test_square.c

/*******************************************************************************

   test_square

   Timed loops to compare the floating point calculation using f * f directly,
   as an inline and regular function compared to using the intrinsic math pow()
   function.

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

#define LOOP 10000
#define SIZE 10000

__attribute__((always_inline))
inline static float inline_sq(float n) { return n * n; }

float square(float n) { return n * n; }

int main(int argc, char *argv[])
{
   float reals[SIZE];
   float result = 0.0;
   double dummy;
   clock_t start, stop;

   printf("%s\t%'dx%'d\n", argv[0], LOOP, SIZE);

   // random array of floats 1 & 10
   for (int i = 0; i < SIZE; i++)
      reals[i] = 1 + 9 * (float) rand() / (float) RAND_MAX;

   // test multiplication
   start = clock();
   dummy = 0;
   for (int t = 0; t < LOOP; t++) {
      result = 0;
      for (int i = 0; i < SIZE; i++) {
         float f = reals[i];
         result += f * f;
      }
      dummy += result;
   }
   stop = clock();
   printf("f * f\t\t%0.6f\t%0.6f\n", (float) (stop - start) / (float) CLOCKS_PER_SEC, dummy);

   // test function inline
   start = clock();
   dummy = 0;
   for (int t = 0; t < LOOP; t++) {
      result = 0;
      for (int i = 0; i < SIZE; i++) {
         float f = reals[i];
         result += inline_sq(f);
      }
      dummy += result;
   }
   stop = clock();
   printf("inline_sq(f)\t%0.6f\t%0.6f\n", (float) (stop - start) / (float) CLOCKS_PER_SEC, dummy);

   // test function square
   start = clock();
   dummy = 0;
   for (int t = 0; t < LOOP; t++) {
      result = 0;
      for (int i = 0; i < SIZE; i++) {
         float f = reals[i];
         result += square(f);
      }
      dummy += result;
   }
   stop = clock();
   printf("square(f, 2)\t%0.6f\t%0.6f\n", (float) (stop - start) / (float) CLOCKS_PER_SEC, dummy);

   // test pow()
   start = clock();
   dummy = 0;
   for (int t = 0; t < LOOP; t++) {
      result = 0;
      for (int i = 0; i < SIZE; i++) {
         float f = reals[i];
         result += pow(f, 2);
      }
      dummy += result;
   }
   stop = clock();
   printf("pow(f, 2)\t%0.6f\t%0.6f\n", (float) (stop - start) / (float) CLOCKS_PER_SEC, dummy);

} /* main */