Subject: [FFC-dev] Raviart-Thomas

From: "Garth N. Wells" <[email-masked]>
Date: Thu, 10 May 2007 23:34:11 -0600

Has anyone tried using Raviart-Thomas elements with FFC? Should they 
work (in principle)?

Garth

---

From: Anders Logg <[email-masked]>
Date: Fri, 11 May 2007 09:23:20 +0200

> Has anyone tried using Raviart-Thomas elements with FFC? Should they 

Yes, in principle, but there are still a few missing pieces.

Marie Rognes has been working hard to get support for BDM and RT
elements into FFC and we're almost there. BDM and RT are mapped from
the reference element by the Piola mapping (not the affine) so it has
involved some major work on how FFC treats basis functions. We also
need to flip the sign of basis functions on edges so two neighboring
triangles agree on the direction of the normal. The Piola mapping is
there now and seems to work fine. The flipping of signs on edges has
also been implemented, but we still need to track down a few bugs.
(In particular in the simplification of forms to precontract terms
containing dx_i/dX_k dX_k/dx_j = \delta_{ij} that may pop out when you
take the derivative of a Piola-mapped basis function.)

/Anders