[YLUG] Why is this so much faster on an Opteron?

[Robert Hulme]

I have this code:

#include <stdio.h>

int main(char **argv,int argc) {
 double f=0;
 int i=0;
 int j=0;
 int c=1;
 for(i=0;i<10000;i++)
 for(j=0;j<10000;j++,c++)
   f=f+0.505/(j+i/(1.0+j+i));
 return (int)f%10;
}

If I compile it with -O2 it takes about 40 seconds to run on my
Pentium D (dual core pentium 4) desktop, but only about 2 seconds
(when using time) to run on a 2.2Ghz Opteron.

Why is there such an enormous difference?

How long does it take to run on peoples machines?

-Rob

-- 
http://www.robhulme.com/
http://robhu.livejournal.com/

I think therefore I am an atheist
-- Ryan Evans