[petsc-users] clarification on extreme eigenvalues from KSPComputeEigenvalues

[Mark Adams]

The extreme eigenvalues are the lowest and highest.
A perfect preconditioner would give all eigenvalues = 1.0

Mark

On Tue, Oct 4, 2022 at 1:03 PM feng wang <snailsoar at hotmail.com> wrote:

> Dear All,
>
> I am using the KSPComputeEigenvalues to understand the performance of my
> preconditioner, and I am using the right-preconditioned GMRES with ASM. In
> the user guide, it says this routine computes the extreme eigenvalues of
> the preconditioned operator. If I understand it correctly, these
> eigenvalues are the ones furthest away from (1,0)? If the preconditioning
> is perfect, all the eigenvalues should be (1,0).
>
> Thanks,
> Feng
>
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