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

[Mark Adams]

valgrind on Edison does seem to give a lot of false positives.  The line
number are accurate (not always the case).  "assert" triggers it, as does
SETERRQ.

On Tue, Nov 10, 2015 at 8:51 AM, Mark Adams <mfadams at lbl.gov> wrote:

> 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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