fiat team mailing list archive

[Anders Logg <logg@xxxxxxxxx>]

On Thu, Jan 24, 2008 at 10:06:19AM -0600, Robert Kirby wrote:
> I will also point out that, even if FIAT had these element shapes, it would be
> some work for FFC to adapt to use them.  We would be in the world of non-affine
> transformations, which means that the tensor representation in FFC would not
> work.  It can be generalized, but with some cost in run-time operation count.
> 
> Rob 

Yes, or we could just go for quadrature in that case (ffc -r quadrature).

-- 
Anders


> On Jan 24, 2008 9:15 AM, Martin Sandve Aln s <martinal@xxxxxxxxx> wrote:
> 
>     2008/1/24, Anders Logg <logg@xxxxxxxxx>:
>     > On Thu, Jan 24, 2008 at 07:57:43AM -0600, Robert Kirby wrote:
>     > > Well, FIAT really does simplices because they're hard.  Hexes and
>     rectangles
>     > > have tensor-product bases for H(div), H(curl), and H1, so you should
>     really be
>     > > doing spectral-type techniques.  See the thesis of Heintsch (sp?) at
>     NYU for
>     > > some interesting work on high order H(div) and H(curl) a few years ago.
>      Not
>     > > sure if it got published, but it was very good
>     > >
>     > > I now have a user at Sandia who wants the other shapes, so I will be
>     looking at
>     > > doing this, either in Python or else with straight tensor-products in
>     C++.  Of
>     > > course, pyramids and prisms present wrinkles of being somewhere
>     in-between.
>     >
>     > There has also been some interest in adding quads and hexes to the DOLFIN
>     > mesh library (which should not be very hard) so this might also happen
>     > (if someone has time to implement it).
>     >
> 
>     As a sidenote, SyFi supports code generation for quads and hexes (at
>     least Lagrange elements).
> 
> 
> 
>     > > On Jan 23, 2008 9:07 PM, Harish Narayanan <harish@xxxxxxxxxxx > wrote:
>     > >
>     > >     Greetings,
>     > >
>     > >     I understand from the documentation in FIAT that all its reference
>     > >     elements treat spaces as simplicial complexes. Is there an obvious
>     > >     difficulty in extending this to non-simplicial elements (assuming
>     the
>     > >     mesh is suitably generated elsewhere)?
>     > >
>     > >     I would be curious to read some literature on this topic if someone
>     were
>     > >     willing to point me to it.
>     > >
>     > >     Thanks,
>     > >     Harish
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