[petsc-users] odd SNES behavior

[Dmitry Karpeev]

On Thu, Mar 7, 2013 at 10:08 AM, Mark F. Adams <mark.adams at columbia.edu>wrote:

> >
> >
> >  So you could add PCMGSetUseTrue(PC) and -pc_mg_true  that would trigger
> setting the true (outer) operator inside the PCSetUp_MG() even if it was
> already set. You would still change/fix the current GAMG to always set the
> operators on the finest level using the pmat (which could be overwritten by
> the user with the PCMGSetUseTrue() or -pc_mg_true option.
> >
> >  It may also make sense to move the use true flag and functionality up
> to the PC level (out of the subclasses) thus unifying its usage (or not)?
> PCSetUseTrue(), -pc_true.**
> >
>
> This seems like it should be in PC to me.  Some PCs will want to give
> finer grain control but this will work for many (e.g., me, for now).
>
> I prefer the default to be !true so that the semantics match hypre, etc.
>  I can set it manually before GetOptions if we do not want this to be the
> default for everyone … although that would make -help not correct.
>
> -pc_true is pretty ambiguous.  how about
>
> -pc_true_op <false>
>
> ?  or <true> if you prefer.
>
Name the two matrices kspop and pcop and then -pc_use_kspop?

>
>
>
> >  Suggestions to alternatives to "True" (that are concise yet
> descriptive) are also solicited.
> >
> >
> >   Barry
> >
> > ** note that in some complicated PCs there may be several different
> applications of the full (or part of the full) operator inside the
> application of the PC. Conceivably one may want to use True on some and not
> on others but we've never dealt with that.
> >
> >
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