[petsc-users] Step size for adaptive stepper when running on several MPI threads

[Matthew Knepley]

On Tue, Jan 19, 2021 at 10:16 AM Roland Richter <roland.richter at ntnu.no>
wrote:

> Hei,
>
> during recent experiments with the adaptive stepper in odeint I noticed
> that the step size used for each step can vary if I am using more than
> one thread at the same time (i.e. thread 1 can have a different step
> size than thread 2 when doing the same step). This is not suitable for
> my project, after the function calculating the right hand side relies on
> having the same step size for each thread.
>
> Before starting deeper experiments with the adaptive steppers in PETSc,
> I therefore wanted to ask if those steppers synchronize the step size of
> the sub-steps between the different mpi processes at each step, or if not?
>

Yes, the timestep is the same across the communicator that you create the
TS with.

  Thanks,

     Matt


> Thanks!
>
> Regards,
>
> Roland
>
>

-- 
What most experimenters take for granted before they begin their
experiments is infinitely more interesting than any results to which their
experiments lead.
-- Norbert Wiener

https://www.cse.buffalo.edu/~knepley/ <http://www.cse.buffalo.edu/~knepley/>
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