#include <stdio.h>
#include "mpi.h"
#include "trap.h"
int main(int argc, char** argv) {
  int me, nproc, n = 10, src, dst = 0, tag = 50;  
  float a = 0.0, b = 1.0, h, local_a, local_b, local_n;   
  float integral, total;     
  MPI_Status sts;
  MPI_Init(&argc, &argv);
  MPI_Comm_rank(MPI_COMM_WORLD, &me);
  MPI_Comm_size(MPI_COMM_WORLD, &nproc);
  h = (b-a)/n;  
  local_n = n/nproc; 
  local_a = a + me*local_n*h;
  local_b = local_a + local_n*h;
  integral = Trap(local_a, local_b, local_n, h);
  if(me == 0) {
    total = integral;
    for (src = 1; src < nproc; src++){
      MPI_Recv(&integral,1,MPI_FLOAT,src,tag,MPI_COMM_WORLD,&sts);
      total += integral;
    }
  } else {   
    MPI_Send(&integral,1,MPI_FLOAT,dst,tag,MPI_COMM_WORLD);
  }
  if(me == 0) {
    printf("With n = %d trapezoids\n", n);
    printf("The integral from %f to %f is approx %f\n", 
           a, b, total); 
  }
  MPI_Finalize();
  return 0;
}