Fix MPI_COMM_TYPE_HW_GUIDED split

[jjhursey]

• The wrong split type was being passed to the
  ompi_comm_split_type_get_part function. It was passing the
  "original" (MPI_COMM_TYPE_HW_GUIDED) split type and not the
  "converted" (e.g., MPI_COMM_TYPE_SHARED) split type. This resulted
  in an error indicating that the split type was invalid.

[dalcinl]

@jjhursey All good from my side ([link] ignore the failure, your branch is missing a fix already in main).

[dalcinl]

@jjhursey Sorry, but last time I confirmed things were OK, I got confused.

Running mpi4py tests in one process isOK, but running in two processes is not. See the [[failure]] (https://github.com/mpi4py/mpi4py-testing/runs/7953805209?check_suite_focus=true#step:18:1236) yourself.

My best guess is that you are not handling MPI_UNDEFINED properly. Any process passing MPI_UNDEFINED must be filtered-out of the new communicator, and the calling process must return MPI_COMM_NULL.

Reproducer

from mpi4py import MPI

comm = MPI.COMM_WORLD
size = comm.Get_size()
rank = comm.Get_rank()

info = MPI.Info.Create()
info.Set("mpi_hw_resource_type", "mpi_shared_memory")

for root in range(size):
    if rank == root:
        split_type = MPI.COMM_TYPE_HW_GUIDED
    else:
        split_type = MPI.UNDEFINED

    comm = comm.Split_type(split_type, info=info)
    if rank == root:
        assert comm != MPI.COMM_NULL
        assert comm.size == 1
        assert comm.rank == 0
        comm.Free()
    else:
        assert comm == MPI.COMM_NULL

info.Free()

Output

$ mpiexec -n 1 python test.py 

$ mpiexec -n 2 python test.py 
[kw61149:1129015] Error: Mismatched info values for MPI_COMM_TYPE_HW_GUIDED
Traceback (most recent call last):
  File "/home/dalcinl/Devel/mpi4py/tmp3.py", line 16, in <module>
    comm = comm.Split_type(split_type, info=info)
  File "mpi4py/MPI/Comm.pyx", line 219, in mpi4py.MPI.Comm.Split_type
mpi4py.MPI.Exception: MPI_ERR_ARG: invalid argument of some other kind
Traceback (most recent call last):
  File "/home/dalcinl/Devel/mpi4py/tmp3.py", line 16, in <module>
    comm = comm.Split_type(split_type, info=info)
  File "mpi4py/MPI/Comm.pyx", line 219, in mpi4py.MPI.Comm.Split_type
mpi4py.MPI.Exception: MPI_ERR_ARG: invalid argument of some other kind

[jjhursey]

I see the case now. I'll work on a fix and update the unit test in ompi-tests-public. Thanks for the update!

[jjhursey]

• PR to fix comm_split_type HW_GUIDED fix MPI_UNDEFINED handling #10702
• PR to update the unit test Extend MPI_COMM_TYPE_HW_GUIDED test to include MPI_UNDEFINED ompi-tests-public#21