ex4_cond.c

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

#define SIZE 100000000

#define GET_SEC(a, b)  ((b - a) / (double)CLOCKS_PER_SEC)  

static int cmp_dbl(const void* a, const void* b)
{
   const double* aa = a;
   const double* bb = b;

   if (aa < bb)
      return -1;
   if (aa > bb)
      return 1;
   return 0;
}

int main(int argc, char** argv)
{
   clock_t start;
   int* x = malloc(SIZE * sizeof(*x));
   double  sum;
   int     q;
   
   for(int i = 0; i < SIZE; i++)
      x[i] = (rand() % 256);
   
   sum = 0.0; start = clock();

   /* In order 1 */
   for(int i = 0; i < SIZE; i++)
      sum += x[i];

   printf("IO time=%.3f sum=%.1f\n", GET_SEC(start, clock()), sum);

   sum = 0.0; start = clock(); q = 0;

   /* In order 1 */
   for(int i = 0; i < SIZE; i++)
      if (x[i] <= 128)
         sum += x[i];
      else
         q++;

   printf("IO time=%.3f sum=%.1f %d\n", GET_SEC(start, clock()), sum, q);

   qsort(x, SIZE, sizeof(*x), cmp_dbl);
   
   sum = 0.0; start = clock(); q = 0;

   /* In order 1 */
   for(int i = 0; i < SIZE; i++)
      if (x[i] <= 128)
         sum += x[i];
      else
         q++;

   printf("IO time=%.3f sum=%.1f %d\n", GET_SEC(start, clock()), sum, q);

}