dolfin team mailing list archive

[Johan Hake <hake@xxxxxxxxx>]

On Tuesday 04 November 2008 19:45:10 Martin Sandve Alnæs wrote:
> 2008/11/4 Johan Hake <hake@xxxxxxxxx>:
> > On Tuesday 04 November 2008 15:00:42 Martin Sandve Alnæs wrote:
> >> 2008/11/4 Johan Hake <hake@xxxxxxxxx>:
> >> > On Tuesday 04 November 2008 13:59:22 Martin Sandve Alnæs wrote:
> >> >> 2008/11/4 Johan Hake <hake@xxxxxxxxx>:
> >> >> > On Tuesday 04 November 2008 13:07:07 Martin Sandve Alnæs wrote:
> >> >> >> 2008/11/4 Johan Hake <hake@xxxxxxxxx>:
> >> >> >> > Hello!
> >> >> >> >
> >> >> >> > I have started the work on the PyDOLFIN. We can now define the
> >> >> >> > forms in the poisson demo, using the syntax previously
> >> >> >> > discussed, see python poisson demo.
> >> >> >> >
> >> >> >> > A FunctionSpace now inherits both dolfin::FunctionSpace and
> >> >> >> > ffc.FiniteElement, and it can be used to instantiate user
> >> >> >> > defined Functions which can be used to define forms.
> >> >> >> >
> >> >> >> > We need to discuss how to implement a discrete function. This is
> >> >> >> > a bit complicated using the metaclass magic that is implemented
> >> >> >> > now. Now we cannot do:
> >> >> >> >
> >> >> >> >  u = Function(V)
> >> >> >> >  x = u.vector()
> >> >> >> >
> >> >> >> > as Function is just a dummy class for creation of userdefined
> >> >> >> > functions.
> >> >>
> >> >> I don't quite understand the problem here.
> >> >> Are you saying that type(u) is not a subclass of cpp_Function or
> >> >> what?
> >> >
> >> > With the metaclass implementation, Function cannot inherit
> >> > cpp_Function or ffc.Function. A derived class of Function will inherit
> >> > Function, cpp_Function and ffc.Function though. Function is as it is
> >> > now, only an more or less empty class that can be inherited.
> >> >
> >> > The syntax above can be valid with some __new__ magic in Function,
> >> > probably much in line with what you had in mind.
> >>
> >> But in the metaclass __new__ function you have explicit control of the
> >> bases of the new class you're building, so where's the problem?
> >> Just set bases = (cpp_Function, ufl.Function).
> >
> > Of course. When I wrote the code I never intended Function to be
> > instantiated.
>
> Sure. With the new Function design that will of course happen all the time.
>
> > Would it make sense to always create a Function that is discrete when we
> > just write, u = Function(V)?
>
> Yes, just like cpp_Function(V). Anything else would be insane :-)
>
> By the way, this gives a segmentation fault:
>
> from dolfin import *
> mesh = UnitSquare(2,2)
> V = FunctionSpace(mesh, "CG", 1)
> u = cpp_Function(V)
> v = u.vector()
>
> Happy debugging :-/

The same to you ;)

Urgh... I used two hours to track a similare bug yesterday. It was a forgotten 
NoDeleter to a shared pointer that caused the havoc.

Johan