dolfin team mailing list archive

[A Navaei <axnavaei@xxxxxxxxxxxxxx>]

2009/2/17 Anders Logg <logg@xxxxxxxxx>:
> On Tue, Feb 17, 2009 at 03:55:58PM +0000, A Navaei wrote:
>> 2009/2/17 Anders Logg <logg@xxxxxxxxx>:
>> > On Tue, Feb 17, 2009 at 03:28:08PM +0000, Garth N. Wells wrote:
>> >>
>> >>
>> >> A Navaei wrote:
>> >> > The following minimal test for Function in c++ reveals some bugs. I
>> >> > guess this example can help me with dealing with the current issues of
>> >> > ImageFunction.
>> >> >
>> >> > (1) interpolate.py does not work when a Function is created in c++ and
>> >> > wrapped (see comment [2]). It seems that the bug is originated from
>> >> > the copy constructor (see comment [3])
>> >> >
>> >> > (2) In order to perform the interpolation, why is it necessary to
>> >> > create another Function and then copy it?
>> >> >
>> >> > (3) Signature checkes seem not working properly (see comment [1]). The
>> >> > signature-based assignments are error-prone anyway, why the
>> >> > object-oriented approach is not used?
>> >> >
>> >>
>> >> Signatures are used to permit reading/writing Functions to a file. They
>> >> are indeed error prone, so I believe that we reached a consensus a short
>> >> while ago that we would remove pre-compiled elements.
>> >>
>> >> Garth
>> >
>> > Instead of signatures, I'd recommend that you define a simple form
>> > file for each of the different types of FunctionSpace you need, for
>> > example:
>> >
>> >  element = FiniteElement("CG", "triangle", 1)
>> >
>> >  v = TestFunction(element)
>> >  u = TrialFunction(element)
>> >  a = v*u*dx
>> >
>> > If you put this in a file named My.form and compile it with FFC using
>> > -l dolfin, you will get a class named MyFunctionSpace that you can
>> > then instantiate using just a mesh:
>> >
>> >  MyFunctionSpace V(mesh);
>> >
>> > Create one form file for each of the different types of FunctionSpace
>> > that you need, name the files to something suitable and use the
>> > generated code. That way you won't need to worry about signatures,
>> > dofmaps and finite elements.
>>
>> Maybe this should be provided in the main library with a global
>> access, as this is not specific?
>>
>> A more robust way, which does not need code generation, is simply
>> defining the available options as types in an enum or struct. In this
>> way, in both python and c++ we can have the form-like style:
>>
>> element = FiniteElement(ElemBasisType.CG, ElemGeoType.Triangle, 1);
>>
>> which is error-safe.
>>
>> Any comments on the main subject?
>
> As Garth says, we might be removing the precompiled elements and
> initialization from signatures in future releases so it's best not to
> use it.

I'm a bit confused here. The pre-compiled elements and the signatures
are going to be removed, avoiding these, are there any other ways of
creating Functions in c++?


-Ali

>
> --
> Anders
>
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