[petsc-users] Problems about tolerances set in TS

[Yingjie Wu]

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> 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> 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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