/* * mpipi2.c * Neil Gershenfeld 7/1/19 * MPI pi calculation benchmark, with multiple iterations * pi = 3.14159265358979323846 */ #include <stdio.h> #include <mpi.h> #include <sys/time.h> #include <stdint.h> #define NPTS 10000000000 #define NLOOP 10 void main(int argc, char** argv) { uint32_t rank,nproc; uint64_t i,j,istart,iend,start_time,end_time; struct timeval start,end; double sum,pi,mflops,max; MPI_Init(&argc,&argv); MPI_Comm_rank(MPI_COMM_WORLD,&rank); MPI_Comm_size(MPI_COMM_WORLD,&nproc); max = 0; if (rank == 0) { istart = 1+rank*NPTS; iend = (rank+1)*NPTS; for (j = 0; j < NLOOP; ++j) { MPI_Barrier(MPI_COMM_WORLD); gettimeofday(&start,NULL); sum = 0.0; for (i = istart; i <= iend; ++i) sum += 0.5/((i-0.75)*(i-0.25)); MPI_Reduce(&sum,&pi,1,MPI_DOUBLE,MPI_SUM,0,MPI_COMM_WORLD); gettimeofday(&end,NULL); start_time = start.tv_sec*1e6+start.tv_usec; end_time = end.tv_sec*1e6+end.tv_usec; mflops = nproc*NPTS*(5.0/(end_time-start_time)); printf("processes = %d, NPTS = %ld, pi = %f\n",nproc,NPTS,pi); if (mflops > max) max = mflops; printf("time = %f, estimated MFlops = %f, max = %f\n",(end_time-start_time)/1.0e6,mflops,max); } } else { istart = 1+rank*NPTS; iend = (rank+1)*NPTS; for (j = 0; j < NLOOP; ++j) { MPI_Barrier(MPI_COMM_WORLD); sum = 0.0; for (i = istart; i <= iend; ++i) sum += 0.5/((i-0.75)*(i-0.25)); MPI_Reduce(&sum,&pi,1,MPI_DOUBLE,MPI_SUM,0,MPI_COMM_WORLD); } } MPI_Finalize(); }