From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Delivered-To: caml-list@yquem.inria.fr Received: from concorde.inria.fr (concorde.inria.fr [192.93.2.39]) by yquem.inria.fr (Postfix) with ESMTP id 9AC49BC75 for ; Sat, 26 Feb 2005 17:09:05 +0100 (CET) Received: from pauillac.inria.fr (pauillac.inria.fr [128.93.11.35]) by concorde.inria.fr (8.13.0/8.13.0) with ESMTP id j1QG95mq024654 for ; Sat, 26 Feb 2005 17:09:05 +0100 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 RAA23268 for ; Sat, 26 Feb 2005 17:09:04 +0100 (MET) Received: from biscayne-one-station.mit.edu (BISCAYNE-ONE-STATION.MIT.EDU [18.7.7.80]) by nez-perce.inria.fr (8.13.0/8.13.0) with ESMTP id j1QG93Mu016996 (version=TLSv1/SSLv3 cipher=DHE-RSA-AES256-SHA bits=256 verify=NO) for ; Sat, 26 Feb 2005 17:09:04 +0100 Received: from outgoing.mit.edu (OUTGOING-AUTH.MIT.EDU [18.7.22.103]) by biscayne-one-station.mit.edu (8.12.4/8.9.2) with ESMTP id j1QG92i3000116 for ; Sat, 26 Feb 2005 11:09:02 -0500 (EST) Received: from psi-phi.mit.edu (PSI-PHI.MIT.EDU [18.187.1.35]) (authenticated bits=56) (User authenticated as jfc@ATHENA.MIT.EDU) by outgoing.mit.edu (8.12.4/8.12.4) with ESMTP id j1QG8t0b001796 (version=TLSv1/SSLv3 cipher=DHE-RSA-AES256-SHA bits=256 verify=NOT) for ; Sat, 26 Feb 2005 11:08:55 -0500 (EST) Received: (from jfc@localhost) by psi-phi.mit.edu (8.12.9) id j1QG8tE5008133; Sat, 26 Feb 2005 11:08:55 -0500 Message-Id: <200502261608.j1QG8tE5008133@psi-phi.mit.edu> To: caml-list@inria.fr Subject: Re: [Caml-list] NBody (one more question) In-Reply-To: Your message of "Fri, 25 Feb 2005 18:17:54 +0100." <20050225.181754.69456034.debian00@tiscali.be> Date: Sat, 26 Feb 2005 11:08:55 -0500 From: John Carr X-Scanned-By: MIMEDefang 2.42 X-Miltered: at concorde with ID 42209F21.000 by Joe's j-chkmail (http://j-chkmail.ensmp.fr)! X-Miltered: at nez-perce with ID 42209F1F.000 by Joe's j-chkmail (http://j-chkmail.ensmp.fr)! X-Spam: no; 0.00; caml-list:01 jfc:01 gcc:01 gcc:01 speedup:01 gcc's:01 optimization:03 intermediate:03 generated:05 combining:06 observed:07 edu:07 john:08 analysis:08 carr:09 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: > > Optimizations in gcc -O1 compared to gcc -O0 include register > > allocation, dead code elimination, branch straightening, common > > subexpression elimination, instruction combining, and instruction > > scheduling. > > Ok, but do you know which one(s) account for the speedup observed in > this particular case? There is no way to be sure without careful analysis of generated code and possibly the state of gcc's internal representation at intermediate steps. Most of the optimizations at -O1 can not be turned on or off independently of the general optimization level.