dolfin team mailing list archive

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

Anders Logg wrote:
> On Wed, Apr 09, 2008 at 06:32:48PM +0100, Garth N. Wells wrote:
> > Anders Logg wrote:
> > > On Wed, Apr 09, 2008 at 06:14:35PM +0200, Ola Skavhaug wrote:
> > > > Dag Lindbo skrev den 09/04-2008 følgende:
> > > > > Hello again!
> > > > >
> > > > > Why is it not possible any longer to get the Vector associated with a 
> > > > > Function? E.g:
> > > > >
> > > > > #include <dolfin.h>
> > > > > using namespace dolfin;
> > > > >
> > > > > int main()
> > > > > {
> > > > >    Function u;
> > > > >    Vector& v = u.vector();
> > > > > }
> > > > int main()
> > > > {
> > > >      Function u;
> > > >      Vector v;
> > > >      v = u.vector();
> > > >      return 0;
> > > > }
> > > >
> > > > Should work. A Function returns a GenericVector reference, and the Vector
> > > > reference needs to be a Vector. Then the operator= in Vector is applied in the
> > > > assignment.
> > > >
> > > > Ola
> > > I don't think one should need to make a copy of the vector. It should
> > > work to either use the vector you get by calling vector() directly,
> > > for example
> > >
> > >   solve(A, u.vector(), b); // Doesn't work currently but it should!
> > >
> > > You may also do
> > >
> > >   GenericVector& x = u.vector();
> > This works. Can someone remind me how to convert a GenericVector into 
> > the underlying vector type( e.g. a uBlasVector or a PETScVector)?
> >
> > Garth
>
> If x is a GenericVector, then
>
>   PETScVector* xx = dynamic_cast<PETScVector*>(&x);
>   if (xx == 0)
>     error("Not a PETSc Vector.");

Could we add a member function to GenericVector/GenericMatrix to do this?

  template < class T>
  T* foo(GenericVector& x)
  {
    T* xx = dynamic_cast<T*>(&x);
    if (xx == 0)
      error("Not a ??? Vector.");
    return xx;
  }

Garth