Dear PETSc community,
I wonder if you could give me a hint on how to compute the condition number of
a preconditioned matrix in a proper way.
I have a MatSchurComplement matrix S and a preconditioner P of the type PCSHELL
(P is a diffusion matrix, which itself is inverted by KSPCG).
I tried to compute the condition number of P^{-1}S "for free" during the outer
PCG procedure using KSPComputeExtremeSingularValues() routine.
Unfortunately, \sigma_min does not converge even if the solution is computed
with very high precision.
I also looked at SLEPc interface, but did not realised how PC should be
included.
Thanks!
Sincerely,
Vladislav Pimanov
