mpimppi.c

/*
* mpimppi.c
* Neil Gershenfeld  10/8/19
* MPI+OpenMP pi calculation benchmark
* pi = 3.14159265358979323846
*/

#include <stdio.h>
#include <mpi.h>
#include <omp.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;
         #pragma omp parallel for reduction(+:sum)
         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, threads = %d, NPTS = %ld, pi = %f\n",nproc,omp_get_max_threads(),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;
         #pragma omp parallel for reduction(+:sum)
         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();
   }