[petsc-users] [Libmesh-users] Really Really Really Weird SNES behaviour

[Matthew Knepley]

On Sun, Jul 14, 2013 at 12:29 PM, Barry Smith <bsmith at mcs.anl.gov> wrote:

>
> >>
> >>
> > I think it breaks down more on the C++ side.  I always get a ton of
> > false positives.  Another point for C?  :)
>
>    +1


It vomits and kernel panics most times when I run MPI code in 10.6.

   Matt


> >
> > Cody
> >
> >
> >> Barry
> >>
> >>> If you have an older OS, it's fine.
> >>>
> >>> Sent from my iPhone
> >>>
> >>> On Jul 14, 2013, at 9:59 AM, Dmitry Karpeyev <karpeev at mcs.anl.gov>
> wrote:
> >>>
> >>>> Are there known problems with valgrind for macos?
> >>>> I have it installed from macports and it seems to work fine.
> >>>> Dmitry.
> >>>>
> >>>>
> >>>> On Sun, Jul 14, 2013 at 7:26 AM, Cody Permann <codypermann at gmail.com>
> wrote:
> >>>> Sounds like a memory corruption problem. I know several users that are
> >>>> experts at writing code like that.
> >>>>
> >>>> Unfortunately, it can be difficult to track down on OS X due to a lack
> >>>> of working memory analysis tools.
> >>>> 1. Since this problem popped up after you changed your initial
> >>>> condition, you may just want to start by carefully looking at your
> >>>> code and thinking about cases where your variables might not be
> >>>> initialized, or where calculations could potentially produce underflow
> >>>> or overflow conditions.
> >>>> 2. If you have access to a Linux box, then you will have bounds
> >>>> checked STL containers at your disposal in debug mode.  You'll also be
> >>>> able to run your code through valgrind.  Both of those operations are
> >>>> relatively easy to perform.  Let us know if you have any questions.
> >>>>
> >>>> Cody
> >>>>
> >>>> Sent from my iPhone
> >>>>
> >>>> On Jul 13, 2013, at 11:17 PM, subramanya sadasiva <
> potaman at outlook.com> wrote:
> >>>>
> >>>>> Hi, I am observing some really really really weird SNES behavior in
> my SNESVI code called through Libmesh. This behaviour appeared after I
> changed some initial conditions and only happens in an optimized build. I
> am running this code on a Macbook pro running os x 10.8..
> >>>>> When the debug code is run, the residuals computed for the initial
> conditions provided give norms which are of the expected magnitude.. so the
> SNES_Monitor output is,
> >>>>> solving the cahn hilliard time step  0 SNES Function norm
> 8.223262421671e-01  1 SNES Function norm 3.793806858333e-03Nonlinear solve
> did not converge due to DIVERGED_MAX_IT iterations 1
> >>>>> The output from SNES_Monitor with the optimized code on the other
> hand is,
> >>>>> solving the cahn hilliard time step  0 SNES Function norm
> 5.153882032022e+19  1 SNES Function norm 1.446612980133e+19Nonlinear solve
> did not converge due to DIVERGED_MAX_IT iterations 1
> >>>>>
> >>>>> Absolutely nothing else has changed in the code except that one code
> is built with a debugging and one with an optimized version of the code.
> >>>>> Any ideas?Subramanya
> >>>>>
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> >>
>
>


-- 
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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