[petsc-users] How to compute the condition number of SchurComplementMat preconditioned with PCSHELL.

[Vladislav Pimanov]

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

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