[petsc-dev] misleading that ROSW uses SNES

[Matthew Knepley]

On Tue, Oct 16, 2012 at 3:52 PM, Barry Smith <bsmith at mcs.anl.gov> wrote:

>
> On Oct 15, 2012, at 11:48 PM, Matthew Knepley <knepley at gmail.com> wrote:
>
> > On Tue, Oct 16, 2012 at 3:24 PM, Barry Smith <bsmith at mcs.anl.gov> wrote:
> >
> >    It is seriously misleading that TSType rosw uses SNES as the solver
> since it is only using SNESKSP and the algorithm really is built around
> only linear solves.  Are you sure that using SNES is the right model for
> this family of algorithms? Convince me.
> >
> >    I realize one person among us thinks we should use SNES for both
> linear and nonlinear solves, but he is wrong :-)
> >
> > Let me try a Venn Diagram:
> >  _________________________________
> > /                                _____________   \
> > |                               /                        \  |
> > |  Nonlinear problems | Linear problems |  |
> > |                               \ _____________/  |
> > \_________________________________/
> >
> > Also, there is no overhead using SNES, so I would say Do Not Multiply
> Entities Beyond The Necessary.
>
>    I am not concerned about overhead. I am concerned about things looking
> like they are doing one thing but that are actually doing something else.
> In this case, there is actually a nonlinear problem hanging around but the
> rosw algorithms avoid solving it, which is ok but I find the fact that it
> prints SNES is then misleading because given a nonlinear problem and SNES
> one would think it is actually solving a nonlinear problem with SNES, when
> it is not.


It is solving a nonlinear problem, just a really easy one :) I guess you
could setup the SNES to
turn on the KSP monitor instead.

   Matt


> >
> >   Matt
> >
> >    Matt
> >
> >
> >   Barry
> >
> >
> >
> >
> > --
> > 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
>
>


-- 
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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