/* nag_lapackeig_dtgexc (f08yfc) Example Program.
 *
 * Copyright 2024 Numerical Algorithms Group.
 *
 * Mark 30.2, 2024.
 */

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

int main(void) {
  /* Scalars */
  double alpha, beta;
  Integer i, ifst, ilst, j, n, pdq, pds;
  Integer pdt, pdz, exit_status = 0;
  /* Arrays */
  double *q = 0, *s = 0, *t = 0, *z = 0;
  char nag_enum_arg[40];

  /* Nag Types */
  NagError fail;
  Nag_OrderType order;
  Nag_Boolean wantq, wantz;

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

  INIT_FAIL(fail);

  printf("nag_lapackeig_dtgexc (f08yfc) Example Program Results\n\n");

  /* Skip heading in data file */
  scanf("%*[^\n]");
  scanf("%" NAG_IFMT "%*[^\n]", &n);
  if (n < 0) {
    printf("Invalid n\n");
    exit_status = 1;
    goto END;
  }
  scanf(" %39s%*[^\n]", nag_enum_arg);
  /* nag_enum_name_to_value (x04nac).
   * Converts NAG enum member name to value
   */
  wantq = (Nag_Boolean)nag_enum_name_to_value(nag_enum_arg);
  scanf(" %39s%*[^\n]", nag_enum_arg);
  wantz = (Nag_Boolean)nag_enum_name_to_value(nag_enum_arg);

  pds = n;
  pdt = n;

  pdq = (wantq ? n : 1);
  pdz = (wantz ? n : 1);

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

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

  /* Initialize Q an Z to identity matrices using nag_blast_dge_load (f16qhc).
   */
  alpha = 0.0;
  beta = 1.0;
  if (wantq)
    nag_blast_dge_load(order, n, n, alpha, beta, q, pdq, &fail);
  if (wantz)
    nag_blast_dge_load(order, n, n, alpha, beta, z, pdz, &fail);
  if (fail.code != NE_NOERROR) {
    printf("Error from nag_blast_dge_load (f16qhc).\n%s\n", fail.message);
    exit_status = 1;
    goto END;
  }

  /* Read the row indices of diagonal elements or blocks to be swapped. */
  scanf("%" NAG_IFMT "%" NAG_IFMT "%*[^\n]", &ifst, &ilst);

  /* Reorder S and T */
  nag_lapackeig_dtgexc(order, wantq, wantz, n, s, pds, t, pdt, q, pdq, z, pdz,
                       &ifst, &ilst, &fail);
  if (fail.code != NE_NOERROR) {
    printf("Error from nag_lapackeig_dtgexc (f08yfc).\n%s\n", fail.message);
    exit_status = 1;
    goto END;
  }

  /* normalize signs so that last column and diagonal of T is positive. */
  for (i = 1; i <= n; i++) {
    if (T(i, n) < 0.0) {
      for (j = i; j <= n; j++) {
        S(i, j) = -S(i, j);
        T(i, j) = -T(i, j);
      }
      if (i > 1 && fabs(S(i, i - 1)) > 0.0) {
        S(i, i - 1) = -S(i, i - 1);
      }
    }
  }
  for (j = 1; j <= n - 1; j++) {
    if (T(j, j) < 0.0) {
      for (i = 1; i <= j; i++) {
        S(i, j) = -S(i, j);
        T(i, j) = -T(i, j);
      }
      if (fabs(S(j + 1, j)) > 0.0) {
        S(j + 1, j) = -S(j + 1, j);
      }
    }
  }

  /* nag_file_print_matrix_real_gen (x04cac): Print reordered S and T. */
  fflush(stdout);
  nag_file_print_matrix_real_gen(order, Nag_GeneralMatrix, Nag_NonUnitDiag, n,
                                 n, s, pds, "Reordered matrix S", 0, &fail);
  printf("\n");
  if (fail.code != NE_NOERROR)
    goto PRERR;
  fflush(stdout);
  nag_file_print_matrix_real_gen(order, Nag_GeneralMatrix, Nag_NonUnitDiag, n,
                                 n, t, pdt, "Reordered matrix T", 0, &fail);
  printf("\n");
PRERR:
  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(s);
  NAG_FREE(t);
  NAG_FREE(z);

  return exit_status;
}