[mpich-discuss] Is it okay to remove F77 support?

Gus Correa gus at ldeo.columbia.edu
Wed Jan 27 10:53:59 CST 2021

On Wed, Jan 27, 2021 at 9:45 AM Raffenetti, Kenneth J. <raffenet at mcs.anl.gov>

> On 1/26/21, 9:10 PM, "Gus Correa via discuss" <discuss at mpich.org> wrote:
>     Is it okay to remove F77 support?
>     No, NO, NO!!!! NO!
>     Removing the support to Fortran 77 from MPI is a disastrous idea!
>     Sorry to say, but it is really stupid to suppose that only because
> compilers support F90
>     that you can remove F77 support from MPI.
>     A lot of people, academic institutions, and probably industry,
> continue to use,
>     and develop new code in F77.
>     What matters is if the CODE is written in Fortran 90 or in Fortran 77,
>     and whether it uses the Fortran 77 MPI API or the Fortran 90 MPI API,
>     not whether the compiler supports Fortran 90 (and yes, if not all, do).
>     There is an enormous Fortran 77 code base, written using MPI, and that
> is not likely to change for the foreseeable future.
>     That is true in the Atmospheric/Climate/Ocean sciences, where I work,
>     but would guess this is true in other areas of science as well.
>     Just one example: The MITgcm, which has an huge community of users,
>     is the backbone for many research projects, supports many PhD thesis,
>     is 100% written in Fortran-77 and will not be changed anytime soon,
>     as there is no financial support to do that.
>     Also, this type of inquiry to the MPICH community is way too narrow.
>     I don't think you should be using emails on a mailing list to base
> such a consequential decision.
>     Argonne should know better which community it supports, which codes
> out there use MPI.
> I think there is some misunderstanding of the question here. The MPICH
> team is asking if it would be OK to drop support for building MPICH with an
> F77 only compiler. MPICH will still support all standard Fortran language
> bindings: mpif.h, use mpi, and use mpi_f08. Does the code you speak of not
> build with modern Fortran compilers? If so, that is the kind of feedback we
> are looking for.
> Thanks,
> Ken
Well, then the question was very poorly formulated.
It suggests suppressing the Mpich Fortran-77 API.

Hard to gauge the impact of removing support of F77 compiler (ONLY),
but it may cause trouble when building complex code,
and linking it to MPI (mpich),
as some may actually require a compiler that is specific for Fortran-77,
or have Makefiles and other utilities that rely on such a compiler.

Gus Correa
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