dolfin team mailing list archive

[Anders Logg <logg@xxxxxxxxx>]

On Tue, Jun 01, 2010 at 07:13:29PM +0100, Garth N. Wells wrote:
>
>
> On 01/06/10 19:11, Anders Logg wrote:
> >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?
> >
>
> Yes.

ok, thanks.

--
Anders

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