[petsc-users] puzzling arkimex logic

[Zhang, Hong]

Hi Mark,

You might want to try -ts_adapt_time_step_increase_delay to delay increasing the time step after it has been decreased due to a failed solve.

Hong (Mr.)

> On Jan 2, 2023, at 12:17 PM, Mark Adams <mfadams at lbl.gov> wrote:
> 
> I am using arkimex and the logic with a failed KSP solve is puzzling. This step starts with a dt of ~.005, the linear solver fails and cuts the time step by 1/4. So far, so good. The step then works but the next time step the time step goes to ~0.006.
> TS seems to have forgotten that it had to cut the time step back.
> Perhaps that logic is missing or my parameters need work?
> 
> Thanks,
> Mark
> 
> -ts_adapt_dt_max 0.01 # (source: command line)
> -ts_adapt_monitor # (source: file)
> -ts_arkimex_type 1bee # (source: file)
> -ts_dt .001 # (source: command line)
> -ts_max_reject 10 # (source: file)
> -ts_max_snes_failures -1 # (source: file)
> -ts_max_steps 8000 # (source: command line)
> -ts_max_time 14 # (source: command line)
> -ts_monitor # (source: file)
> -ts_rtol 1e-6 # (source: command line)
> -ts_type arkimex # (source: file)
> 
>   Nonlinear solve converged due to CONVERGED_SNORM_RELATIVE iterations 2
>       TSAdapt basic arkimex 0:1bee step   1 accepted t=0.001      + 2.497e-03 dt=5.404e-03  wlte=0.173  wltea=   -1 wlter=  
>  -1
> 2 TS dt 0.00540401 time 0.00349731
>     0 SNES Function norm 1.358886930084e-05 
>     Linear solve did not converge due to DIVERGED_ITS iterations 100
>   Nonlinear solve did not converge due to DIVERGED_LINEAR_SOLVE iterations 0
>       TSAdapt basic step   2 stage rejected (DIVERGED_LINEAR_SOLVE) t=0.00349731 + 5.404e-03 retrying with dt=1.351e-03 
>     0 SNES Function norm 1.358886930084e-05 
>     Linear solve converged due to CONVERGED_RTOL iterations 19
>     1 SNES Function norm 4.412110425362e-10 
>     Linear solve converged due to CONVERGED_RTOL iterations 6
>     2 SNES Function norm 4.978968053066e-13 
>   Nonlinear solve converged due to CONVERGED_SNORM_RELATIVE iterations 2
>     0 SNES Function norm 8.549322067920e-06 
>     Linear solve converged due to CONVERGED_RTOL iterations 14
>     1 SNES Function norm 8.357075378456e-11 
>     Linear solve converged due to CONVERGED_RTOL iterations 4
>     2 SNES Function norm 4.983138402512e-13 
>   Nonlinear solve converged due to CONVERGED_SNORM_RELATIVE iterations 2
>     0 SNES Function norm 1.044832467924e-05 
>     Linear solve converged due to CONVERGED_RTOL iterations 13
>     1 SNES Function norm 1.036101875301e-10 
>     Linear solve converged due to CONVERGED_RTOL iterations 4
>     2 SNES Function norm 4.984888077288e-13 
>   Nonlinear solve converged due to CONVERGED_SNORM_RELATIVE iterations 2
>       TSAdapt basic arkimex 0:1bee step   2 accepted t=0.00349731 + 1.351e-03 dt=6.305e-03  wlte=0.0372  wltea=   -1 wlter= 
>   -1
> 3 TS dt 0.00630456 time 0.00484832
>     0 SNES Function norm 8.116559104264e-06 
>     Linear solve did not converge due to DIVERGED_ITS iterations 100