[petsc-users] CG+GAMG convergence issues in GHEP Krylov-Schur for some MPI runs

[Mark Adams]

I ran an 8 processor job on Edison of a small code for a short run (just a
linear solve) and got 37 Mb of output!

Here is a 'Petsc' grep.

Perhaps we should build an ignore file for things that we believe is a
false positive.

On Tue, Nov 3, 2015 at 11:55 AM, Barry Smith <bsmith at mcs.anl.gov> wrote:

>
>   I am more optimistic about valgrind than Mark. I first try valgrind and
> if that fails to be helpful then use the debugger. valgrind has the
> advantage that it finds the FIRST place that something is wrong, while in
> the debugger it is kind of late at the crash.
>
>   Valgrind should not be noisy, if it is then the applications/libraries
> should be cleaned up so that they are valgrind clean and then valgrind is
> useful.
>
>   Barry
>
>
>
> > On Nov 3, 2015, at 7:47 AM, Mark Adams <mfadams at lbl.gov> wrote:
> >
> > BTW, I think that our advice for segv is use a debugger.  DDT or
> Totalview, and gdb if need be, will get you right to the source code and
> will get 90% of bugs diagnosed.  Valgrind is noisy and cumbersome to use
> but can diagnose 90% of the other 10%.
> >
> > On Tue, Nov 3, 2015 at 7:32 AM, Denis Davydov <davydden at gmail.com>
> wrote:
> > Hi Jose,
> >
> > > On 3 Nov 2015, at 12:20, Jose E. Roman <jroman at dsic.upv.es> wrote:
> > >
> > > I am answering the SLEPc-related questions:
> > > - Having different number of iterations when changing the number of
> processes is normal.
> > the change in iterations i mentioned are for different preconditioners,
> but the same number of MPI processes.
> >
> >
> > > - Yes, if you do not destroy the EPS solver, then the preconditioner
> would be reused.
> > >
> > > Regarding the segmentation fault, I have no clue. Not sure if this is
> related to GAMG or not. Maybe running under valgrind could provide more
> information.
> > will try that.
> >
> > Denis.
> >
>
>
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