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
