dolfin team mailing list archive

[Anders Logg <logg@xxxxxxxxx>]

On Fri, Feb 02, 2007 at 09:32:13PM +0100, Garth N. Wells wrote:
> Anders Logg wrote:
> > On Fri, Feb 02, 2007 at 02:46:35PM +0100, Johan Hoffman wrote:
> >>> Johan Hoffman wrote:
> >>>> About the global dof numbering for the different components in a
> >>>> function
> >>>> defined by a mixed element: I get the impression that we use a different
> >>>> ordering for the mixed dofs than for the dofs of a regular vector valued
> >>>> function?
> >>>>
> >>> I don't think so. For both mixed and vector elements, dofs at the same
> >>> node do not lie next to each other in the dof mapping.
> >>>
> >>> It will be possible to choose the dof ordering soon when the new
> >>> assembly is  up and running. There is already a new class DofMap which
> >>> will handle this.
> >>>
> >>> Garth
> > 
> > Generally, you can never be sure how the dofs are ordered. This could
> > potentially change between different versions of FFC or between
> > different form compilers. As long as the generated code follows the
> > UFC specification, the dof maps may be different.
> >
> 
> This sounds strange. DofMap will provide the functionality to influence 
> the dof mapping. UFC should provide the input to DofMap, but the user 
> should then be able to manipulate it if they wish.

I don't mind documenting how FFC actually orders the dofs, but the
idea of the UFC interface is that one should not need to know intimate
details of FFC to work with the generated code.

/Anders