Is Anyone Here Successfully Using OpenMPI with Ubuntu 18.04?

[EdH]

I've been using OpenMPI with 16.04 and earlier for years, but I can't get it to work with slaves at all on 18.04. It will run fine on any of the machines with localhost only, but as soon as I try to add a slave machine it segfaults.

$ mpirun -np 4 ../mpitest
Task 0: Sent message 103 to task 1 with tag 1
Task 0: Sent message -58 to task 2 with tag 1
Task 0: Sent message 105 to task 3 with tag 1
Task 2: Received 1 char(s) (-58) from task 0 with tag 1 
Task 3: Received 1 char(s) (105) from task 0 with tag 1 
Task 1: Received 1 char(s) (103) from task 0 with tag 1

$ mpirun -np 8 --hostfile ../hostfile ../mpitest
[math20:29182] *** Process received signal ***
[math20:29182] Signal: Segmentation fault (11)
[math20:29182] Signal code:  (128)
[math20:29182] Failing at address: (nil)
[math20:29182] [ 0] /lib/x86_64-linux-gnu/libpthread.so.0(+0x12890)[0x7fbea4796890]
[math20:29182] [ 1] /lib/x86_64-linux-gnu/libc.so.6(__libc_malloc+0x197)[0x7fbea442a207]
[math20:29182] [ 2] /lib/x86_64-linux-gnu/libc.so.6(__strdup+0x1a)[0x7fbea44309ba]
[math20:29182] [ 3] /usr/lib/x86_64-linux-gnu/libopen-rte.so.20(+0x2897f)[0x7fbea4c7d97f]
[math20:29182] [ 4] /usr/lib/x86_64-linux-gnu/libopen-rte.so.20(orte_util_add_hostfile_nodes+0xc1)[0x7fbea4c7e3f1]
[math20:29182] [ 5] /usr/lib/x86_64-linux-gnu/libopen-rte.so.20(orte_plm_base_setup_virtual_machine+0xc4f)[0x7fbea4cacedf]
[math20:29182] [ 6] /usr/lib/x86_64-linux-gnu/openmpi/lib/openmpi/mca_plm_rsh.so(+0x5e86)[0x7fbe9e43fe86]
[math20:29182] [ 7] /usr/lib/x86_64-linux-gnu/libopen-pal.so.20(opal_libevent2022_event_base_loop+0xdc9)[0x7fbea4a09209]
[math20:29182] [ 8] mpirun(+0x74a3)[0x561386b7b4a3]
[math20:29182] [ 9] mpirun(+0x5aea)[0x561386b79aea]
[math20:29182] [10] /lib/x86_64-linux-gnu/libc.so.6(__libc_start_main+0xe7)[0x7fbea43b4b97]
[math20:29182] [11] mpirun(+0x59ea)[0x561386b799ea]
[math20:29182] *** End of error message ***
Segmentation fault (core dumped)