On 2 September 2012 11:10, Anders Logg <l...@simula.no> wrote: > 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. >
I think that this is very clumsy and mixes concepts. Say I have one mesh but want to perform two different simulations with different bcs. It's opaque. What happens if I have markers in a Mesh and markers attached to a Form -> ambiguous. Better would be to store the markers as part of the mesh, but pull them out and attach them to a form. I was already planning to have mesh markers in a mesh file that are identified by strings (e.g. "top", "inner sphere", etc) rather than integers (which are error prone because they convey no meaning). A user could query which markers a mesh has (via a set of identifier strings), and attach the right ones. > 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. > This is nice. > 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. > We have a bug that I'm more interested in fixing simply and robustly than in preserving a clumsy interface, so I'd cut it. Users can update their code. Garth > 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 _______________________________________________ Mailing list: https://launchpad.net/~dolfin Post to : dolfin@lists.launchpad.net Unsubscribe : https://launchpad.net/~dolfin More help : https://help.launchpad.net/ListHelp
