On 09/03/2012 10:24 AM, Garth N. Wells wrote: > On 3 September 2012 09:06, Marie E. Rognes <m...@simula.no> wrote: >> On 09/02/2012 12:23 PM, Garth N. Wells wrote: >>> >>> 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? >> >> >> Agree! >> >> >>>> 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. >> >> >> Yes, I would find this less confusing and more useful. >> > > Yes, I was getting confused. Also, I was trying convert a common 3rd > party format the uses names for sub-domains. > >> >>>> 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. >>>> >> >> I think in order to cut the third one, there needs to be a reliable and >> flexible way of replacing subdomains in a given form cf Johan's comment. >> This might exist today, but I'm not entirely sure. >> > > Should be easy via shared pointers. >
Not sure how to do this robustly in the context of a ufl.Form, which is what a user is exposed to in the Python interface. Now one is not allowed to alter: ufl.Form.cell_domains We could require the user to instantiate a dolfin.Form, then it is straightforward. But that solution introduces another abstraction, which is not intuitive. Johan >> >>> 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. >> >> >> Cutting this interface is a significant change, so I would suggest >> adding a deprecation warning and making a release before doing so. >> > > Could be tricky because the interface is the bug, due to ambiguities > with all the default arguments. > > Garth > >> -- >> Marie >>> >>> 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 >> >> >> >> _______________________________________________ >> Mailing list: https://launchpad.net/~dolfin >> Post to : dolfin@lists.launchpad.net >> Unsubscribe : https://launchpad.net/~dolfin >> More help : https://help.launchpad.net/ListHelp > > _______________________________________________ > Mailing list: https://launchpad.net/~dolfin > Post to : dolfin@lists.launchpad.net > Unsubscribe : https://launchpad.net/~dolfin > More help : https://help.launchpad.net/ListHelp > _______________________________________________ Mailing list: https://launchpad.net/~dolfin Post to : dolfin@lists.launchpad.net Unsubscribe : https://launchpad.net/~dolfin More help : https://help.launchpad.net/ListHelp
