ffc team mailing list archive

[Anders Logg <logg@xxxxxxxxx>]

These are functions that are best treated as Functions (coefficients).
We already have MeshSize as a default function in DOLFIN and we will
soon have (probably this week) a function FacetNormal that we will use
for DG.

The mapping we need to make is from FFC to DOLFIN so that one can
write h = MeshSize() in FFC without having to declare the
corresponding function in DOLFIN.

/Anders


On Mon, Dec 04, 2006 at 03:26:56PM +0100, Johan Hoffman wrote:
> In connection with the dof-discussion; could we add geometry info to FFC?
> Like diameter, normals, tangents etc. From what I understand this info is
> already in FIAT, so it would amount to adding a mapping to FFC?
> 
> /Johan
> 
> 
> 
> 
> > Anders Logg wrote:
> >> On Mon, Dec 04, 2006 at 02:14:51PM +0100, Garth N. Wells wrote:
> >>> Could we add something to FFC to describe where the various degrees of
> >>> freedom live (on vertices, edges, internal)?
> >>>
> >>> Garth
> >>
> >> Yes we could, but I'd rather not. Why do we need it? I'd prefer if
> >> DOLFIN did not know anything about dofs, other than how to reorder
> >> them.
> >>
> >
> > Not sure that it's this simple if you want to assemble some terms
> > block-wise. Also, for parallel assembly we might need to know where dofs
> > lie. I'm still thinking about this so I can't be concrete in what's
> > needed just yet.
> >
> >> I see two options:
> >>
> >>  1. Reorder the dofs computed by FFC, not knowing why and how they
> >>     are numbered.
> >>
> >
> > This is one option I'm considering. Just take the FFC numbering, and run
> > a renumbering algorithm over it to minimise bandwidth.
> >
> >>  2. Compute a different mapping in FFC.
> >>
> >
> > This could be difficult as it depends on properties of the mesh,
> > partition, etc. I think that this should remain simple.
> >
> >> I can be convinced otherwise of course, but I don't understand why
> >> this is needed.
> >>
> >> /Anders
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> >>
> >
> >
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> 
> 
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