benchmark different int log2 options

NettyLog2Benchmark.java

package com.github.netudima.cassandra;

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.concurrent.TimeUnit;

@BenchmarkMode(Mode.AverageTime)
@OutputTimeUnit(TimeUnit.NANOSECONDS)
public class NettyLog2Benchmark {

    public static void main(String[] args) throws RunnerException {
        Options opt = new OptionsBuilder()
                .include(NettyLog2Benchmark.class.getSimpleName())
                .forks(3)
                .build();

        new Runner(opt).run();

        // check equivalence of the implementations in range [0; Integer.MAX_VALUE]
//        for(int i = 0; i < Integer.MAX_VALUE; i++) {
//            int log1 = log2LeadingZeroes(i);
//            int log2 = log2Cycle(i);
//            int log3 = log2Bits(i);
//            if (log1 != log2 || log2 != log3) {
//                System.out.println("i: " + i + ", log1: " + log1 + ", log2: " + log2 + ", log3: " + log3);
//            }
//        }
    }


    @State(Scope.Thread)
    public static class MyState {
        public int value = 1234567;
    }

    @Benchmark
    public int leadingZeroes(MyState myState) {
        return log2LeadingZeroes(myState.value);
    }

    @Benchmark
    public int cycle(MyState myState) {
        return log2Cycle(myState.value);
    }

    @Benchmark
    public int bits(MyState myState) {
        return log2Bits(myState.value);
    }

    private static int log2LeadingZeroes(int val) {
        if (val == 0) {
            return 0;
        }
        return 31 - Integer.numberOfLeadingZeros(val);
    }

    private static int log2Cycle(int val) {
        int res = 0;
        while (val > 1) {
            val >>= 1;
            res++;
        }
        return res;
    }

    private static int log2Bits(int val) {
        int log = 0;
        if( ( val & 0xffff0000 ) != 0 ) { val >>>= 16; log = 16; }
        if( val >= 256 ) { val >>>= 8; log += 8; }
        if( val >= 16  ) { val >>>= 4; log += 4; }
        if( val >= 4   ) { val >>>= 2; log += 2; }
        return log + ( val >>> 1 );
    }
}