[MPI3 Fortran] Proposing changes to Fortran 2008

Supalov, Alexander alexander.supalov at intel.com
Thu Mar 27 16:15:30 CDT 2008

PPS. John apparently retired from the Rutherford Labs but remained
active. Please pass my best wishes to him next time you meet. 

-----Original Message-----
From: mpi3-fortran-bounces at lists.mpi-forum.org
[mailto:mpi3-fortran-bounces at lists.mpi-forum.org] On Behalf Of
Aleksandar Donev
Sent: Thursday, March 27, 2008 9:31 PM
To: MPI-3 Fortran working group
Subject: Re: [MPI3 Fortran] Proposing changes to Fortran 2008


MPI_ISend has many more issues than MPI_Send. Which one are we

For MPI_Send, I see no problem with copy in/out, in fact, I see it as 
desirable because the compiler does the work of copying things like
of arrays into contig buffers. Is there a problem with copy in/out and
blocking calls?

> The C_LOC functionality is not far away from this requirement
C_LOC exactly satisfies the requirement of no copy in/out and probably
be used for MPI_ISend. It requires TARGET, which should in fact be
if you are retaining a pointer to an array (even if this pointer is only
in C 
and not visible to the Fortran compiler).

> the ASYNCHRONOUS attribute also avoids any copying of the actual
In the case of MPI_ISend even with C_LOC, ASYNCHRONOUS (actually
be exact) is necessary on the array whose values are being modified
the compiler's back. This is independent of the issue of copying.


P.S. John Reid is still the head of the Fortran committee

Aleksandar Donev, Ph.D.
Lawrence Postdoctoral Fellow @ Lawrence Livermore National Laboratory
High Performance Computational Materials Science and Chemistry
E-mail: donev1 at llnl.gov
Phone: (925) 424-6816  Fax: (925) 423-0785
Address: P.O.Box 808, L-367, Livermore, CA 94551-9900
Web: http://cherrypit.princeton.edu/donev
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