Node numbering for raviart-thomas element

On 02/21/2012 05:30 PM, Melanie Jahny wrote:
> New question #188414 on DOLFIN:
> https://answers.launchpad.net/dolfin/+question/188414
>
> I just have a short question concerning the Raviart-Thomas element of lowest order:
>
> How are the degrees of freedom handled for the Raviart-Thomas Element?
> First all dofs in the first triangle and then second triangle...
> Or are they handles by the number of the dof: first dofs of all triangles, second dofs of all triangles...
> And which is the first dof of a triangle, which is the second and which the third?
>
> Sorry I didn't find the answer in the documentation
> Thanks for any help!
>

For the Raviart-Thomas element of the lowest order, there is
one degree of freedom per facet (edge in 2D, face in 3D). They are
numbered according to the numbering of the edges.

(Caveat: The numbering is internal information and may be subject to
change.)

In case it is useful, here is a code snippet for examining which degrees
of freedom that are associated with which cells, and "where they are
located";

from dolfin import *

n = 1
mesh = UnitSquare(n, n)
RT = FunctionSpace(mesh, "RT", 1)

for (i, cell) in enumerate(cells(mesh)):
     print "Global dofs associated with cell %d: " % i,
     print RT.dofmap().cell_dofs(i)
     print "Dof coordinates:",
     print RT.dofmap().tabulate_coordinates(cell)

--
Marie