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>
