Simulations can take a long time, and I’d like to see if the results are heading in the right direction without waiting for it to finish. This is why I’d like to render the current state using pyvista every n simulation steps. However, I’m having trouble getting this to work with MPI.

Consider the following minimal example:

```
from mpi4py import MPI
from dolfinx import *
comm = MPI.COMM_WORLD
nx = 20
msh = mesh.create_rectangle(comm, points=((-1.5, -1.0), (1.5, 1.0)), n=(nx, nx), cell_type=mesh.CellType.triangle)
V = fem.FunctionSpace(msh, ("CG", 1))
uh = fem.Function(V)
uh.interpolate(lambda x: x[0]+x[1])
if comm.rank == 0:
try:
import pyvista
cells, types, x = plot.create_vtk_mesh(msh)
grid = pyvista.UnstructuredGrid(cells, types, x)
grid.point_data["u"] = uh.x.array.real
grid.set_active_scalars("u")
plotter = pyvista.Plotter()
plotter.add_mesh(grid, show_edges=True)
plotter.show()
except ModuleNotFoundError:
print("'pyvista' is required to visualise the solution")
print("Install 'pyvista' with pip: 'python3 -m pip install pyvista'")
```

Running this without MPI or with `mpirun -n 1`

gives:

However, when I run the code with `mpirun -n 4`

:

Only the subdomain of rank 0 gets rendered, which shouldn’t be a surprise. But how can I fix this? What’s the easiest way to piece together the function from all rank’s subdomains?