StreamVsLoopLanger.java

package benchmarks;

import org.openjdk.jmh.annotations.*;

import java.util.*;
import java.util.concurrent.*;

@Fork(value = 1)
@Warmup(iterations = 5, time = 3)
@Measurement(iterations = 10, time = 3)
@BenchmarkMode(Mode.AverageTime)
@OutputTimeUnit(TimeUnit.MILLISECONDS)
@State(Scope.Benchmark)
public class StreamVsLoopLanger {
  @Param({"500000"})
//  @Param({"1000", "100000", "10000000"})
  private int length;
  private int[] ints;

  @Setup
  public void setup() {
    ints = ThreadLocalRandom.current().ints(length).toArray();
  }

  @Benchmark
  public int findMaxForLoopLanger() {
    int[] a = ints;
    int e = ints.length;
    int m = Integer.MIN_VALUE;
    for (int i = 0; i < e; i++)
      if (a[i] > m) m = a[i];
    return m;
  }

  @Benchmark
  public int findMaxStream() {
    return Arrays.stream(ints)
        .reduce(Integer.MIN_VALUE, Math::max);
  }

  @Benchmark
  public int findMaxStreamParallel() {
    return Arrays.stream(ints)
        .parallel()
        .reduce(Integer.MIN_VALUE, Math::max);
  }
}

/*
Results for 1000, 100_000, 10_000_000 in nanoseconds
Benchmark                                 (length)  Mode  Cnt        Score       Error  Units
StreamVsLoopLanger.findMaxForLoopLanger       1000  avgt   10      369,186 ±     4,529  ns/op
StreamVsLoopLanger.findMaxForLoopLanger     100000  avgt   10    19845,077 ±   289,484  ns/op
StreamVsLoopLanger.findMaxForLoopLanger   10000000  avgt   10  3711871,012 ± 49942,887  ns/op
StreamVsLoopLanger.findMaxForLoopNormal       1000  avgt   10      209,819 ±     1,989  ns/op
StreamVsLoopLanger.findMaxForLoopNormal     100000  avgt   10    19769,689 ±   280,703  ns/op
StreamVsLoopLanger.findMaxForLoopNormal   10000000  avgt   10  3715386,078 ± 25319,267  ns/op
StreamVsLoopLanger.findMaxStream              1000  avgt   10      524,544 ±     6,854  ns/op
StreamVsLoopLanger.findMaxStream            100000  avgt   10    48092,234 ±  2998,737  ns/op
StreamVsLoopLanger.findMaxStream          10000000  avgt   10  6393546,822 ± 44090,159  ns/op
StreamVsLoopLanger.findMaxStreamParallel      1000  avgt   10    28137,221 ±  1316,457  ns/op
StreamVsLoopLanger.findMaxStreamParallel    100000  avgt   10    33863,617 ±   656,033  ns/op
StreamVsLoopLanger.findMaxStreamParallel  10000000  avgt   10  1303320,663 ± 15932,859  ns/op

Results for 500_000 in milliseconds
Benchmark                                 (length)  Mode  Cnt  Score   Error  Units
StreamVsLoopLanger.findMaxForLoopLanger     500000  avgt   10  0,099 ± 0,001  ms/op
StreamVsLoopLanger.findMaxStream            500000  avgt   10  0,237 ± 0,003  ms/op
StreamVsLoopLanger.findMaxStreamParallel    500000  avgt   10  0,059 ± 0,002  ms/op
 */