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@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>