Compare division module with module by reciprocal

div.c

#include <stdlib.h>
#include <stdio.h>
#include <inttypes.h>
#include <math.h>

static inline uint32_t
div_mult(uint32_t n, uint32_t d, uint32_t r)
{
    uint64_t m = (uint64_t)n*r;
    return n - d*(m>>32);
}

static inline uint32_t
div_div(uint32_t n, uint32_t d)
{
    return n % d;
}

static inline uint32_t
div_and(uint32_t n, uint32_t d)
{
    return n & (d-1);
}

int
main(int argc, char** argv)
{
    uint32_t n = argc > 1 ? atoi(argv[1]) : 100000;
    uint32_t D = argc > 2 ? atoi(argv[2]) : 1024;
    uint32_t m = argc > 3 ? atoi(argv[3]) : 2;
    uint32_t d,r,i;
	uint64_t s = 0;

	for (d = 2; d <= D; d++)
	{
    	r = ceil((double)(1ll<<32)/d);
    	if (m == 0)
    	{
        	for (i = 0; i < n; i++)
            	s += div_div(i + s, d);
    	}
    	else if (m == 1)
    	{
        	for (i = 0; i < n; i++)
            	s += div_mult(i + s, d, r);
    	}
    	else if (m == 2)
    	{
        	for (i = 0; i < n; i++)
        	{
            	s = div_div(i, d);
            	if (s == div_mult(i, d, r))
                	continue;
            	printf("d:%u i:%u r:%u dd:%u dm:%u\n",
            		d, i, r, (uint32_t)s, div_mult(i, d, r));
            	break;
        	}
    	}
    	else if (m == 3)
    	{
        	for (i = 0; i < n; i++)
            	s += div_and(i + s, d);
    	}
	}

	printf("%llu\n", (long long)s);
}