From owner-sc22wg5@open-std.org Wed Dec 3 21:21:27 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 5E273C56CF8; Wed, 3 Dec 2008 21:21:27 +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 CA4A4C4596D for ; Wed, 3 Dec 2008 21:21:25 +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 mB3KLDYk010503 (version=TLSv1/SSLv3 cipher=DHE-RSA-AES256-SHA bits=256 verify=OK); Wed, 3 Dec 2008 14:21:19 -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 mB3KLCTG007563; Wed, 3 Dec 2008 14:21:12 -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); Wed, 3 Dec 2008 14:21:12 -0600 Message-ID: <4936EAB7.4090401@cray.com> Date: Wed, 03 Dec 2008 14:23:19 -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: sc22wg5 Subject: Re: (j3.2006) (SC22WG5.3715) [ukfortran] Atomic stuff References: <20081203025222.12F4BC178E0@www2.open-std.org> <20081203174656.5AF23C4596D@www2.open-std.org> <20081203181454.82657C4596D@www2.open-std.org> <20081203183634.42E63C178DC@www2.open-std.org> In-Reply-To: <20081203183634.42E63C178DC@www2.open-std.org> Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit X-OriginalArrivalTime: 03 Dec 2008 20:21:12.0505 (UTC) FILETIME=[AF7D7A90:01C95584] X-Cray-VirusStatus: clean Sender: owner-sc22wg5@open-std.org Precedence: bulk Jim Xia wrote: > > > > Atomic loads and stores on mis-aligned variables are nearly impossible > on many hardwares (The solution to fix up the mis-alignment by either > hardware or OS causes the operation become non-atomic, let along the > performance hit). > > Three places I think will likely cause this mis-alignment: > EQUIVELENCE, COMMON BLOCK and structure component level. The one that > is relevant to coarrays is structure component. The other two will > apply to local objects only. We need to think how to fix that. > I agree that the place where this issue is relevant is components of a coarray structure. But certainly an implementation is not going to mis-align structure components in this way. The performance hit would be horrible. Cheers, Bill -- 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