[Trilinos-Users] null space removal

Nico Schlömer nico.schloemer at ua.ac.be
Wed Sep 8 12:58:47 MDT 2010

> There was once an implementation in Loca, but I do not know the
> details.

There's LOCA::MultiContinuation::ConstraintInterface which I believe
was created for this exact situation. We've been using it successfully
for one particular PDE here, and if you're doing continuation then this
is probably what you want to look at.


On Wed, 08 Sep 2010 12:53:14 -0600, "David Day" <dmday at sandia.gov>
> Chris and Mike,
> The problem arises in continuation problems.  It can be addressed
> using a projection.  Often the projection is oblique (unsymmetric),
> and may be unstable.  A much better solution is to instead constrain the
> Krylov supspace.  A description of how to do this is presented in
> HF Walker, An adaptation of Krylov subspace methods to path following
> problems, SIAM J. Sci. Comput. 21(3),1191-1198.
> There was once an implementation in Loca, but I do not know the
> details.  I'm happy to discuss this further, particularly offline.
> --David Day
> On Wed, 2010-09-08 at 12:07 -0600, Christopher K. Newman wrote:
>> Is there a way to automatically remove a known null space during an
>> iterative solve?  Dare I say, similar to KSPSetNullSpace in Petsc.  Or
>> is the preferred method user implementation of a projection operator?
>> Thanks,
>> Chris
>> --
>> Christopher K. Newman
>> Los Alamos National Laboratory, T-3     Email: cnewman at lanl.gov
>> PO Box 1663 MS B216                           Phone: 505 606 0647
>> Los Alamos, NM 87545                          Fax: 505 665 5926
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