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

[Constantinescu, Emil M.]

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 oscilates a few time 
> and comes back to the steady solution.
> 
> Can this be prevented?
> 
> Thank you,
> 
> Moritz
>