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 19510BC84 for ; Wed, 30 Mar 2005 11:00:31 +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 j2U81kxK020281 for ; Wed, 30 Mar 2005 10:01:46 +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 KAA22483 for ; Wed, 30 Mar 2005 10:01:46 +0200 (MET DST) Received: from mail.exomi.com (mail.exomi.com [217.169.64.72]) by nez-perce.inria.fr (8.13.0/8.13.0) with ESMTP id j2U81jNo020277 for ; Wed, 30 Mar 2005 10:01:46 +0200 Received: from dsws (dsws.exomi.com [10.0.20.63]) by mail.exomi.com (Postfix) with ESMTP id 38A1A5E1C; Wed, 30 Mar 2005 11:01:43 +0300 (EEST) Subject: Re: [Caml-list] 32- and 64-bit performance From: Ville-Pertti Keinonen To: Alex Baretta Cc: Jon Harrop , Ocaml In-Reply-To: <424A593A.5050608@barettadeit.com> References: <200503300340.15874.jon@ffconsultancy.com> <424A593A.5050608@barettadeit.com> Content-Type: text/plain Date: Wed, 30 Mar 2005 11:00:58 +0300 Message-Id: <1112169658.27768.1.camel@dsws> Mime-Version: 1.0 X-Mailer: Evolution 2.0.3 Content-Transfer-Encoding: 7bit X-Miltered: at nez-perce with ID 424A5CEA.000 by Joe's j-chkmail (http://j-chkmail.ensmp.fr)! X-Miltered: at nez-perce with ID 424A5CE9.001 by Joe's j-chkmail (http://j-chkmail.ensmp.fr)! X-Spam: no; 0.00; caml-list:01 baretta:01 pointers:01 alignment:01 ocaml:01 integers:01 wrote:01 structures:01 data:02 benchmark:02 alex:03 generally:03 generally:03 compiled:04 suppose:05 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: On Wed, 2005-03-30 at 09:46 +0200, Alex Baretta wrote: > 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. 64-bit data structures (due to bigger pointers, alignment, and in OCaml bigger default integers) are bigger, so things that are constrained by memory bandwidth are obviously going to be faster as 32-bit. On other architectures where you can use 32-bit or 64-bit that are otherwise identical, 32-bit is generally faster.