ffc team mailing list archive

[Johan Hake <hake@xxxxxxxxx>]

On Wednesday 19 August 2009 14:21:12 Garth N. Wells wrote:
> 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
>
> I see now that we need to have the above option since the everything
> (e.g. the dof map) is created and compiled inside functionspace.py.

We could implement it in FunctionSpaceBase, as an operator, returning a new 
FunctionSpaceBase, with the restricted element as arguemnt.

However my concerns go to a sub space of a restricted mixed space (if such 
exists) see the other email. 

If we go for 1, (as you have already done ;) ), we cannot create a restricted 
mixed space using the addition syntax.

  mixed = V1 + V2

If we want a restricted mixed space we need to use the constructor.

  mixed = MixedFunctionSpace((V1,V2),restriction="facet")

Johan

> Garth
>
> > or
> >
> >     V_dg = FunctionSpace(mesh, "DG", 3)
> >     V_cg = FunctionSpace(mesh, "CG", 3)
> >
> >     mixed = V_cg["scalar"] + V_dg
> >
> > Garth
> >
> >> Kent
> >>
> >> _______________________________________________
> >> DOLFIN-dev mailing list
> >> DOLFIN-dev@xxxxxxxxxx
> >> http://www.fenics.org/mailman/listinfo/dolfin-dev
> >
> > ------------------------------------------------------------------------
> >
> > _______________________________________________
> > DOLFIN-dev mailing list
> > DOLFIN-dev@xxxxxxxxxx
> > http://www.fenics.org/mailman/listinfo/dolfin-dev
>
> _______________________________________________
> DOLFIN-dev mailing list
> DOLFIN-dev@xxxxxxxxxx
> http://www.fenics.org/mailman/listinfo/dolfin-dev