/* nag_lapackeig_dsbgv (f08uac) Example Program.
 *
 * Copyright 2024 Numerical Algorithms Group.
 *
 * Mark 30.2, 2024.
 */

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

int main(void) {
  /* Scalars */
  Integer i, j, ka, kb, n, pdab, pdbb, pdz, zsize;
  Integer exit_status = 0;

  /* Arrays */
  double *ab = 0, *bb = 0, *w = 0, *z = 0;
  char nag_enum_arg[40];

  /* Nag Types */
  NagError fail;
  Nag_UploType uplo;
  Nag_OrderType order;
  Nag_JobType job;

#ifdef NAG_COLUMN_MAJOR
#define AB_UPPER(I, J) ab[(J - 1) * pdab + ka + I - J]
#define AB_LOWER(I, J) ab[(J - 1) * pdab + I - J]
#define BB_UPPER(I, J) bb[(J - 1) * pdbb + kb + I - J]
#define BB_LOWER(I, J) bb[(J - 1) * pdbb + I - J]
  order = Nag_ColMajor;
#else
#define AB_UPPER(I, J) ab[(I - 1) * pdab + J - I]
#define AB_LOWER(I, J) ab[(I - 1) * pdab + ka + J - I]
#define BB_UPPER(I, J) bb[(I - 1) * pdbb + J - I]
#define BB_LOWER(I, J) bb[(I - 1) * pdbb + kb + J - I]
  order = Nag_RowMajor;
#endif

  INIT_FAIL(fail);

  printf("nag_lapackeig_dsbgv (f08uac) Example Program Results\n\n");

  /* Skip heading in data file */
  scanf("%*[^\n]");
  scanf("%" NAG_IFMT "%" NAG_IFMT "%" NAG_IFMT "%*[^\n]", &n, &ka, &kb);
  if (n < 0 || ka < kb || kb < 0) {
    printf("Invalid n, ka or kb\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
   */
  uplo = (Nag_UploType)nag_enum_name_to_value(nag_enum_arg);
  scanf(" %39s%*[^\n]", nag_enum_arg);
  job = (Nag_JobType)nag_enum_name_to_value(nag_enum_arg);
  if (job == Nag_EigVals) {
    zsize = 1;
    pdz = 1;
  } else {
    zsize = n * n;
    pdz = n;
  }

  pdab = ka + 1;
  pdbb = kb + 1;
  /* Allocate memory */
  if (!(ab = NAG_ALLOC((ka + 1) * n, double)) ||
      !(bb = NAG_ALLOC((kb + 1) * n, double)) ||
      !(z = NAG_ALLOC(zsize, double)) || !(w = NAG_ALLOC(n, double))) {
    printf("Allocation failure\n");
    exit_status = -1;
    goto END;
  }

  /* Read the triangular parts of the matrices A and B from data file */
  if (uplo == Nag_Upper) {
    for (i = 1; i <= n; ++i)
      for (j = i; j <= MIN(i + ka, n); ++j)
        scanf("%lf", &AB_UPPER(i, j));
    scanf("%*[^\n]");
    for (i = 1; i <= n; ++i)
      for (j = i; j <= MIN(i + kb, n); ++j)
        scanf("%lf", &BB_UPPER(i, j));
  } else {
    for (i = 1; i <= n; ++i)
      for (j = MAX(1, i - ka); j <= i; ++j)
        scanf("%lf", &AB_LOWER(i, j));
    scanf("%*[^\n]");
    for (i = 1; i <= n; ++i)
      for (j = MAX(1, i - kb); j <= i; ++j)
        scanf("%lf", &BB_LOWER(i, j));
  }
  scanf("%*[^\n]");

  /* Solve the generalized symmetric band eigenvalue problem  A*x = lambda*B*x
   * using nag_lapackeig_dsbgv (f08uac).
   */
  nag_lapackeig_dsbgv(order, job, uplo, n, ka, kb, ab, pdab, bb, pdbb, w, z,
                      pdz, &fail);

  if (fail.code != NE_NOERROR) {
    printf("Error from nag_lapackeig_dsbgv (f08uac).\n%s\n", fail.message);
    exit_status = 1;
    goto END;
  }

  /* Print eigensolution */
  printf(" Eigenvalues\n    ");
  for (j = 0; j < n; ++j)
    printf(" %9.4f%s", w[j], j % 6 == 5 ? "\n" : " ");
  printf("\n");

  if (job == Nag_DoBoth) {
    /* nag_file_print_matrix_real_gen (x04cac): Print Matrix of eigenvectors Z.
     */
    printf("\n");
    fflush(stdout);
    nag_file_print_matrix_real_gen(order, Nag_GeneralMatrix, Nag_NonUnitDiag, n,
                                   n, z, pdz, "Eigenvectors (by Column)", 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;
    }
  }

END:
  NAG_FREE(ab);
  NAG_FREE(bb);
  NAG_FREE(z);
  NAG_FREE(w);

  return exit_status;
}