[MPI3 Fortran] [Mpi-comments] MPI 3.0: Fortran 2008 interface - issue with the LOGICAL kind

Craig Rasmussen rasmus at cas.uoregon.edu
Tue Mar 26 11:41:02 CDT 2013

On Mar 26, 2013, at 6:38 AM, Jeff Squyres (jsquyres) wrote:

> On Mar 25, 2013, at 2:35 PM, Bill Long <longb at cray.com> wrote:
>>> I'm strongly in favor of option 3.  It is the only option that allows
>>> the possibility of underscore name mangling disappearing in the future.
>>> I think most (if not all) MPI Fortran implementations will eventually
>>> evolve to thin wrappers calling the C API.  
> Remember that Open MPI can never do this approach since our C handles != Fortran handles, and Fortran wrappers will not be able to reach back into the back-end C MPI objects (at least, not without a truckload of extra interop code -- the Fortran bindings layer would have to gain an understanding of the back-end MPI C objects, and that seems like a terrible idea).

I'm a hacker at heart and so I'm not as pessimistic as Jeff is.  I'll have a conversation with Jeff see if I can convince him.

This may be beyond the scope of an errata but I don't want to close off this possibility.  Otherwise the MPI standard will still REQUIRE implementations to go OUTSIDE of the Fortran standard.  This to me is a big deal and was one of the two big reasons in my opinion why we did MPI-3 for Fortran in the first place (the other was type safety).  I really hate to go to all the work we did and then give up on an MPI standard that is out of compliance with language standards.

Craig Rasmussen
CAS Scientific Programmer
rasmus at cas.uoregon.edu

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