[petsc-users] Turning off TSADAPT still adapts time step
Mark Lohry
mlohry at princeton.edu
Mon Apr 27 12:16:29 CDT 2015
-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!
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