Function.assign in Dolfinx

[cvillette]

Hi there,

Is there an equivalent to function.assign() method in dolfinx?
Would something along the lines of
receiver_function=function_to_be_assigned.copy() do the trick?

Many thanks

[dokken]

See for instance:

Copying a function in dolfinx

For now you can make a workaround as follows: func = Function(V) copy = Function(V) copy.x.array[:] = func.x.array There is an issue registered on github, and a proposed fix is added in: Fix function copy option by jorgensd · Pull Request #1916 · FEniCS/dolfinx · GitHub

Or

How to correctly assign values to mixed elements in FEniCS-X?

@JLorenteMacias Consider the following up to date example: import dolfinx from mpi4py import MPI import dolfinx.io import ufl import numpy as np mesh = dolfinx.mesh.create_unit_square(MPI.COMM_WORLD, 10, 10) el = ufl.FiniteElement("CG", mesh.ufl_cell(), 1) mel = ufl.MixedElement([el, el]) V = dolfinx.fem.FunctionSpace(mesh, mel) num_subs = V.num_sub_spaces spaces = [] maps = [] for i in range(num_subs): space_i, map_i = V.sub(i).collapse() spaces.append(space_i) maps.append(map_i)…

[cvillette]

Thank you!
What if the assignment holds only for a subfunction as below in dolfin?

assign(V1function, V2function.sub(0))

I have tried the below which returned ‘NotImplementedError: Cannot take length of non-vector expression.’

space_0, map_0 = V2function.sub(0).collapse()
        V1function.x.array[:]=np.arange(len(map_0))

[dokken]

I dont follow. Please make a minimal code example that produces this error message. It is not clear what V1function and V2function is.

[cvillette]

Sorry for the confusion. I was manipulating a function that defined three fields (V2function), of which I wanted to assign only one to another function (V1function).
I solved it using:

V1function.x.array[:] = V2function.sub(0).collapse().x.array

Many thanks