dolfin team mailing list archive

["Matthew Knepley" <knepley@xxxxxxxxx>]

On Tue, Jul 22, 2008 at 10:42 AM, Anders Logg <logg@xxxxxxxxx> wrote:
> On Tue, Jul 22, 2008 at 05:05:45PM +0200, Martin Sandve Alnæs wrote:
>> UFC 1.1 already has a function for tabulating the number of dofs
>> associated with each mesh entity, but I don't think FFC implements UFC
>> 1.1 completely yet.
>
> True. FFC does not yet implement tabulate_entity_dofs but it would be
> fairly easy to add.
>
>> Shouldn't this be all that's needed from FFC for
>> DOLFIN to compute/estimate the max non-zeroes per row? Sum the local
>> dimension of all elements and subtract the number of dofs for each
>> entity shared by neighbouring elements.
>
> How should this be done? It seems that to do this, we would need to
> compute all cell-cell connectivity which is fairly expensive. On the
> other hand, we need to compute it anyway to initialize edges and
> facets when there are dofs on those entities.

You can do it on the fly. I just use adj(c) = closure(start(c)). With a suitable
global order, you can distinguish between diagonal and offdiagonal, and
you are done.

  Matt

> --
> Anders
>
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