What do you think of my code ? I implemented this in C using qsort, but I’m not sure about the reliability and correctness. And can I make it faster? I call this piece of code a lot.

#include <stdio.h> #include <stdlib.h> #include <time.h>  #define DIM 1 #define POWDIM 4  typedef unsigned long keytype;  typedef struct{     keytype k;     int idx; }sort_child;  int compare(const void *a, const void *b){     const keytype *x = a, *y = b;     if(*x > *y)         return 1;     else         return (*x < *y) ? -1 : 0; }  int main(int argc, char **argv){     srand(time(NULL));     sort_child sc[POWDIM];      printf("Before qsort()\n");     for(int i=0; i<POWDIM; i++){         sc[i].k = rand()%100;         sc[i].idx = i;          printf("sc[%d].k = %lu sc[%d].idx = %d\n", i, sc[i].k, i, sc[i].idx);     }      qsort (sc, POWDIM, sizeof(sort_child), compare);      printf("\n");     printf("After qsort()\n");     for(int i=0; i<POWDIM; i++){         printf("sc[%d].k = %lu sc[%d].idx = %d\n", i, sc[i].k, i, sc[i].idx);     }  }