[Mpi3-rma] Urgent: Target displacement sign issue

[William Gropp]

I think this is fine.  Any other comments?

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 12, 2012, at 5:36 PM, Jim Dinan wrote:

> Hi All,
> 
> We're down to the wire on this change.  As specified, dynamic windows will /not/ work reliably in MPI 3.0.  We currently see "negative" displacements for dynamic windows in MPICH on 32-bit platforms. Earlier, I suggested a change stating that the implementation will ignore the sign for dynamic windows.  Here's a revised proposal.
> 
> In the paragraph on page 425, line 1, add the bracketed sentence:
> 
> In the case of a window created with MPI_WIN_CREATE_DYNAMIC, the target_disp for all RMA functions is the address at the target; i.e., the effective window_base is MPI_BOTTOM and the disp_unit is one. [Thus, for dynamic windows, the target_disp argument to RMA communication operations is not restricted to non-negative values.] Users should use MPI_GET_ADDRESS at the target process to determine the address of a target memory location and communicate this address to the origin process.
> 
> ~Jim.
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