BitCount

.gitignore

*.class

BitCountRunner.java

class BitCountRunner {
    static final int MAX_INT = 1 << 14;
    static final long MAX_LONG = 1 << 14;

    int intIntrinsic() {
        int cnt = 0;
        for (int i = 0; i < MAX_INT; i++)
            cnt += Integer.bitCount(i);
        return cnt;
    }

    int intJDK() {
        int cnt = 0;
        for (int i = 0; i < MAX_INT; i++)
            cnt += BitCounts.bitCountInt(i);
        return cnt;
    }

    int intNew() {
        int cnt = 0;
        for (int i = 0; i < MAX_INT; i++)
            cnt += BitCounts.bitCountIntNew(i);
        return cnt;
    }


    int longIntrinsic() {
        int cnt = 0;
        for (long i = 0; i < MAX_LONG; i++)
            cnt += Long.bitCount(i);
        return cnt;
    }

    int longJDK() {
        int cnt = 0;
        for (long i = 0; i < MAX_LONG; i++)
            cnt += BitCounts.bitCountLong(i);
        return cnt;
    }

    int longNew() {
        int cnt = 0;
        for (long i = 0; i < MAX_LONG; i++)
            cnt += BitCounts.bitCountLongNew(i);
        return cnt;
    }
}

BitCounts.java

public class BitCounts {
  public static final int bitCountLong(long i) {
    // HD, Figure 5-2
    i = i - ((i >>> 1) & 0x5555555555555555L);
    i = (i & 0x3333333333333333L) + ((i >>> 2) & 0x3333333333333333L);
    i = (i + (i >>> 4)) & 0x0f0f0f0f0f0f0f0fL;
    i = i + (i >>> 8);
    i = i + (i >>> 16);
    i = i + (i >>> 32);
    return (int)i & 0x7f;
  }

  public static final int bitCountLongNew(long i)
  {
      i -= (i >>> 1) & 0x5555555555555555L;
      i = (i & 0x3333333333333333L) + ((i >>> 2) & 0x3333333333333333L);
      i = (i + (i >>> 4)) & 0x0f0f0f0f0f0f0f0fL;
      return (int)((i * 0x0101010101010101L) >>> 56);
  }

  public static final int bitCountInt(int i) {
      // HD, Figure 5-2
      i = i - ((i >>> 1) & 0x55555555);
      i = (i & 0x33333333) + ((i >>> 2) & 0x33333333);
      i = (i + (i >>> 4)) & 0x0f0f0f0f;
      i = i + (i >>> 8);
      i = i + (i >>> 16);
      return i & 0x3f;
  }


  public static final int bitCountIntNew(int i) {
      i -= (i >>> 1) & 0x55555555;
      i = (i & 0x33333333) + ((i >>> 2) & 0x33333333);
      i = (i + (i >>> 4)) & 0x0f0f0f0f;
      return (i * 0x01010101) >>> 24;
  }
}

BitCountTest.scala

package org.openjdk.jmh.samples

import org.openjdk.jmh.annotations._

import java.util.concurrent.TimeUnit

import org.BitCounts

@State(Scope.Thread)
@BenchmarkMode(Array(Mode.AverageTime))
@OutputTimeUnit(TimeUnit.NANOSECONDS)
class BitCountTest {
  @Benchmark
  def bitCountInt = {
    var i = 0
    var cnt = 0
    val max = 1 << 14
    while (i < max) {
      cnt += BitCounts.bitCountInt(i)
      i += 1
    }
    cnt
  }

  @Benchmark
  def bitCountIntNew = {
    var i = 0
    var cnt = 0
    val max = 1 << 14
    while (i < max) {
      cnt += BitCounts.bitCountIntNew(i)
      i += 1
    }
    cnt
  }

  @Benchmark
  def bitCountLong = {
    var i = 0l
    var cnt = 0
    val max = 1l << 14
    while (i < max) {
      cnt += BitCounts.bitCountLong(i)
      i += 1l
    }
    cnt
  }

  @Benchmark
  def bitCountLongNew = {
    var i = 0l
    var cnt = 0
    val max = 1l << 14
    while (i < max) {
      cnt += BitCounts.bitCountLongNew(i)
      i += 1l
    }
    cnt
  }
}