ffc team mailing list archive

[Shawn Walker <walker@xxxxxxxxxxxxxxx>]

Alright.  I'm looking at these quad rules, the 4-pt rule doesn't match the 
weights that show up in the Poisson.h file I have right now.  Also, the 
coordinates seem weird.  Are all of these points evaluated outside the ref 
triangle?

- Shawn

On Mon, 22 Jun 2009, Martin Sandve Alnæs wrote:

> SFC doesn't use the same quadrature rules as
> FFC, so that makes no sense in my head.
> Either install SyFi properly with dependencies,
> or keep using FFC and ignore my suggestion.
>
> (If you still want them, the rules SFC use are in
> site-packages/sfc/quadrature/quad_tables.py)
>
> Martin
>
>
>
> On Mon, Jun 22, 2009 at 11:09 PM, Shawn Walker<walker@xxxxxxxxxxxxxxx> wrote:
> > Actually, would it be possible for you to just give me the 4-pt quad rule on
> > a triangle.  The problem is, I don't have GiNAC setup, which is needed to
> > run SyFi, right?
> >
> > - Shawn
> >
> > On Mon, 22 Jun 2009, Martin Sandve Alnæs wrote:
> >
> > > Ok. Temporarily, maybe you'll be happy with the code
> > > generated by SFC (see the demo/*/cpp/ directories in SyFi).
> > > There both weights and points are embedded directly in the code.
> > >
> > > Martin
> > >
> > >
> > >
> > > On Mon, Jun 22, 2009 at 10:50 PM, Shawn Walker<walker@xxxxxxxxxxxxxxx>
> > > wrote:
> > > > On Mon, 22 Jun 2009, Anders Logg wrote:
> > > >
> > > > > I think Shawn just wants to get the quadrature points so he can
> > > > > hand-modify the code for tabulate_tensor to handle higher-order mapped
> > > > > elements (to make a prototype for higher-order elements).
> > > > >
> > > > > Correct me if I'm wrong.
> > > >
> > > > Yes!
> > > >
> > > > > In that case, we won't need to make them available since they are
> > > > > available to the form compiler when the code is being generated, but
> > > > > it would help if they were available in a comment in the generated code.
> > > >
> > > > I agree that having them in a comment would be good.
> > > >
> > > > - Shawn
> > > >
> > > > > On Mon, Jun 22, 2009 at 10:28:29PM +0200, Martin Sandve Alnæs wrote:
> > > > > > On Mon, Jun 22, 2009 at 9:10 PM, Kristian
> > > > > > Oelgaard<k.b.oelgaard@xxxxxxxxxx> wrote:
> > > > > > > Quoting Shawn Walker <walker@xxxxxxxxxxxxxxx>:
> > > > > > >
> > > > > > > > Actually, I am still a little confused.  Whenever you compute an
> > > > > > > > integral
> > > > > > > > by quadrature, you need to evaluate the integrand at the quadrature
> > > > > > > > points.  Those are the points I need.
> > > > > > >
> > > > > > > If you have a quadrature element in your form
> > > > > > >
> > > > > > > element = FiniteElement("Quadrature", triangle, 2)
> > > > > > >
> > > > > > > you can call the
> > > > > > > tabulate_coordinates() function of the dof_map associated with the
> > > > > > > quadrature
> > > > > > > element. If you don't have a quadrature element there is no direct way
> > > > > > > of
> > > > > > > getting the quadrature points.
> > > > > > >
> > > > > > > > I just need the quad rule that is used in a particular case.  I see
> > > > > > > > the
> > > > > > > > weights are defined in the tabulate_tensor routine.  Are the points
> > > > > > > > listed
> > > > > > > > in a comment somewhere?
> > > > > > >
> > > > > > > No, currently not. But it might be a natural thing to have. I'll look
> > > > > > > into it.
> > > > > >
> > > > > > It could be an idea to make it available through UFC,
> > > > > > but then again each ufc::*_integral may use different
> > > > > > quadrature rules for different terms...
> > > > > > However, an exception can be thrown if there is no unique rule in use.
> > > > > >
> > > > > > Martin
> > > > > > _______________________________________________
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> > > >
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