io.druid.extendedset.utilities.BitCount Maven / Gradle / Ivy
/*
* (c) 2010 Alessandro Colantonio
*
*
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
package io.druid.extendedset.utilities;
import java.util.Random;
/**
* Population count (a.k.a. Hamming distance) of a bitmap represented by an
* array of int.
*
* Derived from http
* ://dalkescientific.com/writings/diary/popcnt.c
*
* @author Alessandro Colantonio
* @version $Id: BitCount.java 157 2011-11-14 14:25:15Z cocciasik $
*/
public class BitCount
{
/**
* Population count
*
* @param buffer array of int
*
* @return population count
*/
public static int count(int[] buffer)
{
return count(buffer, buffer.length);
}
/**
* Population count
*
* It counts 24 words at a time, then 3 at a time, then 1 at a time
*
* @param buffer array of int
* @param n number of elements of buffer to count
*
* @return population count
*/
public static int count(int[] buffer, int n)
{
final int n1 = n - n % 24;
final int n2 = n - n % 3;
int cnt = 0;
int i;
for (i = 0; i < n1; i += 24) {
cnt += merging3(buffer, i);
}
for (; i < n2; i += 3) {
cnt += merging2(buffer, i);
}
cnt += popcount_fbsd2(buffer, i, n);
return cnt;
}
// used by count()
private static int merging3(int[] buffer, int x)
{
int cnt1;
int cnt2;
int cnt = 0;
for (int i = x; i < x + 24; i += 3) {
cnt1 = buffer[i];
cnt2 = buffer[i + 1];
final int w = buffer[i + 2];
cnt1 = cnt1 - ((cnt1 >>> 1) & 0x55555555) + (w & 0x55555555);
cnt2 = cnt2 - ((cnt2 >>> 1) & 0x55555555) + ((w >>> 1) & 0x55555555);
cnt1 = (cnt1 & 0x33333333) + ((cnt1 >>> 2) & 0x33333333);
cnt1 += (cnt2 & 0x33333333) + ((cnt2 >>> 2) & 0x33333333);
cnt += (cnt1 & 0x0F0F0F0F) + ((cnt1 >>> 4) & 0x0F0F0F0F);
}
cnt = (cnt & 0x00FF00FF) + ((cnt >>> 8) & 0x00FF00FF);
cnt += cnt >>> 16;
return cnt & 0x00000FFFF;
}
// used by count()
private static int merging2(int[] buffer, int x)
{
int cnt1 = buffer[x];
int cnt2 = buffer[x + 1];
final int w = buffer[x + 2];
cnt1 = cnt1 - ((cnt1 >>> 1) & 0x55555555) + (w & 0x55555555);
cnt2 = cnt2 - ((cnt2 >>> 1) & 0x55555555) + ((w >>> 1) & 0x55555555);
cnt1 = (cnt1 & 0x33333333) + ((cnt1 >>> 2) & 0x33333333);
cnt2 = (cnt2 & 0x33333333) + ((cnt2 >>> 2) & 0x33333333);
cnt1 += cnt2;
cnt1 = (cnt1 & 0x0F0F0F0F) + ((cnt1 >>> 4) & 0x0F0F0F0F);
cnt1 += cnt1 >>> 8;
cnt1 += cnt1 >>> 16;
return cnt1 & 0x000000FF;
}
// used by count()
private static int popcount_fbsd2(int[] data, int x, int n)
{
int cnt = 0;
for (; x < n; x++) {
cnt += Integer.bitCount(data[x]);
}
return cnt;
}
/**
* Population count, skipping words at even positions
*
* @param buffer array of int
*
* @return population count
*/
public static int count_2(int[] buffer)
{
return count_2(buffer, buffer.length);
}
/**
* Population count, skipping words at even positions
*
* It counts 24 words at a time, then 3 at a time, then 1 at a time
*
* @param buffer array of int
* @param n number of elements of buffer to count
*
* @return population count
*/
public static int count_2(int[] buffer, int n)
{
final int n1 = n - n % 48;
final int n2 = n - n % 6;
int cnt = 0;
int i;
for (i = 0; i < n1; i += 48) {
cnt += merging3_2(buffer, i);
}
for (; i < n2; i += 6) {
cnt += merging2_2(buffer, i);
}
cnt += popcount_fbsd2_2(buffer, i, n);
return cnt;
}
// used by count_2()
private static int merging3_2(int[] buffer, int x)
{
int cnt1;
int cnt2;
int cnt = 0;
for (int i = x; i < x + 48; i += 6) {
cnt1 = buffer[i + 1];
cnt2 = buffer[i + 3];
final int w = buffer[i + 5];
cnt1 = cnt1 - ((cnt1 >>> 1) & 0x55555555) + (w & 0x55555555);
cnt2 = cnt2 - ((cnt2 >>> 1) & 0x55555555) + ((w >>> 1) & 0x55555555);
cnt1 = (cnt1 & 0x33333333) + ((cnt1 >>> 2) & 0x33333333);
cnt1 += (cnt2 & 0x33333333) + ((cnt2 >>> 2) & 0x33333333);
cnt += (cnt1 & 0x0F0F0F0F) + ((cnt1 >>> 4) & 0x0F0F0F0F);
}
cnt = (cnt & 0x00FF00FF) + ((cnt >>> 8) & 0x00FF00FF);
cnt += cnt >>> 16;
return cnt & 0x00000FFFF;
}
// used by count_2()
private static int merging2_2(int[] buffer, int x)
{
int cnt1 = buffer[x + 1];
int cnt2 = buffer[x + 3];
final int w = buffer[x + 5];
cnt1 = cnt1 - ((cnt1 >>> 1) & 0x55555555) + (w & 0x55555555);
cnt2 = cnt2 - ((cnt2 >>> 1) & 0x55555555) + ((w >>> 1) & 0x55555555);
cnt1 = (cnt1 & 0x33333333) + ((cnt1 >>> 2) & 0x33333333);
cnt2 = (cnt2 & 0x33333333) + ((cnt2 >>> 2) & 0x33333333);
cnt1 += cnt2;
cnt1 = (cnt1 & 0x0F0F0F0F) + ((cnt1 >>> 4) & 0x0F0F0F0F);
cnt1 += cnt1 >>> 8;
cnt1 += cnt1 >>> 16;
return cnt1 & 0x000000FF;
}
// used by count_2()
private static int popcount_fbsd2_2(int[] data, int x, int n)
{
int cnt = 0;
for (x++; x < n; x += 2) {
cnt += Integer.bitCount(data[x]);
}
return cnt;
}
/**
* Test
*
* @param args
*/
public static void main(String[] args)
{
final int trials = 10000;
final int maxLength = 10000;
Random rnd = new Random();
final int seed = rnd.nextInt();
System.out.print("Test correctness... ");
rnd = new Random(seed);
for (int i = 0; i < trials; i++) {
int[] x = new int[rnd.nextInt(maxLength)];
for (int j = 0; j < x.length; j++) {
x[j] = rnd.nextInt(Integer.MAX_VALUE);
}
int size1 = 0;
for (int j = 0; j < x.length; j++) {
size1 += Integer.bitCount(x[j]);
}
int size2 = count(x);
if (size1 != size2) {
System.out.println("i = " + i);
System.out.println("ERRORE!");
System.out.println(size1 + ", " + size2);
for (int j = 0; j < x.length; j++) {
System.out.format("x[%d] = %d --> %d\n", j, x[j], Integer.bitCount(x[j]));
}
return;
}
}
System.out.println("done!");
System.out.print("Test correctness II... ");
rnd = new Random(seed);
for (int i = 0; i < trials; i++) {
int[] x = new int[rnd.nextInt(maxLength << 1)];
for (int j = 1; j < x.length; j += 2) {
x[j] = rnd.nextInt(Integer.MAX_VALUE);
}
int size1 = 0;
for (int j = 1; j < x.length; j += 2) {
size1 += Integer.bitCount(x[j]);
}
int size2 = count_2(x);
if (size1 != size2) {
System.out.println("i = " + i);
System.out.println("ERRORE!");
System.out.println(size1 + ", " + size2);
for (int j = 1; j < x.length; j += 2) {
System.out.format("x[%d] = %d --> %d\n", j, x[j], Integer.bitCount(x[j]));
}
return;
}
}
System.out.println("done!");
System.out.print("Test time count(): ");
rnd = new Random(seed);
long t = System.currentTimeMillis();
for (int i = 0; i < trials; i++) {
int[] x = new int[rnd.nextInt(maxLength)];
for (int j = 0; j < x.length; j++) {
x[j] = rnd.nextInt(Integer.MAX_VALUE);
}
@SuppressWarnings("unused")
int size = 0;
for (int j = 0; j < x.length; j++) {
size += Integer.bitCount(x[j]);
}
}
System.out.println(System.currentTimeMillis() - t);
System.out.print("Test time BitCount.count(): ");
rnd = new Random(seed);
t = System.currentTimeMillis();
for (int i = 0; i < trials; i++) {
int[] x = new int[rnd.nextInt(maxLength)];
for (int j = 0; j < x.length; j++) {
x[j] = rnd.nextInt(Integer.MAX_VALUE);
}
count(x);
}
System.out.println(System.currentTimeMillis() - t);
System.out.print("Test II time count(): ");
rnd = new Random(seed);
t = System.currentTimeMillis();
for (int i = 0; i < trials; i++) {
int[] x = new int[rnd.nextInt(maxLength << 1)];
for (int j = 1; j < x.length; j += 2) {
x[j] = rnd.nextInt(Integer.MAX_VALUE);
}
@SuppressWarnings("unused")
int size = 0;
for (int j = 1; j < x.length; j += 2) {
size += Integer.bitCount(x[j]);
}
}
System.out.println(System.currentTimeMillis() - t);
System.out.print("Test II time BitCount.count(): ");
rnd = new Random(seed);
t = System.currentTimeMillis();
for (int i = 0; i < trials; i++) {
int[] x = new int[rnd.nextInt(maxLength << 1)];
for (int j = 1; j < x.length; j += 2) {
x[j] = rnd.nextInt(Integer.MAX_VALUE);
}
count_2(x);
}
System.out.println(System.currentTimeMillis() - t);
}
}