On Mon, May 30, 2011 at 10:24:48AM -0700, Johan Hake wrote: > On Monday May 30 2011 04:33:29 Martin Sandve Alnæs wrote: > > On 30 May 2011 12:51, Marie E. Rognes <m...@simula.no> wrote: > > > On 05/30/2011 11:26 AM, Martin Sandve Alnæs wrote: > > >> Since this feature implementation relies on modifying immutable objects, > > >> I'm not the least surprised you're getting problems. The bug is not that > > >> dolfin subdomains are not passed with forms, but that they are allowed > > >> to be attached in the first place on an existing and assumed immutable > > >> form object. > > > > > > Yes... > > > > > >> The short term solution to this bug is to revert pydolfin back to > > >> providing subdomains as arguments to assemble and variationalproblem > > >> where they belong, instead of attaching them to forms. I think this > > >> should be done for fenics 1.0 if this bug is a problem. > > >> > > >> Improvements to the language for expressing subdomains of various kinds > > >> is in the design stage, but that won't happen before the summer. > > > > > > Specifications of subdomain does not belong as arguments to assemble and > > > variational problem. If you have a form > > > > > > L = g*v*dG > > > > > > where G is a part of a boundary (In semi-math, semi-UFL notation), G > > > should be related to the form. Not to the matrix resulting from the > > > assembly of the form. > > > > > > (cc to DOLFIN since the below involves DOLFIN mainly) > > > > > > The interface to VariationalProblem > > > > > > VariationalProblem(., ., bcs, exterior_facet_domains, > > > interior_facet_domains, cell_facet_domains) > > > > > > was rather suboptimal because it assumed implicitly that the bilinear and > > > the linear form were defined over the same subdomains. That in, > > > combination with dx = dx(0) etc, is highly bugprone. > > > > > > I care of course because if you want to use the same patent for an > > > variational problem with automatic adaptivity, and take care of the > > > above, the required input will look something like this > > > > > > VariationalProblem(., ., bcs, > > > primal_bilinear_exterior_facet_domains, > > > primal_bilinear_interior_facet_domains, > > > primal_bilinear_cell_domains, > > > primal_linear_exterior_facet_domains, > > > primal_linear_interior_facet_domains, > > > primal_linear_cell_domains, > > > goal_exterior_facet_domains, > > > goal_interior_facet_domains, > > > goal_cell_domains) > > > > > > which I can't live with. > > > > > > The Coefficient/Function magic must involve some of the same issues as > > > this. I imagine that a similar way of fixing it should be possible. > > > > I'm not saying it can't be implemented, only that it can't > > be implemented well within the FEniCS 1.0 timeframe, and > > that fixing the current solution will lead down a bad path. > > I'm hoping for a much better solution later this year, but > > that will require some design work first. > > > > An alternative short term approach could be to attach the data to the > > measures. > > > > dxp = dx(cell_domains=primal_cell_domains) > > dsp = ds(exterior_facet_domains=primal_exterior_facet_domains) > > L = g*dxp(1) + f*dsp(0) > > > > and making sure that this data follows measure objects around. > > They can then be collected in ufl preprocess just like functions > > and function spaces. Then the connection between the > > meshfunction and the dx(i) index looks more explicit as well. > > I like that syntax. I guess we only allow one type of cell integral within one > form? > > My conserns regards changing the subdomains after creating the form, as this > can be a convinient way of reusing a compiled form. But I guess letting domain > arguments in assemble override domains in the form should fix that.
I like the current syntax and would not like to change it again. An important point is that it allows the same syntax to be used in both Python and C++: a.exterior_facet_domains = exterior_facet_domains a.exterior_facet_domains = exterior_facet_domains; This won't work with dx etc. I suggest we keep the current syntax and find an improved implementation later. -- 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
