ทำไมเขียนโปรแกรมโดยใช้การ คูณ ถึงดีกว่าการ หาร ครับ

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

int main()
{
   int i;
   double a[6];
   time_t st;

#define AVG1   a[0] = (a[0]+a[1]+a[2]+a[3]+a[4]+a[5]) / 6;
#define AVG2   a[0] = (a[0]+a[1]+a[2]+a[3]+a[4]+a[5]) * 0.16667;

   for (i=0; i<6; ++i)
      a[i]=i;
   st=time(NULL);
   for (i=0; i<10000000; ++i)
   {
      AVG1 AVG1 AVG1 AVG1 AVG1 AVG1 AVG1 AVG1 AVG1 AVG1
      AVG1 AVG1 AVG1 AVG1 AVG1 AVG1 AVG1 AVG1 AVG1 AVG1
      AVG1 AVG1 AVG1 AVG1 AVG1 AVG1 AVG1 AVG1 AVG1 AVG1
      AVG1 AVG1 AVG1 AVG1 AVG1 AVG1 AVG1 AVG1 AVG1 AVG1
      AVG1 AVG1 AVG1 AVG1 AVG1 AVG1 AVG1 AVG1 AVG1 AVG1
      AVG1 AVG1 AVG1 AVG1 AVG1 AVG1 AVG1 AVG1 AVG1 AVG1
      AVG1 AVG1 AVG1 AVG1 AVG1 AVG1 AVG1 AVG1 AVG1 AVG1
      AVG1 AVG1 AVG1 AVG1 AVG1 AVG1 AVG1 AVG1 AVG1 AVG1
      AVG1 AVG1 AVG1 AVG1 AVG1 AVG1 AVG1 AVG1 AVG1 AVG1
      AVG1 AVG1 AVG1 AVG1 AVG1 AVG1 AVG1 AVG1 AVG1 AVG1
   }
   printf("AVG1 use %ld sec\n",time(NULL)-st);

   for (i=0; i<6; ++i)
      a[i]=i;
   st=time(NULL);
   for (i=0; i<10000000; ++i)
   {
      AVG2 AVG2 AVG2 AVG2 AVG2 AVG2 AVG2 AVG2 AVG2 AVG2
      AVG2 AVG2 AVG2 AVG2 AVG2 AVG2 AVG2 AVG2 AVG2 AVG2
      AVG2 AVG2 AVG2 AVG2 AVG2 AVG2 AVG2 AVG2 AVG2 AVG2
      AVG2 AVG2 AVG2 AVG2 AVG2 AVG2 AVG2 AVG2 AVG2 AVG2
      AVG2 AVG2 AVG2 AVG2 AVG2 AVG2 AVG2 AVG2 AVG2 AVG2
      AVG2 AVG2 AVG2 AVG2 AVG2 AVG2 AVG2 AVG2 AVG2 AVG2
      AVG2 AVG2 AVG2 AVG2 AVG2 AVG2 AVG2 AVG2 AVG2 AVG2
      AVG2 AVG2 AVG2 AVG2 AVG2 AVG2 AVG2 AVG2 AVG2 AVG2
      AVG2 AVG2 AVG2 AVG2 AVG2 AVG2 AVG2 AVG2 AVG2 AVG2
      AVG2 AVG2 AVG2 AVG2 AVG2 AVG2 AVG2 AVG2 AVG2 AVG2
   }
   printf("AVG2 use %ld sec\n",time(NULL)-st);

   return 0;
}

#define AVG1   a[0] = (a[0]+a[1]+a[2]+a[3]+a[4]+a[5]) / 6;
#define AVG2   a[0] = (a[0]+a[1]+a[2]+a[3]+a[4]+a[5]) * 0.16667;

gcc -O -o bm bm.c
./bm
AVG1 use 23 sec
AVG2 use 9 sec
./bm
AVG1 use 23 sec
AVG2 use 9 sec

gcc -o bm bm.c
./bm
AVG1 use 25 sec
AVG2 use 12 sec
./bm
AVG1 use 25 sec
AVG2 use 11 sec

;>)