[petsc-dev] resurrecting the finite element energy functions thread

[Geoffrey Irving]

On Sun, Jan 19, 2014 at 4:46 PM, Jed Brown <jed at jedbrown.org> wrote:
> Geoffrey Irving <irving at naml.us> writes:
>> For anything other than MPI_SUM, the evaluation points would likely
>> want to be different, so the structure of the code would be
>> significantly changed.  For example, MPI_MAX probably wants evaluation
>> points at the vertices, which can't be optimally coded using the same
>> code structure used for MPI_SUM (since different elements share
>> vertices).
>
> That's fair, though extrema can also occur internally to an element.
>
>> The main difference is that the quadrature rule has to be specified
>> independent of the PetscFE objects, since the PetscFE elements for the
>> different fields might have incompatible quadrature rules.
>
> How is that different from evaluating coupling terms between fields in
> different spaces?

It isn't, the only difference is that the function I'm imagining needs
an extra quadrature rule argument.  Nothing here is complicated, so if
there are no particular opinions I'll write the function and send a
patch.  Can I write it hard coded to MPI_SUM first, and we can discuss
how to generalize it after that?  I am less clear on how to best write
the generalized version.

Geoffrey