dolfin team mailing list archive

[Anders Logg <logg@xxxxxxxxx>]

On Tue, Apr 10, 2007 at 06:14:12PM +0200, Garth N. Wells wrote:
> Connected to Kristian's work on quadrature in FFC, we should think about 
> how to work with functions which do not come from a finite element 
> space. Such functions (like stress for a plasticity model or viscosity 
> for a non-Newtonian flow) are evaluated at quadrature points, rather 
> than at nodes.
> 
> Garth

The current design (including UFC) assumes that all functions can be
interpolated to a finite element basis, but I think it will work for
the quadrature code generation to imagine that you have a finite
element basis where the quadrature points are the same as the nodes.
(But you never need to know the basis functions.)

The array of coefficients (double** w) that comes in to the function
tabulate_tensor() should contain the coefficients, but for the
quadrature these will be the same as the values at the quadrature
points, and this should work out fine since the values that go in to w
are decided by the evaluate_dof() function that also gets
generated.

So the quadrature code generator just needs to make sure that
evaluate_dof() picks the values at the quadrature points.

/Anders