From owner-sc22wg5+sc22wg5-dom8=www.open-std.org@open-std.org Sat Jun 21 18:05:32 2014 Return-Path: X-Original-To: sc22wg5-dom8 Delivered-To: sc22wg5-dom8@www.open-std.org Received: by www.open-std.org (Postfix, from userid 521) id 2FB8C358290; Sat, 21 Jun 2014 18:05:32 +0200 (CEST) Delivered-To: sc22wg5@open-std.org Received: from ppsw-50.csi.cam.ac.uk (ppsw-50.csi.cam.ac.uk [131.111.8.150]) by www.open-std.org (Postfix) with ESMTP id C5C9F35723F for ; Sat, 21 Jun 2014 18:05:30 +0200 (CEST) X-Cam-AntiVirus: no malware found X-Cam-ScannerInfo: http://www.cam.ac.uk/cs/email/scanner/ Received: from hermes-1.csi.cam.ac.uk ([131.111.8.51]:48530) by ppsw-50.csi.cam.ac.uk (smtp.hermes.cam.ac.uk [131.111.8.158]:25) with esmtpa (EXTERNAL:nmm1) id 1WyNnF-0001eg-qW (Exim 4.82_3-c0e5623) (return-path ); Sat, 21 Jun 2014 17:05:29 +0100 Received: from prayer by hermes-1.csi.cam.ac.uk (hermes.cam.ac.uk) with local (PRAYER:nmm1) id 1WyNnF-0001mz-6V (Exim 4.72) (return-path ); Sat, 21 Jun 2014 17:05:29 +0100 Received: from [66.237.29.114] by old-webmail.hermes.cam.ac.uk with HTTP (Prayer-1.3.5); 21 Jun 2014 17:05:29 +0100 Date: 21 Jun 2014 17:05:29 +0100 From: "N.M. Maclaren" To: Dan Nagle Cc: Ian Chivers , WG5 List Subject: Re: [ukfortran] (SC22WG5.5277) Alessandro's slides Message-ID: In-Reply-To: <20140620132709.BBEF7357222@www.open-std.org> References: <20140619225451.0033F358638@www.open-std.org> <001601cf8c7d$d0ef0640$72cd12c0$%chivers@chiversandbryan.co.uk> <20140620132709.BBEF7357222@www.open-std.org> X-Mailer: Prayer v1.3.5 Mime-Version: 1.0 Content-Type: text/plain; format=flowed; charset=ISO-8859-1 Sender: owner-sc22wg5@open-std.org Precedence: bulk On Jun 20 2014, Dan Nagle wrote: > >The idea is to have libcaf work with any mpi, >and it's been tested with the mpis on several systems. > >I don't know exactly which mpi was used on which system. Yes. I wrote a draft of a proposed design, which was used as a basis, though I have not been involved recently (or with the actual development). As people will know, one of my main hobby-horses is to ensure that the standard does not specify anything that is not reasonably implementable on top of any plausible MPI. Bill, Reinhold and I had an, er, robust debate by Email over 14-158, and I drafted a paper during the flight on the progress issue. My point is that this is a problem as deceptively simple and actually fiendishly tricky as the data consistency one, and we need a proper debate (and probably decision) at the WG5 level over what Fortran can reasonably assume of an implementation. The problems are, of course, mainly the atomics and multi-count events. I am 99% sure that the rest of the design is reasonably implementable, though some codes may be efficient on a specialist coarray implementation and direly inefficient on the general ones. Regards, Nick.