[Mpi3-rma] Target displacement in dynamic windows

[Jeff Hammond]

do the Fortran 2008 bindings support a hook for C unsigned ints?
since FORTRAN77 bindings are still optional, maybe we can just accept
that they don't work as well as the C bindings, which isn't too
different than the existing situation where all sorts of things aren't
certain to work.

jeff

On Mon, Sep 17, 2012 at 9:18 PM, William Gropp <wgropp at illinois.edu> wrote:
> Thanks - I think the 3.0 errata is a reasonable solution.  I'll note that the 3.1 solutions may not be practical in Fortran (e.g., a larger integer may not be available).
>
> Bill
>
> William Gropp
> Director, Parallel Computing Institute
> Deputy Director for Research
> Institute for Advanced Computing Applications and Technologies
> Paul and Cynthia Saylor Professor of Computer Science
> University of Illinois Urbana-Champaign
>
>
>
> On Sep 17, 2012, at 4:12 PM, Jim Dinan wrote:
>
>> Hi All,
>>
>> In today's meeting, we arrived at the following approach to addressing the target displacements issue for dynamic windows:
>>
>> The MPI 3.0 errata should include the following two statements:
>>
>> 1. For dynamic windows, the target_disp argument to RMA communication operations is not restricted to non-negative values.
>>
>> 2. Users are cautioned that displacement arithmetic can overflow in variables with MPI_Aint type and result in unexpected values on some platforms.  This issue will be addressed in a future version of MPI.
>>
>> In MPI 3.1, we will look at two possible mechanisms for providing safe offset arithmetic:
>>
>> 1. MPI_Get_pointer(MPI_Aint address, void *ptr), which will allow a user to convert between addresses and pointers.
>>
>> 2. MPI_Auint -- an address integer which can represent the full range of MPI_Aint as a positive integer.  This could be an unsigned integer, but for Fortran compatibiliy, it may need to be a singed integer that's larger than MPI_Aint.  The following conversion functions would be provided:
>>
>> MPI_Get_auint(MPI_Aint addr, MPI_Auint *uaddr)
>> MPI_Get_aint(MPI_Auint uaddr, MPI_Aint *addr)
>>
>> Please send comments.  Thanks,
>>
>> ~Jim.
>
>
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-- 
Jeff Hammond
Argonne Leadership Computing Facility
University of Chicago Computation Institute
jhammond at alcf.anl.gov / (630) 252-5381
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