dolfin team mailing list archive

["Garth N. Wells" <gnw20@xxxxxxxxx>]

Johan Hake wrote:
> On Monday 24 August 2009 09:56:55 Garth N. Wells wrote:
> > Johan Hake wrote:
> > > 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!
> > So a constructor
> >
> >      Function::Function(uint i)
> >
> > would be better? 
>
> Yes, but then we could not fetch the shared Vector?
>
> > I'm reluctant to add a constructor since it breaks the
> > paradigm that a Function constructor gives a deep copy. 
>
> Ok.
>
> > Could you create
> > an empty Function internally on the PyDOLFIN side and then pass it to
> >
> >      Function::sub_function(Function& sub_function, uint i)
> >
> > to attach the shared data to create the sub-Function 'sub_function'?
>
> Yes, this should be fine. I guess such a function will then just destroy any 
> present vector and exchange it with the one shared with the FullFunction?

Yes. We can throw an error if there is any data already attached to the 
Function.

It would be neat if we could somehow make member functions 'private' to 
PyDOLFIN.

Garth

> Johan
>
> > Garth
> >
> > > 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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