[Trilinos-Users] null space removal

David Day dmday at sandia.gov
Wed Sep 8 12:53:14 MDT 2010


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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