[MPI3 Fortran] [Mpi-comments] MPI 3.0: Fortran 2008 interface - issue with the LOGICAL kind
rabenseifner at hlrs.de
Wed Mar 20 12:09:46 CDT 2013
This mail contains a proposal how we can solve the current
Fortran problems and possibly making the tools people also happy.
I need at least answers for
- mpich (Bill Long),
- OpenMPI (Jeff or Craig),
- some tools people.
Let me summarize what I've learnt so far for mpi_f08:
- #364 about LOGICAL correction is a must.
- MPI-3.0 allows BIND(C) and non-BIND(C), with the
new restrictions in #364
- BIND(C) needs TR29113, therefore any implementation now
should use non-BIND(C) for all non-TR29113 compilers.
- Most (or all) try to use the non-BIND(C) interface.
- Best way to do this are thin wrappers in Fortran that
- the oficial MPI-3.0 C binding
(here, the tools people have a problem because they
expect to wrap the Fortran interface and may therefore
- or an internal MPI-3.0 C routine
(which is half-perfect for the tools folk, because
they have to handle the implementation-dependant
Fortran names with underscores).
- And at least Bill wants to include the Fortran MPI
library routines itselves in the mpi_f08 module.
This is in conflict with the current MPI-3.0
linker naming rules.
Implications and proposal:
- We should rewrite the linker names section MPI-3.0 17.1.5
with following goals:
- Allow additionally to define that the PMPI is provided
only on the MPI C interface and the Fortran MPI routines
internally call the C interface;
again, a macro definition in mpi.h tells whether this
Question: Would this cause a problem when linking a
C or Fortran user application with some own
MPI_Test etc. profiling routines that internally call
- If Fortran profiling is done through the MPI C binding
then there are no rules about the Fortran linker names
needed, and therefore, one may put the thin Fortran
wrappers into a Fortran module.
- We can define BIND(C) for MPI routine groups as a
future option that is currently not used.
This would reduce the current effort for the tools people.
Is there anybody who wants to implement one of the Fortran
routine groups with BIND(C)?
I would expect, that this is the best to solve the problem
that #364 prohibits BIND(C) for some routines and implementors
want to do the same method for all routines.
Don't forget that BIND(C) and TR29113 is still important
for implementing these thin wrappers internally.
Without using BIND(C) on the official mpi_f08 and mpi module
interface, some features of TR29113 are not used:
- the extension for interoperabple CHARACTER(LEN=*),
- the extension for OPTIONAL dummy arguments.
Other TR29113 features are heavily used:
- The DIMENSION(..), TYPE(*) is needed for some internal
- The ASYNCHRONOUS usage for communication buffers.
Should we go in this direction?
----- Original Message -----
> From: "Bill Long" <longb at cray.com>
> To: "Jeff Squyres (jsquyres)" <jsquyres at cisco.com>
> Cc: "Martin Schulz" <schulzm at llnl.gov>, "MPI-3 Fortran working group" <mpi3-fortran at lists.mpi-forum.org>
> Sent: Wednesday, March 20, 2013 4:01:52 PM
> Subject: Re: [MPI3 Fortran] [Mpi-comments] MPI 3.0: Fortran 2008 interface - issue with the LOGICAL kind
> On 3/20/13 8:26 AM, Jeff Squyres (jsquyres) wrote:
> > On Mar 20, 2013, at 6:25 AM, Bill Long <longb at cray.com> wrote:
> >> interface !--> MPI_Test
> >> ! int MPI_Test(MPI_Request *request, int *flag, MPI_Status
> >> *status);
> >> Function MPI_Test_C( request, flag, status) &
> >> BIND(C, name="MPI_Test") RESULT (res)
> >> import :: C_request, c_int, MPI_Status_C
> >> integer(C_request) :: request
> > This is not correct. You cannot assume that MPI handles are integers
> > (they're pointers in Open MPI).
> This is correct for mpich. OpenMPI would evidently have a different
> version. But the concept is still the same - make a correct interface
> to the C library routine, however it is defined by the implementation,
> and then call that from a thin Fortran wrapper that takes care of the
> issues related to LOGICAL, the use of default INTEGER, and OPTIONAL
> Bill Long longb at cray.com
> Fortran Technical Support & voice: 651-605-9024
> Bioinformatics Software Development fax: 651-605-9142
> Cray Inc./Cray Plaza, Suite 210/380 Jackson St./St. Paul, MN 55101
> mpi3-fortran mailing list
> mpi3-fortran at lists.mpi-forum.org
Dr. Rolf Rabenseifner . . . . . . . . . .. email rabenseifner at hlrs.de
High Performance Computing Center (HLRS) . phone ++49(0)711/685-65530
University of Stuttgart . . . . . . . . .. fax ++49(0)711 / 685-65832
Head of Dpmt Parallel Computing . . . www.hlrs.de/people/rabenseifner
Nobelstr. 19, D-70550 Stuttgart, Germany . . . . (Office: Room 1.307)
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