[petsc-users] Help with SLEPc eigenvectors convergence.

[Pierre Jolivet]

It seems your A is rank-deficient.
If you slightly regularize the GEVP, e.g., -st_target 1.0E-6, you’ll get errors closer to 0.

Thanks,
Pierre

> On 6 Mar 2024, at 8:57 PM, Eric Chamberland via petsc-users <petsc-users at mcs.anl.gov> wrote:
> 
> This Message Is From an External Sender
> This message came from outside your organization.
> Hi,
> 
> we have a simple generalized Hermitian problem  (Kirchhoff plate 
> vibration) for which we are comparing SLEPc results with Matlab results.
> 
> SLEPc computes eigenvalues correctly, as Matlab does.
> 
> However, the output eigenvectors are not fully converged and we are 
> trying to understand where we have missed a convergence parameter or 
> anything else about eigenvectors.
> 
> SLEPc warns us at the end of EPSSolve with this message:
> 
> ---
>   Problem: some of the first 10 relative errors are higher than the 
> tolerance
> ---
> 
> And in fact, when we import the resulting vectors into Matlab, 
> "A*x-B*Lambda*x" isn't close to 0.
> 
> Here are attached the EPS view output as the A and B matrices used.
> 
> Any help or insights will be appreciated! :)
> 
> Thanks,
> Eric
> <epsview.txt><matrice0_gen.m><matrice1_gen.m>

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