CPUBranchPredictionTest.java

package ddzj.learnjava;


import lombok.extern.slf4j.Slf4j;
import org.openjdk.jmh.annotations.*;
import org.openjdk.jmh.runner.Runner;
import org.openjdk.jmh.runner.RunnerException;
import org.openjdk.jmh.runner.options.Options;
import org.openjdk.jmh.runner.options.OptionsBuilder;

import java.util.Random;
import java.util.concurrent.TimeUnit;

/**
 * ClassName: CPUBranchPredictionTest <br/>
 * Function:  <br/>
 * Date: 2019-10-23 9:15<br/>
 *
 * @author timedcy
 * @version 0.1
 */

@Slf4j
@BenchmarkMode(Mode.AverageTime)
@OutputTimeUnit(TimeUnit.MILLISECONDS)
@State(Scope.Thread)
public class CPUBranchPredictionTest {
    int[] data;

    @Setup
    public void setUp() {
        int loopNum = 2_000_000;
        data = new int[loopNum];
        Random random = new Random(42);
        for (int i = 0; i < loopNum; i++) {
            data[i] = random.nextInt();
        }
    }

    @Benchmark
    public long testIfBranch() {
        long sum = 0L;
        int loopNum = data.length;
        for (int i = 0; i < loopNum; i++) {
            if ((data[i] & 1) == 1) {
                sum += i;
            }
        }
        return sum;
    }

    @Benchmark
    public long testNoBranch() {
        long sum = 0L;
        int loopNum = data.length;
        for (int i = 0; i < loopNum; i++) {
            sum += (data[i] & 1) * i;
        }
        return sum;
    }

    @Benchmark
    public long testIsDebugedNoBranch() {
        long sum = 0L;
        int loopNum = data.length;
        for (int i = 0; i < loopNum; i++) {
            if (log.isDebugEnabled()) {
                sum += (data[i] & 1) * i;
            }
        }
        return sum;
    }

    public static void main(String[] args) throws RunnerException {
        log.info("log.isDebugEnabled(): {}", log.isDebugEnabled());
        Options opt = new OptionsBuilder()
                .include(CPUBranchPredictionTest.class.getSimpleName())
                .forks(1)
                .warmupIterations(1)
                .measurementIterations(5)
                .build();

        new Runner(opt).run();
    }

}