Hi, I am trying to compute the gradient of the test function at a point. I use Expression for this and here is the MWE;

```
from dolfinx.cpp.geometry import determine_point_ownership
from dolfinx.fem import Expression, FunctionSpace
from dolfinx.mesh import create_unit_cube
from mpi4py import MPI
import numpy as np
import ufl
nx = ny = nz = 10
mesh = create_unit_cube(MPI.COMM_WORLD, nx,ny,nz)
point = np.array([0.5,0.5,0.5])
V = FunctionSpace(mesh, ('CG',1))
gdim = mesh.geometry.dim
num_dofs_x = mesh.geometry.dofmap[0].size # NOTE: Assumes same cell geometry in whole mesh
t_imap = mesh.topology.index_map(mesh.topology.dim)
num_cells = t_imap.size_local + t_imap.num_ghosts
x_dofs = mesh.geometry.dofmap.reshape(num_cells, num_dofs_x)
_, _, owning_points, cell = determine_point_ownership( mesh._cpp_object, point, 1e-10)
point_ref = np.zeros((len(cell), mesh.geometry.dim), dtype=mesh.geometry.x.dtype)
if len(cell) > 0: # Only add contribution if cell is owned
cell_geometry = mesh.geometry.x[x_dofs[cell[0]], :gdim]
cmap = mesh.geometry.cmaps[0]
x_ref = cmap.pull_back([point[:gdim]], cell_geometry)
n = ufl.as_vector([0,0,1])
expr = ufl.inner(ufl.grad(ufl.TestFunction(V)), n)
E = Expression(expr, x_ref)
d_dphi_j = E.eval(mesh, cell)[0]
else:
pass
```

It works perfectly fine in serial, but freezes in parallel? Is is because eval function of Expression is expensive to run?