From owner-sc22wg5@open-std.org Thu Oct 22 19:59:09 2009 Return-Path: X-Original-To: sc22wg5-dom8 Delivered-To: sc22wg5-dom8@www2.open-std.org Received: by www2.open-std.org (Postfix, from userid 521) id 30478C76BC4; Thu, 22 Oct 2009 19:59:09 +0200 (CET DST) X-Original-To: sc22wg5@open-std.org Delivered-To: sc22wg5@open-std.org Received: from ppsw-7.csi.cam.ac.uk (ppsw-7.csi.cam.ac.uk [131.111.8.137]) by www2.open-std.org (Postfix) with ESMTP id 9085DC178E4 for ; Thu, 22 Oct 2009 19:59:06 +0200 (CET DST) X-Cam-AntiVirus: no malware found X-Cam-SpamDetails: not scanned X-Cam-ScannerInfo: http://www.cam.ac.uk/cs/email/scanner/ Received: from hermes-1.csi.cam.ac.uk ([131.111.8.51]:35355) by ppsw-7.csi.cam.ac.uk (smtp.hermes.cam.ac.uk [131.111.8.157]:25) with esmtpa (EXTERNAL:nmm1) id 1N11wI-0007Jd-No (Exim 4.70) for sc22wg5@open-std.org (return-path ); Thu, 22 Oct 2009 18:59:06 +0100 Received: from prayer by hermes-1.csi.cam.ac.uk (hermes.cam.ac.uk) with local (PRAYER:nmm1) id 1N11wI-000752-Bk (Exim 4.67) for sc22wg5@open-std.org (return-path ); Thu, 22 Oct 2009 18:59:06 +0100 Received: from [83.67.89.123] by webmail.hermes.cam.ac.uk with HTTP (Prayer-1.3.2); 22 Oct 2009 18:59:06 +0100 Date: 22 Oct 2009 18:59:06 +0100 From: "N.M. Maclaren" To: SC22WG5 Subject: Re: [ukfortran] (SC22WG5.4115) (j3.2006) Parallel random numbers Message-ID: In-Reply-To: <20091022172236.755B9C76BB7@www2.open-std.org> References: <20091020111544.C0F5CC178E3@www2.open-std.org> <20091020154252.946EAC178E3@www2.open-std.org> <20091021161933.1B2FCC178E3@www2.open-std.org> <20091021171501.21FA4C178E3@www2.open-std.org> <20091021175702.E4D26C178E3@www2.open-std.org> <20091022043326.83DB9C178E4@www2.open-std.org> <20091022051613.0AEF5C178E4@www2.open-std.org> <20091022062554.CF066C178E4@www2.open-std.org> <20091022115243.E875EC178E4@www2.open-std.org> <20091022160201.90187C76BB7@www2.open-std.org> <20091022172236.755B9C76BB7@www2.open-std.org> X-Mailer: Prayer v1.3.2 Mime-Version: 1.0 Content-Type: text/plain; format=flowed; charset=ISO-8859-1 Sender: owner-sc22wg5@open-std.org Precedence: bulk On Oct 22 2009, Bill Long wrote: >Aleksandar Donev wrote: >> >>> Specifying what is defined and what is not is very hard when >>> you need to allow for two different models. >> >> Perhaps then we should pick one of the models, namely, the independent >> sequence one. > >Yes, I'm convinced this is the only practical option. But that's precisely what we CAN'T do! Requiring independence is just far too much to demand of implementors. What we could require is complete DEPENDENCE, which would make the generators useless for many purposes. I think that what you actually mean is separate copies of probably identical generators, perhaps seeded differently. We certainly shouldn't forbid that. >> 3) No restrictions on calling RANDOM_SEED and RANDOM_NUMBER ala ordering >> of segments. > >This approach is certainly the easiest to implement. It also makes the >most sense when trying to write portable code. I will draft something along these lines, that leaves maximum flexibility. Regards, Nick.