From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Original-To: caml-list@yquem.inria.fr Delivered-To: caml-list@yquem.inria.fr Received: from mail1-relais-roc.national.inria.fr (mail1-relais-roc.national.inria.fr [192.134.164.82]) by yquem.inria.fr (Postfix) with ESMTP id 470DBBC57 for ; Tue, 16 Nov 2010 23:13:28 +0100 (CET) X-IronPort-Anti-Spam-Filtered: true X-IronPort-Anti-Spam-Result: AqMBAD2R4kzU436rkGdsb2JhbACDSJ8cFQEBAQEJCQwHEQMfr1KQZQKBIIM2cwSHCIZc X-IronPort-AV: E=Sophos;i="4.59,207,1288566000"; d="scan'208";a="87624127" Received: from moutng.kundenserver.de ([212.227.126.171]) by mail1-smtp-roc.national.inria.fr with ESMTP; 16 Nov 2010 23:13:27 +0100 Received: from office1.lan.sumadev.de (dslb-084-059-065-230.pools.arcor-ip.net [84.59.65.230]) by mrelayeu.kundenserver.de (node=mrbap2) with ESMTP (Nemesis) id 0MGoe9-1PDrDq1rxR-00E3VD; Tue, 16 Nov 2010 23:13:27 +0100 Received: from [192.168.0.29] (dslb-084-058-005-030.pools.arcor-ip.net [84.58.5.30]) by office1.lan.sumadev.de (Postfix) with ESMTPA id 1029F5F702; Tue, 16 Nov 2010 23:13:27 +0100 (CET) Subject: Re: [Caml-list] SMP multithreading From: Gerd Stolpmann To: Eray Ozkural Cc: caml-list@yquem.inria.fr In-Reply-To: References: <20101115182737.42b8dcae@loki.yggdrasil.draxit.de> <4CE228CA.3030503@gmail.com> <1289927042.16005.176.camel@thinkpad> Content-Type: text/plain; charset="UTF-8" Date: Tue, 16 Nov 2010 23:13:25 +0100 Message-ID: <1289945605.16005.205.camel@thinkpad> Mime-Version: 1.0 X-Mailer: Evolution 2.28.1 Content-Transfer-Encoding: 7bit X-Provags-ID: V02:K0:LoY37HgKXoMuZA0LTQ5b2eYt+fAvRth0P9i23zq4Tg7 JCENvbP/m3F3ZjZDYSnISZ4+oRVXsWOn3TKFcREcZ95NM3Hc7s nTIsTxgicsDBE4dMTB7PWdwMwB1vq/hGuU7cW0YtaaaZZ79e7Q vxs29Mshs9RcJzhtH/A5Cv+Dhzn0jNXiXkpxOztLILmQuq43QZ ScssL3mevknOy7M2GY3Zg== X-Spam: no; 0.00; gerd:01 stolpmann:01 eray:01 ozkural:01 gerd:01 stolpmann:01 compiler:01 runtime:01 runtime:01 compiler:01 subroutines:01 tackled:01 darmstadt:01 6151:01 6151:01 Am Dienstag, den 16.11.2010, 22:35 +0200 schrieb Eray Ozkural: > > > On Tue, Nov 16, 2010 at 7:04 PM, Gerd Stolpmann > wrote: > Am Montag, den 15.11.2010, 22:46 -0800 schrieb Edgar > Friendly: > * As somebody mentioned "implicit parallelization": Don't > expect > anything from this. Even if a good compiler finds ways > to > parallelize 20% of the code (which would be a lot), the > runtime > effect would be marginal. 80% of the code is run at > normal speed > (hopefully) and dominates the runtime behavior. The > point is > that such compiler-driven code improvements are only > local > optimizations. For getting good parallelization results > you need > to restructure the design of the program - well, maybe > compiler2.0 can do this at some time, but this is not > in sight. > > I think you are underestimating parallelizing compilers. I was more citing Amdahl's law, and did not want to criticize any effort in this area. It's more the usefulness for the majority of problems. How useful is the best parallelizing compiler if only a small part of the program _can_ actually benefit from it? Think about it. If you are not working in an area where many subroutines can be sped up, you consider this way of parallelizing as a waste of time. And this is still true for the majority of problems. Also, for many problems that can be tackled, the scalability is very limited. Gerd -- ------------------------------------------------------------ Gerd Stolpmann, Bad Nauheimer Str.3, 64289 Darmstadt,Germany gerd@gerd-stolpmann.de http://www.gerd-stolpmann.de Phone: +49-6151-153855 Fax: +49-6151-997714 ------------------------------------------------------------