warn message in log summary

[Barry Smith]

   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.

    Barry

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
>