Things were working fine when I was launching 1 node jobs under Slurm 20.11.8, but when I launched a 20 node job, MPICH hangs in MPI_Init. The output of "mpiexec -verbose" is attached, and the stack trace at the point where it hangs is below. In the "mpiexec -verbose" output, I wonder why variables such as PATH_modshare point to our Intel MPI implementation, which I am no using. I am using MPICH 4.0 with a patch that Ken Raffenetti provided (which makes MPICH recognize the "host" info key). My $PATH and $LD_LIBRARY_PATH variables definitely point to the correct MPICH installation. I appreciate any help you can give. Here is the Slurm sbatch command: sbatch --nodes=20 --ntasks=20 --job-name $job_name --exclusive -verbose Here is the mpiexec command: mpiexec -verbose -launcher ssh -print-all-exitcodes -np 20 -wdir ${work_dir} -env DISPLAY localhost:10.0 --ppn 1 <many more args...> Stack trace at MPI_Init: #0 0x00007f6d85f499b2 in read () from /lib64/libpthread.so.0 #1 0x00007f6d87a5753a in PMIU_readline (fd=5, buf=buf@entry=0x7ffd6fb596e0 "", maxlen=maxlen@entry=1024) at ../mpich-slurm-patch-4.0/src/pmi/simple/simple_pmiutil.c:134 #2 0x00007f6d87a57a56 in GetResponse (request=0x7f6d87b48351 "cmd=barrier_in\n", expectedCmd=0x7f6d87b48345 "barrier_out", checkRc=0) at ../mpich-slurm-patch-4.0/src/pmi/simple/simple_pmi.c:818 #3 0x00007f6d87a29915 in MPIDI_PG_SetConnInfo (rank=rank@entry=0, connString=connString@entry=0x1bbf5a0 "description#n001$port#33403$ifname#172.16.56.1$") at ../mpich-slurm-patch-4.0/src/mpid/ch3/src/mpidi_pg.c:559 #4 0x00007f6d87a38611 in MPID_nem_init (pg_rank=pg_rank@entry=0, pg_p=pg_p@entry=0x1bbf850, has_parent=<optimized out>) at ../mpich-slurm-patch-4.0/src/mpid/ch3/channels/nemesis/src/mpid_nem_init.c:393 #5 0x00007f6d87a2ad93 in MPIDI_CH3_Init (has_parent=<optimized out>, pg_p=0x1bbf850, pg_rank=0) at ../mpich-slurm-patch-4.0/src/mpid/ch3/channels/nemesis/src/ch3_init.c:83 #6 0x00007f6d87a1b3b7 in init_world () at ../mpich-slurm-patch-4.0/src/mpid/ch3/src/mpid_init.c:190 #7 MPID_Init (requested=<optimized out>, provided=provided@entry=0x7f6d87e03540 <MPIR_ThreadInfo>) at ../mpich-slurm-patch-4.0/src/mpid/ch3/src/mpid_init.c:76 #8 0x00007f6d879828eb in MPII_Init_thread (argc=argc@entry=0x7ffd6fb5a5cc, argv=argv@entry=0x7ffd6fb5a5c0, user_required=0, provided=provided@entry=0x7ffd6fb5a574, p_session_ptr=p_session_ptr@entry=0x0) at ../mpich-slurm-patch-4.0/src/mpi/init/mpir_init.c:208 #9 0x00007f6d879832a5 in MPIR_Init_impl (argc=0x7ffd6fb5a5cc, argv=0x7ffd6fb5a5c0) at ../mpich-slurm-patch-4.0/src/mpi/init/mpir_init.c:93 #10 0x00007f6d8786388e in PMPI_Init (argc=0x7ffd6fb5a5cc, argv=0x7ffd6fb5a5c0) at ../mpich-slurm-patch-4.0/src/binding/c/init/init.c:46 #11 0x000000000040640d in main (argc=23, argv=0x7ffd6fb5ad68) at src/NeedlesMpiManagerMain.cpp:53