Can you show the outputs of -ts_monitor for both cases (one with oscillations and one without)?
Thanks, Hong On Dec 13, 2018, at 9:48 AM, [email protected]<mailto:[email protected]> wrote: Hi, Sure after reaching a steady state it looks like this: 0 SNES Function norm 3.767377637168e-03 1 SNES Function norm 2.529971638368e-05 2 SNES Function norm 4.433873358247e-09 3 SNES Function norm 4.535675922104e-11 0 SNES Function norm 9.898938706929e-04 1 SNES Function norm 1.322473621975e-05 2 SNES Function norm 1.672724799379e-09 3 SNES Function norm 1.338501638801e-11 0 SNES Function norm 1.624500221071e-03 1 SNES Function norm 2.448515345247e-05 2 SNES Function norm 6.225549426481e-09 3 SNES Function norm 1.062516222150e-10 4 SNES Function norm 6.493758120241e-13 0 SNES Function norm 1.106311709708e-03 1 SNES Function norm 2.475673243430e-05 2 SNES Function norm 9.969586735411e-09 3 SNES Function norm 2.479591395229e-10 4 SNES Function norm 1.542689576708e-12 0 SNES Function norm 6.070943996748e-04 1 SNES Function norm 1.648134285171e-05 2 SNES Function norm 8.461078655420e-09 3 SNES Function norm 2.480863447790e-10 4 SNES Function norm 1.513977618851e-12 TSAdapt basic arkimex 0:4 step 15 accepted t=5.67201 + 4.328e+00 dt=4.687e+00 wlte$ 0.477 wltea= -1 wlter= -1 If I set the next target time (in tssolve) to be tlast+1e-3 it looks like this: 0 SNES Function norm 4.734802409365e-03 1 SNES Function norm 6.173939866359e-13 0 SNES Function norm 5.633294284900e-04 1 SNES Function norm 3.575533754564e-13 0 SNES Function norm 9.651618110271e-04 1 SNES Function norm 6.863177319359e-13 0 SNES Function norm 7.706102281617e-04 1 SNES Function norm 8.490865565002e-13 0 SNES Function norm 5.028108294534e-04 1 SNES Function norm 6.905750968862e-13 TSAdapt basic arkimex 0:4 step 16 accepted t=10 + 1.000e-03 dt=2.612e-03 wlte$ 0.0141 wltea= -1 wlter= -1 The SNES solver has a atoll of 1e-10, setting the atoll to lower values does not change the result. Thank you, Moritz Von: Zhang, Hong <[email protected]<mailto:[email protected]>> Gesendet: Donnerstag, 13. Dezember 2018 16:42 An: Huck, Moritz <[email protected]<mailto:[email protected]>> Cc: [email protected]<mailto:[email protected]> Betreff: Re: [petsc-users] Solution "jumps" after setting timestep Can you please add command line options -ts_monitor -snes_monitor and show us the outputs? Thanks, Hong (Mr.) On Nov 4, 2018, at 6:19 AM, Moritz.Huck--- via petsc-users <[email protected]<mailto:[email protected]>> wrote: Hi, I using the basic adaptor. If I let the adaptor handle everything it does not oscillates. I don’t mean setting the timestep at the start (which does not produces the problem), I need to set during runtime between two steps. Best Regards, Moritz -----Ursprüngliche Nachricht----- Von: Constantinescu, Emil M. <[email protected]<mailto:[email protected]>> Gesendet: Samstag, 3. November 2018 15:43 An: Huck, Moritz <[email protected]<mailto:[email protected]>>; [email protected]<mailto:[email protected]> Betreff: Re: [petsc-users] Solution "jumps" after setting timestep On 11/3/18 4:56 AM, Moritz.Huck--- via petsc-users wrote: Hi, I am using the IMEX Runge Kutta to solve an implicit DAE (G=0). When I manually set the time step (TSSetTimestep) my solution jumps. When you don't set the time step, does it still oscillates? If not, can you check if it oscillates when reducing the fixed initial time step? Did you turn the adaptivity off (-ts_adapt_type none)? Emil If I go from a steady state to the same state, it oscillates a few time and comes back to the steady solution. Can this be prevented? Thank you, Moritz
