ufl team mailing list archive

[Kent Andre <kent-and@xxxxxxxxx>]

On fr., 2009-02-13 at 14:03 +0100, Kristian Oelgaard wrote:
> Quoting "Garth N. Wells" <gnw20@xxxxxxxxx>:
> 
> > 
> > 
> > Kent Andre wrote:
> > > On fr., 2009-02-13 at 13:32 +0100, Martin Sandve Alnæs wrote:
> > >> On Fri, Feb 13, 2009 at 1:20 PM, Kristian Oelgaard
> > >> <k.b.oelgaard@xxxxxxxxxx> wrote:
> > >>> Quoting Martin Sandve Alnæs <martinal@xxxxxxxxx>:
> > >>>
> > >>>> On Fri, Feb 13, 2009 at 11:53 AM, Kristian Oelgaard
> > >>>> <k.b.oelgaard@xxxxxxxxxx> wrote:
> > >>>>>
> > >>>>> Hello,
> > >>>>>
> > >>>>> Any thoughts on how to implement a better rule for determining the
> > >>>> polynomial
> > >>>>> order of a form?
> > >>>>>
> > >>>>> as it is now the forms:
> > >>>>>
> > >>>>> a = v*u*dx
> > >>>>> a = f*v*u*dx
> > >>>>> a = f*f*f*.....*v*u*dx
> > >>>>> a = inner(grad(v), grad(u))*dx
> > >>>>>
> > >>>>> all result in the same order (2 for linear basis functions)
> > >>>> What do we want? Add the degrees of all functions and basis functions
> > >>>> that are multiplied? Should be possible to do.
> > > 
> > > In general I don't think this is what you 'want' to do. 
> > > It is common to use the same quadrature rules for 
> > > a = inner(grad(v), grad(u))*dx
> > > and 
> > > a = f*inner(grad(v), grad(u))*dx
> > > 
> > > even though f is a function. 
> 
> Sure, but I do believe the default should be correct integration.

As it is now it is correct in the sense that the integration is accurate
up to a certain order and this accuracy is consistent with the order of
the element independently of the number of coefficients or variational
form.

Anyway, I think this is just a decision to be made. One can argue in
both directions. I'm fine with you choice. 

Kent

> If it is possible to have different orders it might have an impact on the
> performance of the code which will allow the default for the compilers to be
> 'correct AND fast' code.
> Through the meta data the user is given the opportunity of changing the rules,
> typically decreasing the order to gain speed by sacrificing accuracy.
>  
> > > It would however be nice to choose quadrature rule by setting some kind
> > > of meta data. 
> > >
> > 
> > We discussed attaching this data to the integration operators a while 
> > ago and there was general agreement.
> 
> Yes, and it would not be a problem to override the default values if any
> instructions are set.
> 
> Kristian
> 
> 
> > Garth
> > 
> > > Kent
> > > 
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> > 
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> 
>