To call() or not to call() that is the question.

functionCall.c

//2012-06-28 functionCall.c jorge@jorgechamorro.com

/*
$ gcc -O0 /Users/jorge/Desktop/functionCall.c 
$ ./a.out
without a function call: 2.789478 ns per iteration
with a function call   : 3.574004 ns per iteration

With the function call it's 28.124473 percent slower than without the function call
*/

#include <stdio.h>
#include <unistd.h>
#include <sys/time.h>

static int flag= 0;
#define kLoops 1e9


int f (int flag) {
  if (flag) return 1;
  else return 0;
}


long long now () {
    struct timeval time;
    gettimeofday(&time, NULL);
    return (long long) ((time.tv_sec*  1000000) + time.tv_usec);
}


long long dsp (long long t, char* msg) {
  t= now()- t;
  printf("%s: %lf ns per iteration\n", msg, ((double)t)*1e3/kLoops);
  fflush(stdout);
  return t;
}


int main (int argc, char** argv) {
  long long t, wfc, wofc;
  long ctr, i;
  
  ctr= 0;
  i= kLoops;
  t= now();
  while (i--) if (flag) f(flag);
  wofc= dsp(t, "without a function call");
  
  ctr= 0;
  i= kLoops;
  t= now();
  while (i--) f(flag);
  wfc= dsp(t, "with a function call   ");
  
  printf("\nWith the function call it's %lf percent slower than without the function call\n", ((double)wfc-(double)wofc)/((double)wofc/1e2));
}