dolfin team mailing list archive

[Anders Logg <logg@xxxxxxxxx>]

On Tue, Jun 01, 2010 at 07:01:48PM +0100, Garth N. Wells wrote:
>
>
> On 01/06/10 18:59, Anders Logg wrote:
> >On Tue, Jun 01, 2010 at 06:57:33PM +0100, Garth N. Wells wrote:
> >>
> >>
> >>On 01/06/10 18:51, Anders Logg wrote:
> >>>On Tue, Jun 01, 2010 at 05:13:11PM +0100, Garth N. Wells wrote:
> >>>>
> >>>>
> >>>>On 01/06/10 17:07, Anders Logg wrote:
> >>>>>On Tue, Jun 01, 2010 at 03:19:50PM +0100, Garth N. Wells wrote:
> >>>>>>
> >>>>>>
> >>>>>>On 01/06/10 15:10, Anders Logg wrote:
> >>>>>>>What is the difference from before? Is it only that the dofs are
> >>>>>>>always tabulated and stored (never computed on the fly)?
> >>>>>>>
> >>>>>>
> >>>>>>More or less. There are some bug fixes and some missing features
> >>>>>>have been added (collapsed dof maps for renumbered maps, work in
> >>>>>>parallel now).
> >>>>>>
> >>>>>>It was too complicated (for me at least) to have both tabulated dofs
> >>>>>>and on the fly computation via UFC in the same class. It's much
> >>>>>>easier to follow now (which helped in finding some bugs).
> >>>>>>
> >>>>>>Garth
> >>>>>
> >>>>>Can you remind me of what collapse do? What is a contiguous dofmap?
> >>>>>
> >>>>
> >>>>A sub-dofmap will be, by default, a view into the original dof map.
> >>>>It will extract the the relevant indices, but it won't change them.
> >>>>It's suitable for when the sub-function shares the vector with the
> >>>>original equation, e.g.
> >>>>
> >>>>   Function&   u = U[0];
> >>>>   Function&   p = U[1];  // U, u and p shared the same vector
> >>>>
> >>>>A collapsed dof map is independent of the original dof map, with the
> >>>>lowest index = 0 and the greatest = global_dimension -1. It's used
> >>>>when a sub-function is extracted from a Function such that it has
> >>>>it's own vector, e.g.
> >>>>
> >>>>   Function u = U[0]; // u has its own vector
> >>>>   Function p = U[1]; // p has its own vector
> >>>>
> >>>>Garth
> >>>
> >>>ok. And is it the case that if the dof map has not been renumbered,
> >>>then collapsing it is the same as subtracting the offset,
> >>
> >>Yes.
> >>
> >>>but when it
> >>>has been renumbered, a new numbering will be computed?
> >>>
> >>
> >>Yes, and a map from the ufc dof index (as given by the ufc_dofmap
> >>object) to the actual dof index.
> >
> >Why is that map needed? If the dof map has been renumbered (in build),
> >why do we need to ever think about the old UFC dof map?
> >
>
> When we want to extract a sub-dof map. We first get the ufc
> sub-dofmap which uses UFC numbering, which we then need to map to
> the current numbering.

Is that because the separation between sub systems may be lost in the
renumbered map while being clearly separated in the UFC dof map?

--
Anders

Attachment: signature.asc
Description: Digital signature