On 6/20/13 7:39 AM, "Jim Dinan" <[email protected]<mailto:[email protected]>> wrote: I agree with the general statement that the nonblocking call marks the end of the epoch. In the case of MPI_Win_test, it's trying to close an exposure epoch -- not an access epoch -- so communication operations from the origin process are not being completed by synchronization (although, the test/wait synchronization could be waiting for a self communication, that operation is completed by start/complete not post/wait). I think an MPI_Win_iwait operation that uses the semantic you described should be identical to MPI_Win_test. Unless I'm missing something, which never happens when discussing RMA. :) You're right; I always get the exposure / access sides of generalized active target mixed up. With that clarification, I think that MPI_Win_iwait and MPI_Win_test could be made equivalent fairly easily. Brian -- Brian W. Barrett Scalable System Software Group Sandia National Laboratories