/* nag_real_form_q (f01qec) Example Program.
 *
 * Copyright 1990 Numerical Algorithms Group.
 *
 * Mark 1, 1990.
 * Mark 8 revised, 2004.
 */

#include <nag.h>
#include <stdio.h>
#include <nag_stdlib.h>
#include <nagf01.h>

#define A(I, J) a[(I) *tda + J]
#define Q(I, J) q[(I) *tdq + J]
int main(void)
{
  Integer  exit_status = 0, i, j, m, n, ncolq, tda, tdq;
  double   *a = 0, *q = 0, *zeta = 0;
  NagError fail;

  INIT_FAIL(fail);

  printf("nag_real_form_q (f01qec) Example Program Results\n");
  scanf(" %*[^\n]"); /* skip headings in data file */
  scanf(" %*[^\n]");

  scanf("%ld%ld", &m, &n);
  if (n >= 0 && m >= n)
    {
      if (!(zeta = NAG_ALLOC(n, double)) ||
          !(a = NAG_ALLOC(m*n, double)) ||
          !(q = NAG_ALLOC(m*m, double)))
        {
          printf("Allocation failure\n");
          exit_status = -1;
          goto END;
        }
      tda = n;
      tdq = m;
    }
  else
    {
      printf("Invalid n or m.\n");
      exit_status = 1;
      return exit_status;
    }
  scanf(" %*[^\n]");
  for (i = 0; i < m; ++i)   /* Read matrix data */
    for (j = 0; j < n; ++j)
      scanf("%lf", &A(i, j));

  /* Find the QR factorization of A */
  /* nag_real_qr (f01qcc).
   * QR factorization of real m by n matrix (m >= n)
   */
  nag_real_qr(m, n, a, tda, zeta, &fail);
  if (fail.code != NE_NOERROR)
    {
      printf("Error from nag_real_qr (f01qcc).\n%s\n", fail.message);
      exit_status = 1;
      goto END;
    }

  /* Copy the array a into q and form the m by m matrix Q */
  for (j = 0; j < n; ++j)
    for (i = 0; i < m; ++i)
      Q(i, j) = A(i, j);
  ncolq = m;
  /* nag_real_form_q (f01qec).
   * Form columns of Q after factorization by nag_real_qr
   * (f01qcc)
   */
  nag_real_form_q(Nag_ElementsSeparate, m, n, ncolq, q, tdq,
                  zeta, &fail);
  if (fail.code != NE_NOERROR)
    {
      printf("Error from nag_real_form_q (f01qec).\n%s\n",
              fail.message);
      exit_status = 1;
      goto END;
    }

  printf("Matrix  Q\n");
  for (i = 0; i < m; ++i)
    {
      for (j = 0; j < ncolq; ++j)
        printf(" %8.4f", Q(i, j));
      printf("\n");
    }

 END:
  if (zeta) NAG_FREE(zeta);
  if (a) NAG_FREE(a);
  if (q) NAG_FREE(q);

  return exit_status;
}