warn message in log summary

[Lisandro Dalcin]

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