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# KSPMonitorResidual
Print the (possibly preconditioned) residual norm at each iteration of an iterative solver. 
## Synopsis
```
#include "petscksp.h" 
PetscErrorCode KSPMonitorResidual(KSP ksp, PetscInt n, PetscReal rnorm, PetscViewerAndFormat *vf)
```
Collective


## Input Parameters

- ***ksp   -*** iterative context
- ***n     -*** iteration number
- ***rnorm -*** 2-norm (preconditioned) residual value (may be estimated).
- ***vf    -*** The viewer context



## Options Database Key

- ***-ksp_monitor -*** Activates `KSPMonitorResidual()`





## Note
For some methods, such as `KSPGMRES`, the norm is not computed directly from the residual.

The type of norm used by the method can be controlled with `KSPSetNormType()`

This is not called directly by users, rather one calls `KSPMonitorSet()`, with this function as an argument, to cause the monitor
to be used during the KSP solve.


## See Also
 [](ch_ksp), `KSP`, `KSPMonitorSet()`, `KSPMonitorTrueResidual()`, `KSPMonitorResidualDraw()`, `KSPMonitorResidualDrawLG()`,
`KSPMonitorResidualRange()`, `KSPMonitorTrueResidualDraw()`, `KSPMonitorTrueResidualDrawLG()`, `KSPMonitorTrueResidualMax()`,
`KSPMonitorSingularValue()`, `KSPMonitorSolutionDrawLG()`, `KSPMonitorSolutionDraw()`, `KSPMonitorSolution()`,
`KSPMonitorErrorDrawLG()`, `KSPMonitorErrorDraw()`, KSPMonitorError()`

## Level
intermediate

## Location
<A HREF="PETSC_DOC_OUT_ROOT_PLACEHOLDER/src/ksp/ksp/interface/iterativ.c.html#KSPMonitorResidual">src/ksp/ksp/interface/iterativ.c</A>

## Examples
<A HREF="PETSC_DOC_OUT_ROOT_PLACEHOLDER/src/ksp/ksp/tutorials/ex2f.F90.html">src/ksp/ksp/tutorials/ex2f.F90</A><BR>


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[Edit on GitLab](https://gitlab.com/petsc/petsc/-/edit/release/src/ksp/ksp/interface/iterativ.c)


[Index of all KSP routines](index.md)  
[Table of Contents for all manual pages](/manualpages/index.md)  
[Index of all manual pages](/manualpages/singleindex.md)