(j3.2006) [MPI3 Fortran] Feedback from Fortran J3 meeting

Bill Long longb
Thu May 29 13:35:00 EDT 2008

I generally agree with Aleks here.  We should not embed particular 
libraries like MPI in the standard - it is possibly subject to 
obsolescence (we might have picked PVM before), and inevitably subject 
to incompleteness (...I want LaPack!).  Instead, we have chosen to 
interface with C under the assumption that the combination of C and 
Fortran calling conventions should cover most libraries.  The problem 
with some C library routines (including many in MPI)  is that our 
interface does not handle (void *) dummy arguments well.  Fixing that is 
a big part of the current discussion. 

Vendors, for performance reasons, of course, can recognize MPI routines 
as additional intrinsics and optimize their calls.  Ditto for BLAS and 
LaPack routines.  But I think this sort of thing should remain outside 
the Fortran standard.  We're in the business of defining a language, not 
writing people's programs or picking their library packages for them.  
(Yeah, I know there is a gray area with the Fortran intrinsics, but most 
of those are not really library routines.)


Aleksandar Donev wrote:
> On Wednesday 28 May 2008 10:11, Keith Bierman wrote:
>> it might just be a  
>> lot easier to have an optional part of the Standard which puts MPI in  
>> as special modules
> While not opposed to this in principle, I believe that it is a mistake to not 
> spend the time making a general facility. There are a lot more libraries out 
> there than MPI. Sure, vendors won't spend the time to support them explicitly 
> because few users use each of them. But if you add all the libraries in use, 
> it will come out to more than MPI.
> That said, MPI is a good prototype of what all we need to be able to handle, 
> mostly because it is soo big and has so many things in it.
> Also, I am not convinced providing the generic support is that difficult. 
> Especially if all vendors already do it by crutches (directives, compiler 
> switches, special modules, whatever).
> Aleks
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Bill Long                                   longb at 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


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