On Nov 12, 2013, at 5:40 PM, Rajeev Thakur <[email protected]> wrote:

Think of Comm_disconnect as "whatever connection was there between client and server is gone".

Rajeev -- This sentence has been bugging me, and I just figured out why. I've always thought of COMM_DISCONNECT just as you describe: whatever connection was there between client and server is gone. But what about other types of MPI handles -- like MPI_File and MPI_Window? For example: ----- MPI_Comm_spawn(..., &child); MPI_Intercomm_merge(child, 0, &child_intra); MPI_File_open(child_intra, ..., &file); MPI_Comm_disconnect(&child_intra); MPI_Comm_disconnect(&child); ----- At this point, all communicators between parent and child are gone, but there's still a File (the same example could be done with an RMA window). So the processes are *not* actually disconnected (in the MPI sense of the word "disconnected). Indeed, in the above example, if there was no File, you still have to do *2* disconnects before the parent and child are truly disconnected. Hence, I think that this is a very poorly named function -- it *doesn't* necessarily disconnect MPI processes. It really performs and operation that is something like MPI_COMM_FREE_WAIT. I wonder if this is worth an AtoU... -- Jeff Squyres [email protected] For corporate legal information go to: http://www.cisco.com/web/about/doing_business/legal/cri/