[MPIWG Fortran] Provide Fortran datatypes if Fortran bindings not provided?

Jeff Squyres (jsquyres) jsquyres at cisco.com
Thu Feb 18 11:50:37 CST 2016

-----Original Message-----
From: Bill Long <longb at cray.com>
Reply: MPI-WG Fortran working group <mpiwg-fortran at lists.mpi-forum.org>
Date: February 18, 2016 at 11:11:11 AM
To: MPI-WG Fortran working group <mpiwg-fortran at lists.mpi-forum.org>
Subject:  Re: [MPIWG Fortran] Provide Fortran datatypes if Fortran	bindings	not provided?

> > It would seem peculiar to have no Fortran compiler installed. Even if that was the case  
> at the moment, it could change in the future, and you would not want to have to rebuild MPI  
> in that case.
> >
> > It is not peculiar. LLVM does not yet have a usable Fortran front-end, so anyone that  
> uses this compiler toolchain exclusively does not have a Fortran compiler.

I agree -- it is not peculiar to not have a Fortran compiler installed (or, stated without the double negative: it's common to only have a C/C++ compiler available).

Don't get me wrong; I think Fortran is still hugely important to MPI (which is why I participate  in this WG!).  I'm just saying that non-Fortran is also pretty hugely important to MPI.

Here's some more supporting points:

- Many MPI applications are written without Fortran
- gfortran is not a default-installed package in the "developer" flavor of Centos/RHEL (and probably others?)
- Intel sells their Fortran compiler separately from their C compiler
- Apple/OS X does not include a Fortran compiler *at all* (you can download a 3rd-party compilation of gfortran, but Apple itself doesn't support Fortran)
- Open MPI users reported *so many times* over the years "I don't have a Fortran compiler; why can't I install Open MPI?" that we added the option for installing Open MPI without Fortran support
- Microsoft fought hard and won the ability to make *all* the Fortran bindings in MPI-3.1 be optional (because they don't support a Fortran compiler, either)

In short: MPI is a major portion of the Fortran market, but the reverse is not necessarily true.

Jeff Squyres
jsquyres at cisco.com  
For corporate legal information go to: http://www.cisco.com/web/about/doing_business/legal/cri/

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