dolfin team mailing list archive

["Garth N. Wells" <gnw20@xxxxxxxxx>]

Shawn Walker wrote:
> So, when you do
>
> mesh.refine()
>
> that automatically replaces the old mesh with the new one?  This seems ok. 
> As long as the user still has the option of storing the old unrefined mesh 
> and associated functions.
>
> How will functions be updated?  Just interpolation?  Is that easy to do if 
> you use some non-standard elements, i.e. H(div), etc...  I guess the 
> question is this:   Is there a unique way to update the functions?  

No.

If so,
> then this should be safe.  If not, then there might be headaches with 
> this...

We could provide a default, but make the relevant functions virtual so 
that a user can provide their own update method.

Garth

> - Shawn
>
> On Mon, 2 Nov 2009, Anders Logg wrote:
>
> > I've thought some more on the problem of mesh refinement and updating
> > of Functions.
> >
> > The main problem seems to be the following:
> >
> >  mesh.refine()
> >
> > If we want to allow this, then we need to provide some kind of
> > automated updating of functions and function spaces to the new mesh,
> > since this call will otherwise destroy all function spaces and
> > functions that refer to that mesh:
> >
> >  V = FunctionSpace(mesh, "CG", 1)
> >  v = Function(V)
> >  mesh.refine() # V and v no longer make any sense
> >
> > This gives us two options. Either we disallow refinement of a mesh
> > without making a copy. Or we provide automated updating. I think we
> > should do the latter.
> >
> > What is needed compared to what we have now is to let a call to
> > Mesh::refine trigger a call to FunctionSpace::update for all function
> > spaces defined on the mesh, which in turn will trigger calls to
> > Function::update for all functions defined on the function spaces.
> >
> > We can make the update functions private.
> >
> > Comments or objections? I think I can make this work.
> >
> > --
> > Anders
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