dolfin team mailing list archive

[Anders Logg <logg@xxxxxxxxx>]

On Mon, Nov 03, 2008 at 11:22:26AM +0000, Garth N. Wells wrote:
> 
> 
> Anders Logg wrote:
> > On Sun, Nov 02, 2008 at 06:29:25PM +0000, Garth N. Wells wrote:
> >>
> >> Anders Logg wrote:
> >>> On Sun, Nov 02, 2008 at 05:52:21PM +0000, Garth N. Wells wrote:
> >>>> Do we want to insist that Dirichlet bc functions that do not appear 
> >>>> inside a form are constructed with a FunctionSpace? DirichletBC is 
> >>>> supplied with a FunctionSpace, so if the bc Function does not have a 
> >>>> FunctionSpace, we could attach one automatically.
> >>>>
> >>>> Garth
> >>>> _______________________________________________
> >>>> DOLFIN-dev mailing list
> >>>> DOLFIN-dev@xxxxxxxxxx
> >>>> http://www.fenics.org/mailman/listinfo/dolfin-dev
> >>> I think this is already handled. Look in the Poisson demo. It uses a
> >>> Constant to set the BC and it does not have a FunctionSpace attached
> >>> to it. The DirichletBC class now uses its own FunctionSpace rather
> >>> than the one that the Function has (if any). There is a check (in
> >>> DirichletBC::check()) that checks that the FunctionSpace for the
> >>> Function is the same as the one in the DirichletBC.
> >>>
> >> It works for Constant, but not for Functions. I was getting an error 
> >> when Function::interpolate is called. Function::interpolate leads to 
> >> eval being called, in which case there is a test for the FunctionSpace 
> >> which fails. Constant provides its own eval and therefore doesn't have a 
> >> problem.
> >>
> >> For now, I've added a test in DirichletBC for the FunctionSpace. What we 
> >> can add is an attach function if there is no FunctionSpace associated.
> >>
> >> Garth
> > 
> > In which demo does this show up? Is there a simple way I can comment
> > something out to reproduce the error so I understand what goes wrong?
> >
> 
> Look at /demo/nls/nonlinearpoisson/cpp.
> 
> If you change
> 
>    DirichletBoundaryCondition g(V, t);
> 
> to
> 
>    DirichletBoundaryCondition g(t);
> 
> it will break down.
> 
> Garth

ok I see the problem now.

The problem is a user may choose to either overload a scalar eval
function or a tensor eval function and we need to decide which one
after the callback from ufc::function::evaluate(). If the
FunctionSpace is not known, we can't decide which one to pick.

If we insist that one should be able to pass a Function without a
FunctionSpace to a DirichletBC, then we must remove the scalar eval
function.

-- 
Anders

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