/* nag_lapackeig_dsyevd (f08fcc) Example Program.
 *
 * Copyright 2024 Numerical Algorithms Group.
 *
 * Mark 30.2, 2024.
 */

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

int main(void) {
  /* Scalars */
  Integer i, j, n, pda, w_len;
  Integer exit_status = 0;
  NagError fail;
  Nag_JobType job;
  Nag_UploType uplo;
  Nag_OrderType order;
  /* Arrays */
  char nag_enum_arg[40];
  double *a = 0, *w = 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_dsyevd (f08fcc) Example Program Results\n\n");

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

  /* Allocate memory */
  if (!(a = NAG_ALLOC(n * n, double)) || !(w = NAG_ALLOC(w_len, double))) {
    printf("Allocation failure\n");
    exit_status = -1;
    goto END;
  }
  /* Read whether Upper or Lower part of A is stored */
  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);
  /* Read A from data file */
  if (uplo == Nag_Upper) {
    for (i = 1; i <= n; ++i) {
      for (j = i; j <= n; ++j)
        scanf("%lf", &A(i, j));
    }
    scanf("%*[^\n] ");
  } else {
    for (i = 1; i <= n; ++i) {
      for (j = 1; j <= i; ++j)
        scanf("%lf", &A(i, j));
    }
    scanf("%*[^\n] ");
  }
  /* Read type of job to be performed */
  scanf("%39s%*[^\n] ", nag_enum_arg);
  job = (Nag_JobType)nag_enum_name_to_value(nag_enum_arg);
  /* Calculate all the eigenvalues and eigenvectors of A */
  /* nag_lapackeig_dsyevd (f08fcc).
   * All eigenvalues and optionally all eigenvectors of real
   * symmetric matrix (divide-and-conquer)
   */
  nag_lapackeig_dsyevd(order, job, uplo, n, a, pda, w, &fail);
  if (fail.code != NE_NOERROR) {
    printf("Error from nag_lapackeig_dsyevd (f08fcc).\n%s\n", fail.message);
    exit_status = 1;
    goto END;
  }
  /* Normalize the eigenvectors */
  for (j = 1; j <= n; j++) {
    for (i = n; i >= 1; i--) {
      A(i, j) = A(i, j) / A(1, j);
    }
  }
  /* Print eigenvalues and eigenvectors */
  printf("Eigenvalues\n");
  for (i = 0; i < n; ++i)
    printf("  %8.4f", w[i]);
  printf("\n");
  /* 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, a, pda, "Eigenvectors", 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(a);
  NAG_FREE(w);
  return exit_status;
}