This question has come up in the Open MPI community: ----- MPI_Info_set(myinfo, "use_shared_memory", "yes"); MPI_Comm_set_info(comm, myinfo); MPI_Comm_get_info(comm, myinfo_returned);  // Assume here that there was not enough shared memory available to use shared-memory for  // communication on this comm, so MPI_Info_get() tells us that use_shared_memory is "no". // ...time passes, and now assume there is more shared-memory available MPI_Comm_dup_with_info(comm, &newcom); MPI_comm_get_info(newcom, myinfo_returned); ----- Should newcom have "use_shared_memory" set to "yes" or "no"? Arguments for "yes": - the user originally asked for "yes" - now there is shared memory available Arguments for "no": - the current value for "used_shared_memory" on the parent communicator is "no" Which should it be? MPI-3.1 6.4.2 p238 says: "...Returns in newcomer a new communicator with the same group or groups, same topology, same info hints, any copied cached information, but a new context (see Section 6.7.1)." So the specific question here is: what exactly does "Same info hints" mean?  The user-specific hint, or the current value of the hint? -- Jeff Squyres [email protected] For corporate legal information go to: http://www.cisco.com/web/about/doing_business/legal/cri/