From owner-sc22wg5+sc22wg5-dom8=www.open-std.org@open-std.org Sat Dec 7 23:06:20 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 499BF3582EC; Sat, 7 Dec 2013 23:06:20 +0100 (CET) Delivered-To: sc22wg5@open-std.org Received: from exprod6og111.obsmtp.com (exprod6og111.obsmtp.com [64.18.1.27]) by www.open-std.org (Postfix) with ESMTP id E2E7A3572E7 for ; Sat, 7 Dec 2013 23:06:16 +0100 (CET) Received: from CFWEX01.americas.cray.com ([136.162.34.11]) (using TLSv1) by exprod6ob111.postini.com ([64.18.5.12]) with SMTP ID DSNKUqOb19l0yO6/BzS422HR8T3cDrALO/5E@postini.com; Sat, 07 Dec 2013 14:06:19 PST Received: from cfasa-vpn-192-168-233-28.us.cray.com (192.168.233.28) by CFWEX01.americas.cray.com (172.30.88.25) with Microsoft SMTP Server id 14.2.347.0; Sat, 7 Dec 2013 16:06:14 -0600 Message-ID: <52A39BE9.2060403@cray.com> Date: Sat, 7 Dec 2013 16:06:33 -0600 From: Bill Long Reply-To: Organization: Cray Inc. User-Agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10.6; rv:17.0) Gecko/20130801 Thunderbird/17.0.8 MIME-Version: 1.0 To: CC: sc22wg5 Subject: Re: (j3.2006) (SC22WG5.5124) image selectors References: <20131204000730.3A09F3582D0@www.open-std.org> <1386116202.16299.164.camel@math.jpl.nasa.gov> In-Reply-To: <1386116202.16299.164.camel@math.jpl.nasa.gov> Content-Type: text/plain; charset="ISO-8859-1"; format=flowed Content-Transfer-Encoding: 7bit Sender: owner-sc22wg5@open-std.org Precedence: bulk On 12/3/13 6:16 PM, Van Snyder wrote: > On Tue, 2013-12-03 at 18:02 -0600, Bill Long wrote: >> The identification of the correct physical PE containing the coarray >> being referenced using the new syntax involves two steps: Using the >> specified cosubscripts and the current cobounds for the coarray, an >> image index is computed. The image index is then converted to a >> physical PE by a team-specific mapping. > > This is an important step that is not explained in the TS, or at least > if it is, I couldn't find it. It needs to be in Subclause 5.1. > OK. Reinhold's revised ballot reworded this idea in terms of the image index in the initial team rather than physical processors. That is arguably better terminology to use. The image's image index in the initial team never changes throughout the program execution. I think a key point here is that the image is physically unchanged by changing teams - it is still executing on the same processor/thread and has all the same variables as before. What changes are the current number of images and the current image index (i.e the values of NUM_IMAGES() and THIS_IMAGE()). As side effects, the scope of collective operations is (possibly) changed (if the number of images changed), and the mapping from image index to physical processor (probably) changed because the image index value (probably) changed but the underlying processor/thread did not. 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