:orphan:
# TSComputeIJacobian
Evaluates the Jacobian of the DAE 
## Synopsis
```
#include "petscts.h"  
PetscErrorCode TSComputeIJacobian(TS ts, PetscReal t, Vec U, Vec Udot, PetscReal shift, Mat A, Mat B, PetscBool imex)
```
Collective

Input

## Input Parameters

- ***ts -*** the `TS` context
- ***t -*** current timestep
- ***U -*** state vector
- ***Udot -*** time derivative of state vector
- ***shift -*** shift to apply, see note below
- ***imex -*** flag indicates if the method is `TSIMEX` so that the RHSJacobian should be kept separate



## Output Parameters

- ***A -*** Jacobian matrix
- ***B -*** matrix from which the preconditioner is constructed; often the same as `A`





## Notes
If F(t,U,Udot)=0 is the DAE, the required Jacobian is
```none
   dF/dU + shift*dF/dUdot
```

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


## See Also
 [](ch_ts), `TS`, `TSSetIJacobian()`

## Level
developer

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


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