dolfin team mailing list archive

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

Johan Hake wrote:
> On Saturday 17 October 2009 12:32:54 Garth N. Wells wrote:
> > Will
> >
> >      uh = U[1]
> >
> > return a deep or shallow copy of the sub-Function?
>
> To avoid confusion with the ufl interface we have limited the interface for 
> SubFunctions in PyDOLFIN to split. split returns a shallow copy by default. 
> pass True to split and it will return a deepcopy. In your case it would be:
>
>   uh = U.split()[0]
>
> and
>
>   uh = U.split(True)[0]
>
> operator[] is used when you define forms. We have not yet managed to merge the 
> two operations into one.

OK. Do we still have the function 'sub'?


> > Where is the operator [] define for sub-Functions?
>
> The operator you are using is the ufl one, which is defined in 
> ufl.exproperators.py. 

OK, but it's not clear to me then what's happing with this extract of my 
code:

 problem = VariationalProblem(a, L, bcs)
 Uh = problem.solve()

 u = Expression("epx(x[0])", V = Vexact)

 uh = Uh[1]
 M = (uh-u)*(uh-u)*dx
 error = sqrt(assemble(M, mesh=mesh))

Garth


> Johan