[petsc-users] Control adaptive time step

[Tang, Qi]

Thanks, Hong. That’s exactly what I need.




On Mar 5, 2022, at 11:55 AM, Zhang, Hong <hongzhang at anl.gov<mailto:hongzhang at anl.gov>> wrote:

You can control the factors with

-ts_adapt_clip <low>,<high>- to set admissible time step decrease and increase factors

The default setting uses low=0.1, high=10.

https://petsc.org/release/docs/manualpages/TS/TSAdaptSetClip.html#TSAdaptSetClip<https://urldefense.com/v3/__https://petsc.org/release/docs/manualpages/TS/TSAdaptSetClip.html*TSAdaptSetClip__;Iw!!HXCxUKc!m-lJp6aSKp23rrCtOhTe5dlbe4g0ZsN_lEboynDzYQjVwitW64j-4SARMU4MSw$>

Hong (Mr.)

On Mar 5, 2022, at 12:26 PM, Tang, Qi <tangqi at msu.edu<mailto:tangqi at msu.edu>> wrote:

Hi,
Is there a simple way to control the first few adaptive time step? Currently, I am using the following options but dt grows too fast initially. The first few time steps increase dt by a factor of 10 in each time step. Is there a way to do a slow start, say, a factor of 2 instead of 10? Thanks.

-ts_type arkimex
-ts_arkimex_type 2e
-ts_arkimex_fully_implicit
-ts_adapt_dt_min 1.0e-5
-ts_adapt_dt_max 1.0e-2
-ts_adapt_type basic

Qi
T-5 at LANL


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