From owner-sc22wg5@open-std.org Tue Nov 11 19:14:17 2008 Return-Path: X-Original-To: sc22wg5-dom7 Delivered-To: sc22wg5-dom7@www2.open-std.org Received: by www2.open-std.org (Postfix, from userid 521) id 92B50C178D9; Tue, 11 Nov 2008 19:14:17 +0100 (CET) X-Original-To: sc22wg5@open-std.org Delivered-To: sc22wg5@open-std.org Received: from smtp.llnl.gov (nspiron-3.llnl.gov [128.115.41.83]) by www2.open-std.org (Postfix) with ESMTP id 963A2C178D6 for ; Tue, 11 Nov 2008 19:14:15 +0100 (CET) X-Attachments: None X-IronPort-AV: E=McAfee;i="5300,2777,5430"; a="48889086" X-IronPort-AV: E=Sophos;i="4.33,584,1220252400"; d="scan'208";a="48889086" Received: from corineus.llnl.gov (HELO [128.15.97.74]) ([128.15.97.74]) by smtp.llnl.gov with ESMTP; 11 Nov 2008 10:14:13 -0800 Message-ID: <4919CB73.1030303@llnl.gov> Date: Tue, 11 Nov 2008 10:14:11 -0800 From: Aleksandar Donev User-Agent: Mozilla/5.0 (Windows; U; Windows NT 5.1; en-US; rv:1.8.1.8) Gecko/20071009 SeaMonkey/1.1.5 MIME-Version: 1.0 Cc: WG5 Subject: Re: (j3.2006) (SC22WG5.3657) N1755: Request for new features from MPI Forum References: <49137AD3.1070402@lrz.de> <20081110124449.AEBF1C178E0@www2.open-std.org> <20081111030258.C9550C178D9@www2.open-std.org> <49193B79.8030807@lrz.de> <20081111083358.6613AC178D9@www2.open-std.org> <20081111092010.7FFB8C178D9@www2.open-std.org> <20081111095252.882B2C178D6@www2.open-std.org> In-Reply-To: <20081111095252.882B2C178D6@www2.open-std.org> Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit Sender: owner-sc22wg5@open-std.org Precedence: bulk N.M. Maclaren wrote: >> We should explicitly allow a variable with the ASYNCHRONOUS attribute to >> be modified or examined by means external to the processor, similarly to >> VOLATILE variables. If such a variable is modified or examined externally >> during a segment, that variable must not be referenced or define during >> that segment. > > That will introduce performance implications, though perhaps less > serious. Can you be more specific please? > But I really don't like the idea of having to teach kiddies about > coarrays when they want to learn MPI. You don't have to. Segments make sense even without co-arrays, as a way to control optimizations (code motion) in order to facilitate interaction with "things" not visible to the compiler. > What is actually needed is a way of allowing user code to set and clear > a variable's pending state, in the sense used in 9.6.4. While it would > be a bit tricky to add to Fortran, it would be semantically clean, and > be as efficient as possible. Sure. But, I can bet that others will have a different feeling about what is "clean" and "efficient". This seems to be the problem here---we are not likely to make any progress...and the issue will remain. Imperfect is better than non-existent, IMO. Best, Aleks -- Aleksandar Donev, Ph.D. Lawrence Postdoctoral Fellow @ LLNL High Performance Computational Materials Science and Chemistry E-mail: donev1@llnl.gov Phone: (925) 424-6816 Fax: (925) 423-0785 Address: P.O.Box 808, L-367, Livermore, CA 94551-9900 Web: http://cherrypit.princeton.edu/donev