GMRES and PC_RIGHT

[Lisandro Dalcin]

Well, all you say that GMRES is not coded for right PC's, however,
after reviewing (in a hurry) the code for GMRES, it seems to handle
right preconditioner. Moreover, I've just tested solving (with SNES) a
steady lid-driven cavity flow in 2d with linear quads using SUPG/PSPG,
default tolerances, default restart, no diag-scaling, starting with
zero nonlinear guess ... in short, using -ksp_right_pc and just
changing -ksp_type to gmres/fgmres, and ALL the SNES iterates (up to 3
nonlinear its) and GMRES|FGMRES iterates (64, 169, 177 linear its) are
almost the same (except the last four digits using default KSP
monitor).

Sorry for the insistence, but ...  Am I missing something? Do any of
you remember exactly what part of GMRES had problems with right
preconditioning?


On Mon, Jun 8, 2009 at 4:27 PM, Jed Brown<jed at 59a2.org> wrote:
> Barry Smith wrote:
>
>>    The FGMRES code was written for right preconditioning (but the FGMRES
>> algorithm itself does not support left preconditioning.)
>
> LGMRES has both so that's another option.
>
> Jed
>
>



-- 
Lisandro Dalcín
---------------
Centro Internacional de Métodos Computacionales en Ingeniería (CIMEC)
Instituto de Desarrollo Tecnológico para la Industria Química (INTEC)
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