[petsc-dev] BDF implementation

[Matthew Knepley]

On Wed, Mar 30, 2016 at 4:00 PM, Lisandro Dalcin <dalcinl at gmail.com> wrote:

> On 30 March 2016 at 18:50, Hong Zhang <hongzhang at anl.gov> wrote:
> > If there are state changes in the post event callback, then multistep
> methods would not be a good choice for the application.
> > I would use multistage methods such as RK type instead.
> >
>
> It all depends on the frequency of events respect to the timestep.
>
> > However, restarting the time stepper may still be necessary for other
> types of discontinuities, e.g. changes in the RHS function.
>
> Oh! Very good point. Then, the only way to know is the postevent
> callback flagging the timestepper about it. Well, A
> VecGetArray()/RestoreArray() on the solution would still work, even if
> the postevent callback does not actually modify the state. However,
> this is sounds like a bad API for users to flag the restart.
>
> > So I would suggest to do unconditional restart at discontinuity points
> for safety.
> >
>
> So ARKIMEX has to be fixed. Unless we agree and document that
> VecGetArray()/RestoreArray() is the way to flag discontinuities in the
> RHS function.
>

Or
http://www.mcs.anl.gov/petsc/petsc-current/docs/manualpages/Sys/PetscObjectStateIncrease.html

   Matt


>
> --
> Lisandro Dalcin
> ============
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>
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