#include <stdio.h>
#include "mpi.h"
#include "trap.h"
#define MainProcess 0

typedef struct {
  float a;
  float b;
  int n;
} INDATA_TYPE;

int main(int argc, char** argv) {
  int me, nproc, local_n;          
  float h, local_a, local_b, integral, total;         
  INDATA_TYPE indata;

  MPI_Init(&argc, &argv);
  MPI_Comm_rank(MPI_COMM_WORLD, &me);
  MPI_Comm_size(MPI_COMM_WORLD, &nproc);

  if (me == MainProcess){
    printf("Enter a, b, and n\n");
    scanf("%f %f %d", &(indata.a), &(indata.b), &(indata.n));
  }
  MPI_Bcast(&indata, sizeof(INDATA_TYPE), MPI_BYTE, MainProcess, MPI_COMM_WORLD);

  h = (indata.b-indata.a)/indata.n; 
  local_n = indata.n/nproc; 
  local_a = indata.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, MainProcess, MPI_COMM_WORLD);
  if(me == MainProcess) {
    printf("With n = %d trapezoids, our estimate\n", indata.n);
    printf("of the integral from %f to %f = %f\n", 
           indata.a, indata.b, total); 
  }

  MPI_Finalize();
  return 0;
}