dolfin team mailing list archive

[Anders Logg <logg@xxxxxxxxx>]

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.");

-- 
Anders