#include "petscksp.h" #include "petscmat.h" PetscErrorCode KSPComputeExtremeSingularValues(KSP ksp,PetscReal *emax,PetscReal *emin)Not Collective
| ksp | - iterative context obtained from KSPCreate() |
| emin, emax | - extreme singular values |
| -ksp_view_singularvalues | - compute extreme singular values and print when KSPSolve completes. |
Many users may just want to use the monitoring routine KSPMonitorSingularValue() (which can be set with option -ksp_monitor_singular_value) to print the extreme singular values at each iteration of the linear solve.
Estimates of the smallest singular value may be very inaccurate, especially if the Krylov method has not converged. The largest singular value is usually accurate to within a few percent if the method has converged, but is still not intended for eigenanalysis.
Disable restarts if using KSPGMRES, otherwise this estimate will only be using those iterations after the last restart. See KSPGMRESSetRestart() for more details.