[Dune] a question about quadrature rules

[Arya Fallahi]

Dear Christian,

Thank you very much for your response. It is now clear for me.

For the tutorial statement I referred to, look at the following lines:

page 34, line 25 in the presented code
page 35, line 37 in the presented code
page 36, the following statement: "Running the executable integration on a
YaspGrid in two space dimensions with a quadrature rule of order two the
following output is obtained:"

Thanks and best regards,
Arya


On Tue, Feb 25, 2014 at 3:40 PM, Christian Engwer <
christian.engwer at uni-muenster.de> wrote:

> Dear Arya,
>
> > I got to have a question about the quadrature rules implemented in Dune.
> > There seems to be something strange in the Dune tutorial. First,
> according
> > to the comments, if one aims to do integration with quadrature order p,
> the
> > rule should be initialized as:
> >
> > const Dune::QuadratureRule <ctype ,dim >& rule = Dune::QuadratureRules
> > <ctype ,dim >::rule(gt,p);
> >
> > However, later for calculation with order two the p value is set to 1.
> > Would you explain a little about this?
>
> Please be a bit more specific. Where in the tutorial is this
> statement. We need to have a closer look...
>
> > My main question is that if I want to consider only one point for the
> > integration (first order quadrature rule), what should I set for the rule
> > order? one or zero?
>
> In general the order you specify is the order for which you compute
> the exact integral (modulo fp errors). In particular this means that
> integrating a first order function you set the rule to 1. The obtained
> rule will be the same as for zero order, but this a detail you don't
> have to think about.
>
> Ciao
>
> Christian
>
> >
> > Thank you in advance for your help and best regards,
> > Arya
>
> > _______________________________________________
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> > Dune at dune-project.org
> > http://lists.dune-project.org/mailman/listinfo/dune
>
>
> --
> Prof. Dr. Christian Engwer
> Institut für Numerische und Angewandte Mathematik
> Fachbereich Mathematik und Informatik der Universität Münster
> Einsteinstrasse 62
> 48149 Münster
>
> E-Mail  christian.engwer at uni-muenster.de
> Telefon +49 251 83-35067
> FAX             +49 251 83-32729
>
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