# TaoMonitor
Monitor the solver and the current solution.  This routine will record the iteration number and residual statistics, and call any monitors specified by the user. 
## Synopsis
```
#include "petsctao.h" 
PetscErrorCode TaoMonitor(Tao tao, PetscInt its, PetscReal f, PetscReal res, PetscReal cnorm, PetscReal steplength)
```

## Input Parameters

- ***tao -*** the Tao context
- ***its -*** the current iterate number (>=0)
- ***f -*** the current objective function value
- ***res -*** the gradient norm, square root of the duality gap, or other measure indicating distince from optimality.  This measure will be recorded and
used for some termination tests.
- ***cnorm -*** the infeasibility of the current solution with regard to the constraints.
- ***steplength -*** multiple of the step direction added to the previous iterate.



## Output Parameters

- ***reason -*** The termination reason, which can equal `TAO_CONTINUE_ITERATING`



## Options Database Key

- ***-tao_monitor -*** Use the default monitor, which prints statistics to standard output





## See Also
 `Tao`, `TaoGetConvergedReason()`, `TaoMonitorDefault()`, `TaoSetMonitor()`

## Level
developer

## Location
<A HREF="PETSC_DOC_OUT_ROOT_PLACEHOLDER/src/tao/interface/taosolver.c.html#TaoMonitor">src/tao/interface/taosolver.c</A>


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


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