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Re: warn message in log summary

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()...