warn message in log summary

[Barry Smith]

    When we started PETSc 2 I thought of PETSc errors as ALWAYS being
catastrophic: that is the program could NOT continue running.

   Later we started to play with possibly recovering from some errors
and I added the crude PetscException mechanism. For example
I used it to allow the user in their SNES FormFunction to indicate
the input vector was not in the domain, SNES would catch this
and allow the program to continue.

   I am very nervous about mixing a catastrophic error handling system
WITH an exception system. I'd like to go back to the model:
"once seterrq() is called ANYWHERE there is no possibility of
continuing the program. " This means that all "exceptions" have to
be handled on a case by case basis directly with the code. For
example I just added SNESSetFunctionDomainError() to
replace the previous use of SETERRQ(PETSC_ERR_ARG_DOMAIN).
The "handling" of these custom code is then required to properly
handle the resources like PetscLogEventEnd().

   Comments?


   Barry





On Nov 26, 2007, at 4:19 PM, Lisandro Dalcin wrote:

> On 11/26/07, Barry Smith <bsmith at mcs.anl.gov> wrote:
>>   I've looked long and hard for a PETSc bug that would cause this
>> problem.
>> No luck. It seems to happen mostly (only?) on certain machines.
>
> Ups! I've found a possilbe source of the problem, at least for my
> case! Those negative times I got  Order(-1e9) were in fact originated
> from premature returns due to CHKERRQ macros.
>
> As I was doing Python unittesting, I was making calls generating
> error, and catching exceptions, in order to check the error was
> correctly set.
>
> However, this way of using PETSc is not safe at all, in general PETSc
> does not always recover correctly after an error, and this seems to be
> specially true for log machinery.
>
> After surfing the code and hacked PetscLogPrintSummary(),  I added a
> check (eventInfo[event].depth == 0) in order to skip reductions of
> time values for 'unterminated' events. This worked as expected, and
> the even info did not show-up and the warning was not generated...
>
> Could this be a possible 'fix' for this issue??
>
> Richard... Are you completelly sure the negative timmings you were
> getting are not related to an error being silenced because of a
> missing CHKERRQ macro???
>
>
>
>> On Nov 26, 2007, at 11:03 AM, Lisandro Dalcin wrote:
>>
>>> I even get consistent time deltas using 'gettimeofday' on my box!!
>>> Perhaps PETSc has some bug somewere?? What do you think??
>>>
>>> On 11/26/07, Richard Tran Mills <rmills at ornl.gov> wrote:
>>>> Lisandro,
>>>>
>>>> Unfortunately, I see the same negative timings problem on the Cray
>>>> XT3/4
>>>> systems when I configure PETSc to use MPI_Wtime() for all its
>>>> timings.  So
>>>> that doesn't necessarily fix anything...
>>>>
>>>> --Richard
>>>>
>>>> Lisandro Dalcin wrote:
>>>>
>>>>> Perhaps PETSc should use MPI_Wtime as default timer. If a better  
>>>>> one
>>>>> is available, then use it. But then MPIUNI have to also provide an
>>>>> useful, default implementation.
>>>>>
>>>>> Runing a simple test, like this (MPICH2):
>>>>>
>>>>> int main(void)
>>>>> {
>>>>> int i;
>>>>> double t0[100],t1[100];
>>>>> MPI_Init(0,0);
>>>>> for (i=0; i<100; i++) {
>>>>>   t0[i] = MPI_Wtime();
>>>>>   t1[i] = MPI_Wtime();
>>>>> }
>>>>> for (i=0; i< 100; i++) {
>>>>>   printf("t0=%e, t1=%e, dt=%e\n",t0[i],t1[i],t1[i]-t0[i]);
>>>>> }
>>>>> MPI_Finalize();
>>>>> return 0;
>>>>> }
>>>>>
>>>>> and in the SAME box I get the PETSc warning, it consistently gives
>>>>> me
>>>>> positive time deltas of the order of MPI_Wtick()...
>>>>
>>>>
>>>
>>>
>>> --
>>> Lisandro Dalcín
>>> ---------------
>>> Centro Internacional de Métodos Computacionales en Ingeniería  
>>> (CIMEC)
>>> Instituto de Desarrollo Tecnológico para la Industria Química  
>>> (INTEC)
>>> Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET)
>>> PTLC - Güemes 3450, (3000) Santa Fe, Argentina
>>> Tel/Fax: +54-(0)342-451.1594
>>>
>>
>>
>
>
> -- 
> Lisandro Dalcín
> ---------------
> Centro Internacional de Métodos Computacionales en Ingeniería (CIMEC)
> Instituto de Desarrollo Tecnológico para la Industria Química (INTEC)
> Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET)
> PTLC - Güemes 3450, (3000) Santa Fe, Argentina
> Tel/Fax: +54-(0)342-451.1594
>