[petsc-users] Solution "jumps" after setting timestep

[Moritz.Huck at isea.rwth-aachen.de]

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> 
Gesendet: Samstag, 3. November 2018 15:43
An: Huck, Moritz <Moritz.Huck at isea.rwth-aachen.de>; 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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