dolfin team mailing list archive

[Anders Logg <logg@xxxxxxxxx>]

On Tue, Feb 17, 2009 at 04:12:15PM +0000, A Navaei wrote:
> 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++?

Yes, as I suggested earlier: compile the function space and include
the code.

-- 
Anders


> 
> -Ali
> 
> >
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