From owner-sc22wg5@open-std.org Fri Jun 12 01:40:23 2009 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 DC79FC76BB7; Fri, 12 Jun 2009 01:40:23 +0200 (CET DST) X-Original-To: sc22wg5@open-std.org Delivered-To: sc22wg5@open-std.org X-Greylist: delayed 1597 seconds by postgrey-1.18 at www2.open-std.org; Fri, 12 Jun 2009 01:40:22 CET DST Received: from mail1.cray.com (mail1.cray.com [136.162.0.111]) by www2.open-std.org (Postfix) with ESMTP id 71A37C4596B for ; Fri, 12 Jun 2009 01:39:57 +0200 (CET DST) 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 n5BNDHWp027028 (version=TLSv1/SSLv3 cipher=DHE-RSA-AES256-SHA bits=256 verify=OK); Thu, 11 Jun 2009 18:13:18 -0500 (CDT) Received: from CFEXFE01.us.cray.com (CFEXFE01.americas.cray.com [172.30.74.93]) by beaver.us.cray.com (8.13.8/8.13.3/hub-5273) with ESMTP id n5BNDGK4013115; Thu, 11 Jun 2009 18:13:16 -0500 Received: from fortran.us.cray.com ([172.31.19.200]) by CFEXFE01.us.cray.com with Microsoft SMTPSVC(6.0.3790.3959); Thu, 11 Jun 2009 18:13:15 -0500 Message-ID: <4A318FF5.3080601@cray.com> Date: Thu, 11 Jun 2009 18:15:01 -0500 From: Bill Long Reply-To: longb@cray.com Organization: Cray Inc. User-Agent: Thunderbird 2.0.0.21 (Macintosh/20090302) MIME-Version: 1.0 To: fortran standards email list for J3 Cc: WG5 Subject: Re: (j3.2006) (SC22WG5.3998) [ukfortran] New summary of coarrays References: <20090609092023.32AF5C178DC@www2.open-std.org> <20090609093907.2863CC178DC@www2.open-std.org> <4A2E63B2.6020400@cray.com> <4A306193.5050708@nag-j.co.jp> In-Reply-To: <4A306193.5050708@nag-j.co.jp> Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit X-OriginalArrivalTime: 11 Jun 2009 23:13:15.0900 (UTC) FILETIME=[33330BC0:01C9EAEA] X-Cray-VirusStatus: clean Sender: owner-sc22wg5@open-std.org Precedence: bulk Malcolm Cohen wrote: > Hi Bill and Craig, > > Craig Dedo, and then Bill Long, wrote to J3 replying to a WG5 message... > > Once again I reiterate my "watch what you are replying to" : J3 list > readers please use "Reply All" or manually reinsert the WG5 list when > replying to a WG5 message. > > I am copying this to WG5 just so I can stick my oar in on the substance. > > Craig Dedo wrote replying to Nick (I think): >> Everyone: >> I believe that a better wording for the last sentence would be: >> >> The exact details are left processor dependent. Therefore, >> programmers should read their processor documentation before using atomic >> subroutines. >> >> I believe that "processor documentation" is the recommended term. >> Also, breaking it up into two sentences makes it read better. >> > > And Bill Long replied: >> Both versions presume something that seems very unlikely - that vendors >> discuss such implementation and performance details in their >> documentation. I think the whole addition should be dropped. At best it >> is confusing to an ordinary user; at worst is encourages vendors to not >> bother doing a good job. >> > No, as I understand it existing hardware and physical constraints > encourages some vendors not to have global consistency; *and* we allow > them not to have global consistency. I didn't see any relation to global consistency here. The context was user written synchronization schemes. The issue is whether the atomic operations take near-infinite time to execute. > > As for "confusing to an ordinary user", not nearly as confusing as > getting wildly different answers or program hangs/crashes from the same > data on the same machine on a Thursday. The same machine should have pretty consistent performance for a single atomic memory operation. Cheers, Bill > > Cheers, -- 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