MPI failure with num_ranks = 3

[gzagaris]

The code fails when the number of ranks is 3.

15:34 $ mpiexec -np 3 ./fvsand.exe
Warning: PAMI CUDA HOOK disabled
Warning: PAMI CUDA HOOK disabled
Warning: PAMI CUDA HOOK disabled
rank 0, cnt 1
rank 0, dev 0, prop Tesla V100-SXM2-32GB, pci 4, 0, 4
rank 2, cnt 1
rank 2, dev 0, prop Tesla V100-SXM2-32GB, pci 6, 0, 4
rank 1, cnt 1
rank 1, dev 0, prop Tesla V100-SXM2-32GB, pci 5, 0, 4
nfaces=0
[tra015:2355786] *** An error occurred in MPI_Isend
[tra015:2355786] *** reported by process [823525377,2]
[tra015:2355786] *** on communicator MPI_COMM_WORLD
[tra015:2355786] *** MPI_ERR_RANK: invalid rank
[tra015:2355786] *** MPI_ERRORS_ARE_FATAL (processes in this communicator will now abort,
[tra015:2355786] ***    and potentially your MPI job)
[tra015:2355760] PMIX ERROR: UNREACHABLE in file server/pmix_server.c at line 2193
[tra015:2355760] 1 more process has sent help message help-mpi-errors.txt / mpi_errors_are_fatal
[tra015:2355760] Set MCA parameter "orte_base_help_aggregate" to 0 to see all help / error messages

Notice nfaces=0 above. Seems that this may be a bug with the partitioner?