[petsc-dev] automatic preconditioners for Stokes type problems?

[Mark F. Adams]

Jed brings up good points about false negatives, there are also false  
positives to worry about.  This is a bad idea, at least as a default  
solver.

That said, there is work on "adaptive" solvers like bootstrap AMG and  
using machine learning to formalize what it sounds like Barry is  
driving at.  Perhaps make a '-ksp_type black_box' solver type where  
you put any heuristics methods like this.  (this would require the KSP  
method to change the PC method which is ugly...)

Mark

On Aug 5, 2010, at 5:36 AM, Matthew Knepley wrote:

> On Thu, Aug 5, 2010 at 2:10 AM, Jed Brown <jed at 59a2.org> wrote:
> On Thu, 5 Aug 2010 00:21:13 -0500, Matthew Knepley  
> <knepley at gmail.com> wrote:
> > If someone tells us, "I have a Stokes problem", we could search  
> for 0
> > diagonals and create the partition for FS.
>
> I suppose this would work for some common cases, but there are lot of
> discretizations and pressure-dependent constitutive relations/boundary
> conditions that have nonzeros in the pressure block.  I think some  
> slip
> conditions can also produce zero or negative values in the momentum
> block.
>
> Do not disagree.
>
> I'm not convinced that it's so much to ask people to provide an index
> set, considering that FieldSplit is a somewhat advanced thing anyway
> (based on sheer number of choices available, and (typical) sensitivity
> to those choices).
>
> I guess the point here is somewhat like the point of DAs. It is a  
> very limited
> thing, but something many people do. So we provide a way to most  
> easily
> do the very limited thing.
>
> Not sure if this is useful enough, but it might be.
>
>    Matt
>
>
> Jed
>
>
>
> -- 
> 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

-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://lists.mcs.anl.gov/pipermail/petsc-dev/attachments/20100805/7e275749/attachment.html>