# TSComputeI2Function
Evaluates the DAE residual written in implicit form F(t,U,U_t,U_tt) = 0 
## Synopsis
```
#include "petscts.h"  
PetscErrorCode TSComputeI2Function(TS ts, PetscReal t, Vec U, Vec V, Vec A, Vec F)
```
Collective on ts


## Input Parameters

- ***ts -*** the `TS` context
- ***t -*** current time
- ***U -*** state vector
- ***V -*** time derivative of state vector (U_t)
- ***A -*** second time derivative of state vector (U_tt)



## Output Parameter

- ***F -*** the residual vector





## Note
Most users should not need to explicitly call this routine, as it
is used internally within the nonlinear solvers.


## See Also
 [](chapter_ts), `TS`, `TSSetI2Function()`, `TSGetI2Function()`

## Level
developer

## Location
<A HREF="PETSC_DOC_OUT_ROOT_PLACEHOLDER/src/ts/interface/ts.c.html#TSComputeI2Function">src/ts/interface/ts.c</A>


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