From owner-sc22wg5@open-std.org Thu Oct 22 19:22:36 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 4B34FC76BC4; Thu, 22 Oct 2009 19:22:36 +0200 (CET DST) X-Original-To: sc22wg5@open-std.org Delivered-To: sc22wg5@open-std.org Received: from mail1.cray.com (mail1.cray.com [136.162.62.100]) by www2.open-std.org (Postfix) with ESMTP id 85A68C76BB7 for ; Thu, 22 Oct 2009 19:22:34 +0200 (CET DST) 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 n9MHMVYo016635 (version=TLSv1/SSLv3 cipher=DHE-RSA-AES256-SHA bits=256 verify=FAIL); Thu, 22 Oct 2009 12:22:31 -0500 (CDT) Received: from cfexcas01.americas.cray.com (cfexcas01-2.us.cray.com [172.30.74.227]) by beaver.us.cray.com (8.13.8/8.13.3/hub-5273) with ESMTP id n9MHMU6E017487; Thu, 22 Oct 2009 12:22:30 -0500 Received: from fortran.us.cray.com (172.31.19.200) by cfexcas01.americas.cray.com (172.30.74.226) with Microsoft SMTP Server (TLS) id 8.1.393.1; Thu, 22 Oct 2009 12:22:30 -0500 Message-ID: <4AE094EE.5080309@cray.com> Date: Thu, 22 Oct 2009 12:22:54 -0500 From: Bill Long Reply-To: Organization: Cray Inc. User-Agent: Thunderbird 2.0.0.23 (Macintosh/20090812) MIME-Version: 1.0 To: fortran standards email list for J3 Cc: SC22WG5 Subject: Re: (j3.2006) (SC22WG5.4114) Parallel random numbers 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> In-Reply-To: <20091022160201.90187C76BB7@www2.open-std.org> Content-Type: text/plain; charset="ISO-8859-1"; format=flowed Content-Transfer-Encoding: 7bit X-Cray-VirusStatus: clean Sender: owner-sc22wg5@open-std.org Precedence: bulk Aleksandar Donev wrote: > On 10/22/2009 4:52 AM, N.M. Maclaren 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. > > What I believe we ought to do is provide the simplest model and not try > to do much: > 1) All the sequencies are independent > 2) The same random number generator is used on each image (same seed, > same sequence). You want the "same default seed", right? Each image should be able to independently change its own seed. > 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. 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