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...
Could you please try the small example in previous mail? Just to be sure that the problem is in Cray's MPI_Wtime and not somewere deep in PETSc code? > --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 Dalc?n --------------- Centro Internacional de M?todos Computacionales en Ingenier?a (CIMEC) Instituto de Desarrollo Tecnol?gico para la Industria Qu?mica (INTEC) Consejo Nacional de Investigaciones Cient?ficas y T?cnicas (CONICET) PTLC - G?emes 3450, (3000) Santa Fe, Argentina Tel/Fax: +54-(0)342-451.1594