Re: [petsc-users] "-ts_exact_final_time matchstep" leads to DIVERGED_STEP_REJECTED

[Jed Brown]

Can you make a PETSc example exhibit this behavior, or otherwise share a 
reproduce?

"Blondel, Sophie" <sblon...@utk.edu> writes:

> Good morning Barry,
>
> Changing the initial timestep on the commandline didn't change anything. It's 
> like there is something happening afterwards that sets the initial dt to 0 s 
> that doesn't happen with TS_EXACTFINALTIME_STEPOVER.
>
> Cheers,
>
> Sophie
> ________________________________
> From: Barry Smith <bsm...@petsc.dev>
> Sent: Friday, December 13, 2024 22:27
> To: Blondel, Sophie <sblon...@utk.edu>
> Cc: Jed Brown <j...@jedbrown.org>; Zhang, Hong <hongzh...@anl.gov>; Emil 
> Constantinescu <emcon...@anl.gov>; petsc-users@mcs.anl.gov 
> <petsc-users@mcs.anl.gov>; xolotl-psi-developm...@lists.sourceforge.net 
> <xolotl-psi-developm...@lists.sourceforge.net>
> Subject: Re: [petsc-users] "-ts_exact_final_time matchstep" leads to 
> DIVERGED_STEP_REJECTED
>
>
>    Ok, the SNES reason DIVERGED_FNORM_NAN is likely due to the TS using a dt 
> of zero, and hence, the evaluation of the TS causing a divide by zero.
>
>    So the TS adapt needs to be understood better in this situation. My guess 
> is still TS_EXACTFINALTIME_MATCHSTEP is buggy when one actually does get an 
> exact match.
>
>   Please try using a different initial timestep like 0.5e-12 s on the command 
> line.
>
>   Barry
>
>
> On Dec 13, 2024, at 4:40 PM, Blondel, Sophie <sblon...@utk.edu> wrote:
>
> Barry,
>
> The short output is "SNESSolve has not converged due to Nan or Inf norm", the 
> full one is attached.
>
> Cheers,
>
> Sophie
> ________________________________
> From: Barry Smith <bsm...@petsc.dev<mailto:bsm...@petsc.dev>>
> Sent: Friday, December 13, 2024 14:56
> To: Blondel, Sophie <sblon...@utk.edu<mailto:sblon...@utk.edu>>
> Cc: Jed Brown <j...@jedbrown.org<mailto:j...@jedbrown.org>>; Zhang, Hong 
> <hongzh...@anl.gov<mailto:hongzh...@anl.gov>>; Emil Constantinescu 
> <emcon...@anl.gov<mailto:emcon...@anl.gov>>; 
> petsc-users@mcs.anl.gov<mailto:petsc-users@mcs.anl.gov> 
> <petsc-users@mcs.anl.gov<mailto:petsc-users@mcs.anl.gov>>; 
> xolotl-psi-developm...@lists.sourceforge.net<mailto:xolotl-psi-developm...@lists.sourceforge.net>
>  
> <xolotl-psi-developm...@lists.sourceforge.net<mailto:xolotl-psi-developm...@lists.sourceforge.net>>
> Subject: Re: [petsc-users] "-ts_exact_final_time matchstep" leads to 
> DIVERGED_STEP_REJECTED
>
>
>     There is a bit of complicated logic to determine the "adjusted" timestep 
> in TSAdaptChoose() when if (*accept && ts->exact_final_time == 
> TS_EXACTFINALTIME_MATCHSTEP) {
>
>     Is it possible that hmax = tmax - t; is exactly zero, and the logic below 
> does not correctly handle that case?
>
> 0 TS dt 0. time 0.
> 0 TS dt 0. time 0.
> 0 TS dt 0. time 0.
> 0 TS dt 0. time 0.
>       TSAdapt basic step   0 stage rejected (SNES reason DIVERGED_FNORM_NAN) 
> t=0          + 0.000e+00 retrying with dt=0.000e+00
>       TSAdapt basic step   0 stage rejected (SNES reason DIVERGED_FNORM_NAN) 
> t=0          + 0.000e+00 retrying with dt=0.000e+00
>       TSAdapt basic step   0 stage rejected (SNES reason DIVERGED_FNORM_NAN) 
> t=0          + 0.000e+00 retrying with dt=0.000e+00
>       TSAdapt basic step   0 stage rejected (SNES reason DIVERGED_FNORM_NAN) 
> t=0          + 0.000e+00 retrying with dt=0.000e+00
>       TSAdapt basic step   0 stage rejected (SNES reason DIVERGED_FNORM_NAN) 
> t=0          + 0.000e+00 retrying with dt=0.000e+00
>       TSAdapt basic step   0 stage rejected (SNES reason DIVERGED_FNORM_NAN) 
> t=0          + 0.000e+00 retrying with dt=0.000e+00
>       TSAdapt basic step   0 stage rejected (SNES reason DIVERGED_FNORM_NAN) 
> t=0          + 0.000e+00 retrying with dt=0.000e+00
>       TSAdapt basic step   0 stage rejected (SNES reason DIVERGED_FNORM_NAN) 
> t=0          + 0.000e+00 retrying with dt=0.000e+00
>       TSAdapt basic step   0 stage rejected (SNES reason DIVERGED_FNORM_NAN) 
> t=0          + 0.000e+00 retrying with dt=0.000e+00
>       TSAdapt basic step   0 stage rejected (SNES reason DIVERGED_FNORM_NAN) 
> t=0          + 0.000e+00 retrying with dt=0.000e+00
>       TSAdapt basic step   0 stage rejected (SNES reason DIVERGED_FNORM_NAN) 
> t=0          + 0.000e+00 retrying with dt=0.000e+00
>
>   Sophie,
>
>      Any idea why SNES reason DIVERGED_FNORM_NAN?   Could you run with 
> -snes_error_if_not_converged?
>
> On Dec 13, 2024, at 2:34 PM, Blondel, Sophie 
> <sblon...@utk.edu<mailto:sblon...@utk.edu>> wrote:
>
> Hi everyone,
>
> The first max time it is trying to reach is 1.0e-12 s, and the initial dt is 
> set to 1.0e-12 s from the commandline options. I believe it's not a 
> formatting issue and that the dt is actually set somewhere to 0 s because 
> that's why the step is rejected.
>
> Best,
>
> Sophie
> ________________________________
> From: Barry Smith <bsm...@petsc.dev<mailto:bsm...@petsc.dev>>
> Sent: Friday, December 13, 2024 14:21
> To: Blondel, Sophie <sblon...@utk.edu<mailto:sblon...@utk.edu>>; Jed Brown 
> <j...@jedbrown.org<mailto:j...@jedbrown.org>>; Zhang, Hong 
> <hongzh...@anl.gov<mailto:hongzh...@anl.gov>>; Emil Constantinescu 
> <emcon...@anl.gov<mailto:emcon...@anl.gov>>
> Cc: petsc-users@mcs.anl.gov<mailto:petsc-users@mcs.anl.gov> 
> <petsc-users@mcs.anl.gov<mailto:petsc-users@mcs.anl.gov>>; 
> xolotl-psi-developm...@lists.sourceforge.net<mailto:xolotl-psi-developm...@lists.sourceforge.net>
>  
> <xolotl-psi-developm...@lists.sourceforge.net<mailto:xolotl-psi-developm...@lists.sourceforge.net>>
> Subject: Re: [petsc-users] "-ts_exact_final_time matchstep" leads to 
> DIVERGED_STEP_REJECTED
>
>
>    Hm, what is the final time you are stepping towards in this run?
>
>    There is something wrong with the adapt code since it seems to start with 
> a dt of 0 but then tries "adapting" several times, but it could be the
> monitor function does not correctly format numbers smaller than 1.e-12 and it 
> is just using truly small dt.
>
>    Jed, Hong, Emil?
>
>    Barry
>
>
> On Dec 10, 2024, at 11:08 AM, Blondel, Sophie 
> <sblon...@utk.edu<mailto:sblon...@utk.edu>> wrote:
>
> Good morning Barry,
>
> Attached are the updated files, there is more useful information in them.
>
> Cheers,
>
> Sophie
> ________________________________
>
> From: Blondel, Sophie via Xolotl-psi-development 
> <xolotl-psi-developm...@lists.sourceforge.net<mailto:xolotl-psi-developm...@lists.sourceforge.net>>
> Sent: Monday, December 9, 2024 17:29
> To: Barry Smith <bsm...@petsc.dev<mailto:bsm...@petsc.dev>>
> Cc: petsc-users@mcs.anl.gov<mailto:petsc-users@mcs.anl.gov> 
> <petsc-users@mcs.anl.gov<mailto:petsc-users@mcs.anl.gov>>; 
> xolotl-psi-developm...@lists.sourceforge.net<mailto:xolotl-psi-developm...@lists.sourceforge.net>
>  
> <xolotl-psi-developm...@lists.sourceforge.net<mailto:xolotl-psi-developm...@lists.sourceforge.net>>
> Subject: Re: [Xolotl-psi-development] [petsc-users] "-ts_exact_final_time 
> matchstep" leads to DIVERGED_STEP_REJECTED
>
> Hi Barry,
>
> I hope you are doing well.
>
> Attached are the output. To give a little more context, this is a "new" way 
> of running the code where multiple instances are created and communicate 
> together every few time steps (like coupling the code with itself in memory). 
> Here there are 3 instances that each have a separate TS object, plus one 
> "main" instance that doesn't solve anything but compute rates to exchange 
> between the other instances.
>
> Cheers,
>
> Sophie
> ________________________________
>
> From: Barry Smith <bsm...@petsc.dev<mailto:bsm...@petsc.dev>>
> Sent: Monday, December 9, 2024 15:12
> To: Blondel, Sophie <sblon...@utk.edu<mailto:sblon...@utk.edu>>
> Cc: petsc-users@mcs.anl.gov<mailto:petsc-users@mcs.anl.gov> 
> <petsc-users@mcs.anl.gov<mailto:petsc-users@mcs.anl.gov>>; 
> xolotl-psi-developm...@lists.sourceforge.net<mailto:xolotl-psi-developm...@lists.sourceforge.net>
>  
> <xolotl-psi-developm...@lists.sourceforge.net<mailto:xolotl-psi-developm...@lists.sourceforge.net>>
> Subject: Re: [petsc-users] "-ts_exact_final_time matchstep" leads to 
> DIVERGED_STEP_REJECTED
>
>
>
> On Dec 9, 2024, at 2:56 PM, Blondel, Sophie via petsc-users 
> <petsc-users@mcs.anl.gov<mailto:petsc-users@mcs.anl.gov>> wrote:
>
> Hi,
>
> I am trying to understand a strange behavior I'm encountering: when running 
> my application with "-ts_exact_final_time stepover" everything goes well, but 
> when I switch to "matchstep" I get DIVERGED_STEP_REJECTED before the first 
> time step is finished.
>
>    This is in the very first time-step in TSSolve?
>
>     Please run with -ts_monitor and send all the output (best for a short 
> time interval and do it twice once with -ts_exact_final_time stepover and 
> once with exact.
>
>    Barry
>
>
> I tried increasing the maximum number of rejections and it just takes longer 
> to diverge, and if I set the value to "unlimited" it is basically an infinite 
> loop.
>
> Is there a way to check why is the step rejected? Could the "matchstep" 
> option change tolerances somewhere that would cause that behavior?
>
> Let me know if I should provide more information.
>
> Best,
>
> Sophie Blondel
>
> <matchstep_reason.txt>