I would expect that the intent is also that the memory should not be freed/unmapped before the matching call to MPI_Win_free() correct? -Nathan On Jan 02, 2018, at 01:19 PM, William Gropp <[email protected]> wrote: It was certainly the intent that the memory be allocated.  Specifically, if a is the pointer and the region is of length L, then (assuming char *a and ) a[0] … a[L-1] must be valid r and l values at the point of the call. Bill William Gropp Director and Chief Scientist, NCSA Thomas M. Siebel Chair in Computer Science University of Illinois Urbana-Champaign On Jan 2, 2018, at 1:52 PM, Jeff Hammond <[email protected]> wrote: If a user passes a (base,size) pair that corresponds to a range of addresses that are not allocated and/or mapped, is that a correct MPI program? The only text I can find that implies that buffers passed to MPI_Win_create have to be allocated is the following, assuming that one interprets "existing memory" this way.   "Each process specifies a window of existing memory that it exposes to RMA accesses by the processes in the group of comm." (MPI 3.1 11.2.1) The Fortran-specific text is similarly suggestive, but it only says that a user can pass a simply contiguous array, not that such a thing is required. "In Fortran, one can pass the first element of a memory region or a whole array, which must be ‘simply contiguous’" Thanks, Jeff -- Jeff Hammond [email protected] http://jeffhammond.github.io/ _______________________________________________ mpiwg-rma mailing list [email protected] https://lists.mpi-forum.org/mailman/listinfo/mpiwg-rma _______________________________________________ mpiwg-rma mailing list [email protected] https://lists.mpi-forum.org/mailman/listinfo/mpiwg-rma