#include #include #include int main(int argc,char *argv[]) { int done = 0, n, myid, numprocs, i; double PI25DT = 3.141592653589793238462643; double mypi, pi, h, sum, x, mflops; double startwtime = 0.0, endwtime; int namelen; char processor_name[MPI_MAX_PROCESSOR_NAME]; MPI_Init(&argc,&argv); MPI_Comm_size(MPI_COMM_WORLD,&numprocs); MPI_Comm_rank(MPI_COMM_WORLD,&myid); MPI_Get_processor_name(processor_name,&namelen); fprintf(stdout,"Process %d of %d on %s\n", myid, numprocs, processor_name); n = 0; while (!done) { if (myid == 0) { /* printf("Enter the number of intervals: (0 quits) "); scanf("%d",&n); */ if (n==0) n=1000000000; else n=0; startwtime = MPI_Wtime(); } MPI_Bcast(&n, 1, MPI_INT, 0, MPI_COMM_WORLD); if (n == 0) done = 1; else { h = 1.0 / (double) n; sum = 0.0; /* A slightly better approach starts from large i and works back */ for (i = myid + 1; i <= n; i += numprocs) { x = h * ((double)i - 0.5); sum += ( 4.0 / ( 1.0 + x * x )); } mypi = h * sum; MPI_Reduce(&mypi, &pi, 1, MPI_DOUBLE, MPI_SUM, 0, MPI_COMM_WORLD); if (myid == 0) { printf("pi is approximately %.16f, Error is %.16f\n", pi, fabs(pi - PI25DT)); endwtime = MPI_Wtime(); printf("wall clock time = %f\n", endwtime-startwtime); mflops = ((6.0 * (double)n) / (endwtime - startwtime)) / 1000000.0; printf("Estimated MFLOPs = %f\n", mflops); fflush( stdout ); } } } MPI_Finalize(); return 0; }