[petsc-users] Problems about tolerances set in TS

[Zhang, Hong]

Please send the list of your command line options and the screen output with -ts_monitor.

Hong (Mr.)

On Apr 28, 2020, at 11:00 PM, Yingjie Wu <yjwu16 at gmail.com<mailto:yjwu16 at gmail.com>> wrote:

Thank you very much for your reply.

I tried both switches, but unfortunately they didn't seem to meet my needs.
 -ts_adapt_always_accept      The switch doesn't seem to work, reporting errors when the maximum number of steps is reached without convergence, then the program exits.
 -ts_error_if_step_fails  0        This switch accepts the non-convergence time step and outputs the result, but does not continue into the next time step calculation ( The time step hasn't reached the maximum time step I set). And I wonder if the variable behind this switch is optional? What does it mean?
I hope to achieve in the case of non-convergence Newton step( for example, the maximum number of Newton iteration steps reached -snes_max_it 50), can go in the next time step calculation.

Thanks,
Yingjie

Zhang, Hong <hongzhang at anl.gov<mailto:hongzhang at anl.gov>> 于2020年4月28日周二 下午10:51写道：
-ts_error_if_step_fails 0

You might want to find out why the nonlinear solver does not converge first. If you have a hand-written Jacobian, you can validate it with -snes_test_jacobian 1 (for a small test case).

Hong (Mr.)

> On Apr 28, 2020, at 8:21 AM, Yingjie Wu <yjwu16 at gmail.com<mailto:yjwu16 at gmail.com>> wrote:
>
> Dear PETSc developers
> Hi,
>
> I have recently used TS to solve nonlinear equations with time terms. since the convergence of my model is not very good, i would like to set to iterative fixed nonlinear steps per time step. If the problem does not meet the SNES convergence criteria after fixed number of nonlinear steps , then go to the next time step calculation. I tried -snes_max_it , but didn't achieve the effect I wanted, and the program stopped after iterating the fixed number of steps. How should I set up in the program?
>
> Thanks,
> Yingjie


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