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=0.1 required=5.0 tests=AWL 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 7EBFEBBAF for ; Mon, 26 May 2008 17:29:54 +0200 (CEST) X-IronPort-Anti-Spam-Filtered: true X-IronPort-Anti-Spam-Result: AqgBALdzOkjAXQImiGdsb2JhbACSOgEBAQ8gmTY X-IronPort-AV: E=Sophos;i="4.27,543,1204498800"; d="scan'208";a="11131335" Received: from discorde.inria.fr ([192.93.2.38]) by mail2-smtp-roc.national.inria.fr with ESMTP; 26 May 2008 17:29:54 +0200 Received: from mail2-relais-roc.national.inria.fr (mail2-relais-roc.national.inria.fr [192.134.164.83]) by discorde.inria.fr (8.13.6/8.13.6) with ESMTP id m4QFTsiw007226 (version=TLSv1/SSLv3 cipher=RC4-SHA bits=128 verify=OK) for ; Mon, 26 May 2008 17:29:54 +0200 X-IronPort-AV: E=Sophos;i="4.27,543,1204498800"; d="scan'208";a="11131334" Received: from 250-112.msr-inria.inria.fr ([193.55.250.112]) by mail2-relais-roc.national.inria.fr with ESMTP/TLS/AES128-SHA; 26 May 2008 17:29:53 +0200 Message-Id: <4EDC5A3B-DFD2-47EA-9C22-F0B355D7BBC7@inria.fr> From: Damien Doligez To: caml-list In-Reply-To: <4833D7E8.8060502@doc.ic.ac.uk> Content-Type: text/plain; charset=US-ASCII; format=flowed Content-Transfer-Encoding: 7bit Mime-Version: 1.0 (Apple Message framework v919.2) Subject: Re: [Caml-list] Re: Where's my non-classical shared memory concurrency technology? Date: Mon, 26 May 2008 17:29:53 +0200 References: <200805181735.50621.jon@ffconsultancy.com> <4831686F.8010903@doc.ic.ac.uk> <1211206144.11053.15.camel@flake.lan.gerd-stolpmann.de> <4833D7E8.8060502@doc.ic.ac.uk> X-Mailer: Apple Mail (2.919.2) X-Miltered: at discorde with ID 483AD772.000 by Joe's j-chkmail (http://j-chkmail . ensmp . fr)! X-Spam: no; 0.00; damien:01 damien:01 model:01 neglecting:01 model:01 broadcasting:98 doligez:01 doligez:01 wrote:01 caml-list:01 century:98 parameter:02 concurrency:04 concurrency:04 passing:05 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. -- Damien