On Tue, Feb 17, 2009 at 03:55:58PM +0000, A Navaei wrote: > 2009/2/17 Anders Logg <[email protected]>: > > 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. -- Anders
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