[petsc-dev] questions regarding TSDM

[Jed Brown]

On Tue, Nov 20, 2012 at 5:21 PM, Barry Smith <bsmith at mcs.anl.gov> wrote:

>    How do they "get out a coarse level and explicitly change it" for
>
> 1) KSP?
>

PCMG


> 2) SNES?
>

SNESFAS


> 3) TS?
>

Doesn't exist now, but will if we do multilevel in time methods.


>
> >
> >
> > The DMTSGetContext() business uses PetscObjectCompose to attach the TSDM
> to a dm. Why not just have DM's have opaque pointers to KSPDM, SNESDM, and
> TSDM built into the DM and things
> > like DMGetKSPDM() that do the usual dm->kspdm access instead of
> composing business.  Since the business of DM's is to talk to TS, SNES, and
> KSP there is no reason to go through the more complicated object compose
> business is there? (The object compose business is for out-of-the-ordinary
> stashing of stuff, not ordinary stashing of stuff, it is kind of like using
> object compose to attach the ksp to the snes).
> >
> > Okay, but when the optimizers need to attach something, do we add
> special support for that in DM as well?
>
>    Sure
>
> > What about UQ and so on? The idea here was to keep DM as ignorant as
> possible, but allow it to carry this extra data around for the various
> solver objects that need it.
>
>   Ok, objectcompose is certainly more extensible.
>
>   BTW: DMTSGetContext() is kind of a funky name, context is a very general
> term, this function returns a TSDM  (or DMTS) so could be DMGetDMTS() or
> DMTSGetDMTS()
>

Sure.
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