dolfin team mailing list archive

[Anders Logg <logg@xxxxxxxxx>]

On Mon, Jan 28, 2013 at 10:37:46PM +0100, Johan Hake wrote:
> On 01/28/2013 10:22 PM, Anders Logg wrote:
> > On Mon, Jan 28, 2013 at 10:10:40PM +0100, Johan Hake wrote:
> >> Hello!
> >>
> >> I have now added a method to DofMap, which tabulate a map between
> >> vertices and dofs. It will only work for DofMaps with dofs on vertices.
> >> So basically for any CG 1 FunctionSpaces and will raise error else wise.
> >>
> >> Usage:
> >>
> >>   from dolfin import *
> >>   import numpy as np
> >>   mesh = UnitSquareMesh(10,10)
> >>   V = VectorFunctionSpace(mesh, "CG", 1)
> >>   u = Function(V)
> >>   u.interpolate(Constant((1,2)))
> >>   vert_values = np.zeros(mesh.num_vertices()*2)
> >>   vert_values[V.dofmap().tabulate_vertex_map(mesh)] = \
> >>   u.vector().array()
> >>   print vert_values
> >>
> >> In parallel the map will follow the local dofs. This means that some
> >> values in vert_values above will still be 0. The 0 values will then
> >> correspond to vertex values which are owned by another process.
> >>
> >> In C++ the method returns a std::vector<std::size_t>.
> >>
> >> Questions:
> >> Does the name "tabulate_vertex_map" work?
> >
> > Sounds ok.
> >
> >> Should a version of this method exist in other classes. FunctionSpace,
> >> Function (without the mesh argument of course)?
> >
> > Yes, would be good to have for convenience.
> >
> > What is the relation to Function::compute_vertex_values?
>
> compute_vertex_values works on any GenericFunction. However, for all
> Functions from CG 1 families I guess one could use this map to just
> tabulate the entries.

What does the tabulate_vertex_map method do which
compute_vertex_values doesn't? Enable writing to dofs?

--
Anders