dolfin team mailing list archive

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

Kent Andre wrote:
> On ma., 2008-09-15 at 11:48 +0100, Garth N. Wells wrote:
> > Kent Andre wrote:
> > > On ma., 2008-09-15 at 11:19 +0100, Garth N. Wells wrote:
> > > > 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:   4751:df802d1b2b349e91a51b70f799ba6d0d3b825376
> > > > > tag:         tip
> > > > > user:        Anders Logg <logg@xxxxxxxxx>
> > > > > date:        Sat Sep 13 08:55:34 2008 +0200
> > > > > files:       dolfin/function/DiscreteFunction.cpp
> > > > > description:
> > > > > Don't initialize vector in DiscreteFunction if already initialized.
> > > > Vector::init() only resizes the vector if necessary, but it also zeroes 
> > > > the vector. Looks to me like it is desirable to zero the vector?
> > > >
> > > > Garth
> > > The reason for this, I think, is initialization as such: 
> > >
> > > solve(A, x, b, cg, amg)
> > > u = Function(element, mesh, x)
> > > plot(u)
> > The problem is that I could also create the function, and then use it 
> > with a vector that hasn't been initialised properly.
>
> But then you would not use this constructor? 
>
> > The most robust approach, which I've been working towards, is that a 
> > DiscreteFunction always owns it's vector and can't be initialised with a 
> > Vector. The above code would be
> >
> >    u = Function(element, mesh)
> >    solve(A, u.vec(), b, cg, amg)
> >    plot(u)
> >
> > Garth
>
> It is fine by me if DiscreteFunction owns the vector, then the entries
> of x has to be copied. 

I've set it up now such that if a Function is created using the simple 
constructor interface (no smart pointers), it always owns the vector and 
a reference to the vector is returned by Function::vector(). This vector 
is initialised to zero.

It's possible to create a Function and associate it with a particular 
vector by using the interface with smart pointers, in which case the 
vector is not initialised to zero.

Garth


> I'm having similar design decisions in BlockVectors and BlockMatrix.
> Should they own the subvectors and submatrices ?  For now I have a
> boolean flag. In general I think it should be possible to set and get
> underlying pointers. This is dangerous but it is often something one
> would like to do particulary when coupling to other software packages. 
>
> Kent