I'm trying to get a parallel debugger to support debugging MPICH programs. This involves getting the list of application process pids and the hostname or IP address of the host the process is running on so the debugger can attach to those processes. I found a web page at http://www.mcs.anl.gov/research/projects/mpi/mpi-debug/ that discusses using MPIR_proctable and MPIR_proctable_size to get this information from the mpirun or mpiexec process. I have a couple questions 1) Is this the correct way to do this or is there another method I should be using to get this information? 2) I read somewhere that the MPIR_proctable was limited to 64 proceses initially. Is this only an initial size limitation or does MPIR_proctable grow to hold the info all processes regardless of how many processes exist in the application? I also ran into a problem experimenting with this at the MPICH 3.0.4 level. It seems that the pid in all entries of MPIR_proctable is the same for each process and is the pid of the process that is rank zero. All processes are running on the same host that mpirun is also running on. I'm running the program as 'mpirun -n 5 ./shallow' Thanks Dave