ffc team mailing list archive

[Kristian Oelgaard <k.b.oelgaard@xxxxxxxxx>]

On 28 January 2010 21:14, Marie Rognes <meg@xxxxxxxxx> 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?

Yes, that would be one option and we already have MixedElement and RestrictedElement is much the same thing (we should change the name in UFL). Although, one objective of this re-write of FFC was to remove as much as possible w.r.t. FiniteElement.

We could make the RestrictedElement a child class of FIAT.FiniteElement, that should be OK since FFC uses FIAT as the backend for finite elements. Then we just need to modify a few member functions.

Kristian

> No need to make FIAT aware of this.
>
> --
> Marie
>
>
> > I'm not really sure how to handle the restriction onto subdomains, but it
> > should most likely be implemented in FFC.
> >
> > Kristian
> >
> > > Mehdi
> > >
> > > >    QuadratureElement.ufl
> > > >    TensorWeightedPoisson.ufl
> > > >
> > > > Running test programs fails for
> > > >
> > > >    P5tet.bin    (Segmentation faults after evaluate_basis(0, ...)
> > > >
> > > > Differences in output
> > > >
> > > >    evaluate_basis*
> > > >
> > > >    FacetIntegrals.out      (missing value in generated code (many))
> > > >    SubDomain.out            (missing value in generated code
> > > > (tabulate_tensor))
> > > >
> > > >
> > > > Others:
> > > >
> > > >    tabulate_entity_dofs     (errors thrown are all wrong. Marie will
> > > > fix)
> > > >
> > > >
> > > > --
> > > > Marie
> > > >
> > > >
> > > > _______________________________________________
> > > > Mailing list: https://launchpad.net/~ffc
> > > > Post to     : ffc@xxxxxxxxxxxxxxxxxxx
> > > > Unsubscribe : https://launchpad.net/~ffc
> > > > More help   : https://help.launchpad.net/ListHelp
> > >
> > >
> > > _______________________________________________
> > > Mailing list: https://launchpad.net/~ffc
> > > Post to     : ffc@xxxxxxxxxxxxxxxxxxx
> > > Unsubscribe : https://launchpad.net/~ffc
> > > More help   : https://help.launchpad.net/ListHelp

Attachment: signature.asc
Description: OpenPGP digital signature