Referencing solution array when using MixedElement within MixedElement

1

Hello,

I have a problem with five unknowns; four being concentration values, one being an electric potential. The four concentrations have known Dirichlet conditions, while the electric potential has one Dirichlet and one non-zero Nuemann, which forces current to zero. To treat the Nuemann condition in the weak form, a separate subdomain from the four concentration subdomains is defined:

P1 = FiniteElement(‘CG’, triangle, 1)
element = MixedElement([P1, P1, P1, P1])
V = FunctionSpace(mesh, element)
V_phi = FunctionSpace(mesh, P1)
element2 = MixedElement([element, P1])
W = FunctionSpace(mesh, element2)

Although, now when trying to update the trial functions, using the assign function, I get the error:

AttributeError: ‘ListTensor’ object has no attribute ‘assign’

Also, when trying to access the solution array components using .vector() I get:

AttributeError: ‘ListTensor’ object has no attribute ‘vector’

So from here I attempt to extract dof values from the solution tensor indices and get:

AttributeError: ‘Indexed’ object has no attribute ‘vector’

Could someone please help me understand the situation here? Is there a certain way to go about handling MixedElement within MixedElement?

Thank you,

2

Please add the actual code that are causing your errors. Please strip out all code not needed to reproduce the error. Also use 3x` encapsulation of the code.

3

Sorry for not posting my code, as the problem has been resolved.

I had four unknowns with similar boundary conditions, then a fifth unknown with unique boundary conditions. It is from this that I assumed there needed to be some special treatment. I was confused in trying to lump the fifth unknown as a mixed element with the other unknowns. I simply defined it as it’s own space and problem to be solved in an alternating fashion with the other simultaneous weak forms.

Thank you for your time.

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