ffc team mailing list archive

["Martin Sandve Alnæs" <martinal@xxxxxxxxx>]

2008/11/20 Johan Hake <hake@xxxxxxxxx>:
> On Thursday 20 November 2008 00:05:59 Martin Sandve Alnæs wrote:
>> 2008/11/19 Johan Hake <hake@xxxxxxxxx>:
>> > Hello!
>> >
>> > We have been discussing to inherit the ffc.{Test,Trial,Basis}Function in
>> > dolfin, and instantiate the function with a functionspace instead of an
>> > element. Then in assemble.py we extract the functionspaces from the
>> > basisfunctions in Formdata (Anders promised this).
>> >
>> > I had a look in Formdata to try to just extract the basis functions,
>> > similare to the coefficients. But the problem is that these functions are
>> > not represented in the monomial as the original u and v as they were
>> > created by the user.
>> >
>> > I suppose this is a "feature" of the algrebra in ffc or have I
>> > missunderstood it? The function that is used to define the coefficients
>> > can be extracted using with c.f, should this be added for the
>> > basisfunctions too?
>>
>> ...
>>
>> > Will this be an issue in ufl?
>>
>> Let me think aloud:
>>
>> - Subclassing BasisFunction (Test and Trial aren't classes) poses no
>> problems in itself.
>
> This won't be the case. A dolfin.BasisFunction will inherit
> ufl/ffc.BasisFunction, nothing else. It will have a FunctionSpace.
>
>> - Attaching additional member variables and member functions in this
>> class is ok, as long as names don't collide.
>
> Ok. I have added a function_space funciton to extract the FunctionSpace.
>
>> - Implementing any special function "__foo__" other than __init__ in
>> the dolfin subclasses may cause trouble. This includes SWIG-generated
>> functions, which I think should be ok if the UFL class has precedence
>> over the SWIG-generated class in the inheritance list of the PyDOLFIN
>> class.
>
> This won't be the case.
>
>> - BasisFunction and Function objects in a UFL Form are never replaced
>> with anything else, exactly with this in mind.
>
> Nice.
>
>> - Algorithms like "J = derivative(-F)", "b = action(a)" which
>> introduce additional arguments all have options to explicitly pass the
>> BasisFunction or Function to add.
>
> Nice.
>
>> - Retrieving the exact objects used for form arguments from a form
>> will be ok, that is the instances of ufl.Function or its PyDOLFIN
>> subclass.
>
> Nice.
>
>> I don't see any collisions with this design and ufl.
>
> So, when is it due? ;)

In a finite number of days. ;)

--
Martin