From: Robert Roessler <roessler@rftp.com>
To: Ocaml <caml-list@inria.fr>
Subject: Re: [Caml-list] 32- and 64-bit performance
Date: Wed, 30 Mar 2005 00:10:35 -0800 [thread overview]
Message-ID: <424A5EFB.5000509@rftp.com> (raw)
In-Reply-To: <424A593A.5050608@barettadeit.com>
Alex Baretta wrote:
> Jon Harrop wrote:
>
>> I just bought a new Athlon 64 laptop and installed 32- and 64-bit Debian.
>> Here are some timings, showing the performance change when moving from
>> 32-
>> to 64-bit using ocamlopt (3.08.2) and g++ (3.4.4):
>
> ...
>
>>
>> So ocamlopt does seem to generate significantly better code in these
>> examples, particularly when they are floating point intensive. Also,
>> only one test is slower in 64-bit, due to its heavy use of trees.
>>
>
> Why do you suppose is there *any* benchmark faster in 32 bit mode than
> in 64 bit mode on the Athlon64? Since the AMD64 architecture is
> generally better than IA32--were it only for the additional registers--I
> would expect all benchmarks to run as fast or faster when compiled to
> the AMD64 instruction set.
I believe Jon was alluding to the issues that would be encountered on
any structure that is pointer-heavy - every pointer is now 8 bytes
long - you just get *killed* on the [extra] memory accessing, and your
L1/L2 caches holding "less". This effect will be more pronounced for
tasks that are mostly pointer-shuffling...
Robert Roessler
roessler@rftp.com
http://www.rftp.com
next prev parent reply other threads:[~2005-03-30 9:09 UTC|newest]
Thread overview: 17+ messages / expand[flat|nested] mbox.gz Atom feed top
2005-03-30 2:40 Jon Harrop
2005-03-30 7:46 ` [Caml-list] " Alex Baretta
2005-03-30 8:00 ` Ville-Pertti Keinonen
2005-03-30 8:41 ` Alex Baretta
2005-03-30 9:01 ` Ville-Pertti Keinonen
2005-03-30 12:53 ` Jon Harrop
2005-03-30 14:34 ` Ville-Pertti Keinonen
2005-03-30 8:10 ` Robert Roessler [this message]
2005-03-30 8:11 ` Alexander S. Usov
2005-03-30 13:46 ` Eijiro Sumii
2005-03-31 13:42 ` Jon Harrop
2005-03-31 15:05 ` Stefan Monnier
2005-03-31 18:40 ` [Caml-list] " Jon Harrop
2005-03-31 22:41 ` Richard Jones
2005-04-02 20:23 ` Stefan Monnier
2005-04-02 20:50 ` [Caml-list] " David Brown
2005-04-03 10:01 ` Ville-Pertti Keinonen
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