dolfin team mailing list archive

[Marie Rognes <meg@xxxxxxxxx>]

Garth N. Wells wrote:
> Anders Logg wrote:
>   
> > On Fri, Feb 12, 2010 at 05:42:26PM +0000, Garth N. Wells wrote:
> >     
> > > Anders Logg wrote:
> > >       
> > > > On Fri, Feb 12, 2010 at 04:57:05PM +0100, Anders Logg wrote:
> > > >         
> > > > > On Fri, Feb 12, 2010 at 04:23:51PM +0100, Marie Rognes wrote:
> > > > >           
> > > > > > I'm interesting in accessing the vector of a Function after mesh-refinement.
> > > > > > At the moment, I'm getting:
> > > > > >
> > > > > >    RuntimeError: *** Error: You are attempting to access a non-const
> > > > > >    vector from a sub-Function.
> > > > > >
> > > > > > Is this inevitable, a bug or a trigger-happy error message?
> > > > > >
> > > > > >    from dolfin import *
> > > > > >    mesh = UnitSquare(2,2)
> > > > > >    V = FunctionSpace(mesh, "CG", 1)
> > > > > >    u = Function(V)
> > > > > >    mesh.refine()
> > > > > >    u.vector()
> > > > > >             
> > > > > Looks like a bug. The function is not being refined but the mesh, the
> > > > > dofmap and the functionspace is refined. Might be related to the
> > > > > recent work on refinement.
> > > > >           
> > > > It should be fixed now. Someone had commented out register_object in
> > > > the Function constructor.
> > > >         
> > > I'm not too keen on all this magic. Harish I and have an adaptive solver
> > >  in which the function spaces are declared inside a loop and it's slowly
> > > leaking memory, but I can't figure out why. 'Magic' makes it really hard
> > > to figure out what's going on.
> > >       
> > That's unfortunate. But the magic is necessary if we should allow
> > meshes to be refined. The other option would be to remove
> > mesh.refine() and always rely on
> >
> >   new_mesh = refine(mesh)
> >
> > And then explicitly create the new function spaces and project the
> > functions.
> >
> >     
>
> This is what we're doing.
>
> Garth
>
>
>   
> > I'm not sure which implications that would have fore Marie's code.
> > Marie?
> >
> >     

I'm pretty keen on the magic, but can survive without it.

If the automagic updating of function spaces etc is removed.
then mesh.refine() should definitely be disabled.

--
Marie


> > --
> > Anders
> >     
>
>
>