Quoting "Garth N. Wells" <[email protected]>: > > > Johan Hake wrote: > > On Wednesday 19 August 2009 15:12:21 Garth N. Wells wrote: > >> Johan Hake wrote: > >>> On Wednesday 19 August 2009 14:57:20 Garth N. Wells wrote: > >>>> Johan Hake wrote: > >>>>> 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 > >>>> Do you mean to then restrict mixed? I'm already doing > >>> Precisely. > >>> > >>> After a second thought I think that doing it in the constructor is more > >>> clean. Makes life simpler. Is this also possible i UFL, I mean: > >>> > >>> e = FiniteElement("CG",cell,0,"facet")
No, and the above element is not even legal, for CG the degree must be >=1 :) You have to use the __getitem__ operator of FiniteElementBase a = element[cell] or do e = ElementRestriction(element, domain) where domain is either a Measure or Cell and only Cell is supported in FFC. In FFC I might consider adding a default 'domain=None' to the argument list of a FiniteElement since it will make some things easier. Maybe we should add this in UFL too? Kristian > >>> Should it? > >> Is that a PyDOLFIN finite element? If it is, then yes, that's how it > >> should work. > > > > I meant UFL.FiniteElement. > > > > OK. I don't know if that is the syntax. Kristian will know. > > >> Somewhat related, it's a bit annoying in PyDOLFIN that the code is > >> recompiled when the mesh is changed. Can we avoid this? Should one then > >> create a finite element and a dof map with which to initialise the > >> Pythin FunctionSpace? > > > > Do you mean when one has refined a mesh? > > Yes, or just changed from one simulation to the next. > > As far as I understand it is the > > reason for this that we need to recompute the dofmap. > > > > In C++ we create a dolfin::FunctionSpace from a dolfin::FiniteElement, a > dolfin::DofMap and a dolfin::Mesh. The FiniteElement and DofMap are > created with a ufc::finite_element and a ufc::dof_map, respectively. > > In the Python interface, in addition to what we have now, we would need > FiniteElement and DofMap objects, with which we could create a > FunctionSpace (together with a Mesh). Then, hopefully we could avoid > recompilation when just the mesh is changed. > > Garth > > > How is this done in the C++ interface. > > > > Johan > > > >> Garth > >> > >>> Johan > >>> > >>>> V0 = FunctionSpace(mesh, "CG", 3, "facet") > >>>> V1 = FunctionSpace(mesh, "DG", 3) > >>>> > >>>> mixed = V0 + V1 > >>>> > >>>> and it works. This type of restriction (we'll need to sort out our > >>>> terminology) impacts the dofmap, which I why I think it needs to be > >>>> involved in the creation of the function space. > >>>> > >>>> Garth > >>>> > >>>>> 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 > >>>>>>>> [email protected] > >>>>>>>> http://www.fenics.org/mailman/listinfo/dolfin-dev > >>>>>>> --------------------------------------------------------------------- > >>>>>>> -- - > >>>>>>> > >>>>>>> _______________________________________________ > >>>>>>> DOLFIN-dev mailing list > >>>>>>> [email protected] > >>>>>>> http://www.fenics.org/mailman/listinfo/dolfin-dev > >>>>>> _______________________________________________ > >>>>>> DOLFIN-dev mailing list > >>>>>> [email protected] > >>>>>> http://www.fenics.org/mailman/listinfo/dolfin-dev > > > _______________________________________________ > FFC-dev mailing list > [email protected] > http://www.fenics.org/mailman/listinfo/ffc-dev > _______________________________________________ DOLFIN-dev mailing list [email protected] http://www.fenics.org/mailman/listinfo/dolfin-dev
