Path: utzoo!utgpu!news-server.csri.toronto.edu!bonnie.concordia.ca!uunet!elroy.jpl.nasa.gov!decwrl!argosy!ian From: ian@argosy.UUCP (Ian L. Kaplan) Newsgroups: comp.lang.fortran Subject: Re: Fortran 90 status Message-ID: <1266@argosy.UUCP> Date: 27 Apr 91 22:24:57 GMT References: <1991Apr24.202115.16119@dragon.wpd.sgi.com> <123207.25873@timbuk.cray.com> <1991Apr26.210247.17264@ariel.unm.edu> Sender: news@argosy.UUCP Reply-To: ian@bear.UUCP (Ian L. Kaplan) Organization: MasPar Computer Corporation, Sunnyvale, CA Lines: 42 >Second, the >discussion on efficiency continues to skirt what I would regard as the >major issue in scientific computing - parallelism. What about Fortran >Extended is going to improve performance on parallel systems, of whatever >type? >-- >John K. Prentice john@unmfys.unm.edu (Internet) >Dept. of Physics and Astronomy, University of New Mexico, Albuquerque, NM, USA >Computational Physics Group, Amparo Corporation, Albuquerque, NM, USA Fortran 90 is indeed a complex language whose implementation is not entirely understood. As with any compromise, it can be criticized from a number of perspectives. However, I do not believe that it is reasonable to criticize Fortran 90 because it does not support MIMD parallelism. I think that it would have been very difficult, if not impossible, to get a group as large as the Fortran Standards Committee to agree on features for MIMD parallelism. There is not much in the way of "industry practice" in this area and few people will agree on what constitutes a "good" feature. Some of the differing view points stem from the diversity in MIMD systems, which range from shared memory systems, to cubes, to mesh connected machines. These machines will all have different communication latencies which may influence how they are programmed. With the exception of experimental languages like SISAL, Id and Lucid, I don't know of any languages that would work well across a range of MIMD machines. C++ was mentioned. However, I suggest that some though should be given to how "parallel C++" would be mapped onto both shared memory (e.g., Alliant or Sequent machines) and distributed memory (e.g., cubes) MIMD machines before making such claims. A final note: while Fortran 90 does nothing to support MIMD programming, the array syntax in Fortran 90 does map pretty well onto SIMD architectures and is supported by both MasPar and Thinking Machines in their Fortran compilers. Ian Kaplan MasPar Computer Corp. The above is the personal opinion of the author.