Efficiency testing between Bresenham’s and floating point methods

circle.c

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

void write_pixel(int a, int b)
{
    int *k = (int*)malloc(2 * sizeof(int));
    k[0] = a; k[1] = b;
    free(k);
    return;
}

int main(void)
{
    unsigned i;
    unsigned n;
    int *r_list;
    double t0, t1, t2;
    srand((unsigned)time(0));
    scanf("%d", &n);
    r_list = (unsigned*)malloc(sizeof(unsigned) * n);
    for(i = 0; i < n; i++)
        r_list[i] = rand();
    t0 = clock();
    for(i = 0; i < n; i++)
    {
        int j;
        int r = r_list[i];
        int x = 0, y = r;
        while(x <= y)
        {
            write_pixel(x, y);  write_pixel(y, x);
            write_pixel(-x, y); write_pixel(y, -x);
            write_pixel(x, -y); write_pixel(-y, x);
            write_pixel(-x, -y); write_pixel(-y, -x);
            x++;
            y = 2*(x*x+y*y-r*r) + 4*x - 2*y + 3 > 0 ? y - 1 : y;
        }
    }
    t1 = clock();
    for(i = 0; i < n; i++)
    {
        int r = r_list[i];
        int x = 0, y = r;
        while(x <= y)
        {
            write_pixel(x, y);  write_pixel(y, x);
            write_pixel(-x, y); write_pixel(y, -x);
            write_pixel(x, -y); write_pixel(-y, x);
            write_pixel(-x, -y); write_pixel(-y, -x);
            x++;
            y = sqrt(r*r - x*x) + 0.5;
        }
    }
    t2 = clock();
    printf("%lf %lf\n", t1-t0, t2-t1);
    return 0;
}