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

[Cody Permann]

It's not guaranteed to work on 10.8 and above.  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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