From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Delivered-To: caml-list@yquem.inria.fr Received: from nez-perce.inria.fr (nez-perce.inria.fr [192.93.2.78]) by yquem.inria.fr (Postfix) with ESMTP id 48D71BC84 for ; Wed, 30 Mar 2005 11:09:53 +0200 (CEST) Received: from pauillac.inria.fr (pauillac.inria.fr [128.93.11.35]) by nez-perce.inria.fr (8.13.0/8.13.0) with ESMTP id j2U8ARoN021469 for ; Wed, 30 Mar 2005 10:10:27 +0200 Received: from nez-perce.inria.fr (nez-perce.inria.fr [192.93.2.78]) by pauillac.inria.fr (8.7.6/8.7.3) with ESMTP id KAA23408 for ; Wed, 30 Mar 2005 10:10:26 +0200 (MET DST) Received: from smtp818.mail.sc5.yahoo.com (smtp818.mail.sc5.yahoo.com [66.163.170.4]) by nez-perce.inria.fr (8.13.0/8.13.0) with SMTP id j2U8APEg021464 for ; Wed, 30 Mar 2005 10:10:26 +0200 Received: from unknown (HELO ?192.168.1.100?) (rftp@pacbell.net@63.194.18.166 with plain) by smtp818.mail.sc5.yahoo.com with SMTP; 30 Mar 2005 08:10:24 -0000 Message-ID: <424A5EFB.5000509@rftp.com> Date: Wed, 30 Mar 2005 00:10:35 -0800 From: Robert Roessler Organization: Robert's High-performance Software User-Agent: Mozilla/5.0 (Windows; U; Windows NT 5.1; en-US; rv:1.7.6) Gecko/20050319 X-Accept-Language: en-us, en MIME-Version: 1.0 To: Ocaml Subject: Re: [Caml-list] 32- and 64-bit performance References: <200503300340.15874.jon@ffconsultancy.com> <424A593A.5050608@barettadeit.com> In-Reply-To: <424A593A.5050608@barettadeit.com> Content-Type: text/plain; charset=us-ascii; format=flowed Content-Transfer-Encoding: 7bit X-Miltered: at nez-perce with ID 424A5EF3.000 by Joe's j-chkmail (http://j-chkmail.ensmp.fr)! X-Miltered: at nez-perce with ID 424A5EF1.000 by Joe's j-chkmail (http://j-chkmail.ensmp.fr)! X-Spam: no; 0.00; caml-list:01 baretta:01 timings:01 ocamlopt:01 ocamlopt:01 pointer:01 ...:98 ...:98 wrote:01 wrote:01 slower:01 caches:01 debian:02 benchmark:02 bytes:03 X-Spam-Checker-Version: SpamAssassin 3.0.2 (2004-11-16) on yquem.inria.fr X-Spam-Status: No, score=0.0 required=5.0 tests=none autolearn=disabled version=3.0.2 X-Spam-Level: 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