ffc team mailing list archive

[Kristian Oelgaard <k.b.oelgaard@xxxxxxxxxx>]

Quoting Peter Brune <prbrune@xxxxxxxxx>:

> Some recent discussions and problems that have cropped up have led me to
> need/want to add some specialized quadrature rules to FFC.  These include
> "optimal" combinatorially-derived rules for given order polynomials for the
> n-simplex, as well as rules that can be explicitly guaranteed to have
> certain properties (positivity, all-internal-nodes, etc)
>
> Does anyone else need anything like this?  I already have implementations of
> a few nice rules for higher-dimensional applications, but have started to
> adapt them for this purpose.  Ideally we would be able to specify a rule in
> the ffc command.  I'm looking at where to put this.

So on the command line we should be able to do:

ffc --quadrature-rule some_string
or
ffc -q some_string

and then in the file ffc/fem/quadrature.py in the function
make_quadrature() there should be an extra argument

make_quadrature(shape, n, quad_rule)

with default None? Then you can just put your code and some switches in this
file.
I can add the command line option and propagate it to the make_quadrature()
function, at least for quadrature representation, if nobody objects.


> There are other potential benefits to this move.  If we were to switch to
> rules we have definite information about, we could use, say, group symmetry
> properties, combined with symmetry properties of the unknowns, for further
> optimization of the form compilation by quadrature.  We would already win,
> especially in 3D, by getting away from the squashed rules and towards rules
> that are more optimal.

This would be nice.

Kristian

> - Peter
>