[petsc-users] Amortizing calls to PetscOptionsFindPair_Private()

[Matthew Knepley]

On Fri, Jan 15, 2016 at 6:15 PM, Bhalla, Amneet Pal S <amneetb at live.unc.edu>
wrote:

>
>
> On Jan 15, 2016, at 3:53 PM, Jed Brown <jed at jedbrown.org> wrote:
>
> Do you need to create new objects versus merely resetting them?  I
> suspect that calling KSPReset() between timesteps instead of creating a
> new object and calling KSPSetFromOptions() will fix your performance
> woes.
>
>
> We definitely need to destroy Mat associated with KSP everytime. This is a
> dynamic fluid-structure
> interaction problem on AMR grid, where the Cartesian grid and the
> structure moves at every timestep.
> Is it possible to reset a KSP with a different Mat? Are you suggesting to
> call KSPCreate() and
> KSPSetFromOptions() only once at the beginning of simulation, KSPReset()
> after every timestep,
> and KSPDestroy() at the end of the simulation?
>

That is how KSPReset() is supposed to work, but no one is really exercising
it now. I am inclined to try
Barry's experiment first, since this may have bugs that we have not yet
discovered. However, Jed is
correct that this is probably the best design.

  Matt

-- 
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
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