[petsc-users] Solution "jumps" after setting timestep
Moritz.Huck at isea.rwth-aachen.de
Moritz.Huck at isea.rwth-aachen.de
Fri Dec 14 10:28:06 CST 2018
Hello,
thank you this seems to be a reasonable explanation.
I will try this for my "steady" phases.
I have also phases where my Neumann boundary conditions change with time (in my real application, here I uses constant conditions), in this time I also need the results at exact time points.
Can I get these without setting explicit end times?
Best Regards,
Moritz
-----Ursprüngliche Nachricht-----
Von: Zhang, Hong <hongzhang at anl.gov>
Gesendet: Freitag, 14. Dezember 2018 17:13
An: Huck, Moritz <Moritz.Huck at isea.rwth-aachen.de>
Cc: petsc-users <petsc-users at mcs.anl.gov>
Betreff: Re: [petsc-users] Solution "jumps" after setting timestep
> On Dec 14, 2018, at 5:16 AM, Moritz.Huck at isea.rwth-aachen.de wrote:
>
> Correction.
> Not exactly more like this
> While t<2
> t=TSGetTime
> h=TSGetTimeStep
> TSSetMaxTime(min(t+h,2)
> TSSolve
> t=TSGetTime
> TSSetMaxTime(t+1e-3)
> TSSolve
> While t<10
> t=TSGetTime
> h=TSGetTimeStep
> TSSetMaxTime(min(t+h,10)
> TSSolve
>
> @Hong
> No did not reset the time. Shouldn’t the time already 2 in this case?
My mistake. The time looks fine. Now I understand what your code does.
You might want to use TSSetTimeStep() to change the step size and there is no need to have loops. You can define a TSPostStep function and call TSSolve() just once. When solving a DAE, each call to TSSolve() would trigger a restart step internally to calculate an initial slope for the DAE. I suspect that the jump was caused by these restart steps.
Hong
> -----Ursprüngliche Nachricht-----
> Von: petsc-users <petsc-users-bounces at mcs.anl.gov> Im Auftrag von
> Moritz.Huck--- via petsc-users
> Gesendet: Freitag, 14. Dezember 2018 12:06
> An: Emil Constantinescu <emconsta at mcs.anl.gov>; Zhang, Hong
> <hongzhang at anl.gov>
> Cc: petsc-users <petsc-users at mcs.anl.gov>
> Betreff: Re: [petsc-users] Solution "jumps" after setting timestep
>
> In this example yes.
>
> -----Ursprüngliche Nachricht-----
> Von: Emil Constantinescu <emconsta at mcs.anl.gov>
> Gesendet: Donnerstag, 13. Dezember 2018 20:21
> An: Zhang, Hong <hongzhang at anl.gov>; Huck, Moritz
> <Moritz.Huck at isea.rwth-aachen.de>
> Cc: petsc-users <petsc-users at mcs.anl.gov>
> Betreff: Re: [petsc-users] Solution "jumps" after setting timestep
>
> Okay, so you start your integration with "TSSetMaxTime and then call TSSolve (TSSetExactFinalTime is set to TS_EXACTFINALTIME_MATCHSTEP)"
>
> Then after it's done at t=2 you tell TS that TSSetTimeStep(ts,1e-3) and call TSSolve again?
>
> Emil
>
>
>
> On 12/13/18 11:36 AM, Zhang, Hong via petsc-users wrote:
>> Please make sure your messages go to petsc-users when replying.
>>
>>> On Dec 13, 2018, at 11:25 AM, Moritz.Huck at isea.rwth-aachen.de
>>> <mailto:Moritz.Huck at isea.rwth-aachen.de> wrote:
>>>
>>> The first solve to 1e-3
>>> TSAdapt basic arkimex 0:1bee step 0 rejected t=0 +
>>> 1.000e-03 dt=1.000e-04 wlte= 102 wltea= -1 wlter= -1
>>> TSAdapt basic arkimex 0:1bee step 0 rejected t=0 +
>>> 1.000e-04 dt=1.000e-05 wlte= 127 wltea= -1 wlter= -1
>>> TSAdapt basic arkimex 0:1bee step 0 rejected t=0 +
>>> 1.000e-05 dt=1.995e-06 wlte= 5.09 wltea= -1 wlter= -1
>>> TSAdapt basic arkimex 0:1bee step 0 accepted t=0 +
>>> 1.995e-06 dt=3.232e-06 wlte=0.309 wltea= -1 wlter= -1
>>> TSAdapt basic arkimex 0:4 step 1 accepted t=1.99488e-06+
>>> 3.232e-06 dt=3.232e-05 wlte=1.65e-06 wltea= -1 wlter= -1
>>> TSAdapt basic arkimex 0:4 step 2 accepted t=5.22663e-06+
>>> 3.232e-05 dt=3.232e-04 wlte=3.96e-05 wltea= -1 wlter= -1
>>> TSAdapt basic arkimex 0:4 step 3 accepted t=3.75441e-05+
>>> 3.232e-04 dt=6.393e-04 wlte=0.000973 wltea= -1 wlter= -1
>>> TSAdapt basic arkimex 0:4 step 4 accepted t=0.000360719+
>>> 6.393e-04 dt=2.962e-03 wlte=0.00142 wltea= -1 wlter= -1 the
>>> solve steps afterwards:
>>> TSAdapt basic arkimex 0:4 step 5 accepted t=0.001 +
>>> 2.962e-03 dt=7.110e-03 wlte=0.0197 wltea= -1 wlter= -1
>>> TSAdapt basic arkimex 0:4 step 6 accepted t=0.00396151 +
>>> 7.110e-03 dt=2.489e-02 wlte=0.00437 wltea= -1 wlter= -1
>>> TSAdapt basic arkimex 0:4 step 7 accepted t=0.0110717 +
>>> 2.489e-02 dt=7.079e-02 wlte= 0.01 wltea= -1 wlter= -1
>>> TSAdapt basic arkimex 0:4 step 8 accepted t=0.03596 +
>>> 7.079e-02 dt=9.672e-02 wlte=0.188 wltea= -1 wlter= -1
>>> TSAdapt basic arkimex 0:4 step 9 accepted t=0.106753 +
>>> 9.672e-02 dt=1.329e-01 wlte=0.184 wltea= -1 wlter= -1 around
>>> here it reaches a steady state
>>> TSAdapt basic arkimex 0:4 step 10 accepted t=0.203478 +
>>> 1.329e-01 dt=2.432e-01 wlte=0.0586 wltea= -1 wlter= -1
>>> TSAdapt basic arkimex 0:4 step 11 accepted t=0.336424 +
>>> 2.432e-01 dt=4.536e-01 wlte=0.0542 wltea= -1 wlter= -1
>>> TSAdapt basic arkimex 0:4 step 12 accepted t=0.579616 +
>>> 4.536e-01 dt=1.112e+00 wlte=0.0182 wltea= -1 wlter= -1
>>> TSAdapt basic arkimex 0:4 step 13 accepted t=1.03324 +
>>> 9.668e-01 dt=3.286e+00 wlte=0.00492 wltea= -1 wlter= -1 here I
>>> set the timestep to 1e-3 artificially and the solution deviates from
>>> the steady state solution
>>
>> The TS time jumps between step 13 and step 14, which is probably the
>> cause of the jump in the solution.
>> Did you reset the time to t=2 by calling TSSetTime() after step 13?
>>
>> Hong
>>
>>> TSAdapt basic arkimex 0:4 step 14 accepted t=2 +
>>> 1.000e-03 dt=3.845e-03 wlte=0.003 wltea= -1 wlter= -1
>>> TSAdapt basic arkimex 0:4 step 15 accepted t=2.001 +
>>> 3.845e-03 dt=3.845e-02 wlte=6.95e-06 wltea= -1 wlter= -1
>>> TSAdapt basic arkimex 0:4 step 16 accepted t=2.00485 +
>>> 3.845e-02 dt=3.845e-01 wlte=4.31e-05 wltea= -1 wlter= -1
>>> TSAdapt basic arkimex 0:4 step 17 accepted t=2.0433 +
>>> 3.845e-01 dt=2.473e+00 wlte=0.000384 wltea= -1 wlter= -1
>>> TSAdapt basic arkimex 0:4 step 18 accepted t=2.42784 +
>>> 2.473e+00 dt=4.540e+00 wlte=0.0578 wltea= -1 wlter= -1 this
>>> point is "back on track"
>>> TSAdapt basic arkimex 0:4 step 19 accepted t=4.90058 +
>>> 4.540e+00 dt=4.649e+00 wlte=0.596 wltea= -1 wlter= -1
>>> *Von:*Zhang, Hong <hongzhang at anl.gov <mailto:hongzhang at anl.gov>>
>>> *Gesendet:*Donnerstag, 13. Dezember 2018 17:39 *An:*Huck, Moritz
>>> <Moritz.Huck at isea.rwth-aachen.de
>>> <mailto:Moritz.Huck at isea.rwth-aachen.de>>
>>> *Cc:*petsc-users at mcs.anl.gov <mailto:petsc-users at mcs.anl.gov>
>>> *Betreff:*Re: [petsc-users] Solution "jumps" after setting timestep
>>> 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,Moritz.Huck at isea.rwth-aachen.de
>>> <mailto:Moritz.Huck at isea.rwth-aachen.de>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 <hongzhang at anl.gov <mailto:hongzhang at anl.gov>>
>>> *Gesendet:*Donnerstag, 13. Dezember 2018 16:42
>>> *An:*Huck, Moritz <Moritz.Huck at isea.rwth-aachen.de
>>> <mailto:Moritz.Huck at isea.rwth-aachen.de>>
>>> *Cc:*petsc-users at mcs.anl.gov <mailto:petsc-users at mcs.anl.gov>
>>> *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
>>> <petsc-users at mcs.anl.gov <mailto:petsc-users at mcs.anl.gov>> 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. <emconsta at anl.gov
>>> <mailto:emconsta at anl.gov>>
>>> Gesendet: Samstag, 3. November 2018 15:43
>>> An: Huck, Moritz <Moritz.Huck at isea.rwth-aachen.de
>>> <mailto:Moritz.Huck at isea.rwth-aachen.de>>;petsc-users at mcs.anl.gov
>>> <mailto:petsc-users at mcs.anl.gov>
>>> 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
>>>
>>
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