ffc team mailing list archive

[Shawn Walker <walker@xxxxxxxxxxxxxxx>]

I think you are right.  I would propose the following:

1. Add a meshfunction to the mesh.xml file.  The name of it will 
correspond to a new enum variable in ufc::cell.  For example, say we have 
piecewise quadratics for the local map, so we call it "P2_map".  Maybe
later this could be made a more permanent xml data type, but for now this 
should be ok.  The mesh function would just be a vector lagrange 2nd 
order function.  And there would also be a boolean function on each cell 
to say whether the element is straight or not.  This of course rules out 
mixing curved types, i.e. having P3 and P2 in the same mesh.  But I am ok 
with that for now.

2. In ufc::cell, we have another enum variable called "map_type":

enum map_type {P1_map, P2_map, P3_map, etc...}

Of course, this will only be for lagrange type polynomial maps.  But this 
enum variable can have other types (i.e. iso-geometric).  We then create a 
variable "map_type cell_map_type;"

3. When the mesh is read in, and the element is created, I think the 
"coordinates" variable can store the vertex positions of the element, 
including the extra ones for the curved sides.  If not, then some other 
variable would need to be created to store it; actually, that may be 
better.  Also, the "cell_map_type" will be set to either P1_map, or 
P2_map, or etc...

4. The tabulate_tensor routine will have a switch to pick the correct 
routine for computing the tensor coefs.  This will require modifying FFC 
which I don't know yet.

5. Another thing that should change will be the basis function 
evaluations.  This may be a pain.  Computing the inverse map to get the 
location of the coordinates in the reference element may be inconvenient. 
This can be ignored for now; this isn't really critical for what I would 
like to do.

I am a little confused on where the ufc::cell data gets set by the data in 
the mesh.xml file.  I'm still very new to this code.  Any help would be 
appreciated.  If I am totally off on this, please say so!

- Shawn

On Thu, 14 Aug 2008, Anders Logg wrote:

> On Thu, Aug 14, 2008 at 09:02:06AM -0400, Shawn Walker wrote:
> > I'm not against changing the xml format.  Actually, it would be nice to
> > have a format that is backwards compatible; that way you could ignore the
> > curved information and just use the mesh as straight if you want.  That
> > seems do-able.
> >
> > And then add a local struct to the UFC format that is accessible by the
> > tabulate_tensor routine.  This local struct would have the local nonlinear
> > map for each cell and facet in place.  I need to look at the UFC manual
> > some more and see how this might work...
> >
> > - Shawn
>
> The mesh XML format has a data section that may contain arbitrarily
> named data so it should be easy to extend (if/when we decide to
> implement this).
>
> --
> Anders