# DMTSSetIFunction
set `TS` implicit function evaluation function 
## Synopsis
```
#include "petscts.h" 
PetscErrorCode DMTSSetIFunction(DM dm, TSIFunction func, void *ctx)
```
Not Collective


## Input Parameters

- ***dm -*** `DM` to be used with `TS`
- ***func -*** function evaluating f(t,u,u_t)
- ***ctx -*** context for residual evaluation



## Calling sequence of func
```none
PetscErrorCode func(TS ts,PetscReal t,Vec u,Vec u_t,Vec F,ctx);
```


- ***t   -*** time at step/stage being solved
- ***u   -*** state vector
- ***u_t -*** time derivative of state vector
- ***F   -*** function vector
- ***ctx -*** [optional] user-defined context for matrix evaluation routine





## Note
`TSSetFunction()` is normally used, but it calls this function internally because the user context is actually
associated with the `DM`.  This makes the interface consistent regardless of whether the user interacts with a `DM` or
not. If DM took a more central role at some later date, this could become the primary method of setting the residual.


## See Also
 [](chapter_ts), `TS`, `DM`, `DMTSSetContext()`, `TSSetIFunction()`, `DMTSSetJacobian()`

## Level
advanced

## Location
<A HREF="PETSC_DOC_OUT_ROOT_PLACEHOLDER/src/ts/utils/dmts.c.html#DMTSSetIFunction">src/ts/utils/dmts.c</A>


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[Edit on GitLab](https://gitlab.com/petsc/petsc/-/edit/release/src/ts/utils/dmts.c)


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