[MPI3 Fortran] [Mpi-comments] MPI 3.0:Fortran 2008 interface - issue with the LOGICAL kind
rabenseifner at hlrs.de
Thu Mar 14 16:14:03 CDT 2013
I would like to learn
- Who is implementing the new mpi_f08 module
-- for mpich?
Is this you, Bill Long?
-- for OpenMPI?
Is this you, Craig?
-- who else is currently implementing the
new Fortran mpi_f08 module?
- Do I understand correctly that both implementations:
-- do use Fortran-written wrappers as MPI user-API?
-- I.e., it is simple to change it to BIND(C) or non-BIND(C)?
-- I.e., only for the tools people, it is of
interest whether BIND(C) or non-BIND(C) was chosen?
-- What are other implementations do?
I ask this, to learn whether the BIND(C)/non-BIND(C) freedom
for the implementations can/should be reduced
to make life easier.
The current proposal #364 is based on minimal restrictions
based on the missing C-interoperability of LOGICAL.
I expect, that life can be more simple if we make more
restrictions, e.g., same BIND(C) roule for all routine groups
(this would mean no BIND(C) in the moment).
----- Original Message -----
> From: "Bill Long" <longb at cray.com>
> To: mpi3-fortran at lists.mpi-forum.org
> Cc: rabenseifner at hlrs.de, "Kathryn Mohror" <kathryn at llnl.gov>, "Nick Maclaren" <nmm1 at cam.ac.uk>
> Sent: Monday, March 11, 2013 2:01:37 PM
> Subject: Re: [MPI3 Fortran] [Mpi-comments] MPI 3.0:Fortran 2008 interface - issue with the LOGICAL kind
> Hi Martin,
> Ultimately, the problem is that some Fortran compilers (one out of
> that I tried) will give an error for a dummy argument declared default
> LOGICAL in a BIND(C) interface. This is because there is not really a
> good corresponding type in C for all Fortran compilers, and the
> representation of LOGICAL in Fortran might not even match the _Bool
> in C.
> One solution to the problem, at least for the "normal" MPI functions,
> the write the Fortran wrapper in Fortran, with no BIND(C) [gets around
> the compiler error message] and within the wrapper, convert the
> value to an int value that is passed in a call to the actual C
> [since the corresponding C argument is an int]. If the argument is
> intent(out) then you convert it back from int to LOGICAL after the C
> function call, before returning from the wrapper. These conversions
> each single lines of Fortran code, and (if the wrapper is in a module)
> will probably get inlined, and possibly optimized away for some
> implementations. The goal is that C should never have to be confronted
> with the foreign Fortran default LOGICAL directly.
> I believe that the current wording of the MPI 3 spec for using mpif.h
> still requires dealing with the no/single/double underscore issue, and
> that is assuming one of those is the choice for default linker names
> Fortran for a particular implementation. There is nothing in the
> Fortran standard that requires any of these three options.
> I noted that Nick Maclaren replied to this message as well. For those
> not aware, Nick is in a rather unique position of having participated
> both the C and Fortran standardization committees. He pretty much
> knows where all the [Fortran-C interoperability] dead bodies are
> On 3/11/13 12:18 AM, Schulz, Martin wrote:
> > Hi all,
> > I am trying to catch up with the various threads on this (sorry,
> > last week was hectic and I didn't get to all emails). I have to
> > admit that I am still confused why there is a problem, but we can
> > clarify this during a phone call or during the march meeting.
> > However, doesn't not doing BINDC create a problem, since I now have
> > to again deal with the no/one/two underscore issue? This sounds like
> > a bad interface design to me, especially when we starting mixing
> > things.
> > Martin
> > On Mar 4, 2013, at 9:47 AM, Rolf Rabenseifner <rabenseifner at hlrs.de>
> > wrote:
> >> Dear all,
> >> I forget to say thank you to all of you who helped to solve
> >> this hard problem. It was a really helpful discussion.
> >> It is a pity that we could not keep the BIND(C) for
> >> all routines in mpi_f08, which was one goal with mpi_f08 and TS
> >> 29113.
> >> In my proposal #364, we have to remove BIND(C) from
> >> - the 30 normal MPI routines with LOGICAL arguments,
> >> - the 9 MPI routines with callbacks in the argument list,
> >> - and 10 predefined callbacks,
> >> i.e., from 49 out of 357 MPI routines.
> >> I do not see a better solution that can be done by the MPI Forum.
> >> Better solutions are still possible for the 30 normal routines
> >> and/or for the 9 routines with callback-arguments as soon as
> >> the Fortran standard will include some additions and
> >> those additions are provided by the compilers - but if this
> >> will happen then it will not happen soon.
> >> It was luck that all routines with buffer arguments do not
> >> have also a LOGICAL argument.
> >> Best regards
> >> Rolf
> >> ------------------
> >> Malcolm and all MPI implementors,
> >> and TOOLS implementors,
> >> First Malcolm, thank you for your helpful answer.
> >> After all the discussion, the MPI-3.0 errata decision is
> >> very simple: Remove BIND(C) everywhere where LOGICAL is around.
> >> I did it in the ticket #364
> >> https://svn.mpi-forum.org/trac/mpi-forum-web/ticket/364
> >> I hope that one of the implementors with Fortran knowledge goes
> >> through my proposal and returns an "okay" as a review on the
> >> ticket.
> >> The major changes:
> >> - BIND(C) removed on all callback abstract interfaces.
> >> - BIND(C) removed on all predefined callbacks.
> >> - Creating a new routine group "MPI_TEST" for all MPI routines
> >> with LOGICAL arguments, except MPI_OP_CREATE, which is already
> >> in an own group.
> >> - Telling that the routines in the groups MPI_TEST,
> >> MPI_OP_CREATE, MPI_REGISTER_DATEREP, and MPI_COMM_KEYVAL_CREATE
> >> cannot be implemented with BIND(C) in Fortran 2008 + TS 29113
> >> and earlier.
> >> TOOLS implementors should be aware that I added this new routine
> >> group.
> >> Best regards
> >> Rolf
> >> ----- Original Message -----
> >>> From: "Malcolm Cohen" <malcolm at nag-j.co.jp>
> >>> To: "MPI-3 Fortran working group"
> >>> <mpi3-fortran at lists.mpi-forum.org>
> >>> Sent: Monday, March 4, 2013 3:56:50 AM
> >>> Subject: Re: [MPI3 Fortran] Fwd: [Mpi-comments] MPI 3.0:Fortran
> >>> 2008 interface - issue with the LOGICAL kind
> >>>> (B1) Is it possible, that a BIND(C) routine
> >>>> has a dummy argument that is a non-BIND(C)
> >>>> ABSTRACT INTERFACE procedure argument?
> >>> That is not possible: all dummy arguments of a BIND(C) routine
> >>> must be
> >>> interoperable - for procedures that requires BIND(C).
> >>> It would be reasonable to extend C_FUNLOC and C_F_PROCPOINTER to
> >>> permit
> >>> non-interoperable procedures, similarly to how we permit
> >>> non-interoperable
> >>> variables in C_LOC and C_F_POINTER. Then the argument could be
> >>> C_FUNPTR (by
> >>> value). I don't know whether this would help you though.
> >>>> (B2) Do we have any problem with
> >>>> the TYPE(C_PTR), VALUE dummy arguments
> >>>> in the ABSTRACT INTERFACE MPI_User_function
> >>>> on MPI-3.0 page 183 line 45 - page 184 line 3
> >>>> if the we remove the BIND(C) from this
> >>>> ABSTRACT INTERFACE (i.e. on page 183, line 47).
> >>> No problem.
> >>> Cheers,
> >>> --
> >>> ................................Malcolm Cohen, Nihon NAG, Tokyo.
> >>> _______________________________________________
> >>> mpi3-fortran mailing list
> >>> mpi3-fortran at lists.mpi-forum.org
> >>> http://lists.mpi-forum.org/mailman/listinfo.cgi/mpi3-fortran
> >> --
> >> Dr. Rolf Rabenseifner . . . . . . . . . .. email
> >> rabenseifner at hlrs.de
> >> High Performance Computing Center (HLRS) . phone
> >> ++49(0)711/685-65530
> >> University of Stuttgart . . . . . . . . .. fax ++49(0)711 /
> >> 685-65832
> >> Head of Dpmt Parallel Computing . . .
> >> www.hlrs.de/people/rabenseifner
> >> Nobelstr. 19, D-70550 Stuttgart, Germany . . . . (Office: Room
> >> 1.307)
> > ________________________________________________________________________
> > Martin Schulz, schulzm at llnl.gov, http://people.llnl.gov/schulzm
> > CASC @ Lawrence Livermore National Laboratory, Livermore, USA
> > _______________________________________________
> > mpi3-fortran mailing list
> > mpi3-fortran at lists.mpi-forum.org
> > http://lists.mpi-forum.org/mailman/listinfo.cgi/mpi3-fortran
> Bill Long longb at cray.com
> Fortran Technical Support & voice: 651-605-9024
> Bioinformatics Software Development fax: 651-605-9142
> Cray Inc./Cray Plaza, Suite 210/380 Jackson St./St. Paul, MN 55101
Dr. Rolf Rabenseifner . . . . . . . . . .. email rabenseifner at hlrs.de
High Performance Computing Center (HLRS) . phone ++49(0)711/685-65530
University of Stuttgart . . . . . . . . .. fax ++49(0)711 / 685-65832
Head of Dpmt Parallel Computing . . . www.hlrs.de/people/rabenseifner
Nobelstr. 19, D-70550 Stuttgart, Germany . . . . (Office: Room 1.307)
More information about the mpiwg-fortran