dolfin team mailing list archive

[Johan Hake <hake@xxxxxxxxx>]

On Wednesday 07 October 2009 22:33:06 Anders Logg wrote:
> On Wed, Oct 07, 2009 at 10:30:42PM +0200, Johan Hake wrote:
> > On Wednesday 07 October 2009 21:58:36 Garth N. Wells wrote:
> > > The Python mixed-poisson demo is failing in parallel because the
> > > extraction of sub-functions via split() is making a deep copy, even
> > > though it should be a 'shallow' copy. Any ideas on how to fix it?
> >
> > Yes I see now whats wrong... I thought that the assignment operator
> > somewhat kept the shallow copy.
> >
> > I think we need to add the hack we had previously in DiscreteFunction to
> > make it work again. Should we add this in Function directly or should I
> > try to subclass Function and implement that particular constructor? I
> > would prefer the first.
> 
> What is the hack? Yes, it would be good to avoid creating a special
> subclass.

It is this constructor we need.

   /// Sub-function constructor (shallow copy of the vector)
   DiscreteFunction(Function& v, uint i)
   {
     // Check that vector exists
     if (!v.has_vector())
       error("Unable to extract sub function, missing coefficients (user-
defined function).");

     // Get sub-function (Function will store pointer to sub-Function)
     Function& sub_function = v[i]; 
     
     // Copy function space pointer
     this->_function_space = sub_function._function_space;

     // Copy vector pointer
     this->_vector = sub_function._vector;
   }

Johan