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Anders Logg wrote: > On Thu, Jan 28, 2010 at 09:14:36PM +0100, Marie Rognes wrote: >> Kristian Oelgaard wrote: >>> >>> 2010/1/27 Medhi Nikbakht <m.nikbakht@xxxxxxxxxx>: >>>> On Wed, 2010-01-27 at 15:50 +0100, Marie Rognes wrote: >>>>> FFC compilation fails for >>>>> >>>>> ElementRestriction.ufl >>>> The error message says that "ElementRestriction" is not supported by >>>> FIAT. >>>> How will the restricted elements be implemented? Wouldn't it be better >>>> to support them inside FFC? >>> There are two types of restrictions supported in UFL (and the old FFC). >>> 1) Restriction onto Measure (like 'dc'), which is what you want. >>> 2) Restriction onto Cell, as for instance restricting a Lagrange >>> element defined on a 'triangle' to its facets. >>> >>> The third restriction that we might want in the future is >>> restriction onto subdomains possible in UFL but not in FFC. >>> >>> To implement 1) I think it is enough to just attach the Measure as >>> a member to the fiat_element and the simply look for it in >>> appropriate places when generating the code. That means handle it >>> in FFC.fiatinterface, could that work? >>> >>> To implement 2) I modified the return value of entity_dofs() and >>> tabulate() accordingly. To do it this way again we will need to >>> make changes in FIAT_NEW.FiniteElement and FFC.MixedElement. I'm >>> not sure it is a good idea to make FIAT_NEW.PolynomialSet aware of >>> restrictions, but I don't know enough about the FIAT internals to >>> back up this claim. >>> >> >> How about adding a class RestrictedElement that contains an element >> and (based on the restriction) >> a list of relevant basis function indices, and overrides the methods >> as FiniteElement/MixedElement? >> >> No need to make FIAT aware of this. > > This sounds good. I think I understand (somewhat) what (2) is supposed > to do, but not (1). > > And as Garth suggests, I think a better name is FacetElement. Does a > FacetElement know that it can only be integrated over facets, not the > interior, or can it? > It's possible that it could be integrated over the interior, but probably not very sensible. I think that FacetElement is a bit misleading, since what it does is just take the dofs of a cell that live on the facets. With FacetElement I think of an element of topological dim 2 embedded in 3D. Garth > -- > Anders > > > ------------------------------------------------------------------------ > > _______________________________________________ > Mailing list: https://launchpad.net/~ffc > Post to : ffc@xxxxxxxxxxxxxxxxxxx > Unsubscribe : https://launchpad.net/~ffc > More help : https://help.launchpad.net/ListHelp
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