dolfin team mailing list archive

[Johan Hake <hake@xxxxxxxxx>]

On Wednesday 19 August 2009 13:31:56 Garth N. Wells wrote:
> Kent Andre wrote:
> >> Not sure what we have to do actually. I suppose I want get any clue from
> >> the
> >>
> >>   demo/function/restriction
> >>
> >> demo?
> >>
> >> I see that Kent has modified the dolfin.FunctionSpace to reflect the
> >> present (broken) implementation of restriction, anything in that line?
> >> Should such an implementation has been done in FunctionSpaceBase instead
> >> of FunctionSpace? Kent?
> >>
> >> Johan
> >
> > This restriction is different in the sense that the restriction is made
> > by the standard element on a sub mesh.
> >
> > The restriction in focus now is on the complete mesh but for only
> > a part of the element.
> >
> > Combined, these two features will be very powerful.  I guess the
> > sub-mesh restriction stuff is broken due to the parallel mesh.
>
> I've attached an example solver. To make it work for P^k with k > 2 we
> need to restrict some functions to cell facets. Using FFC, we do
>
>      scalar  = FiniteElement("Lagrange", "triangle", 3)
>      dscalar = FiniteElement("Discontinuous Lagrange", "triangle", 3)
>
>      # This syntax restricts the space 'scalar' to cell facets.
>      mixed = scalar["facet"] + dscalar
>
> In PyDOLFIN we could do
>
>      V_dg = FunctionSpace(mesh, "DG", 3)
>      V_cg = FunctionSpace(mesh, "CG", 3, "facet")
>
>      mixed = V_cg + V_dg
>
> or
>
>      V_dg = FunctionSpace(mesh, "DG", 3)
>      V_cg = FunctionSpace(mesh, "CG", 3)
>
>      mixed = V_cg["scalar"] + V_dg

I am inclined to go for alternative 1, but I am a bit confused what a 
restricted MixedFunctionSpace is, and what the supspaces of such a Space would 
be.

Our FunctionSpace design in PyDOLFIN is a bit fragile so we need to think of a 
robust way to implement this.


Johan


> Garth
>
> > Kent
> >
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