petsc-3.14.5 2021-03-03
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# KSPMonitorSingularValue

Prints the two norm of the true residual and estimation of the extreme singular values of the preconditioned problem at each iteration.

### Synopsis

    #include "petscksp.h"
    PetscErrorCode  KSPMonitorSingularValue(KSP ksp,PetscInt n,PetscReal rnorm,PetscViewerAndFormat *dummy)

Logically Collective on ksp

### Input Parameters

| ksp | - the iterative context
| n | - the iteration
| rnorm | - the two norm of the residual

### Options Database Key

| -ksp_monitor_singular_value | - Activates KSPMonitorSingularValue()

### Notes

The CG solver uses the Lanczos technique for eigenvalue computation, while GMRES uses the Arnoldi technique; other iterative methods do not currently compute singular values.

### See Also

KSPComputeExtremeSingularValues()

### Level

intermediate

### Location

src/ksp/ksp/interface/iterativ.c

### Examples

src/snes/tutorials/ex30.c.html
Index of all KSP routines
Table of Contents for all manual pages
Index of all manual pages