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# TSSetEventTolerances
Set tolerances for event zero crossings 
## Synopsis
```
#include "petscts.h" 
PetscErrorCode TSSetEventTolerances(TS ts, PetscReal tol, PetscReal vtol[])
```
Logically Collective


## Input Parameters

- ***ts -*** time integration context
- ***tol -*** scalar tolerance, `PETSC_DECIDE` to leave current value
- ***vtol -*** array of tolerances or `NULL`, used in preference to tol if present



## Options Database Key

- ***-ts_event_tol <tol> -*** tolerance for event zero crossing





## Notes
Must call `TSSetEventHandler(`) before setting the tolerances.

The size of `vtol` is equal to the number of events.

The tolerance is some measure of how close the event function is to zero for the event detector to stop
and declare the time of the event has been detected.


## See Also
 [](ch_ts), `TS`, `TSEvent`, `TSSetEventHandler()`

## Level
beginner

## Location
<A HREF="PETSC_DOC_OUT_ROOT_PLACEHOLDER/src/ts/event/tsevent.c.html#TSSetEventTolerances">src/ts/event/tsevent.c</A>


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


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