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/*
* 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();
}