ffc team mailing list archive

[Kristian Oelgaard <k.b.oelgaard@xxxxxxxxxx>]

Quoting Shawn Walker <walker@xxxxxxxxxxxxxxx>:

> Hello.  I would like to know how hard it would be to modify FFC (and UFL)
> to do the following.
>
> Here is the sample .ufl file:
>
> Poisson.ufl
> ------------------------------------------
> element = FiniteElement("Lagrange", "triangle", 2)
> vector  = VectorElement("Lagrange", "triangle", 2)
>
> v = TestFunction(element)
> u = TrialFunction(element)
> f = Function(element)
> G = Function(vector)
>
> a = inner(grad(v), grad(u))*dx
> L = v*f*dx
> ------------------------------------------
>
> And I would like to do the following in C++:
>
> // in C++
> a.G = Some_Function;
>
> Basically, I just want to attach to `a' some external function that does
> NOT appear in the bilinear form.  How hard would that be?  I'm not sure
> what the UFL syntax should be.  This is for the higher order mesh stuff.

I'm sure it's possible, but does it make sense that a has a function attached on
which it does not depend?
The code that will be generated from this form, will not use G in any way, so
how do you plan on using it? For higher order mesh stuff, should one not just
use:
triangle = Cell("triangle", 2) # Cell() is defined in geometry.py in UFL

and then define the finite element as:

element = FiniteElement("CG", triangle, 1)

maybe we should/could attach the function G to the cell if you intend to use
this to compute the geometry?

Kristian

> - Shawn
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