# TaoGetResidualNorm
Gets the current value of the norm of the residual at this time. 
## Synopsis
```
#include "petsctao.h" 
PetscErrorCode TaoGetResidualNorm(Tao tao, PetscReal *value)
```
Not Collective


## Input Parameter

- ***tao -*** Tao context



## Output Parameter

- ***value -*** the current value





## Developer Note
This is the 2-norm of the residual, we cannot use `TaoGetGradientNorm()` because that has
a different meaning. For some reason Tao sometimes calls the gradient the residual.


## See Also
 `Tao`, `TaoGetLinearSolveIterations()`, `TaoGetIterationNumber()`, `TaoGetObjective()`

## Level
intermediate

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