Subj : Re: which for loop is better?
To   : comp.programming.threads
From : Sean Burke
Date : Fri Mar 25 2005 07:06 pm


ssam_iit@yahoo.com (sam) writes:

> 
> David Hopwood <david.nospam.hopwood@blueyonder.co.uk> wrote in message news:<dfL0e.1131$IH3.327@fe3.news.blueyonder.co.uk>...
> > sam wrote:
> > > Hi, 
> > >    which one of the following codes in C would you prefer to print
> > > those "hello"s and why?
> > > int i,j;
> > > 1) for(i=0;i<=99;i++)
> > >     for(j=0;j<=999;j++)
> > >       printf("hello");
> > > 
> > > 2) for(i=0;i<=999;i++)
> > >      for(j=0;j<=99;j++)
> > >        printf("hello");
> > 
> > As if it matters. What a stupid question, teaching people to micro-optimize
> > without thinking about whether it can possibly lead to any difference in
> > perceptible performance. Whoever set this homework question should be
> > ashamed of themselves.

> 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)?


The days when runtime was determined by the number of instructions
executed have long since passed us by. On modern machines, performance
is governed by cache misses.

And please don't top post.

-SEan

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