ufl team mailing list archive

[Kristian Oelgaard <k.b.oelgaard@xxxxxxxxxx>]

Quoting Martin Sandve Alnæs <martinal@xxxxxxxxx>:

> On Sun, Feb 15, 2009 at 10:10 PM, Anders Logg <logg@xxxxxxxxx> wrote:
> > On Fri, Feb 13, 2009 at 02:30:00PM +0100, Martin Sandve Alnæs wrote:
> >> Attaching metadata to an integral is implemented, but we
> >> haven't  decided what format the metadata should be in.
> >
> > I think there needs to be a convention as part of UFL for how to
> > specify the integration rule. Otherwise different form compilers will
> > invent different conventions and interpret the metadata differently.
> 
> Agree.
> 
> > Here's a suggestions:
> >
> >  metadata = ("quadrature", degree)
> >  metadata = ("tensor", degree)
> 
> Here you're already into FFC territory...
> 
> Integration order is an important mathematical
> property, the method for code generation is not.
> "tensor" is in the latter category.
> 
> > Degree would be the degree of polynomials which will be integrated
> > exactly by the quadrature rule. For tensor representation we use
> > quadrature on the reference element so it makes sense there as well.
> >
> > It might even be useful to add a class IntegrationRule with "enums"
> > for quadrature and tensor representation. Then an Integral would have
> >
> >  _integrand
> >  _measure
> >
> > and Measure would have
> >
> >  _domain_type
> >  _domain_id
> >  _integration_rule
> >
> > and possibly metadata.
> 
> In the current implementation _integration_rule == _metadata, but it's
> of course not a problem to replace that with two variables or rename it.
> 
> I think that probably any metadata other than integration order
> will be form compiler specific. We can let Measure have
> 
>   _domain_type
>   _domain_id
>   _integration_order
>   _metadata
> 
> and allow:
> 
>   dx(domain_id)
>   dx(domain_id, integration_order)
>   dx(domain_id, integration_order, metadata)
> 
> where metadata contains compiler hints like "tensor" and
> can be form compiler specific.
> 
> Then the integration order can be interpreted correctly by
> any form compiler, and metadata can be ignored.

This sounds like a very good solution.
If the metadata is irrelevant to a given form compiler it could throw an error,
or maybe a warning is better, rather than just ignoring it?

Kristian
 
> Martin
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