dolfin team mailing list archive

[Johan Hake <hake@xxxxxxxxx>]

On Monday 24 August 2009 09:08:49 Garth N. Wells wrote:
> Johan Hake wrote:
> > On Saturday 22 August 2009 14:02:06 DOLFIN wrote:
> >> One or more new changesets pushed to the primary dolfin repository.
> >> A short summary of the last three changesets is included below.
> >>
> >> changeset:   6833:30ddf63b8a1e25a6234703f1d47736ab90602376
> >> tag:         tip
> >> user:        "Garth N. Wells <gnw20@xxxxxxxxx>"
> >> date:        Sat Aug 22 12:03:42 2009 +0100
> >> files:       dolfin/fem/VariationalProblem.cpp
> >> dolfin/function/Function.cpp dolfin/function/Function.h
> >> dolfin/function/SpecialFunctions.h
> >> dolfin/function/SubFunctionData.h dolfin/function/dolfin_function.h
> >> dolfin/swig/dolfin_docstrings.i dolfin/swig/dolfin_headers.i
> >> description: Work on new sub Function logic.
> >
> > I am not sure we can completely wrap the new logic to PyDOLFIN.
> >
> > To be able to have the double inheritance of cpp.Function and
> > ufl.Function in PyDOLFIN, new Functions have to be constructed in the
> > Python interface (function.py).
> >
> > The operator[] is mapped to a hidden function _sub. The created Function
> > that is returned from this is passed to the copy constructor in the
> > Python version of sub (creating a new Function object). This is basically
> > just how we did it before the new design, because previously operator[]
> > returned a
> > SubFunctionData, which was passed to a Function constructor. The
> > transition to the new logic works in PyDOLFIN because the Function copy
> > constructor is used instead of the removed SubFunctionData constructor.
> >
> > This means that the handy operator[], which returns a Function with a
> > shared vector, cannot fully be used from PyDOLFIN. Would it be possible
> > to add a shallow copy function in some way. Would this work with the
> > present SubFunction design?
>
> Would something like
>
>      Function::sub_function(Function& sub_function, uint i)

Yes I think so. If we could make this a constructor (shallow copy constructor) 
I would be most happy!

Johan

> work?
>
> Garth
>
> > Johan
> >
> >> The new logic is more consistent with conventions.
> >> Function::operator[](uint i) now returns a reference to the sub
> >> Function. A Function keeps track of its sub Functions. Therefore,
> >>
> >>     Function& u0 = u[0];
> >>
> >> and
> >>
> >>    plot(u[0]);
> >>
> >> do not involve copying a vector. u and u0 share the same vector. If a
> >> DofMap is renumbered after construction, the Function can make sure that
> >> all its sub Functions are modified accordingly. Likewise if the mesh is
> >> refined.
> >>
> >> Assignment makes a deep copy, i.e. you will get a new copy of
> >> everything. Therefore with
> >>
> >>   Function u0 = u[0];
> >>
> >> a new vector will be created and u0 will not change when u changes.
> >>
> >> What remains to be done is reseting the dof map for the reduced
> >> dimension of the subfunction and extracting vector components upon
> >> assignment. Eventually, for
> >>
> >>   Function u0 = u[0];
> >>   GenericVector& x = u0.vector();
> >>
> >> the vector x will only contains components related to the sub function
> >> u0.
> >>
> >>
> >> changeset:   6832:887eaeeb4e81b30cf5e2031c77bd2d77f1faed18
> >> user:        "Garth N. Wells <gnw20@xxxxxxxxx>"
> >> date:        Fri Aug 21 18:00:56 2009 +0100
> >> files:       dolfin/fem/DofMap.cpp
> >> description:
> >> Comment out duplicated code in DofMap.
> >>
> >>
> >> changeset:   6831:da5b9081b7cbe9753b9ce833acffe0a9c6cac9e2
> >> user:        "Garth N. Wells <gnw20@xxxxxxxxx>"
> >> date:        Fri Aug 21 17:23:38 2009 +0100
> >> files:       dolfin/log/LogStream.cpp dolfin/log/LogStream.h
> >> dolfin/nls/NonlinearProblem.h description:
> >> dolfin::cout fix for 32 bit systems.
> >>
> >> ----------------------------------------------------------------------
> >> For more details, visit http://www.fenics.org/hg/dolfin
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> >
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