[petsc-users] KSP no longer returning NaNs?

[Barry Smith]

On Jul 25, 2012, at 5:12 PM, Matthew Knepley wrote:

> On Wed, Jul 25, 2012 at 5:04 PM, Jed Brown <jedbrown at mcs.anl.gov> wrote:
> On Wed, Jul 25, 2012 at 4:58 PM, Barry Smith <bsmith at mcs.anl.gov> wrote:
> 
>   As always a COMPLETE error report is useful. There are a million ways you could see this change in behavior but we can't spend time guessing.  At a minimum please send the entire error output.
> 
>    I note in 3.3 the KSPDefaultConverged() still checks for NAN and returns a negative converged reason (not an error) so I can only guess why you are getting different behavior without more information.,
> 
> This is probably the main complaint:
> 
> http://petsc.cs.iit.edu/petsc/petsc-dev/rev/7d6f5cbe67bc
> 
> Yes, but what in PETSc code could possibly create these NaNs?

  Shell MatMult or PC :-)


> 
>    Matt
>  
>  
> 
> 
>      Barry
> 
> On Jul 25, 2012, at 4:35 PM, Kirk, Benjamin (JSC-EG311) wrote:
> 
> > Hello -
> >
> > I've been using PETSc 3.1 for quite a while now and have been hesitant to
> > upgrade because of some new behavior I found in 3.2.  Let me explain...
> >
> > In petsc-3.1, if the KSP encountered a NaN it would return it to the
> > application code.  We actually liked this feature because it gives us an
> > opportunity to catch the NaN and attempt recovery, in our case by decreasing
> > the time step and trying again.
> >
> > It seems in petsc-3.2, however, that PETSc itself aborts internally, so we
> > are unable to recover from the situation.
> >
> > Is there any way to get the old behavior back?
> >
> > Thanks,
> >
> > -Ben
> >
> 
> 
> 
> 
> 
> -- 
> 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