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Message #19331
Re: [Question #122406]: assemble VariationalProblem members
On 23/08/10 18:26, Dominique wrote:
New question #122406 on DOLFIN:
https://answers.launchpad.net/dolfin/+question/122406
Hello,
In Python, I am trying to encapsulate a problem stated in weak form:
a(v,u) = L(v) for all v in V (nonlinear or not). The first option
that came to my mind is to use
problem = VariationalProblem(a, L, bc)
Now I can do
A = assemble(a, mesh=mesh) ; b = assemble(L, mesh=mesh) ;
bc.apply(A,b)
You should just do
A = assemble(a)
b = assemble(L)
but I cannot do
A = assemble(problem.a, mesh=mesh) ; b = assemble(problem.L,
mesh=mesh)
Somehow assemble() doesn't want to work on the members of 'problem'.
It returns:
Unable to convert object to a UFL form:<dolfin.fem.form.Form; proxy
of<Swig Object of type 'dolfin::Form *' at 0x99fa350> > ERROR: An
unexpected error occurred while tokenizing input The following
traceback may be corrupted or invalid The error message is: ('EOF in
multi-line statement', (4, 0)) [...] UFLException: Unable to convert
object to a UFL form:<dolfin.fem.form.Form; proxy of<Swig Object of
type 'dolfin::Form *' at 0x99fa350> >
I don't *have* to use VariationalProblem to encapsulate the data, but
I need to be able to get A and b somehow. I saw in a previous post
that one could subclass NonlinearProblem. That would be fine for me,
but I have 2 questions:
1) Is there a recommended way to encapsulate a and L so that they can
be assemble()'d?
2) Could you please show an example usage of calling problem.F and
problem.J when problem is a VariationalProblem? That just might
answer the question.
You don't want to put a and L in a VariationalProblem if you're not
going to use the member function of VariationalProblem. Just work with a
and L directly.
Garth
Thanks in advance! Dominique
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