From owner-sc22wg5@open-std.org Thu Dec 4 22:36:36 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 270F4C56CFA; Thu, 4 Dec 2008 22:36:36 +0100 (CET) X-Original-To: sc22wg5@open-std.org Delivered-To: sc22wg5@open-std.org Received: from mail1.cray.com (mail1.cray.com [136.162.0.111]) by www2.open-std.org (Postfix) with ESMTP id 0AE0AC56CF8 for ; Thu, 4 Dec 2008 22:36:27 +0100 (CET) Received: from beaver.us.cray.com (beaver.us.cray.com [172.30.74.51]) by mail1.cray.com (8.13.6/8.13.3/gw-5323) with ESMTP id mB4LaP1w025791 (version=TLSv1/SSLv3 cipher=DHE-RSA-AES256-SHA bits=256 verify=OK); Thu, 4 Dec 2008 15:36:26 -0600 (CST) Received: from CFEXFE01.us.cray.com (cfexfe01.us.cray.com [172.30.74.93]) by beaver.us.cray.com (8.13.8/8.13.3/hub-5273) with ESMTP id mB4LaOTr027465; Thu, 4 Dec 2008 15:36:24 -0600 Received: from mh-dhcp-172-31-16-160.us.cray.com ([172.31.16.160]) by CFEXFE01.us.cray.com over TLS secured channel with Microsoft SMTPSVC(6.0.3790.3959); Thu, 4 Dec 2008 15:36:24 -0600 Message-ID: <49384DD8.9000104@cray.com> Date: Thu, 04 Dec 2008 15:38:32 -0600 From: Bill Long Reply-To: longb@cray.com Organization: Cray Inc. User-Agent: Thunderbird 2.0.0.9 (Macintosh/20071031) MIME-Version: 1.0 To: fortran standards email list for J3 Cc: WG5 Subject: Re: (j3.2006) (SC22WG5.3732) Nick's MPI non-blocking proposal References: <200812031523.23143.donev1@llnl.gov> <20081204045036.63332C56CF8@www2.open-std.org> In-Reply-To: <20081204045036.63332C56CF8@www2.open-std.org> Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit X-OriginalArrivalTime: 04 Dec 2008 21:36:24.0517 (UTC) FILETIME=[5B459F50:01C95658] X-Cray-VirusStatus: clean Sender: owner-sc22wg5@open-std.org Precedence: bulk Aleksandar Donev wrote: > Hello, > > I am going to go out of line and actually give a positive review of > Nick's proposal :-) I like the basic design, Actually, I find it massively confusing. It seems to be focused on I/O, which is only a small corner of MPI. The basic send / receive routines have nothing to do with I/O, and yet those are the ones we should be concerned with. The issue is argument passing semantics, not I/O. In particular, we need to avoid copy-in and copy-out for specific arguments. It would seem like a simple attribute for the "buffer" dummy argument, perhaps "STATIC", would be much simpler, and easier to understand. The idea of a subroutine call effectively setting attributes for its arguments in the caller's scope is highly unusual. And it is unsafe in that it is subject to circumvention by EXTERNAL statements. Cheers, Bill > which I have advocated as > well (asynchronous attribute for non-blocking two-sided transfer, and > volatile for one-sided target windows). It is similar to my own proposal > except that it does not use SYNC MEMORY but proposes two new intrinsics > (this sounds like a good idea). > > >> SET_PENDING (ID, INPUT, A1, [A2, ...]) >> SET_PENDING shall be called on an affector before the mechanism >> external to Fortran initiates the asynchronous I/O. >> > OK from Fortran. > > >> If that is too horrible, and I think that it is, then the C interface >> would need to specify the number of arguments that make up the >> affector. >> > Can you please explain why it is needed to call this from C, and what > that would mean in terms of implementation? I see how it tells the > Fortran compiler that asynch I/O starts/ends so it knows when to flush > buffers/registers/etc., but what would it mean to C??? An example would > be great. > > >> A Fortran processor need not do anything other >> than define ID to be a suitable value in SET_PENDING if it does >> not need that information. >> > I missed one thing: What is a "suitable value", i.e., are there > constraints on the values (e.g., they have to be distinct from other > pending states or what?). > > Best, > Aleks > _______________________________________________ > J3 mailing list > J3@j3-fortran.org > http://j3-fortran.org/mailman/listinfo/j3 > -- Bill Long longb@cray.com Fortran Technical Support & voice: 651-605-9024 Bioinformatics Software Development fax: 651-605-9142 Cray Inc., 1340 Mendota Heights Rd., Mendota Heights, MN, 55120