compare rint() to round()

test_rint_round.c

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

#define MAX_NUM 1000

int main() {
    double x;
    double rint_x, round_x;
    double total_x, total_rint_x, total_round_x;
    int i;
    srand((unsigned int)time(NULL));
    for(i = 0; i < MAX_NUM; ++i) {
        x = rand() % 1000;
        x += 0.5;
        rint_x = (double)rint(x);
        round_x = (double)round(x);
        // printf("rint(%.2lf)  = %.2lf\n", x, rint_x);
        // printf("round(%.2lf) = %.2lf\n", x, round_x);
        total_x += x;
        total_rint_x += rint_x;
        total_round_x += round_x;
    }
    
    printf("== result ==\n");
    printf("sum(x)        = %.2lf\n", total_x);
    printf("sum(rint(x))  = %.2lf (diff: %.2lf)\n",
            total_rint_x,
            total_rint_x - total_x);
    printf("sum(round(x)) = %.2lf (diff: %.2lf)\n",
            total_round_x,
            total_round_x - total_x);
    return 0;
}