dolfin team mailing list archive

[Anders Logg <logg@xxxxxxxxx>]

On Mon, Aug 17, 2009 at 01:16:31PM +0100, Garth N. Wells wrote:
>
>
> Anders Logg wrote:
> > On Mon, Aug 17, 2009 at 01:03:55PM +0100, Garth N. Wells wrote:
> >>
> >> Johan Hake wrote:
> >>> On Monday 17 August 2009 13:33:21 Garth N. Wells wrote:
> >>>> Please send any comments on how a SubFunction should work as I'm going
> >>>> to work on it soon (the Cahn-Hilliard demo runs in parallel(!) ;) with
> >>>> the exception of the extraction of sub-Functions for output). I'm
> >>>> inlined to change a sub function such that for
> >>>>
> >>>>    Function u0 = u[0]
> >>>>
> >>>> the Function u0 will only point the vector belonging to u rather than
> >>>> creating a new vector. The advantages are:
> >>>>
> >>>> - No need to copy a vector
> >>>> - DofMap will not require 'is_view'
> >>>> - Possible to do things like
> >>>>     u0  = 0.0;
> >>>>     u1  += v;
> >>>>     u0.interpolate();
> >>> What would Function::vector() for a SubFunction then return? The original full
> >>> Vector?
> >>>
> >> Yes.
> >>
> >>> It would be cool to add a view of the original Vector that only represents the
> >>> values of the dofs in the SubFunction, without coping data. I fiddled around
> >>> with this when adding slicing for the PyDOLFIN la interface, but realized that
> >>> it would be too difficult.
> >>>
> >> This is more or less what I plan to do, although internally. A user
> >> wouldn't see the vector, but operations like interpolate would only
> >> involve part of the vector.
> >>
> >> We could add a class like
> >>
> >>    VectorView(GenericVector& x, DofMap& dof),
> >>
> >> which could derive from GenericVector, to provide views. It isn't a
> >> priority for me though.
> >>
> >> Garth
> >
> > Sounds like this could be coordinated/merged with the functionality
> > required for the parallel get()/gather(). It's much the same thing,
> > being able to address a vector with dofs which don't correspond to the
> > entries in the vector.
> >
>
> Yes.
>
> We need a bug tracking system to keep track of suggested features ;).

I'll check on the status.

--
Anders

Attachment: signature.asc
Description: Digital signature