KSPComputeEigenvalues

Computes the extreme eigenvalues for the preconditioned operator. Called after or during KSPSolve() (SLESSolve()).

Synopsis

int KSPComputeEigenvalues(KSP ksp,int n,double *r,double *c)
Not Collective

Input Parameter

ksp - iterative context obtained from KSPCreate()
n - size of arrays r and c

Output Parameters

r - real part of computed eigenvalues
c - complex part of computed eigenvalues

Options Database Keys

-ksp_compute_eigenvalues - Prints eigenvalues to stdout
-ksp_plot_eigenvalues - Plots eigenvalues in an x-window display

Notes

KSPComputeEigenvalues() does not usually provide accurate estimates; it isintended only for assistance in understanding the convergence of iterativemethods, not for eigenanalysis.

One must call KSPSetComputeEigenvalues() before calling KSPSetUp() in order for this routine to work correctly.

Many users may just want to use the monitoring routineKSPSingularValueMonitor() (which can be set with option -ksp_singmonitor) to print the singular values at each iteration of the linear solve.

Keywords

KSP, compute, extreme, singular, values

See Also

KSPSetComputeSingularValues(), KSPSingularValueMonitor(), KSPComputeExtremeSingularValues()

Location: src/ksp/interface/itfunc.c
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