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[Patrick Riesen <question111370@xxxxxxxxxxxxxxxxxxxxx>]

Question #111370 on DOLFIN changed:
https://answers.launchpad.net/dolfin/+question/111370

    Status: Open => Answered

Patrick Riesen proposed the following answer:
jhameed2@xxxxxxxxxxxx wrote:
> New question #111370 on DOLFIN:
> https://answers.launchpad.net/dolfin/+question/111370
> 
> Hello,
> 
> Is there a nice way to initialize a mixed element function with two of its sub-functions. Specifically,
> 
> element = FiniteElement("Lagrange", tetrahedron, 1)
> vecElement = element + element
> u = Coefficient(vecElement)
> 
> Now, in the code, I want to do this:
> 
> u[0] = func1
> u[1] = func2

you can extract the sub-dofmaps of u corresponding to u[0] and u[1] and 
then in a cell iteration loop place the values of func1 and func2 into 
u[0] and u[1] using subdofmap.tabulate_dofs() and func1.vector().get() / 
u.vector().set() i guess ...

patrick

> 
> where func1 and func2 are functions of "element". I want to do this to initialize u in a newton solver. The above code doesnt copy the values to u's sub-functions. Another way of framing my question could be, given two subfunctions, how do I combine them into a mixed-function?
> 
> I can think of some workarounds, e.g. initializing the function "u" as a vector function using an Expression class, but thats not as clean a solution as I would like. I would like to initialize u, given two input functions which are scalar.
> 
> Thanks,
> -Jehanzeb
>

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