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BITCNTS.C
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C/C++ Source or Header
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1996-11-24
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86 lines
/* +++Date last modified: 12-Jun-1996 */
/*
** BITCNTS.C - Test program for bit counting functions
**
** public domain by Bob Stout & Auke Reitsma
*/
#include <stdio.h>
#include <stdlib.h>
#include <conio.h>
#include <limits.h>
#include <time.h>
#include <float.h>
#include "bitops.h"
#define ITERS 1500000L
#define FUNCS 8
static int CDECL bit_shifter(long int x);
int main(void)
{
clock_t start, stop;
double ct, cmin = DBL_MAX, cmax = 0;
int i, cminix, cmaxix;
long j, n;
static int (* CDECL pBitCntFunc[FUNCS])(long) = {
bit_count,
bitcount,
ntbl_bitcnt,
ntbl_bitcount,
btbl_bitcnt,
BW_btbl_bitcount,
AR_btbl_bitcount,
bit_shifter
};
static char *text[FUNCS] = {
"Optimized 1 bit/loop counter",
"Ratko's mystery algorithm",
"Recursive bit count by nybbles",
"Non-recursive bit count by nybbles",
"Recursive bit count by bytes",
"Non-recursive bit count by bytes (BW)",
"Non-recursive bit count by bytes (AR)",
"Shift and count bits"
};
puts("Bit counter algorithm benchmark\n");
for (i = 0; i < FUNCS; i++)
{
start = clock();
for (j = n = 0; j < ITERS; j++)
n += pBitCntFunc[i](j);
stop = clock();
ct = (stop - start) / (double)CLOCKS_PER_SEC;
if (ct < cmin)
{
cmin = ct;
cminix = i;
}
if (ct > cmax)
{
cmax = ct;
cmaxix = i;
}
printf("%-38s> Time: %7.3f sec.; Bits: %ld\n", text[i], ct, n);
}
printf("\nBest > %s\n", text[cminix]);
printf("Worst > %s\n", text[cmaxix]);
return 0;
}
static int CDECL bit_shifter(long int x)
{
int i, n;
for (i = n = 0; x && (i < (sizeof(long) * CHAR_BIT)); ++i, x >>= 1)
n += (int)(x & 1L);
return n;
}