Hello Is there a way to find out the rank of a process (in COMM_WORLD) by looking at its environment? We use this feature in OpenMPI and srun for displaying the placement of ranks in hwloc tools. By default, we display the PID, but displaying the commworld rank is more useful. Looking in /proc/<pid>/environ is an easy way to find environment variables, but I could not find a clear solution for MPICH. I tried on several machines with different mpich installations. In one case, I found a MPI_LOCALRANKID (which isn't exactly what I want but could be sufficient). There's also PMI_RANK, which may be identical to the commworld rank? Thanks for the help Brice