[petsc-dev] TSSolve web page JED and EMIL READ THIS!

Dmitry Karpeyev karpeev at mcs.anl.gov
Sun Feb 8 20:29:18 CST 2015

This is a bit off-topic, but I'm dealing exactly with this sort of "funky
system" -- particles+field.
Since degrees of freedom do move between processors, it's unclear how it
fits into the current
TS framework short of rebuilding the TS every timestep. That's a bit
inconvenient, since now I
have to do my own error and timestep size control etc.  It might be too
late to do anything about
TS to help this, but I'm also hoping to use TSAdjoint with this system, so
it may be good -- before
TSAdjoint becomes to rigidly entrenched -- to think about how to
accommodate these systems.

On Sun Feb 08 2015 at 8:16:30 PM Barry Smith <bsmith at mcs.anl.gov> wrote:

> > On Feb 8, 2015, at 8:11 PM, Jed Brown <jed at jedbrown.org> wrote:
> >
> > Barry Smith <bsmith at mcs.anl.gov> writes:
> >>   Why can't TS handle that? Users always prefer to use the lowest
> >>   level thing available, that doesn't mean it is right.
> >>
> >>   In the language of TS what does a "funky system, liked mixed
> >>   particle-field," mean, does it require a little more API on our
> >>   side? I'm much rather have Emil and Jed control the time-stepping
> >>   then some ignorant user.
> >
> > Dofs move to different processes at each stage.  That isn't compatible
> > with Vec.  Do we need to overhaul Vec before users can integrate such a
> > system?
>    Well eventually.
> >
> > Practicality wins over purity.
>   I never said remove TSStep() or make it completely private. I just want
> to limit its use to when it is really needed by the user.
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