KSPComputeEigenvaluesExplicitly

Computes all of the eigenvalues of the preconditioned operator using LAPACK.

Synopsis

#include "petscksp.h" 
int KSPComputeEigenvaluesExplicitly(KSP ksp,int nmax,PetscReal *r,PetscReal *c)

Collective on KSP

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

Notes

This approach is very slow but will generally provide accurate eigenvalue estimates. This routine explicitly forms a dense matrix representing the preconditioned operator, and thus will run only for relatively small problems, say n < 500.

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

Keywords