/* nag_lapackeig_dtrexc (f08qfc) Example Program.
 *
 * Copyright 2024 Numerical Algorithms Group.
 *
 * Mark 30.3, 2024.
 */

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

int main(void) {
  /* Scalars */
  Integer i, ifst, ilst, j, n, pdq, pdt;
  Integer exit_status = 0;
  NagError fail;
  Nag_OrderType order;
  /* Arrays */
  double *q = 0, *t = 0;

#ifdef NAG_COLUMN_MAJOR
#define T(I, J) t[(J - 1) * pdt + I - 1]
  order = Nag_ColMajor;
#else
#define T(I, J) t[(I - 1) * pdt + J - 1]
  order = Nag_RowMajor;
#endif

  INIT_FAIL(fail);

  printf("nag_lapackeig_dtrexc (f08qfc) Example Program Results\n\n");

  /* Skip heading in data file */
  scanf("%*[^\n] ");
  scanf("%" NAG_IFMT "%*[^\n] ", &n);
#ifdef NAG_COLUMN_MAJOR
  pdq = 1;
  pdt = n;
#else
  pdq = 1;
  pdt = n;
#endif

  /* Allocate memory */
  if (!(q = NAG_ALLOC(1 * 1, double)) || !(t = NAG_ALLOC(n * n, double))) {
    printf("Allocation failure\n");
    exit_status = -1;
    goto END;
  }

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

  /* Reorder the Schur factorization T */
  /* nag_lapackeig_dtrexc (f08qfc).
   * Reorder Schur factorization of real matrix using
   * orthogonal similarity transformation
   */
  nag_lapackeig_dtrexc(order, Nag_NotQ, n, t, pdt, q, pdq, &ifst, &ilst, &fail);
  if (fail.code != NE_NOERROR) {
    printf("Error from nag_lapackeig_dtrexc (f08qfc).\n%s\n", fail.message);
    exit_status = 1;
    goto END;
  }
  /* Print reordered Schur form */
  /* nag_file_print_matrix_real_gen (x04cac).
   * Print real general matrix (easy-to-use)
   */
  fflush(stdout);
  nag_file_print_matrix_real_gen(order, Nag_GeneralMatrix, Nag_NonUnitDiag, n,
                                 n, t, pdt, "Reordered Schur form", 0, &fail);
  if (fail.code != NE_NOERROR) {
    printf("Error from nag_file_print_matrix_real_gen (x04cac).\n%s\n",
           fail.message);
    exit_status = 1;
    goto END;
  }
END:
  NAG_FREE(q);
  NAG_FREE(t);

  return exit_status;
}