dolfin team mailing list archive

[Anders Logg <logg@xxxxxxxxx>]

On Mon, Apr 20, 2009 at 10:46:11AM -0500, Robert Kirby wrote:
> So garbage in, garbage out :)
> 
> It should be possible and is probably helpful to have the rules natively in
> C++.  The only issue
> is that I need zeros of Jacobi polynomials for somewhat different weights than
> the Gaussian quadrature
> in DOLFIN.  It is not hard to extend what's there.

Yes, it should be fairly straightforward to implement (for someone
with enough time and motivation).

-- 
Anders


> 
> 
> On Sun, Apr 19, 2009 at 1:39 PM, Anders Logg <logg@xxxxxxxxx> wrote:
> 
>     On Fri, Apr 17, 2009 at 03:40:37PM -0500, Robert Kirby wrote:
>     > Are there any 2d quadrature rules built into dolfin?  All I can seem to
>     find
>     > are 1d rules.
>     > Even the dumb collapsed-coordinate ones are fine.
> 
>     We had this a *long* time ago, see for example
> 
>     http://www.fenics.org/hg/dolfin?f=e26c8159ce5e;file=src/kernel/quadrature/
>     dolfin/TriangleMidpointQuadrature.h
> 
>     But we removed this when FIAT was introduced. :-)
> 
>     The 1D rules are used by the ODE solvers.
> 
>     If you want quadrature rules on a triangle or tetrahedron, you can
>     generate code for a single finite element. Put something like this
>     in a .ufl file:
> 
>      element = FiniteElement("Quadrature", "triangle", 5)
> 
>     Then compile and include the generated code. You can call this function
>     from the generated ufc::dof_map:
> 
>      void tabulate_coordinates(double** coordinates,
>                                const cell& c) const = 0;
> 
>     You'll get out the quadrature points you've put into FIAT. :-)
> 
> 
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