[Mpi3-tools] Comments/Questions on Fortran 08 Bindings

[Marc-Andre Hermanns]

Dear Martin,

I gathered some feedback from some of the Scalasca team members on the
proposed changes to profiling with the Fortran 08 interface.

The Scalasca measurement adapter currently creates the Fortran wrappers
for each of the four name-mangling schemes automatically (CPP macros),
as the wrapper is the same, just the symbol name is different. Another
name-mangling scheme for the same wrapper would probably not hurt very much.

However, some questions arose in the discussions that I have to admit
might stem from our limited knowledge of Fortran and Fortran 08 in
particular.

1) Are the Fortran handle types compatible/interchangeable with the C
handle types, or will c2f/f2c still have to be called?

2) Just as John Mellor-Crummey commented: are there standardized
routines to handle the array descriptors in C and C++ which are the
primary languages to implement a measurement layer? If not, how to deal
with it? Can it be interpreted as a void*? How to compare against
MPI_BOTTOM?

3) If the Fortran 08-C/C++ interface for the descriptors is not
available. Does it mean I have to implement the wrappers in Fortran?
Didn't we just agree that MPI_T does not need Fortran bindings? In this
case it would need them again, right?

4) How is the support for '_f' for just the MPI functions to be done in
the Fortran compiler? Won't it be mangled to '_f_' or '_f__' again? What
are the actual benefits of this '_f'?

5) Why deviate from the existing MPI_STATUS_IGNORE in favor of inflating
the API? Is there a real need for it?

I can easily imagine users of the Fortran 08 interface, while fixing
some older MPI code written with the Fortran 77 interface, to get
confused about the (in 77) non-optional status parameter.

7) Along the lines of Todd's comment on function overloading: It would
be great if the _f08 and _f09_nostatus could just be the same
measurement wrapper, to keep maintenance of measurement code to a minimum.

Cheers,
Marc-Andre
-- 
Marc-Andre Hermanns
German Research School for
Simulation Sciences GmbH
c/o Laboratory for Parallel Programming
52056 Aachen | Germany

Tel +49 241 80 99753
Fax +49 241 80 6 99753
Web www.grs-sim.de

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