ufl team mailing list archive

[Martin Sandve Alnæs <martinal@xxxxxxxxx>]

Either way, we can have both algorithms available so the user can
either switch between the two or specify the exact order.

Martin


On Fri, Feb 13, 2009 at 2:32 PM, Kent Andre <kent-and@xxxxxxxxx> wrote:
> 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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>>
>>
>
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