[petsc-users] GMRES for outer solver

[Dave May]

On Sun 1. May 2022 at 07:03, Amneet Bhalla <mail2amneet at gmail.com> wrote:

> How about using a fixed number of Richardson iterations as a Krylov
> preconditioner to a GMRES solver?
>

That is fine.

Would that lead to a linear operation?
>

Yes.



> On Sat, Apr 30, 2022 at 8:21 PM Jed Brown <jed at jedbrown.org> wrote:
>
>> In general, no. A fixed number of Krylov iterations (CG, GMRES, etc.) is
>> a nonlinear operation.
>>
>> A fixed number of iterations of a method with a fixed polynomial, such as
>> Chebyshev, is a linear operation so you don't need a flexible outer method.
>>
>> Ramakrishnan Thirumalaisamy <rthirumalaisam1857 at sdsu.edu> writes:
>>
>> > Hi,
>> >
>> > I have a Krylov solver with a preconditioner that is also a Krylov
>> solver.
>> > I know I can use "fgmres" for the outer solver but can I use gmres for
>> the
>> > outer solver with a fixed number of iterations in the Krylov
>> > preconditioners?
>> >
>> >
>> > Thanks,
>> > Rama
>>
> --
> --Amneet
>
>
>
>
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