On 24 September 2013 09:18, Johan Hake <hake....@gmail.com> wrote: > On Tue, Sep 24, 2013 at 10:04 AM, Garth N. Wells <gn...@cam.ac.uk> wrote: >> >> On 24 September 2013 08:56, Johan Hake <hake....@gmail.com> wrote: >> > On Mon, Sep 23, 2013 at 9:29 PM, Garth N. Wells <gn...@cam.ac.uk> wrote: >> >> >> >> On 23 September 2013 18:20, Johan Hake <hake....@gmail.com> wrote: >> >> > I am working on sub-function assignment. To facilitate caching of dof >> >> > indices for a particular assignment combination I suggest introducing >> >> > a >> >> > FunctionAssigner class which caches the necessary indices (dofs) for >> >> > the >> >> > whole domain. >> >> > >> >> > Something like: >> >> > >> >> > mesh = UnitSquareMesh(10,10) >> >> > V = FunctionSpace(mesh, "CG", 1) >> >> > VV = V*V >> >> > >> >> > # Assign two scalar functions to the components of a mixed function >> >> > assigner0 = FunctionAssigner([V, V], VV) >> >> > >> >> > # Assign components of a mixed function to scalar Functions >> >> > assigner1 = FunctionAssigner(VV, [V, V]) >> >> > >> >> > # Assign a scalar function to a component of a mixed function >> >> > assigner2 = FunctionAssigner(V, VV.sub(1)) >> >> > >> >> > u0, u1 = Function(V), Function(V) >> >> > U = Function(VV) >> >> > >> >> > Then in some time loop: >> >> > >> >> > while t < tstop: >> >> > ... >> >> > assigner0.assign([u0, u1], U) >> >> > ... >> >> > assigner1.assign(U, [u0, u1]) >> >> > ... >> >> > assigner2.assign(u0, U.sub(1)) >> >> > >> >> > In C++ the equivalent to a list of Foo will be a std::vector of >> >> > shared >> >> > Foos. >> >> > >> >> > Comments? >> >> > >> >> > By using sub spaces and sub functions we avoid using indices in the >> >> > interface, which I think is neat. However, there are some limitations >> >> > with >> >> > the present interface: >> >> > >> >> > 1) The FunctionAssigner needs to have access to the local ownership >> >> > range of >> >> > a sub dofmap, but that is not possible as it is set to 0,0 during >> >> > construction. Could we add a proper local ownership range to a sub >> >> > dofmap? >> >> >> >> I need this too in another context (related to field split). I don't >> >> have a resolution, but did think that perhaps a sub-dofmap should hold >> >> pointer to the 'root' dofmap? >> > >> > >> > That would be nice. But we need to make sure circular references do not >> > cause memory leakage. We might also have a name problem as the 'root', >> > 'parent', aso, names are now used by the Hierarchical class. >> > >> > Also, why is it not possible to just copy the owner_ship range from the >> > parent during construction? >> > >> >> That's possible and is simpler, but maybe it should have a different >> name for sub-dofmaps, otherwise it might appear that a sub-dofmap is >> not a view when it really is. > > > Could it lead to unpredictable behavior? The dofs accessed from the sub > dofmap are all correctly interpreted to the subspace, compared to the > _vector data contained in a sub Function. We could add a some member > function which could be queried whenever one need to find out if the dofmap > is a sub dofmap. For example we could store the component vector, like we do > for FunctionSpace. If the component is not empty it is a sub dofmap. >
It's probably all ok. My concern is if anyone relies on DofMap::ownership_range in a way that will lead to problems. >> >> >> > 2) The FunctionAssigner need to be able to access the private _vector >> >> > of >> >> > a >> >> > parent Function during the assignment, as calling subfunc.vector() >> >> > raises an >> >> > error. This can be fixed by a friend statement. Is that acceptable? >> >> > >> >> >> >> Could be ok. Maybe we can come up with a safe way to allow the vector >> >> to be accessed? >> > >> > >> > This could be fixed if the 'root' Function could be accessed from the >> > sub >> > function, similar to the sub dofmap. >> > >> >> Yes. >> > > Any name suggestions, for such a method? parent and root are all taken... > I'm not so keen on holding a reference/pointer to the 'root' it it's not essential because the of circular dependency. Maybe just allowing const access to the vector is enough? Garth > Johan > > >> >> Garth >> >> > Johan >> > >> >> >> >> >> >> Garth >> >> >> >> > Johan >> >> > >> >> > _______________________________________________ >> >> > fenics mailing list >> >> > fenics@fenicsproject.org >> >> > http://fenicsproject.org/mailman/listinfo/fenics >> >> > >> > >> > > > _______________________________________________ fenics mailing list fenics@fenicsproject.org http://fenicsproject.org/mailman/listinfo/fenics
