dolfin team mailing list archive

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

Johan Hake wrote:
> On Monday 22 June 2009 10:51:49 Ola Skavhaug wrote:
> > On Mon, Jun 22, 2009 at 10:44 AM, Garth N. Wells<gnw20@xxxxxxxxx> wrote:
> > > Johan Hake wrote:
> > > > On Saturday 20 June 2009 13:10:46 Garth N. Wells wrote:
> > > > > I tried to do
> > > > >
> > > > >    u0.vector() = u1.vector()
> > > > >
> > > > > where u0 and u1 are both discrete functions, in PyDOLFIN but it doesn't
> > > > > work so I'm using
> > > > >
> > > > >    u0.vector().assign( u1.vector() )
> > > > This is the correct way to do it. Assignment operators are just ignored
> > > > for the dynamically typed languges supported by SWIG. We therefore
> > > > rename the foo.operator= to foo.assign.
> > > >
> > > > However for the Vector and Matrix interfaces we also support the numpy
> > > > lookalike assignment:
> > > >
> > > >   v[:] = u
> > > >
> > > > and
> > > >
> > > >   A[:,:] = B
> > > >
> > > > I have talked to Anders about removing both v.assign and v.set(double *)
> > > > and "force" the PyDOLFIN users to use the numpy assignments.
> > > Is there any difference in performance between the two?
> > >
> > > Garth
> > The slicing means that the actual memory of A is overwritten. I guess
> > that is the same as the operator= did before?
> > Hence, I guess there will be no big difference.
>
> When I implemented the slicing operator I assumed that the operator= would be 
> fastes when a full vector is copied, a la:
>
>   v[:] = u,
>
> because the operator= can use optimized functions from the underlaying la 
> library, for example VecCopy for PETSc. So I added a check for this in the 
> python slicing operator. If a full slice is assigned, as above, we use the 
> assign method, otherwise we use the set(const double*, uint, const uint*) 
> method.

OK, nice.

Garth

> Johan
>
> > Ola
> >
> > > > Johan
> > > >
> > > > > Is there a fundamental reason why '=' can't be used or does SWIG just
> > > > > need to be told how to overload '=' for vectors?
> > > > >
> > > > > Garth
> > > > > _______________________________________________
> > > > > DOLFIN-dev mailing list
> > > > > DOLFIN-dev@xxxxxxxxxx
> > > > > http://www.fenics.org/mailman/listinfo/dolfin-dev
> > > _______________________________________________
> > > DOLFIN-dev mailing list
> > > DOLFIN-dev@xxxxxxxxxx
> > > http://www.fenics.org/mailman/listinfo/dolfin-dev