dolfin team mailing list archive

[Anders Logg <logg@xxxxxxxxx>]

On Sat, Sep 01, 2012 at 03:09:42PM +0100, Garth N. Wells wrote:
> The logic around how we handle integration over domains is confusing.
> I'm trying to fix a small problem which is opening a can of worms.
> Subdomain data can be optionally passed to the assembler, attached to
> a Form or attached to a Mesh (the latter being particularly confusing
> because it's mixing concepts). I suggest that we have just one to do
> things, and I think the most logical and user friendly is to attach
> subdomain data to Forms. Opinions?

I agree that the logic is complex, but it is there for a reason.

There are three ways to specify subdomains, by order of increasing
priority.

First, it can be specified as part of the mesh. This is a good thing
since it allows markers to be stored as part of Mesh XML files. Very
useful for Mesh generators and tools like VMTK.

Second, it can be specified as part of a Form. This is useful for
assembling several forms on the same mesh but with different domains.

Third, it can be specified explicitly as an argument to the assembler.

If we should cut any of these, I would suggest cutting the third one,
but I think it is widely used as part of both user code and examples
so I'm not sure we should cut it.

The logic for extracting which domains could be moved to a special
function that takes care of extracting the correct MeshFunction from
either Mesh, Form or explicit arguments. With some extra diagnostics
and careful error checking, it can be made more robust and
user-friendly.

--
Anders