ufl team mailing list archive

[Kristian Ølgaard <k.b.oelgaard@xxxxxxxxx>]

On 27 April 2011 13:03, Garth N. Wells <gnw20@xxxxxxxxx> wrote:
>
>
> On 27/04/11 12:00, Kristian Ølgaard wrote:
>> On 27 April 2011 12:38, Garth N. Wells <gnw20@xxxxxxxxx> wrote:
>>>
>>>
>>> On 27/04/11 11:08, Kristian Ølgaard wrote:
>>>> On 27 April 2011 11:52, Anders Logg <logg@xxxxxxxxx> wrote:
>>>>> On Wed, Apr 27, 2011 at 10:40:50AM +0100, Garth N. Wells wrote:
>>>>>> We need a quick discussion round to resolve this issue - DOLFIN is now
>>>>>> broken. I guess we need the form compiler to decide on the cell and
>>>>>> element type, and then have UFL return a new form.
>>>>>
>>>>> Yes, Martin mentioned at some point that it would be easy to add such
>>>>> a function to UFL (that takes a form and replacement elements and
>>>>> returns a new form).
>>>>>
>>>>> Martin, could you add such a function?
>>>>
>>>> I think ufl.algorithm.transformations.replace would work if
>>>> FiniteElementBase derived from 'Terminal'.
>>>> Currently, it derives from 'object', what is the reason for that?
>>>> Anyway, it should be simple enough to add something equivalent for elements.
>>>>
>>>
>>> I was thinking that we only need to replace Coefficients, e.g. if a
>>> Coefficient is defined using an 'incomplete element', FFC can create an
>>> element, a Coefficient and the perform the replacement. Looks like UFL
>>> can do this already.
>>
>> Yes, I think that should be possible. But what about quadrature elements?
>>
>> If the scheme is not specified when constructing the element (in the
>> form), then the scheme
>> will be determined by the commandline arguments (or metadata) to FFC. The
>> QuadratureElement needs the scheme information in the constructor in order to
>> generate the points for which it is defined.
>>
>
> I don't see the problem. Couldn't FFC generate a new QuadratureElement
> (of the correct degree) and define a Coefficient on it?

I guess it could.

Another question is if we should have a separate class in UFL for
quadrature elements?
The reason is that UFL uses (family, cell, degree) to check for
uniqueness (through __repr__ --> __hash__),
but the quadrature element will need the 'scheme' as well, which can
be None until FFC determines it.

Either we extend the __repr__ of FiniteElement to include the scheme,
or we can use a separate class QuadratureElement.
For the majority of finite elements the 'scheme' information in
__repr__ is superfluous, so a separate class might be preferable.
If we use a separate class, then the question is if we want to do:

1) element = QuadratureElement(cell, degree, scheme)
or
2) element = FiniteElement(family, cell, degree, scheme=scheme)

when creating a quadrature element object.

For case 2 we probably need to implement FiniteElement.__new__ to
return a QuadratureElement if family == 'Quadrature'.

Kristian

> Garth
>
>> Kristian
>>
>>> The problem from the DOLFIN side is that the new UFL Coefficient will be
>>> different from the DOLFIN/UFL Coefficient, and would be a
>>> ufl.Coefficient and not a dolfin.Coefficient.
>>>
>>> Garth
>>>
>>>> Kristian
>>>>
>>>>> --
>>>>> Anders
>>>>>
>>>>>
>>>>>> Garth
>>>>>>
>>>>>> On 26/04/11 07:32, noreply@xxxxxxxxxxxxx wrote:
>>>>>>> ------------------------------------------------------------
>>>>>>> revno: 1014
>>>>>>> committer: Martin Alnæs <martinal@xxxxxxxxx>
>>>>>>> branch nick: ufl
>>>>>>> timestamp: Fri 2011-04-15 21:44:37 +0200
>>>>>>> message:
>>>>>>>   Add warnings to set_foo functions in finiteelement.py,
>>>>>>>   and remove repr modifications after construction time.
>>>>>>>
>>>>>>>   If this will break your code, it likely wasn't working
>>>>>>>   correctly anyway and you need to rewrite it before you
>>>>>>>   can update to this UFL version.
>>>>>>>
>>>>>>>   The set_foo functions will be removed completely before UFL 1.0.
>>>>>>>
>>>>>>>   Happy easter holiday :)
>>>>>>> modified:
>>>>>>>   ufl/finiteelement.py
>>>>>>>
>>>>>>>
>>>>>>
>>>>>>
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>>>>>
>>>>> _______________________________________________
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>>>>>
>>>
>>>
>
>