < cur)
result.add(last);
last = cur;
}
bh.consume(result);
}
@Benchmark
public void naiveGet(Blackhole bh) {
List<Integer> result = new ArrayList<>();
for (int i = 0; i < input.size() - 1; i++) {
Integer cur = input.get(i), next = input.get(i + 1);
if (cur < next)
result.add(cur);
}
bh.consume(result);
}
@Benchmark
public void stream(Blackhole bh) {
List<Integer> result = IntStream.range(0, input.size() - 1)
.filter(i -> input.get(i) < input.get(i + 1))
.mapToObj(input::get).collect(Collectors.toList());
bh.consume(result);
}
@Benchmark
public void streamParallel(Blackhole bh) {
List<Integer> result = IntStream.range(0, input.size() - 1).parallel()
.filter(i -> input.get(i) < input.get(i + 1))
.mapToObj(input::get).collect(Collectors.toList());
bh.consume(result);
}
@Benchmark
public void streamEx(Blackhole bh) {
List<Integer> result = StreamEx.of(input)
.pairMap((a, b) -> a < b ? a : null).nonNull().toList();
bh.consume(result);
}
@Benchmark
public void streamExParallel(Blackhole bh) {
List<Integer> result = StreamEx.of(input).parallel()
.pairMap((a, b) -> a < b ? a : null).nonNull().toList();
bh.consume(result);
}
@Benchmark
public void reduce(Blackhole bh) {
List<Integer> result = new ArrayList<>();
input.stream().reduce((a, b) -> {
if (a < b)
result.add(a);
return b;
});
bh.consume(result);
}
public static Collector<Integer, ?, List<Integer>> collectPrecedingValues() {
int[] holder = { Integer.MAX_VALUE };
return Collector.of(ArrayList::new, (l, elem) -> {
if (holder[0] < elem)
l.add(holder[0]);
holder[0] = elem;
}, (l1, l2) -> {
throw new UnsupportedOperationException("Don't run in parallel");
});
}
@Benchmark
public void collector(Blackhole bh) {
List<Integer> result = input.stream().collect(collectPrecedingValues());
bh.consume(result);
}
}
Benchmark (n) Mode Cnt Score Error Units
PairTest.collector 10000 avgt 20 112.513 ± 1.087 us/op
PairTest.collector 100000 avgt 20 1404.866 ± 20.467 us/op
PairTest.collector 1000000 avgt 20 14387.239 ± 989.853 us/op
PairTest.naiveGet 10000 avgt 20 99.787 ± 3.674 us/op
PairTest.naiveGet 100000 avgt 20 1084.402 ± 13.105 us/op
PairTest.naiveGet 1000000 avgt 20 11424.225 ± 173.268 us/op
PairTest.naiveIterator 10000 avgt 20 97.719 ± 7.439 us/op
PairTest.naiveIterator 100000 avgt 20 903.956 ± 4.351 us/op
PairTest.naiveIterator 1000000 avgt 20 10592.720 ± 798.484 us/op
PairTest.reduce 10000 avgt 20 112.101 ± 6.526 us/op
PairTest.reduce 100000 avgt 20 1139.526 ± 5.282 us/op
PairTest.reduce 1000000 avgt 20 12001.482 ± 137.221 us/op
PairTest.stream 10000 avgt 20 146.382 ± 1.394 us/op
PairTest.stream 100000 avgt 20 1624.050 ± 14.680 us/op
PairTest.stream 1000000 avgt 20 16600.857 ± 193.994 us/op
PairTest.streamEx 10000 avgt 20 115.237 ± 2.183 us/op
PairTest.streamEx 100000 avgt 20 1247.118 ± 10.179 us/op
PairTest.streamEx 1000000 avgt 20 12966.952 ± 166.885 us/op
PairTest.streamExParallel 10000 avgt 20 53.415 ± 0.432 us/op
PairTest.streamExParallel 100000 avgt 20 516.669 ± 9.072 us/op
PairTest.streamExParallel 1000000 avgt 20 5353.370 ± 31.447 us/op
PairTest.streamParallel 10000 avgt 20 56.874 ± 1.411 us/op
PairTest.streamParallel 100000 avgt 20 582.256 ± 3.028 us/op
PairTest.streamParallel 1000000 avgt 20 6120.523 ± 69.305 us/op
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