My application, which spawns multiple subprocesses via MPI_Comm_spawn, eventually fails on one Slurm cluster as I scale up the number of processes, with the error: [[email protected]] HYDU_create_process (../../../../mpich-4.0.1/src/pm/hydra/utils/launch/launch.c:21): pipe error (Too many open files) [[email protected]] HYDT_bscd_common_launch_procs (../../../../mpich-4.0.1/src/pm/hydra/tools/bootstrap/external/external_common_launch.c:296): create process returned error free(): invalid pointer /var/spool/slurm/job235999/slurm_script: line 296: 3778907 Aborted (core dumped) It works fine on a different (Torque) cluster for very large job sizes. "ulimit -n" (number of open files) on both machines returns 1024. I'm hoping that there is some other system setting on the Slurm cluster that would allow larger jobs. I can provide the "-verbose" output file if that would help. Thanks, Kurt