# Issue with MPI and UnitSquareMesh in python

**URL:** <https://fenicsproject.discourse.group/t/issue-with-mpi-and-unitsquaremesh-in-python/16723>\
**Category:** General\
**Created:** [January 13, 2025, 1:02pm UTC](https://fenicsproject.discourse.group/t/issue-with-mpi-and-unitsquaremesh-in-python/16723 "2025-01-13T13:02:45Z")\
**Posts on this page:** 3\
**Page:** 1

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**Author:** ![babak.maboudi](https://avatars.discourse-cdn.com/v4/letter/b/e36b37/32.png) [@babak.maboudi](https://fenicsproject.discourse.group/u/babak.maboudi)\
**Post date:** [January 13, 2025, 1:02pm UTC](https://fenicsproject.discourse.group/t/issue-with-mpi-and-unitsquaremesh-in-python/16723/1 "2025-01-13T13:02:45Z")

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Hello,

I try to use using FEniCS in an MPI environment. the following code gives me errors:

```auto
import dolfin as dl
from mpi4py import MPI

mesh = dl.UnitSquareMesh(MPI.COMM_SELF, 127, 127)

```

and the error is

```auto
  File "/zhome/93/8/155259/Paper-PAT-RTO/applications/pat_2D/MAP_estimate.py", line 38, in run_MAP
    mesh = dl.UnitSquareMesh(MPI.COMM_SELF, N_points, N_points)
           ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
TypeError: __init__ (): incompatible constructor arguments. The following argument types are supported:
    1. dolfin.cpp.generation.UnitSquareMesh(nx: int, ny: int, diagonal: str = 'right')
    2. dolfin.cpp.generation.UnitSquareMesh(comm: dolfin.cpp.MPICommWrapper, nx: int, ny: int, diagonal: str = 'right')

```

I don’t know how to wrap the MPI communicator into a FEniCS format? Any ideas?

---

<div class="post-metadata">

**Author:** ![dokken](https://yyz2.discourse-cdn.com/free1/user_avatar/fenicsproject.discourse.group/dokken/32/1560_2.png) [@dokken](https://fenicsproject.discourse.group/u/dokken)\
**Post date:** [January 13, 2025, 1:16pm UTC](https://fenicsproject.discourse.group/t/issue-with-mpi-and-unitsquaremesh-in-python/16723/2 "2025-01-13T13:16:12Z")

</div>

In legacy DOLFIN, you should use

```python
dolfin.MPI.comm_self

```

rather than a `mpi4py`-communicator directly.

---

<div class="post-metadata">

**Author:** ![babak.maboudi](https://avatars.discourse-cdn.com/v4/letter/b/e36b37/32.png) [@babak.maboudi](https://fenicsproject.discourse.group/u/babak.maboudi)\
**Post date:** [January 13, 2025, 1:19pm UTC](https://fenicsproject.discourse.group/t/issue-with-mpi-and-unitsquaremesh-in-python/16723/3 "2025-01-13T13:19:39Z")

</div>

Thank you! Solved the issue