Comment 6 for bug 891716

On Thu, Nov 17, 2011 at 10:53:04PM +0100, Andre Massing wrote:
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> On 11/17/2011 10:37 PM, Anders Logg wrote:
> > On Thu, Nov 17, 2011 at 10:24:56PM +0100, Andre Massing wrote: On
> > 11/17/2011 09:40 PM, Anders Logg wrote:
> >>>> Looks like the only remaining thing is periodic BC not
> >>>> working with Trilinos. From running the periodic demo:
> >>>>
> >>>> Error: Unable to add block of values to Epetra matrix. ***
> >>>> Reason: Did not manage to perform
> >>>> Epetra_FECrsMatrix::SumIntoGlobalValues. *** Where: This
> >>>> error was encountered inside EpetraMatrix.cpp.
> >>>>
> >
> > I wrote a somewhat lengthy email about that, explaining what goes
> > wrong and asking for opinons... you have even replied to it :)
> >
> >> I know and I've read it carefully!
>
> I was just a bit confused about the implied desired action :)

No action required at the moment. :-)

> >> I think I responded and said that this needs to be addressed by
> >> incorporating boundary conditions into the FunctionSpace by
> >> implementing constrained spaces. I even linked to a blueprint.
>
> I have seen that, nice. Marie had already registered on at
> https://blueprints.launchpad.net/dolfin/+spec/constrained-spaces
> so these can be merged or the older one can be marked as superseded?

I'll take a look. I actually looked for that blueprint as I had a
vague memory that we should have a blueprint on that from before but
couldn't find it. Maybe I searched for "restricted" instead of
"constrained".

> >> Bottom line: we won't fix this now so I'll add a check in that
> >> demo that it doesn't work with Epetra.
>
> Ok, I had the same feeling...But you could also use crisscross grids
> to fix it (just kidding ... )

Criss-cross grids seem to fix many problems. There was a long review
process for one of the FEniCS book chapters regarding an issue where
the authors had used criss-cross grids to get around some problem
(locking if I remember correctly).

--
Anders

> - --
> Andre
>
>
>
> >
> >> -- Anders
> >
> >
> > The bottom line is that there are several related issues: 1. The
> > sparsity pattern does not consider PeriodicBC thus there will be an
> > error in Trilinos when copying a slave row to a master row since
> > the matrix is filled / finalized.
> >
> > 2. Dirichlet and PeriodicBC calling and matrix.apply() while
> > applying bc. Every such call triggers a finalization of the matrix
> > atm.
> >
> > 3. https://bugs.launchpad.net/dolfin/+bug/891452 (which for some
> > reason does not show up in the bug overview, neither has been sent
> > to the list, strange.)
> >
> > See the original post
> > https://bugs.launchpad.net/dolfin/+bug/864741/comments/2
> >
> > for a more detailed explanation. The point is that it seems like a
> > more fundamental problem where I haven't dared to dirty-hack around
> > without opinions from the devs /maintainers :)
> >
> >
> >
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