Importance: Normal Subject: Re: IEEE Floating point To: mpi-21@XXXXXXXXXXXXX X-Mailer: Lotus Notes Release 5.0.5 September 22, 2000 From: "Marc Snir" Date: Tue, 15 May 2001 10:50:45 -0400 X-MIMETrack: Serialize by Router on D01ML233/01/M/IBM(Release 5.0.7 |March 21, 2001) at 05/15/2001 10:54:48 AM MIME-Version: 1.0 Content-type: text/plain; charset=us-ascii Sender: owner-mpi-21@XXXXXXXXXXXXX Precedence: bulk Reply-To: mpi-21@XXXXXXXXXXXXX What I had in mind is (ISO/IEC TR 15580) Fortran floating point exceptions which will be part of Fortran 2000. But I should have left these dogs sleep, for the time being. Marc Snir IBM T.J. Watson Research Center P.O. Box 218, Yorktown Heights, NY 10598 Tel: 914-945-3204 (8-862-3204) Fax: 914-945-4425 (8-862-4425) URL: http://www.research.ibm.com/people/s/snir James Cownie @mpi-forum.org on 05/15/2001 05:04:06 AM Please respond to mpi-21@mpi-forum.org Sent by: owner-mpi-21@mpi-forum.org To: mpi-21@XXXXXXXXXXXXX cc: Subject: Re: IEEE Floating point Marc Snir wrote :- > Another issue: I expect that most Fortran bindings of MPI are > layered atop a C binding. This implies that the floating point > operations done in the fortran MPI library may not be fully > compliant to the Fortran floating point spec (when and whether one > generates exceptions, how one handles NANs, the handling of > denormalized numbers, etc.). I is worthwhile to add a clarification > to that extent. While it is entirely possible that the numerics inside the library will not be the same as those which would occur were functionally equivalent code implemented in Fortran, this is not a standards issue. The Fortran standards say nothing about NaNs, exceptions or denorms, all of which are IEEE floating point arithmetic issues. Fortran standards certainly do not require that compliant Fortran systems use IEEE arithmetic. (And neither do any C standards). I don't really think that there's much to say here. Whenever you call a library from Fortran you (should) already expect that the exception behaviour and numerics will not be influenced by the way you compiled your code, and that's all that is happening here. -- Jim James Cownie Etnus, LLC. +44 117 9071438 http://www.etnus.com