Hi Lawrence,

It seems to work fine as well. Here is the output:

(firedrake) simone@simone:~/firedrake/src/firedrake$ pytest -s -m parallel tests/regression/test_identity.py
=========================================================== test session starts ============================================================
platform linux -- Python 3.6.8, pytest-4.6.3, py-1.8.0, pluggy-0.12.0
rootdir: /home/simone/firedrake/src/firedrake, inifile: setup.cfg
plugins: xdist-1.29.0, forked-1.0.2
collected 8 items / 4 deselected / 4 selected

tests/regression/test_identity.py ... [100%] [100%]
1 passed in 27.72 seconds

1 passed in 27.72 seconds1 passed in 27.72 seconds

... [100%]

1 passed in 11.00 seconds
1 passed in 11.00 seconds
... [100%]

1 passed in 6.08 seconds
1 passed in 6.08 seconds
... [100%]

1 passed in 6.14 seconds1 passed in 6.14 seconds

.

================================================= 4 passed, 4 deselected in 59.03 seconds ==================================================
(firedrake) simone@simone:~/firedrake/src/firedrake$ pytest -s -m 'not parallel' tests/regression/test_identity.py
=========================================================== test session starts ============================================================
platform linux -- Python 3.6.8, pytest-4.6.3, py-1.8.0, pluggy-0.12.0
rootdir: /home/simone/firedrake/src/firedrake, inifile: setup.cfg
plugins: xdist-1.29.0, forked-1.0.2
collected 8 items / 4 deselected / 4 selected

tests/regression/test_identity.py ....

================================================= 4 passed, 4 deselected in 16.31 seconds ==================================================

Thank you so much, have a wonderful day.

Best regards,

Simone

On Fri, Jun 21, 2019 at 9:16 AM Lawrence Mitchell <wence@gmx.li> wrote:

> On 21 Jun 2019, at 14:40, Simone Puel <spuel@utexas.edu> wrote:
>
> Hi Lawrence,
>
> Thank you so much for your help. Here are the output of the commands:
>
> (firedrake) simone@simone:~/firedrake/src/firedrake$ mpiexec -n 4 python -c "from mpi4py import MPI; print(MPI.COMM_WORLD.rank)"
> 1
> 3
> 2
> 0
> (firedrake) simone@simone:~/firedrake/src/firedrake$ mpiexec -n 4 python -c "from petsc4py import PETSc; print(PETSc.COMM_WORLD.rank)"
> 0
> 3
> 1
> 2
> (firedrake) simone@simone:~/firedrake/src/firedrake$ mpiexec -n 4 python -c "from firedrake import *; mesh = UnitSquareMesh(3, 3); mesh.init(); print(mesh.comm.rank)"
> 0
> 1
> 2
> 3

OK, so some minimal things work fine.

How about:

pytest -s -m parallel tests/regression/test_identity.py

and

pytest -s -m 'not parallel' tests/regression/test_identity.py

Thanks,

Lawrence