From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.1.3 (2006-06-01) on yquem.inria.fr X-Spam-Level: X-Spam-Status: No, score=0.0 required=5.0 tests=AWL,SUBJECT_EXCESS_QP autolearn=disabled version=3.1.3 X-Original-To: caml-list@yquem.inria.fr Delivered-To: caml-list@yquem.inria.fr Received: from mail2-relais-roc.national.inria.fr (mail2-relais-roc.national.inria.fr [192.134.164.83]) by yquem.inria.fr (Postfix) with ESMTP id 782ACBBAF for ; Mon, 26 May 2008 18:13:26 +0200 (CEST) X-IronPort-Anti-Spam-Filtered: true X-IronPort-Anti-Spam-Result: AroCADp+OkjUnw7Wb2dsb2JhbACCM5AHAQwFAgQHEwMTmS4 X-IronPort-AV: E=Sophos;i="4.27,543,1204498800"; d="scan'208";a="11133261" Received: from ptb-relay03.plus.net ([212.159.14.214]) by mail2-smtp-roc.national.inria.fr with ESMTP; 26 May 2008 18:13:26 +0200 Received: from [80.229.56.224] (helo=beast.local) by ptb-relay03.plus.net with esmtp (Exim) id 1K0fK9-0004nM-CF for caml-list@yquem.inria.fr; Mon, 26 May 2008 17:13:25 +0100 From: Jon Harrop Organization: Flying Frog Consultancy Ltd. To: caml-list@yquem.inria.fr Subject: Re: [Caml-list] Re: Where's my non-classical shared =?iso-8859-1?q?memory=09concurrency?= technology? Date: Mon, 26 May 2008 17:08:16 +0100 User-Agent: KMail/1.9.9 References: <4833D7E8.8060502@doc.ic.ac.uk> <4EDC5A3B-DFD2-47EA-9C22-F0B355D7BBC7@inria.fr> In-Reply-To: <4EDC5A3B-DFD2-47EA-9C22-F0B355D7BBC7@inria.fr> MIME-Version: 1.0 Content-Type: text/plain; charset="iso-8859-1" Content-Transfer-Encoding: 7bit Content-Disposition: inline Message-Id: <200805261708.16457.jon@ffconsultancy.com> X-Plusnet-Relay: 8e6aed830493a7ce5fbf15c40f88597b X-Spam: no; 0.00; damien:01 model:01 neglecting:01 model:01 broadcasting:98 fabric:98 frog:98 doligez:01 wrote:01 wrote:01 caml-list:01 century:98 parameter:02 treating:02 concurrency:04 On Monday 26 May 2008 16:29:53 Damien Doligez wrote: > On 2008-05-21, at 10:06, Martin Berger wrote: > > Here I disagree. Shared memory concurrency is a specific form > > of message passing: Writing to a memory cell is in fact sending > > a message to that cell carrying two items, the new value and a > > return channel that is used to inform the writer that sending > > has succeeded, and likewise for reading. > > This is completely wrong. A few machines have a simple model like > that, but they were all built in the last century. Nowadays, writing > to memory is more like broadcasting a message and having no idea when > it will arrive at each destination. And if you write to another piece > of memory, you don't know in what order the updates will become > visible to a given processor. > > You are neglecting a very important parameter, which is called the > "memory model" of your multiprocessor. The memory model of a multiprocessor is just a specific form of communication fabric. That does not disagree with Martin's statement. So he was certainly not "completely wrong". At worst it was a simplification. I suspect he simply did not aticipate anyone treating his comment as a seminal work on multicore computing. -- Dr Jon D Harrop, Flying Frog Consultancy Ltd. http://www.ffconsultancy.com/products/?e