Параллельное программирование в стандарте MPI. Баканов В.М - 46 стр.

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МИРЭА | Москва

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- 46 -
t1=f_time();
MPI_Init (&argc, &argv); /* initialize MPI-system */
t2=f_time();
MPI_Comm_rank (MPI_COMM_WORLD, &myrank); /* my place in MPI system */
MPI_Comm_size (MPI_COMM_WORLD, &ranksize); /* size of MPI system */
if (myrank == 0) /* I am the MASTER */
{
intervals = atoi( argv[1] ); /* get interval’s count from command line */
printf (“Calculation of PI by numerical integration with %ld intervals\n”, intervals);
}
MPI_Barrier(MPI_COMM_WORLD); /* make sure all MPI tasks are running */
if (myrank == 0) /* I am the MASTER */
{ /* distribute parameter */
printf (“Master: Sending # of intervals to MPI-Processes \n”);
t3 = MPI_Wtime();
for (i=1; i<ranksize; i++)
MPI_Send (&intervals, 1, MPI_LONG, i, 98, MPI_COMM_WORLD);
} /* end work MASTER */
else /* I am a SLAVE */
{ /* receive parameters */
MPI_Recv (&intervals, 1, MPI_LONG, 0, 98, MPI_COMM_WORLD, &status);
} // end work SLAVE
/* compute my portion of interval */
t4 = MPI_Wtime();
pi = compute_interval (myrank, ranksize, intervals); /*=======================*/
t5 = MPI_Wtime();
MPI_Barrier (MPI_COMM_WORLD); /* make sure all MPI tasks are running */
t6 = MPI_Wtime();
if (myrank == 0) /* I am the MASTER */
{ /* collect results add up & printing results */
for (i=1; i<ranksize; i++)
{
MPI_Recv (&di, 1, MPI_DOUBLE, i, 99, MPI_COMM_WORLD, &status);
pi += di;
} /* end of collect results */
t7 = MPI_Wtime();
printf (“Master: Has collected sum from MPI-Processes \n”);
printf (“\nPi estimation: %.12lf (rel.error= %.5f %%)\n”,
pi, 1.0e2*(pi_prec-pi)/pi_prec);
printf (“%ld tasks used, execution time: %.3lf sec\n”,ranksize, t7 –t3);
printf(“\nStatistics:\n”);
printf(“Master: startup: %.0lf msec\n”,t2-t1);
printf(“Master: time to send # of intervals:%.3lf sec\n”,t4-t3);
printf(“Master: waiting time for sincro after calculation:%.2lf sec\n”,t6-t5);
printf(“Master: time to collect: %.3lf sec\n”,t7-t6);
printf(“Master: calculation time:%.3lf sec\n”,t5-t4); 
                                            - 46 -


t1=f_time();
MPI_Init (&argc, &argv); /* initialize MPI-system */
t2=f_time();
MPI_Comm_rank (MPI_COMM_WORLD, &myrank); /* my place in MPI system */
MPI_Comm_size (MPI_COMM_WORLD, &ranksize); /* size of MPI system */

if (myrank == 0) /* I am the MASTER */
{
intervals = atoi( argv[1] ); /* get interval’s count from command line */
printf (“Calculation of PI by numerical integration with %ld intervals\n”, intervals);
}

MPI_Barrier(MPI_COMM_WORLD); /* make sure all MPI tasks are running */

if (myrank == 0) /* I am the MASTER */
{ /* distribute parameter */
printf (“Master: Sending # of intervals to MPI-Processes \n”);
t3 = MPI_Wtime();
for (i=1; i

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