[petsc-dev] BDF implementation

[Lisandro Dalcin]

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.


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