#include <stdio.h>
#include "mpi.h"
#include "trap.h"
void Get_data4(int me, float* a_ptr, float* b_ptr, int* n_ptr){
    int root = 0, position = 0; 
    char buffer[100];
    if(me == 0){
      printf("Enter a, b, and n\n");
      scanf("%f %f %d", a_ptr, b_ptr, n_ptr);
      MPI_Pack(a_ptr, 1, MPI_FLOAT, buffer, 100, &position, MPI_COMM_WORLD);
      MPI_Pack(b_ptr, 1, MPI_FLOAT, buffer, 100, &position, MPI_COMM_WORLD);
      MPI_Pack(n_ptr, 1, MPI_INT, buffer, 100, &position, MPI_COMM_WORLD);
      MPI_Bcast(buffer, 100, MPI_PACKED, root, MPI_COMM_WORLD);
    } else {
      MPI_Bcast(buffer, 100, MPI_PACKED, root, MPI_COMM_WORLD);
      MPI_Unpack(buffer, 100, &position, a_ptr, 1, MPI_FLOAT, MPI_COMM_WORLD);
      MPI_Unpack(buffer, 100, &position, b_ptr, 1, MPI_FLOAT, MPI_COMM_WORLD);
      MPI_Unpack(buffer, 100, &position, n_ptr, 1, MPI_INT, MPI_COMM_WORLD);
    }
}

int main(int argc, char** argv) {
  int me, nproc, n, local_n;          
  float h, a, b, local_a, local_b, integral, total;         
  MPI_Init(&argc, &argv);
  MPI_Comm_rank(MPI_COMM_WORLD, &me);
  MPI_Comm_size(MPI_COMM_WORLD, &nproc);
  Get_data4(me, &a, &b, &n);
  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);
  MPI_Reduce(&integral, &total, 1, MPI_FLOAT, MPI_SUM, 0, MPI_COMM_WORLD);
  if (me == 0) {
    printf("With n = %d trapezoids, our estimate\n", n);
    printf("of the integral from %f to %f = %f\n", a, b, total); 
  }
  MPI_Finalize();
  return 0;
}