Using shift-and-invert mode

[Nicolò Abrate]

Dear developers,

I would like to find the smallest magnitude eigenvalues of a non-hermitian matrix. I was successfully using the shift-invert mode in scipy.sparse.linalg.eigs, with eigs(B, M=T, k=nev, which='LM', sigma=0) but this module is much slower than petsc4py, which I would like to use also for this specific case.

My problem is very trivial: I am not able to find any working example in the demos of how setting up correctly the shit-and-invert mode in petsc4py. Can you help me please? By the way, it would be great to add this example in the demos…

I am not sure this is the right section for posting, I apologize if i did something wrong.

Thank you so much,

Nicolo'

[Lisandro Dalcin]

This is not the right repository for your issue, open it in https://gitlab.com/slepc/slepc4py/-/issues

[Lisandro Dalcin]

Maybe you should post your question to the petsc-users mailing list.