Microbenchmarking using JBang and JMH

Loops.java

//DEPS org.openjdk.jmh:jmh-generator-annprocess:1.36
// --javaagent=ap-loader@maxandersen=start,event=cpu,file=profile.html
package com.grokhard.benchmarking;

import org.openjdk.jmh.*;
import org.openjdk.jmh.annotations.*;
import org.openjdk.jmh.infra.Blackhole;

import java.util.stream.*;
import java.util.*;
import java.util.concurrent.TimeUnit;

/**
* This is just an example of using Java Microbenchmark Harness (JHM) used in conjunction with JBang
* to demonstrate how simple it is to do that without heavy tool like Maven or Gradle.
* 
* RUN:
*    jbang Loops.java
*
* This chooses a scenario: sum 10,000 numbers from a list. There are 4 bechmarks of how to use the loops.
*
* The use of Blackhole is important to avoid Dead Code Elimination of Java Compiler.
*/


@State(Scope.Benchmark)
@OutputTimeUnit(TimeUnit.NANOSECONDS)
public class Loops {

  public static void main(String[] args) throws java.io.IOException {
    org.openjdk.jmh.Main.main(args);
  }

  private List<Integer> numbers;

  @Setup(Level.Iteration)
  public void setup() {
    numbers = IntStream.range(0, 10_000).boxed().toList();
  }

  @Fork(value = 1)
  @Warmup(iterations = 5)
  @Benchmark
  @BenchmarkMode(Mode.AverageTime)
  public void sumUsingForEnhanceLoop(Blackhole bh) {
    int sum = 0;
    for (Integer number : numbers) {
      sum += number;
    }

    bh.consume(sum);
  }

  @Fork(value = 1)
  @Warmup(iterations = 5)
  @Benchmark
  @BenchmarkMode(Mode.AverageTime)
  public void sumUsingForLoopWithMethodCall(Blackhole bh) {
    int sum = 0;
    for (int i = 0; i < numbers.size(); i++) {
      sum += numbers.get(i);
    }
    bh.consume(sum);
  }

  @Fork(value = 1)
  @Warmup(iterations = 5)
  @Benchmark
  @BenchmarkMode(Mode.AverageTime)
  public void sumUsingForLoopWithSizeGotOutOfLoop(Blackhole bh) {
    int sum = 0;
    int size = numbers.size();
    for (int i = 0; i < size; i++) {
      sum += numbers.get(i);
    }
    bh.consume(sum);
  }

  @Fork(value = 1)
  @Warmup(iterations = 5)
  @Benchmark
  @BenchmarkMode(Mode.AverageTime)
  public void sumUsingReverseForLoopWithSizeGotOutOfLoop(Blackhole bh) {
    int sum = 0;
    int size = numbers.size();
    for (int i = size - 1; i >= 0; i--) {
      sum += numbers.get(i);
    }
    bh.consume(sum);
  }

}