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 <[email protected]> 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 <[email protected] <mailto:[email protected]>> > Sent: Friday, December 13, 2024 14:56 > To: Blondel, Sophie <[email protected] <mailto:[email protected]>> > Cc: Jed Brown <[email protected] <mailto:[email protected]>>; Zhang, Hong > <[email protected] <mailto:[email protected]>>; Emil Constantinescu > <[email protected] <mailto:[email protected]>>; [email protected] > <mailto:[email protected]> <[email protected] > <mailto:[email protected]>>; > [email protected] > <mailto:[email protected]> > <[email protected] > <mailto:[email protected]>> > 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 <[email protected] >> <mailto:[email protected]>> 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 <[email protected] <mailto:[email protected]>> >> Sent: Friday, December 13, 2024 14:21 >> To: Blondel, Sophie <[email protected] <mailto:[email protected]>>; Jed Brown >> <[email protected] <mailto:[email protected]>>; Zhang, Hong >> <[email protected] <mailto:[email protected]>>; Emil Constantinescu >> <[email protected] <mailto:[email protected]>> >> Cc: [email protected] <mailto:[email protected]> >> <[email protected] <mailto:[email protected]>>; >> [email protected] >> <mailto:[email protected]> >> <[email protected] >> <mailto:[email protected]>> >> 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 <[email protected] >>> <mailto:[email protected]>> 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 >>> <[email protected] >>> <mailto:[email protected]>> >>> Sent: Monday, December 9, 2024 17:29 >>> To: Barry Smith <[email protected] <mailto:[email protected]>> >>> Cc: [email protected] <mailto:[email protected]> >>> <[email protected] <mailto:[email protected]>>; >>> [email protected] >>> <mailto:[email protected]> >>> <[email protected] >>> <mailto:[email protected]>> >>> 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 <[email protected] <mailto:[email protected]>> >>> Sent: Monday, December 9, 2024 15:12 >>> To: Blondel, Sophie <[email protected] <mailto:[email protected]>> >>> Cc: [email protected] <mailto:[email protected]> >>> <[email protected] <mailto:[email protected]>>; >>> [email protected] >>> <mailto:[email protected]> >>> <[email protected] >>> <mailto:[email protected]>> >>> 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 >>>> <[email protected] <mailto:[email protected]>> 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>
