[MPIWG Fortran] Profiling for MPI_SIZEOF?
longb at cray.com
Thu May 15 16:28:31 CDT 2014
On May 15, 2014, at 4:00 PM, Jeff Hammond <jeff.science at gmail.com> wrote:
>>>> That said, the optimal implementation would be to write all of the specific versions (I’m seeing 10) for a generic named MPI_SIZEOF. For each specific version, the executed code reduces to
>>>> size = storage_size(x)/8
>>>> which the compiler will evaluate at compile time based on the type of x.
>>> No, there's 10 * 7 versions, right? One for each type (10), and then 1 for each rank.
>>> The language in the MPI spec explicitly allows you to pass an array as the argument of x (although it does say that it will return the size of the base element -- not the array).
>> You are right. I just looked at one of the example specifics:
>> subroutine MPI_Sizeof_xint8 (x, size, ierror)
>> use,intrinsic :: iso_fortran_env, only: int8
>> integer(int8),dimension(..) :: x
>> INTEGER, intent(out) :: size
>> INTEGER, optional, intent(out) :: ierror
>> size = storage_size(x)/8
>> if (present(ierror)) ierror = 0
>> end subroutine MPI_Sizeof_xint8
>> which is declared assumed-rank, but specific type (which is the interesting thing here). That’s how I got 10. To get them all without assumed-rank, you need 10*15 (the Fortran standard allows array ranks up to 15 now). All the more reason for no intercepting.
> I vote for #1. Does anyone thing that there are linkers that can
> handle 10^15 symbols?
It’s actually 160 = (10 * (1 + 15) ) where the 1 is for scalar, and the 15 for ranks 1..15. Still, an annoying number. If there is compiler support for assumed-rank, the total is 10, since the function result is independent of rank.
> Jeff Hammond
> jeff.science at gmail.com
> mpiwg-fortran mailing list
> mpiwg-fortran at lists.mpi-forum.org
Bill Long longb at cray.com
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