[MPI3 Fortran] MPI_SIZEOF question

[Rolf Rabenseifner]

A) If we are doing BIND(C), I defined for MPI-3.0:

INTERFACE
 SUBROUTINE MPI_Sizeof(x, size, ierror) BIND(C)
  IMPLICIT NONE
  TYPE(*) :: x
  INTEGER, INTENT(OUT) :: size
  INTEGER, OPTIONAL, INTENT(OUT) :: ierror
 END SUBROUTINE
END INTERFACE

This seems to be ***bad*** because TYPE(*) is not enough to
get the dope vector 
TR 29113, 5.2.2, CFI_cdesc_t,
especially its structure element

  size_t elem_len; If the object corresponds to a Fortran
     CHARACTER object, the value equals the length of
     the CHARACTER object times the sizeof() of a scalar
     of the character type; otherwise, the value equals
     the sizeof() of an element of the object.

We should do

  TYPE(*), DIMENSION(..) :: x

which extends the current definition (in a backward compatible way).

Then size = elem_len of the dope vector.

Correct?

B) If an implementation choose Fortran binding:

B1) Does (without assumed-rank)
 
 SUBROUTINE MPI_Sizeof(x, size, ierror)
  IMPLICIT NONE
  TYPE(*) :: x
  INTEGER, INTENT(OUT) :: size
  INTEGER, OPTIONAL, INTENT(OUT) :: ierror
  size = SIZEOF(x)
 END SUBROUTINE

work?

B2) Does (with assumed-rank)
 
 SUBROUTINE MPI_Sizeof(x, size, ierror)
  IMPLICIT NONE
  TYPE(*), DIMENSION(..) :: x
  INTEGER, INTENT(OUT) :: size
  INTEGER, OPTIONAL, INTENT(OUT) :: ierror
  size = SIZEOF(x)
 END SUBROUTINE

work, or how can it be programmed?

Best regards
Rolf


----- Original Message -----
> From: "Bill Long" <longb at cray.com>
> To: mpi3-fortran at lists.mpi-forum.org
> Sent: Monday, May 23, 2011 4:47:26 PM
> Subject: Re: [MPI3 Fortran] MPI_SIZEOF question
>
> The difficulty in writing things like this in Fortran is why the
> standard provides intrinsics. In this case, see STORAGE_SIZE, which
> returns the size of an array element of the type of the argument in
> bits. Dividing by 8 and multiplying by the array size (if the argument
> is not a scalar) should be simple enough for the user.
> 
> On 5/23/11 8:30 AM, Jeff Squyres wrote:
> > I'm re-working Open MPI's Fortran implementation with Craig.
> >
> > The MPI_SIZEOF function is supposed to return the size of any
> > Fortran intrinsic data type. MPI-2.2 16.2.5 p494:31-44 says:
> >
> > -----
> > The following functions allow a user to obtain a size-specific MPI
> > datatype for any intrinsic Fortran type.
> >
> > MPI_SIZEOF(x, size)
> > IN x a Fortran variable of numeric intrinsic type (choice)
> > OUT size size of machine representation of that type (integer)
> >
> 
> This one is very close to STORAGE_SIZE. Just divide by 8.
> 
> > MPI_SIZEOF(X, SIZE, IERROR)
> > <type> X
> > INTEGER SIZE, IERROR
> >
> 
> This one would require also multiplying by the size of an array
> argument. I assume the IERROR is there only to provide a distinction
> for the generic interface. It is hard to imagine an actual run-time
> error with a routine like this.
> 
> Ultimately, I'd be inclined to just scrap the routine as redundant.
> 
> Cheers,
> Bill
> 
> 
> > This function returns the size in bytes of the machine
> > representation of the given variable. It is a generic Fortran
> > routine and has a Fortran binding only.
> > -----
> >
> > Is there any way of implementing that other than an interface with
> > an overloaded subroutine for every single intrinsic type (including
> > dimension)?
> >
> 
> --
> 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)