/* F08GA_P0W_F C++ Header Example Program.
 *
 * Copyright 2019 Numerical Algorithms Group.
 * Mark 27, 2019.
 */

#include <nag.h>
#include <nagad.h>
#include <math.h>
#include <stdio.h>
#include <iostream>
#include <string>

int main(void)
{
  /* Scalars */
  double      eerrbd, eps;
  Integer     exit_status = 0, i, j, n;
  /* Arrays */
  double      *ap = 0, *dummy = 0, *w = 0, *work = 0;
  Integer     ifail;
  std::string uplo = "U";

#define AP(I, J) ap[J * (J - 1) / 2 + I - 1]

  printf("F08GA_P0W_F C++ Example Program Results\n\n");

  void    *ad_handle = 0;

  /* Skip heading in data file */
#ifdef _WIN32
  scanf_s("%*[^\n]");
#else
  scanf("%*[^\n]");
#endif
#ifdef _WIN32
  scanf_s("%" NAG_IFMT "%*[^\n]", &n);
#else
  scanf("%" NAG_IFMT "%*[^\n]", &n);
#endif

  /* Allocate memory */
  ap    = new double [n * (n + 1) / 2];
  dummy = new double [1];
  w     = new double [n];
  work  = new double [3*n];
  
  /* Read the upper triangular part of the matrix A from data file */
  double tmp;
  for (i = 1; i <= n; ++i) {
    for (j = i; j <= n; ++j) {
      AP(i,j) = 0.0;
#ifdef _WIN32
      scanf_s("%lf", &tmp);
#else
      scanf("%lf", &tmp);
#endif
      AP(i, j) = tmp;
    }
  }
#ifdef _WIN32
  scanf_s("%*[^\n]");
#else
  scanf("%*[^\n]");
#endif

  ifail = 0;
  f08ga_p0w_f_(ad_handle, "N", "U", n, ap, w, dummy, 1, work, ifail, 1, 1);

  /* Print solution */
  printf("Eigenvalues\n");
  for (j = 0; j < n; ++j)
    printf("%8.4f%s", w[j], (j + 1) % 8 == 0 ? "\n" : " ");
  printf("\n");
  /* Get the machine precision, eps, using nag_machine_precision (X02AJC)
   * and compute the approximate error bound for the computed eigenvalues. 
   * Note that for the 2-norm, ||A|| = max {|w[i]|, i=0..n-1}, and since 
   * the eigenvalues are in ascending order ||A|| = max( |w[0]|, |w[n-1]|).
   */
  eps = X02AJC;
  eerrbd = eps * MAX(fabs(w[0]), fabs(w[n - 1]));

  /* Print the approximate error bound for the eigenvalues */
  printf("\nError estimate for the eigenvalues\n");
  printf("%11.1e\n", eerrbd);

  delete [] ap;
  delete [] dummy;
  delete [] w;
  delete [] work;

  return exit_status;
}

#undef AP