From owner-sc22wg5+sc22wg5-dom8=www.open-std.org@open-std.org Sat Mar 30 00:29:29 2013 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 B1A78356DBF; Sat, 30 Mar 2013 00:29:26 +0100 (CET) Delivered-To: sc22wg5@open-std.org Received: from exprod6og113.obsmtp.com (exprod6og113.obsmtp.com [64.18.1.31]) by www.open-std.org (Postfix) with ESMTP id 8E1FC356DA7 for ; Sat, 30 Mar 2013 00:29:22 +0100 (CET) Received: from CFWEX01.americas.cray.com ([136.162.34.11]) (using TLSv1) by exprod6ob113.postini.com ([64.18.5.12]) with SMTP ID DSNKUVYj0Sm5P8pdLBZFQ9IFcMVBvvwQND4z@postini.com; Fri, 29 Mar 2013 16:29:25 PDT Received: from fortran.us.cray.com (172.31.19.200) by CFWEX01.americas.cray.com (172.30.88.25) with Microsoft SMTP Server id 14.2.342.3; Fri, 29 Mar 2013 18:07:23 -0500 Message-ID: <51561F23.4080000@cray.com> Date: Fri, 29 Mar 2013 18:09:23 -0500 From: Bill Long Reply-To: Organization: Cray Inc. User-Agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10.6; rv:17.0) Gecko/20130307 Thunderbird/17.0.4 MIME-Version: 1.0 To: sc22wg5 Subject: Re: (j3.2006) (SC22WG5.4940) AW: WG5 ballot on first draft TS 18508, Additional Parallel Features in Fortran (Update) References: <20130329104945.2C28A356BB3@www.open-std.org> In-Reply-To: <20130329104945.2C28A356BB3@www.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 On 3/29/13 5:49 AM, Bader, Reinhold wrote: > (D.1) Add CO_MULT for efficiency > > Nowadays interconnects have support for offloading certain operations > to the infrastructure (e.g., FCA aka "fabric collective acceleration"), > thereby considerably improving performance. > However, it appears unlikely that the relatively general CO_REDUCE > facility would be able to support this facility. Therefore, it may > be desirable to also provide a CO_MULT collective for arguments of > numeric type that supports multiplicative reductions, in order to > obtain the same level of performance for all basic numeric operations. If we added this, it would be CO_PRODUCT since the local one is PRODUCT. The previous proposal had CO_PRODUCT. It was removed because the corresponding MPI_REDUCE for that operation almost never occurs in real codes. Is there any common usage of this operation? Also, is there hardware support in network hardware for a multiply reduction? Cheers, Bill -- Bill Long longb@cray.com Fortran Technical Support & voice: 651-605-9024 Bioinformatics Software Development fax: 651-605-9142 Cray Inc./Cray Plaza, Suite 210/380 Jackson St./St. Paul, MN 55101