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#define _POSIX_C_SOURCE 200809L /* Required to use clock_gettime */
#include <stdio.h>
#include <stdlib.h>
#include <time.h>
typedef struct { int a, b; } pair_t;
pair_t a[ARRAYSIZE];
int compar(const void *x, const void *y) {
pair_t *p = (pair_t *)x;
pair_t *q = (pair_t *)y;
int d = p->a - q->a;
return d > 0 ? 1 : (d < 0 ? -1 : (q->b - p->b));
}
int main() {
srand(time(NULL));
for (int i = 0; i < ARRAYSIZE; i++) {
a[i].a = rand() % 1000000;
a[i].b = rand() % 1000000;
}
struct timespec begin;
clock_gettime(CLOCK_MONOTONIC, &begin);
qsort(a, ARRAYSIZE, sizeof(pair_t), compar);
struct timespec end;
clock_gettime(CLOCK_MONOTONIC, &end);
double time = end.tv_sec - begin.tv_sec +
(end.tv_nsec - begin.tv_nsec) / 1000000000.0;
printf("(%d) C time for %d pairs: %lfs\n",
a[ARRAYSIZE/2].a, ARRAYSIZE, time);
return 0;
}
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