[petsc-dev] who broke petsc-dev

[Barry Smith]

   The simplest fix is to only do this null space business if Amat exists.

   But keep in mind that KSP and SNES now have two modes of operation, the second uses the DM to provide many of the items they need at setup time. This is different then the classic KSP and SNES where the only way to do things were with KSPSetOperators() and SNESSetFunction/Jacobian. This is why Jed is indicating that it may be too soon at this stage to muck with the null space business.

   Barry


On Nov 13, 2011, at 4:47 PM, Matthew Knepley wrote:

> On Sun, Nov 13, 2011 at 10:47 PM, Barry Smith <bsmith at mcs.anl.gov> wrote:
> 
> On Nov 13, 2011, at 4:45 PM, Matthew Knepley wrote:
> 
> > On Sun, Nov 13, 2011 at 10:44 PM, Jed Brown <jedbrown at mcs.anl.gov> wrote:
> > On Sun, Nov 13, 2011 at 16:36, Barry Smith <bsmith at mcs.anl.gov> wrote:
> > 1) It is legitimate to call KSPSetOperators with a null Amat so this is a bug that crashes large parts of PETSc
> >
> > This logic should be moved much later (like to KSPSetUp()).
> >
> > I disagree, since SetOperators() is where we know that the matrix is changing.
> 
>  Yes, but the matrix may not exist.
> 
> I have no problem fixing this, but what does that mean? I can't fix it until I understand what you are doing here.
> 
>   Matt
>  
> >
> >    Matt
> >
> >
> >
> > 2) Do you really want to do this? I am not sure I like it.
> >
> > I think that attaching the null space to the Mat should be the preferred way to communicate it, especially in the case of a deeply nested hierarchy.
> >
> >
> >
> > --
> > 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