[Mpi3-tools] Fortran Wrappers in Fortran?

[Rolf Rabenseifner]

Some answers inline.

----- Original Message -----
> From: "Marc-Andre Hermanns" <m.a.hermanns at grs-sim.de>
> To: mpi3-tools at lists.mpi-forum.org
> Sent: Tuesday, June 4, 2013 5:43:00 PM
> Subject: [Mpi3-tools] Fortran Wrappers in Fortran?
> Dear all,
> 
> with the Fortran wrappers discussion taking off tomorrow, I wanted to
> explicitly ask about something that has spooked around in my head for
> some time, and I am unsure whether this is viable or not.
> 
> It does not solve the name mangling is general, but maybe it is an
> easy approach in some cases, such as simple preinstrumented libraries.
> 
> The new Fortran interface comes only with Fortran 2008+ compilers,
> because older compilers don't know all the new magic that is necessary
> to make it work, right? This would mean that the compiler also has the
> C interface capabilities of Fortran 2003.

The new mpi_f08 module does not require Fortran 2008 + TS 29113.
Preliminary implementations (with MPI_SUBARRAYS_SUPPORTED=.FALSE.)
are possible with Fortran 2003. Same is valid for the new 
requirements on the mpi module (e.g., compile time arument checking).


> Performance tools like Scalasca or Score-P, usually call
> straight-forward C routines in the wrappers to generate the
> measurement
> data and maybe do some simple computations in between. Usually, they
> just pass the initial parameters through.
> 
> As most of our wrapper code is generated anyway. Would it be a viable
> approach to
> 1) generate a C interface definition for the parts of the measurement
> system in question to call the measurement routines from Fortran, and
> 2) generate Fortran wrappers that directly call the measurement system
> through the generated interface and then call the Fortran version of
> "PMPI_Func"?
> 
> Would the Fortran compiler then take care of all the name mangling
> issues in this case?
> 
> Using Fortran wrappers calling the Fortran PMPI routines would also
> make handle conversion (to call the C MPI wrapper) unnecessary and
> could save overhead.

I'm not sure whether I understood your approach.
For me, it looks like that you want to go a similar way as Bill Long
who has Fortran-written wrappers that directly call the 
MPI C routines. For this, he defined a module with the Interfaces
of the MPI C routines in Fortran 2003 syntax with BIND(C).  

He tries to get his Fortran MPI wrappers fully portable,
though the tools intercept only at the C Interface.

See also the Details in c20.comments.txt attached to a previous mail.

Best regards
Rolf

  
> Cheers,
> Marc-Andre
> --
> Marc-Andre Hermanns
> German Research School for
> Simulation Sciences GmbH
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-- 
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
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