analyze preconditioned operator?

Matthew Knepley knepley at
Thu Oct 9 15:51:42 CDT 2008



On Thu, Oct 9, 2008 at 3:38 PM, Matt Funk <mafunk at> wrote:
> Hi Jed,
> what you suggest seems like it might be even more efficient for sparse
> matrices (which i am using) then using the KSPComputeExplicitOperator()
> routine.
> However, what kind of call do i make to apply the preconditioner to the
> matrix. I have not really ever written a MatShell but it seems like there
> should still be some PetscFunction that allows me to apply the
> preconditioner.
> Or am i misunderstanding you ... ?
> matt
> ps: also, did you mean to write B=PA where A is my original preconditioner?
> On Thursday 09 October 2008, Jed Brown wrote:
>> On Thu, Oct 9, 2008 at 20:22, Matt Funk <mafunk at> wrote:
>> > i am using PETSC and on top of it also SLEPC to do some matrix analysis.
>> > In Slepc i simply pass it the Petsc matrix to analyze it.
>> > However, is there anyway to analyze the preconditioned matrix at all?
>> You can certainly write a MatShell which applies B = P^-1 A and hand
>> this to SLEPc with no preconditioner.  This seems like a common thing
>> so maybe SLEPc has an option to use the preconditioned operator.
>> Jed

What most experimenters take for granted before they begin their
experiments is infinitely more interesting than any results to which
their experiments lead.
-- Norbert Wiener

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