// integral.c

#include <stdio.h>
#include "mpi.h"

int main(int argc, char **argv)
{
  double integral;
  double a, b;
  int n;
  double h;
  double x;
  int i, rank, size;

  double f(double x);
//  MPI_Status status;

//  MPI_Init(&argc, &argv);
//  MPI_Comm_rank(MPI_COMM_WORLD, &rank);
//  MPI_Comm_size(MPI_COMM_WORLD, &size);

  printf("Enter a, b, and n\n");
  scanf("%lf %lf %d", &a, &b, &n);

  h = (b - a)/n;

  integral = (f(a) + f(b))/2.0;
  x = a;
  for(i = 1; i <= n-1; i++) {
    x = x + h;
    integral = integral + f(x);
  }
  integral = integral*h;

  printf("With n = %d trapezoids, the estimate ",n);
  printf("of the integral from %lf to %lf = %lf\n", a, b, integral);

//  MPI_Finalize();

  return 0;
}

double f(double x) {
  return x * x;
}

/*
CRAY SV1:

cc integral.c

./a.out

*/