[petsc-users] Turning off TSADAPT still adapts time step

[Mark Lohry]

-snes_converged_reason:

Nonlinear solve did not converge due to DIVERGED_LOCAL_MIN iterations 4

(which is expected)

> Add -snes_converged_reason.  What do you want to do when the solver
> fails?  Pretend like it succeeded and get the wrong answer?  Usually
> people shorten the time step and retry, which is what you see happening
> here.
Well yes, actually - I expected it to fail for this test case but it 
stubbornly gets the right answer. The explicit integrator has no problem 
keeping a fixed timestep and throwing the expected NaNs when it blows up.

It's alarming to see the unexpected behavior of setting TSADAPTNONE and 
seeing it actually adapting (in a rudimentary fashion) the timestep, and 
keeping that reduced timestep even after the stiffness goes away.


> You can call TSAdaptSetCheckStage and have your function unconditionally
> set accept to PETSC_TRUE (and you'll likely get the wrong answer).

Thanks for the help!