Subj : Re: which for loop is better?
To   : comp.programming.threads
From : Elie De Brauwer
Date : Fri Mar 25 2005 11:22 am

sam wrote:
> I should've elaborated the problem. Here it goes : for the same number
> of total iterations(100*1000 in this example) in nested-for-loops, is
> it more effective to have the outer for loop iterate more than the
> inner one (case 2), or the other way around (case 1)?
> 

Why not simply test it ?

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

void printusage(void){
   printf("%s\n", "Three parameters expected:");
   printf("%s\n", " * Number of test cycles");
   printf("%s\n", " * Outer loop repeat");
   printf("%s\n", " * Inner loop repeat");
}

int main(int argc, char **argv){
   if(argc == 4){
     int cycle = atoi(argv[1]);
     int outer = atoi(argv[2]);
     int inner = atoi(argv[3]);
     int i,j,k;
     if(cycle > 0 && outer > 0 && inner > 0){
       for(i=0;i<cycle;i++){
         for(j=0;j<outer;j++){
           for(k=0;k<inner;k++){
             printf("%s\n","Foo");
           }
         }
       }
     }else{
       printusage();
     }
   }else{
     printusage();
   }
   return 0;
}


Using time you can do all the test yourself.

e.g. ./a.out 500 999 99   vs ./a.out 500 99 999 to do the test
500 times (500*999*99 total iterations). If you test it enough
and average it you should have a good idea about the difference
(none at all).

hth
Elie De Brauwer

.