From owner-sc22wg5+sc22wg5-dom9=www.open-std.org@open-std.org Tue Sep 12 19:30:13 2023 Return-Path: X-Original-To: sc22wg5-dom9 Delivered-To: sc22wg5-dom9@www.open-std.org Received: by www.open-std.org (Postfix, from userid 521) id 9CD3D356992; Tue, 12 Sep 2023 19:30:13 +0200 (CEST) Delivered-To: sc22wg5@open-std.org X-Greylist: delayed 487 seconds by postgrey-1.34 at www5.open-std.org; Tue, 12 Sep 2023 19:30:13 CEST Received: from smtp-out-3.tiscali.co.uk (smtp-out-3.tiscali.co.uk [62.24.135.131]) by www.open-std.org (Postfix) with ESMTP id 5490335696B for ; Tue, 12 Sep 2023 19:30:13 +0200 (CEST) Received: from [10.197.1.247] ([2.100.205.99]) by smtp.talktalk.net with SMTP id g75Rqyz5ytzMrg75RqHYS7; Tue, 12 Sep 2023 18:22:05 +0100 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=talktalk.net; s=cmr1711; t=1694539325; bh=DG+XCxSJMPwqkYgU2MYfEkL93jUHmSrCoIIBJeSUVG4=; h=Subject:To:References:From:Date:In-Reply-To; b=GTSAAu3ZvXzIUlTlDSpM1lbFilnF8Z4GD9mFoTUpbyk7E6uoL1ZNH/608hjbwwx/J qFbNuBfqF+WxcCSGj8C86B7bEdvb21lNG/u3018/5WQ+Xga7EfGAkXztTVf2Qws6b3 FMHnxjXodK481xkULGZY+4dT98klJgX8Rr2hSGxY= X-Originating-IP: [2.100.205.99] Subject: Re: [ukfortran] [SC22WG5.6477] [J3] are race conditions allowed in do concurrent? To: WG5 References: <20230912161937.ED0F6356986@www.open-std.org> From: John Reid Message-ID: <42b53b63-5da4-4769-c24e-3ed0576e7654@talktalk.net> Date: Tue, 12 Sep 2023 18:22:05 +0100 User-Agent: Mozilla/5.0 (Windows NT 10.0; WOW64; rv:91.0) Gecko/20100101 Firefox/91.0 SeaMonkey/2.53.17 MIME-Version: 1.0 In-Reply-To: <20230912161937.ED0F6356986@www.open-std.org> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 8bit X-CMAE-Envelope: MS4wfEMOpxqoktpCX+WkUoY5Lv3tCH3TGUYLDg22sTzDSGC3zgpVKmdNyqmd7vqj0Dxkr0W3lGGDJ/sfvuHJqg4Q2S99MDsydQDH0W6XtqoQJX2i8qg35Uvp nl1lAhZVfeOc22tHDFNphv/YpT6L0gHt7WcllOp2EfQiBlxyQswP1RtMAVdEQooR3cGxTdTM6qFCw2D8CQGrRQkG1fEnO60WjsE= Sender: owner-sc22wg5@open-std.org Precedence: bulk Brad and Jeff, What is missing, I think, is to say that if an array is declared as shared, all its elements are shared. Cheers, John. Brad Richardson wrote: > Hi Jeff, > > Based on " If it is defined or becomes undefined during any iteration, > it shall not be referenced, defined, or become undefined during any > other iteration.", the provide program is invalid, because `x` becomes > defined in more than one iteration. > > The way I've heard "definition" applied to arrays is that definition > of an element of an array does not constitute definition of the > variable, because it is then only partially defined. I.e. an array is > only defined once each of its elements has been defined. > > My opinion is that the above constraint simply does not adequately > describe/is still ambiguous about the case of arrays. I think an > interp would be warranted, and we should say that an element of an > array should have the same constraint as above if the variable is shared. > > Regards, > Brad > > On Tue, 2023-09-12 at 14:43 +0000, Jeff Hammond via J3 wrote: >> >> Is this a legal program in Fortran with defined behavior?  If it is >> illegal or the behavior is undefined, where do we say that? >> >> program main >> >>   integer :: k >> >>   real :: x >> >>   x = 0.0 >> >>   do concurrent (k=1:2) shared(x) >> >>     x = real(k) >> >>   end do >> >>   print*,x >> >> end program main >> >> Is that what the following is intended to do? >> >> “If a variable has SHARED locality, appearances of the variable >> within the DO CONCURRENT construct refer to the variable in the >> innermost executable construct or scoping unit that includes the DO >> CONCURRENT construct. If it is defined or becomes undefined during >> any iteration, it shall not be referenced, defined, or become >> undefined during any other iteration.” >> >> If so, then I am struggling to apply this to arrays.  When we say a >> variable has shared locality, is the variable the array or the >> element?  We can only put array names in SHARED(), but applying the >> text regarding “to become defined” from the perspective of arrays >> appears to have interesting consequences. >> >> Thanks, >> >> >> Jeff >> > > > _______________________________________________ > ukfortran mailing list > https://lists.accu.org/mailman/listinfo/ukfortran