mpi 并行计算cos(x)的积分

 

#include <stdio.h>
#include "mpi.h"
#include <math.h>
#define PI acos(-1.0)

int main(int argc, char**argv){
   int rank, size;
   int n, i, start, end;
   double sum, psum, total, rate;
   MPI_Comm comm = MPI_COMM_WORLD;
   MPI_Status status;
   MPI_Init(&argc, &argv);
   MPI_Comm_size(comm, &size);
   MPI_Comm_rank(comm, &rank);

   if (rank == 0){
      printf("Input n:");
      scanf("%d", &n);
      for (i = 1; i < size; i++)
        MPI_Send(&n, 1, MPI_INT, i, 99, comm);
   }
   else{
      MPI_Recv(&n, 1, MPI_INT, 0, 99, comm, &status);
   }

   double h = 2 * PI / n;
   start = n / size * rank +1;
   end = n / size * (rank + 1);
   sum = 0;
   for (i = start; i <= end; i++){
      rate = i*1.0 / n;
      sum += cos(rate*2*PI + h/2) * h;
    }

   if (rank != 0)
       MPI_Send(&sum, 1, MPI_DOUBLE, 0, 99, comm);
   printf("part sum from %d to %d of process %d is %lf.\n", start, end, rank, sum);
   if (rank == 0){
      total = sum;
      for (i = 1; i < size; i++){      
	  MPI_Recv(&psum, 1, MPI_DOUBLE, i, 99,  comm, &status);
        total += psum;
      }
      printf("sum is %lf.\n", total);
   }
   MPI_Finalize();
   return 0;
}