# TSAlpha2SetRadius
sets the desired spectral radius of the method for `TSALPHA2` (i.e. high-frequency numerical damping) 
## Synopsis
```
#include "petscts.h"   
PetscErrorCode TSAlpha2SetRadius(TS ts, PetscReal radius)
```
Logically Collective on ts

The algorithmic parameters \alpha_m and \alpha_f of the
generalized-\alpha method can be computed in terms of a specified
spectral radius \rho in [0,1] for infinite time step in order to

## control high-frequency numerical damping
\alpha_m = (2-\rho)/(1+\rho)
\alpha_f = 1/(1+\rho)


## Input Parameters

- ***ts -*** timestepping context
- ***radius -*** the desired spectral radius



## Options Database Key

- ***-ts_alpha_radius <radius> -*** set the desired spectral radius





## See Also
 [](chapter_ts), `TS`, `TSALPHA2`, `TSAlpha2SetParams()`, `TSAlpha2GetParams()`

## Level
intermediate

## Location
<A HREF="PETSC_DOC_OUT_ROOT_PLACEHOLDER/src/ts/impls/implicit/alpha/alpha2.c.html#TSAlpha2SetRadius">src/ts/impls/implicit/alpha/alpha2.c</A>

## Implementations

<A HREF="PETSC_DOC_OUT_ROOT_PLACEHOLDER/src/ts/impls/implicit/alpha/alpha2.c.html#TSAlpha2SetRadius_Alpha">TSAlpha2SetRadius_Alpha in src/ts/impls/implicit/alpha/alpha2.c</A><BR>


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[Edit on GitLab](https://gitlab.com/petsc/petsc/-/edit/release/src/ts/impls/implicit/alpha/alpha2.c)


[Index of all TS routines](index.md)  
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