On 08/27/2013 07:15 AM, Underwood, Keith D wrote:

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I prefer option #1 -- that a window synchronization (e.g. Win_sync) can be used to order load/store operations with respect to actions performed by other processes in the target's window. If no ordering is enforced, the MPI standard does not define what is seen by load operations at the target process. As a rationale, the local process' view of the window may not be consistent with the window because of performance optimizations or the consistency model of the underlying architecture. This would allow e.g. SHMEM implementations to still use MPI-3 RMA, but they would have to rely on a behavior that is defined by the architecture/implementation, as they currently do.

My statement: this seems to be what SHMEM does - except they don't provide the equivalent of Win_sync. If we are going to hack on the text, I would prefer that we be *very* careful in our wording. Specifically, we need to make it very clear that the SHMEM approach is *legal*, but the burden is on the user to do potentially implementation specific things to make it work right.

Hmm. OK. Just so there's no confusion, by "SHMEM approach", you are saying that the application can use its own platform-specific memory consistency calls and avoid using WIN_SYNC, correct? -- Pavan Balaji http://www.mcs.anl.gov/~balaji