On 4/22/07, Markus Mottl <markus.mottl@gmail.com> wrote:
> On 4/22/07, Xavier Leroy <Xavier.Leroy@inria.fr> wrote:
> > Be careful with timings: I've seen simple changes in code placement
> > (e.g. introducing or removing dead code) cause performance differences
> > in excess of 20%.  It's an unfortunate fact of today's processors that
> > their performance is very hard to predict.

After performing many extensive tests between 32bit/64bit platforms,
it seems that indeed code placement is a major cause of many if not
most timing differences I have seen, especially if the difference is
unusually big.

Other developers who want to make their code run fast independent of
platform should therefore be cautioned that a program compiled for
different architectures may be slower/faster for very random reasons
that have nothing to do with not having optimized well enough for the
special case.  This is especially true for low-level code, where such
effects do not cancel each other out easily.

Regards,
Markus

-- 
Markus Mottl        http://www.ocaml.info        markus.mottl@gmail.com