/* nag_dhseqr (f08pec) Example Program.
 *
 * Copyright 2001 Numerical Algorithms Group.
 *
 * Mark 7, 2001.
 */

#include <stdio.h>
#include <nag.h>
#include <nag_stdlib.h>
#include <nagf08.h>
#include <nagx04.h>

int main(void)
{
  /* Scalars */
  Integer  i, j, n, pdh, pdz, wi_len, wr_len;
  Integer  exit_status=0;
  NagError fail;
  Nag_OrderType order;
  /* Arrays */
  double *h=0, *wi=0, *wr=0, *z=0;

#ifdef NAG_COLUMN_MAJOR
#define H(I,J) h[(J-1)*pdh + I - 1]
  order = Nag_ColMajor;
#else
#define H(I,J) h[(I-1)*pdh + J - 1]
  order = Nag_RowMajor;
#endif

  INIT_FAIL(fail);
  Vprintf("nag_dhseqr (f08pec) Example Program Results\n\n");

  /* Skip heading in data file */
  Vscanf("%*[^\n] ");
  Vscanf("%ld%*[^\n] ", &n);
#ifdef NAG_COLUMN_MAJOR
  pdh = n;
  pdz = n;
#else
  pdh = n;
  pdz = n;
#endif
  wr_len = n;
  wi_len = n;

  /* Allocate memory */
  if ( !(h = NAG_ALLOC(n * n, double)) ||
       !(wi = NAG_ALLOC(wi_len, double)) ||
       !(wr = NAG_ALLOC(wr_len, double)) ||
       !(z = NAG_ALLOC(n * n, double)) )
    {
      Vprintf("Allocation failure\n");
      exit_status = -1;
      goto END;
    }

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

  /* Calculate the eigenvalues and Schur factorization of H */
  /* nag_dhseqr (f08pec).
   * Eigenvalues and Schur factorization of real upper
   * Hessenberg matrix reduced from real general matrix
   */
  nag_dhseqr(order, Nag_Schur, Nag_InitZ, n, 1, n, h, pdh, wr,
             wi, z, pdz, &fail);
  if (fail.code != NE_NOERROR)
    {
      Vprintf("Error from nag_dhseqr (f08pec).\n%s\n", fail.message);
      exit_status = 1;
      goto END;
    }
  Vprintf(" Eigenvalues\n");
  for (i = 1; i <= n; ++i)
    Vprintf(" (%8.4f,%8.4f)", wr[i-1], wi[i-1]);
  Vprintf("\n");

  /* Print Schur form */
  /* nag_gen_real_mat_print (x04cac).
   * Print real general matrix (easy-to-use)
   */
  nag_gen_real_mat_print(order, Nag_GeneralMatrix, Nag_NonUnitDiag, n, n,
                         h, pdh, "Schur form", 0, &fail);
  if (fail.code != NE_NOERROR)
    {
      Vprintf("Error from nag_gen_real_mat_print (x04cac).\n%s\n",
              fail.message);
      exit_status = 1;
      goto END;
    }
  /* Print Schur vectors */
  Vprintf("\n");
  /* nag_gen_real_mat_print (x04cac), see above. */
  nag_gen_real_mat_print(order, Nag_GeneralMatrix, Nag_NonUnitDiag, n, n,
                         z, pdz, "Schur vectors of H", 0, &fail);
  if (fail.code != NE_NOERROR)
    {
      Vprintf("Error from nag_gen_real_mat_print (x04cac).\n%s\n",
              fail.message);
      exit_status = 1;
      goto END;
    }
 END:
  if (h) NAG_FREE(h);
  if (wi) NAG_FREE(wi);
  if (wr) NAG_FREE(wr);
  if (z) NAG_FREE(z);

  return exit_status;
}