[MPI3 Fortran] TYPE(MPI_Status) with SEQUENCE attribute

[Rolf Rabenseifner]

Bill,

This is an interesting idea.
I added also Reinhold's idea to use BIND(C) together with
normal Fortran INTEGER.
I extended my tests and the only tests that did not fail are 
the SEQUENCE derived type. 
All other declarations of a handle or a status fail if the user
has stored such a handle or status in a common block
or a sequence derived type.

This test is based on the requirement that the location of
a MPI-2 handle or status in a Fortran user application 
has to work also with the new definition of handles and statuses,
because we never want that the data structures of a user
program must be significantly modified.
Such a significant modification would be, that
he/she cannot further use a standard common block,
although they are deprecated. Too many Fortran programs
exchange arguments through common blocks.

For the new handles, the principal idea is, to have exactly 
one Fortran numerical unit, i.e., the same as with the MPI-2 
definition of a handle, which was an INTEGER.

Best regards
Rolf
 

----- Original Message -----
> From: "Bill Long" <longb at cray.com>
> To: mpi3-fortran at lists.mpi-forum.org
> Sent: Friday, April 1, 2011 12:24:27 AM
> Subject: Re: [MPI3 Fortran] TYPE(MPI_Status) with SEQUENCE attribute
> Hi Rolf,
> 
> On 3/31/11 2:31 PM, Rolf Rabenseifner wrote:
> > Dear all,
> >
> > as discussed, I had removed the SEQUENCE attribute from form the
> > new TYPE(MPI_Status) derived type within the new mpi_f08 module.
> >
> > I checked now with a test program whether the new status can be used
> > in a user program in the same way as the old status (i.e. an
> > INTEGER,
> > DIMENSION(MPI_STATUS_SIZE) array) and detected, that the compiler
> > will issue a lot of incompatibilities if the newly defined status
> > does not use internally the sequence attribute.
> >
> 
> The messages are valid. However, the use of SEQUENCE seems curious. I
> would have written the module more like this:
> 
> MODULE mpi_f08
> use,intrinsic :: iso_c_binding
> IMPLICIT NONE
> TYPE,bind(c) :: MPI_Comm
> INTEGER(C_int) :: MPI_VAL
> END TYPE MPI_Comm
> 
> TYPE,bind(c) :: MPI_Status
> INTEGER(C_int) :: MPI_SOURCE
> INTEGER(C_int) :: MPI_TAG
> INTEGER(C_int) :: MPI_ERROR
> INTEGER(C_int) :: MPI_intern_highsize
> INTEGER(C_int) :: MPI_intern_lowsize
> END TYPE MPI_Status
> 
> INTEGER(C_int),parameter :: MPI_STATUS_SIZE=5
> 
> END MODULE mpi_f08
> 
> 
> The use of a bind(c) type ensures that the memory layout of the type
> is
> the same as for the corresponding C struct. It would seem like this is
> the goal. The SEQUENCE type does not necessarily have this
> characteristic.
> 
> Cheers,
> Bill
> 
> 
> 
> 
> 
> > It is not expected that this SEQUENCE attribute has any negative
> > impact in scalable applications.
> >
> > Therefore, I had to reinvent the SEQUENCE into the TYPE(MPI_Status).
> >
> > The test program and compiler output is attached.
> > The NON_.... variables are declared with types where
> > the SEQUENCE is missing.
> > All these NON_.... variables cause errors and the abort of the
> > compilation.
> >
> > Same usage patterns with MPI handle and status types internally
> > using
> > SEQUENCE do not cause any errors.
> >
> > Best regards
> > Rolf
> >
> 
> --
> 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
> 
> 
> _______________________________________________
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-- 
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: Allmandring 30)
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