MPI-4: Broken communicator out of MPI_Comm_create_from_group()

[dalcinl]

I'm using current git main branch, configuring with debug arguments and --with-<dep>=internal for all <dep>s.

$ git submodule status
 26ff1684378e1c5859e377249a3e78f287b04216 3rd-party/openpmix (v1.1.3-3523-g26ff1684)
 47b5ad1653123e984a644ef84b9a7aaf4e9b5fb3 3rd-party/prrte (psrvr-v2.0.0rc1-4355-g47b5ad1653)

Looks like something weird is going on with MPI_Comm_create_from_group().

This is a trivial reproducer using mpi4py. Clarification: The C-level call to MPI_Comm_create_from_group() uses arguments stringtag="org.mpi4py", info=MPI_INFO_NULL, and errhandler=MPI_ERRORS_RETURN.

from mpi4py import MPI
group = MPI.COMM_SELF.Get_group()
comm = MPI.Intracomm.Create_from_group(group)
cval = MPI.Comm.Compare(MPI.COMM_SELF, comm)
assert cval == MPI.CONGRUENT

However, the final assert line is never reached, instead I get:

$ python /tmp/test.py 
Traceback (most recent call last):
  File "/tmp/test.py", line 4, in <module>
    cval = MPI.Comm.Compare(MPI.COMM_SELF, comm)
  File "mpi4py/MPI/Comm.pyx", line 111, in mpi4py.MPI.Comm.Compare
mpi4py.MPI.Exception: MPI_ERR_ARG: invalid argument of some other kind

MPI_Comm_compare() fails on the output communicator from MPI_Comm_create_from_group().

[jsquyres]

@hppritcha is likely the one we need to look at this, but he's out this week.

[hppritcha]

taking a look at this....

[hppritcha]

closed via #10495 and #10502

[dalcinl]

@hppritcha Looks like you fixed the issue for INTRAcommunicators, but INTERcommunicators are still broken.

Reproducer:

git clone --branch  update/MPI4-openmpi https://github.com/mpi4py/mpi4py.git
cd mpi4py
make # should build in place, assumes `mpicc` can be found via $PATH
mpiexec -n 2 python test/main.py -i test_comm_inter -k testCreateFromGroups

Output:

...
======================================================================
ERROR: testCreateFromGroups (test_comm_inter.TestIntercomm)
----------------------------------------------------------------------
Traceback (most recent call last):
  File "/home/dalcinl/Devel/mpi4py/test/test_comm_inter.py", line 76, in testCreateFromGroups
    ccmp = MPI.Comm.Compare(self.INTERCOMM, intercomm)
  File "mpi4py/MPI/Comm.pyx", line 111, in mpi4py.MPI.Comm.Compare
mpi4py.MPI.Exception: MPI_ERR_ARG: invalid argument of some other kind
...

[hppritcha]

there are some known problems with the intercomm_create_from_groups function that need to be fixed. I'll open a separate issue to track that.