warn message in log summary

[Richard Tran Mills]

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()...