[petsc-users] Deflated GMRES in PETSc

[domenico lahaye]

FYI: an example of the implementation of deflated GMRES 
in PETSc can be found at: 

http://onlinelibrary.wiley.com/doi/10.1002/nla.1882/full


Possibly this helps. Kind wishes, Domenico Lahaye. 



________________________________
 From: Jed Brown <jedbrown at mcs.anl.gov>
To: Matteo Parsani <parsani.matteo at gmail.com> 
Cc: Mark H. Carpenter <mark.h.carpenter at nasa.gov>; petsc-users <petsc-users at mcs.anl.gov> 
Sent: Monday, June 17, 2013 10:31 AM
Subject: Re: [petsc-users] Deflated GMRES in PETSc
 

[Cc'ing petsc-users since people may be interested.]

Matteo Parsani <parsani.matteo at gmail.com> writes:

> Hi Jed,
> do you know if in PETSc we can start a Krylov iteration with problematic
> eigenmodes in the Krylov subspace at the beginning of the iteration?

Deflation is identical to a Galerkin coarse grid correction.  I would
use PCMG to create a two-level method.  Write your deflation space into
the prolongation operator and use Galerkin.  You can compose a PCMG with
other preconditioners.  I would leave DGMRES to only deal with adaptive
identification of those problematic modes.  Note that the DGMRES basis
vectors will be global, but when you provide vectors a priori, you are
free to localize them.

> Machinery should be there already because we see that this is used when
> GMRES stagnates.
>
> Thanks,
>
> -- 
> Matteo
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://lists.mcs.anl.gov/pipermail/petsc-users/attachments/20130617/35763e9a/attachment.html>