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Slow allocations with 64bit code?
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Date: 2007-04-23 (20:13)
From: Markus Mottl <markus.mottl@g...>
Subject: Re: [Caml-list] Slow allocations with 64bit code?
On 4/22/07, Markus Mottl <> wrote:
> On 4/22/07, Xavier Leroy <> 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.


Markus Mottl