[Mpi3-rma] Target displacement in dynamic windows

[Rajeev Thakur]

The errata will need to identify the page and line at which the exact text should be inserted or changed.

Rajeev

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.