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# PetscDSSetExactSolutionTimeDerivative
Set the pointwise time derivative of the exact solution function for a given test field
## Synopsis
```
#include "petscds.h"
PetscErrorCode PetscDSSetExactSolutionTimeDerivative(PetscDS prob, PetscInt f, PetscErrorCode (*sol)(PetscInt dim, PetscReal t, const PetscReal x[], PetscInt Nc, PetscScalar u[], void *ctx), void *ctx)
```
Not Collective
## Input Parameters
- ***prob -*** The `PetscDS`
- ***f -*** The test field number
- ***sol -*** time derivative of the solution function for the test fields
- ***ctx -*** time derivative of the solution context or `NULL`
## Calling sequence of `sol`
```none
PetscErrorCode sol(PetscInt dim, PetscReal t, const PetscReal x[], PetscInt Nc, PetscScalar u[], void *ctx)
```
- ***dim -*** the spatial dimension
- ***t -*** current time
- ***x -*** coordinates of the current point
- ***Nc -*** the number of field components
- ***u -*** the solution field evaluated at the current point
- ***ctx -*** a user context
## See Also
`PetscDS`, `PetscDSGetExactSolutionTimeDerivative()`, `PetscDSSetExactSolution()`
## Level
intermediate
## Location
src/dm/dt/interface/dtds.c
## Examples
src/ts/tutorials/ex45.c
src/ts/tutorials/ex53.c
src/ts/tutorials/ex76.c
src/ts/tutorials/ex77.c
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[Edit on GitLab](https://gitlab.com/petsc/petsc/-/edit/release/src/dm/dt/interface/dtds.c)
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