Hi Kurt, Let’s say you have a communicator of 10 processes (MPI_COMM_WORLD or any derivatives), and if you use that communicator to spawn process P, the result inter-communicator will be between your original comm (10 processes) and P’s MPI_COMM_WORLD (1 process), right? All original 10 processes should be already connected to P. Did I miss anything? — Hui Zhou On Dec 4, 2019, at 1:31 PM, Mccall, Kurt E. (MSFC-EV41) via discuss <[email protected]<mailto:[email protected]>> wrote: Hi, My job creates 10 processes, and the rank 0 one spawns a distinct process P to function as a master. I’d like to share P’s inter-communicator with the other 9 processes, but it seems that I can’t pass it directly to them through function arguments to those processes (very weird errors happen involving the inter-communicator). What is an efficient way to connect all 10 processes to P? I’ve looked into MPI_Open_port / MPI_Comm_accept / MPI_Comm_connect, but was wondering if there is more streamlined way. (I can’t make rank 0 become the master directly, due to the peculiarities of my PBS/Torque node allocations). Thanks, Kurt _______________________________________________ discuss mailing list [email protected]<mailto:[email protected]> To manage subscription options or unsubscribe: https://lists.mpich.org/mailman/listinfo/discuss