/* nag_lapackeig_dgebrd (f08kec) Example Program.
 *
 * Copyright 2024 Numerical Algorithms Group.
 *
 * Mark 30.3, 2024.
 */

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

int main(void) {
  /* Scalars */
  Integer i, j, m, n, pda, d_len, e_len, tauq_len, taup_len;
  Integer exit_status = 0;
  NagError fail;
  Nag_OrderType order;
  /* Arrays */
  double *a = 0, *d = 0, *e = 0, *taup = 0, *tauq = 0;

#ifdef NAG_COLUMN_MAJOR
#define A(I, J) a[(J - 1) * pda + I - 1]
  order = Nag_ColMajor;
#else
#define A(I, J) a[(I - 1) * pda + J - 1]
  order = Nag_RowMajor;
#endif

  INIT_FAIL(fail);

  printf("nag_lapackeig_dgebrd (f08kec) Example Program Results\n");

  /* Skip heading in data file */
  scanf("%*[^\n] ");
  scanf("%" NAG_IFMT "%" NAG_IFMT "%*[^\n] ", &m, &n);

#ifdef NAG_COLUMN_MAJOR
  pda = m;
#else
  pda = n;
#endif

  d_len = MIN(m, n);
  e_len = MIN(m, n) - 1;
  tauq_len = MIN(m, n);
  taup_len = MIN(m, n);

  /* Allocate memory */
  if (!(a = NAG_ALLOC(m * n, double)) || !(d = NAG_ALLOC(d_len, double)) ||
      !(e = NAG_ALLOC(e_len, double)) ||
      !(taup = NAG_ALLOC(taup_len, double)) ||
      !(tauq = NAG_ALLOC(tauq_len, double))) {
    printf("Allocation failure\n");
    exit_status = -1;
    goto END;
  }

  /* Read A from data file */
  for (i = 1; i <= m; ++i) {
    for (j = 1; j <= n; ++j)
      scanf("%lf", &A(i, j));
  }
  scanf("%*[^\n] ");

  /* Reduce A to bidiagonal form */
  /* nag_lapackeig_dgebrd (f08kec).
   * Orthogonal reduction of real general rectangular matrix
   * to bidiagonal form
   */
  nag_lapackeig_dgebrd(order, m, n, a, pda, d, e, tauq, taup, &fail);
  if (fail.code != NE_NOERROR) {
    printf("Error from nag_lapackeig_dgebrd (f08kec).\n%s\n", fail.message);
    exit_status = 1;
    goto END;
  }

  /* Print bidiagonal form */
  printf("\nDiagonal\n");
  for (i = 1; i <= MIN(m, n); ++i)
    printf("%9.4f%s", d[i - 1], i % 8 == 0 ? "\n" : " ");
  if (m >= n)
    printf("\nSuperdiagonal\n");
  else
    printf("\nSubdiagonal\n");
  for (i = 1; i <= MIN(m, n) - 1; ++i)
    printf("%9.4f%s", e[i - 1], i % 8 == 0 ? "\n" : " ");
  printf("\n");

END:
  NAG_FREE(a);
  NAG_FREE(d);
  NAG_FREE(e);
  NAG_FREE(taup);
  NAG_FREE(tauq);

  return exit_status;
}

#undef A