Anders Logg wrote:
There seems to be a problem (among many) with the current design of
the Function classes (see thread "evaluating higher order mesh function").
In particular, the finite element is missing in DiscreteFunction. My
suggestion would be to just add it and let a DiscreteFunction consist
of the following four items which are always available:
mesh, x, dof_map, finite_element
Is this enough, and what other issues to we need to fix?
One major issue which I just want to reiterate is ownership of data. As
it stands, the DiscreteFunction may or may not be responsible for e.g.
the dof vector x, depending on whether local_vector is a NULL pointer or
not. Take a look at the thread "Ownership" from Garth on 06/26/2008.
A problem related to this is initialization of the DiscreteFunction. We
had a bug previously where the LinearPDE class maintained ownership of
the solution vector. The only way to prevent this was to break the
encapsulation of DiscreteFunction by making it a friend of LinearPDE (as
with XMLFile for the same reasons). Here is some of the code that
handles this initializaton today (L101 in LinearPDE.cpp):
u.init(mesh, *x, a, 1);
DiscreteFunction& uu = dynamic_cast<DiscreteFunction&>(*u.f);
uu.local_vector = x;
This ain't poetry in my opinion :)
