megamorphic.java

// Slightly modified benchmark from Optimize Java book
package de.jawb.jmh.benchmark.example.uniquechars;

import org.openjdk.jmh.annotations.Benchmark;
import org.openjdk.jmh.annotations.BenchmarkMode;
import org.openjdk.jmh.annotations.Fork;
import org.openjdk.jmh.annotations.Measurement;
import org.openjdk.jmh.annotations.Mode;
import org.openjdk.jmh.annotations.OutputTimeUnit;
import org.openjdk.jmh.annotations.Scope;
import org.openjdk.jmh.annotations.State;
import org.openjdk.jmh.annotations.Warmup;
import org.openjdk.jmh.infra.Blackhole;

import java.util.ArrayList;
import java.util.List;
import java.util.concurrent.TimeUnit;

@Warmup(iterations = 15, time = 2, timeUnit = TimeUnit.MILLISECONDS)
@Measurement(iterations = 5, time = 2, timeUnit = TimeUnit.MILLISECONDS)
@Fork(1)
@State(Scope.Benchmark)
@OutputTimeUnit(TimeUnit.MILLISECONDS)
@BenchmarkMode({Mode.Throughput})
public class BimorphicBenchmark {
	private interface Shape {
		int getSides();
	}
	private class Triangle implements Shape {
		public int getSides() {
			return 3;
		}
	}
	private class Square implements Shape {
		public int getSides() {
			return 4;
		}
	}
	private class Octagon implements Shape {
		public int getSides() {
			return 8;
		}
	}


	private java.util.Random random = new java.util.Random();
	private Shape triangle = new Triangle();
	private Shape square = new Square();
	private Shape octagon = new Octagon();

	@Benchmark
	public int runMonomorphic() {
		Shape currentShape = triangle;
		return currentShape.getSides();
	}

	@Benchmark
	public int runBimorphic() {
		Shape currentShape = null;
		switch (random.nextInt(2))
		{
			case 0:
				currentShape = triangle;
				break;
			case 1:
				currentShape = square;
				break;
		}
		return currentShape.getSides();
	}
	@Benchmark
	public int runMegamorphic() {
		Shape currentShape = null;
		switch (random.nextInt(3))
		{
			case 0:
				currentShape = triangle;
				break;
			case 1:
				currentShape = square;
				break;
			case 2:
				currentShape = octagon;
				break;
		}
		return currentShape.getSides();
	}
	@Benchmark
	public int runPeeledMegamorphic() {
		Shape currentShape = null;
		switch (random.nextInt(3))
		{
			case 0:
				currentShape = triangle;
				break;
			case 1:
				currentShape = square;
				break;
			case 2:
				currentShape = octagon;
				break;
		}
		// peel one observed type from the original call site
		if (currentShape instanceof Triangle) {
			return ((Triangle) currentShape).getSides();
		}
		else {
			return currentShape.getSides(); // now only bimorphic
		}
	}
}