/* nag_lapacklin_dsycon (f07mgc) Example Program.
 *
 * Copyright 2024 Numerical Algorithms Group.
 *
 * Mark 30.1, 2024.
 */

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

int main(void) {
  /* Scalars */
  double anorm, rcond;
  Integer i, j, n, pda;
  Integer exit_status = 0;
  NagError fail;
  Nag_UploType uplo;
  Nag_OrderType order;
  /* Arrays */
  char nag_enum_arg[40];
  Integer *ipiv = 0;
  double *a = 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_lapacklin_dsycon (f07mgc) Example Program Results\n\n");

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

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

  /* Read A from data file */
  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);

  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] ");
  }
  /* Compute norm of A */
  /* nag_blast_dsy_norm (f16rcc).
   * 1-norm, infinity-norm, Frobenius norm, largest absolute
   * element, real symmetric matrix
   */
  nag_blast_dsy_norm(order, Nag_OneNorm, uplo, n, a, pda, &anorm, &fail);
  if (fail.code != NE_NOERROR) {
    printf("Error from nag_blast_dsy_norm (f16rcc).\n%s\n", fail.message);
    exit_status = 1;
    goto END;
  }
  /* Factorize A */
  /* nag_lapacklin_dsytrf (f07mdc).
   * Bunch-Kaufman factorization of real symmetric indefinite
   * matrix
   */
  nag_lapacklin_dsytrf(order, uplo, n, a, pda, ipiv, &fail);
  if (fail.code != NE_NOERROR) {
    printf("Error from nag_lapacklin_dsytrf (f07mdc).\n%s\n", fail.message);
    exit_status = 1;
    goto END;
  }
  /* Estimate condition number */
  /* nag_lapacklin_dsycon (f07mgc).
   * Estimate condition number of real symmetric indefinite
   * matrix, matrix already factorized by nag_lapacklin_dsytrf (f07mdc)
   */
  nag_lapacklin_dsycon(order, uplo, n, a, pda, ipiv, anorm, &rcond, &fail);
  if (fail.code != NE_NOERROR) {
    printf("Error from nag_lapacklin_dsycon (f07mgc).\n%s\n", fail.message);
    exit_status = 1;
    goto END;
  }

  /* nag_machine_precision (x02ajc).
   * The machine precision
   */
  if (rcond >= nag_machine_precision)
    printf("Estimate of condition number = %11.2e\n", 1.0 / rcond);
  else
    printf("A is singular to working precision\n");
END:
  NAG_FREE(ipiv);
  NAG_FREE(a);
  return exit_status;
}