dolfin team mailing list archive

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

On 31 August 2012 07:31, Johan Hake <hake.dev@xxxxxxxxx> wrote:
> Hello!
>
> Once in a while (quite often) we get questions about dof management
> based on Mesh subdomains. There are different approaches to handle this.
> Some less robust than others.
>
> I wonder if it would be a good idea to add:
>
>    /// Tabulate all dofs
>    DofMap::tabulate_dofs(Array<uint>& dofs, const& Mesh mesh)
>

It's not clear to me what the above does. Why is the Mesh an argument?

>    /// Tabulate dofs related to a MeshDomain
>    DofMap::tabulate_dofs(Array<uint>& dofs,
>                          const& MeshFunction domains, uint domain)
>

I don't mind the above, but I think the name could be changed.

I'm really coming around to the syntax

    std::vector<uint> DofMap::tabulate_dofs(......)

In most cases it has negligible performance impact. It's much easier
to wrap in Python!

> Then we could iterate over the mesh collect dofs, sort them and last but
> most important make sure they are all local (to processor) dofs.

It's more subtle than just local - on a process there are 'owned' and
'shared but not owned' dofs.

Garth

> This
> would also just work for SubDofMaps.
>
> For safety we could move the method to FunctionSpace, and remove Mesh
> from the top method, so we can make sure the correct Mesh is used.
>
> Johan
>
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