Commit f96c5f47 authored by Neil Gershenfeld's avatar Neil Gershenfeld
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wip

parent 714819ed
Pipeline #3790 passed with stage
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/*
* mpipi2.c
* Neil Gershenfeld 2/5/11
* use MPI to evaluate pi by summation, including overhead
*/
#include <stdio.h>
#include <mpi.h>
#include <sys/time.h>
#include <stdint.h>
#define NPTS 10000000000
void main(int argc, char** argv) {
uint32_t rank,nproc;
uint64_t i,istart,iend,init_time,start_time,end_time;
struct timeval init,start,end;
double sum,pi,mflops;
gettimeofday(&init,NULL);
MPI_Init(&argc,&argv);
MPI_Comm_rank(MPI_COMM_WORLD,&rank);
MPI_Comm_size(MPI_COMM_WORLD,&nproc);
if (rank == 0) {
MPI_Barrier(MPI_COMM_WORLD);
gettimeofday(&start,NULL);
istart = 1+rank*NPTS;
iend = (rank+1)*NPTS;
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);
init_time = init.tv_sec*1e6+init.tv_usec;
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);
printf("init = %f, time = %f, estimated MFlops = %f\n",(start_time-init_time)/1.0e6,(end_time-start_time)/1.0e6,mflops);
}
else {
MPI_Barrier(MPI_COMM_WORLD);
istart = 1+rank*NPTS;
iend = (rank+1)*NPTS;
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();
}
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