[MPI3 Fortran] Deprecate mpif.h?

Supalov, Alexander alexander.supalov at intel.com
Fri Mar 5 04:44:50 CST 2010

Thanks. I like very much the balanced approach you outline, understand the technical reasons for the desire to improve the Fortran interface, and agree that the current interface is basically broken (but it works!) and that something must be done.

I just disagree with the proposed staging. Namely, I think that deprecating or freezing the current binding now will send a wrong signal to the masses and increase fear, uncertainty, and doubt in relation to the MPI standard.

Instead, I argue that we should take a much smoother path into the future, a path that will probably take several decades rather than years, and should not start with a U-turn.

That's all.

-----Original Message-----
From: mpi3-fortran-bounces at lists.mpi-forum.org [mailto:mpi3-fortran-bounces at lists.mpi-forum.org] On Behalf Of N.M. Maclaren
Sent: Friday, March 05, 2010 11:14 AM
To: MPI-3 Fortran working group
Subject: Re: [MPI3 Fortran] Deprecate mpif.h?

On Mar 5 2010, Supalov, Alexander wrote:
> Thanks. I think there's some difference between "deprecating" and 
> "freezing". The former implies people will have to move to the mpi3 
> module once. The latter means they can "just" sit tight and forget about 
> MPI-3. Hence the higher presumed impact of the deprecation.

Yes, and that's why "deprecate" is right.  Regrettably, for unavoidable
reasons, the current MPI interfaces break all of the Fortran standards
from 1966 onwards.  The design minimised the places where they do so,
but some just could not be bypassed.

Worse, the problems that those breaches cause are getting worse, and
that's going to continue.  The two main ways that I know of where that
is happening are inter-procedural optimisation (which conflicts with
the way choice arguments break the type rules) and asynchronicity
(which is increasingly caused by shared memory parallelism, of all
sorts, and also conflicts with inter-procedural optimisation).

I.e., in the long term, all programmers and all programs should convert
to MPI3.  But, given that the TR which it will depend on is still under
development, "in the long term" means decades.  But there really is no
alternative, because the language infrastructure on which the existing
MPI interfaces depend is getting increasingly unreliable.

Nick Maclaren.

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