/* nag_lapacklin_dspcon (f07pgc) 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 ap_len, i, j, n;
  Integer exit_status = 0;
  NagError fail;
  Nag_UploType uplo;
  Nag_OrderType order;
  /* Arrays */
  Integer *ipiv = 0;
  char nag_enum_arg[40];
  double *ap = 0;

#ifdef NAG_COLUMN_MAJOR
#define A_UPPER(I, J) ap[J * (J - 1) / 2 + I - 1]
#define A_LOWER(I, J) ap[(2 * n - J) * (J - 1) / 2 + I - 1]
  order = Nag_ColMajor;
#else
#define A_LOWER(I, J) ap[I * (I - 1) / 2 + J - 1]
#define A_UPPER(I, J) ap[(2 * n - I) * (I - 1) / 2 + J - 1]
  order = Nag_RowMajor;
#endif

  INIT_FAIL(fail);

  printf("nag_lapacklin_dspcon (f07pgc) Example Program Results\n\n");
  /* Skip heading in data file */
  scanf("%*[^\n] ");
  scanf("%" NAG_IFMT "%*[^\n] ", &n);
  ap_len = n * (n + 1) / 2;

  /* Allocate memory */
  if (!(ipiv = NAG_ALLOC(n, Integer)) || !(ap = NAG_ALLOC(ap_len, 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_UPPER(i, j));
    }
    scanf("%*[^\n] ");
  } else {
    for (i = 1; i <= n; ++i) {
      for (j = 1; j <= i; ++j)
        scanf("%lf", &A_LOWER(i, j));
    }
    scanf("%*[^\n] ");
  }

  /* Compute norm of A */
  /* nag_blast_dsp_norm (f16rdc).
   * 1-norm, infinity-norm, Frobenius norm, largest absolute
   * element, real symmetric matrix, packed storage
   */
  nag_blast_dsp_norm(order, Nag_OneNorm, uplo, n, ap, &anorm, &fail);
  if (fail.code != NE_NOERROR) {
    printf("Error from nag_blast_dsp_norm (f16rdc).\n%s\n", fail.message);
    exit_status = 1;
    goto END;
  }
  /* Factorize A */
  /* nag_lapacklin_dsptrf (f07pdc).
   * Bunch-Kaufman factorization of real symmetric indefinite
   * matrix, packed storage
   */
  nag_lapacklin_dsptrf(order, uplo, n, ap, ipiv, &fail);
  if (fail.code != NE_NOERROR) {
    printf("Error from nag_lapacklin_dsptrf (f07pdc).\n%s\n", fail.message);
    exit_status = 1;
    goto END;
  }
  /* Estimate condition number */
  /* nag_lapacklin_dspcon (f07pgc).
   * Estimate condition number of real symmetric indefinite
   * matrix, matrix already factorized by nag_lapacklin_dsptrf (f07pdc),
   * packed storage
   */
  nag_lapacklin_dspcon(order, uplo, n, ap, ipiv, anorm, &rcond, &fail);
  if (fail.code != NE_NOERROR) {
    printf("Error from nag_lapacklin_dspcon (f07pgc).\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\n", 1.0 / rcond);
  else
    printf("A is singular to working precision\n");
END:
  NAG_FREE(ipiv);
  NAG_FREE(ap);
  return exit_status;
}