io.druid.extendedset.utilities

Class BitCount

java.lang.Object

io.druid.extendedset.utilities.BitCount

public class BitCount
extends Object

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

Version:

$Id: BitCount.java 157 2011-11-14 14:25:15Z cocciasik $

Author:

Alessandro Colantonio

Constructor Summary

Constructors

Constructor and Description
BitCount()

Method Summary

Modifier and Type	Method and Description
static int	count_2(int[] buffer) Population count, skipping words at even positions
static int	count_2(int[] buffer, int n) Population count, skipping words at even positions
static int	count(int[] buffer) Population count
static int	count(int[] buffer, int n) Population count
static void	main(String[] args) Test

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Constructor Detail

BitCount

public BitCount()

Method Detail

count

public static int count(int[] buffer)

Population count

Parameters:

buffer - array of int

Returns:

population count

count

public static int count(int[] buffer,
                        int n)

Population count

It counts 24 words at a time, then 3 at a time, then 1 at a time

Parameters:

buffer - array of int

n - number of elements of buffer to count

Returns:

population count

count_2

public static int count_2(int[] buffer)

Population count, skipping words at even positions

Parameters:

buffer - array of int

Returns:

population count

count_2

public static int count_2(int[] buffer,
                          int n)

Population count, skipping words at even positions

It counts 24 words at a time, then 3 at a time, then 1 at a time

Parameters:

buffer - array of int

n - number of elements of buffer to count

Returns:

population count

main

public static void main(String[] args)

Test

Parameters:

args -