/* nag_lapacklin_dpbcon (f07hgc) Example Program.
 *
 * Copyright 2024 Numerical Algorithms Group.
 *
 * Mark 30.2, 2024.
 */

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

int main(void) {
  /* Scalars */
  Integer i, j, k, kd, n, pdab;
  Integer exit_status = 0;
  double anorm, rcond;
  NagError fail;
  Nag_UploType uplo;
  Nag_OrderType order;
  /* Arrays */
  char nag_enum_arg[40];
  double *ab = 0;

#ifdef NAG_COLUMN_MAJOR
#define AB_UPPER(I, J) ab[(J - 1) * pdab + k + I - J - 1]
#define AB_LOWER(I, J) ab[(J - 1) * pdab + 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 + k + J - I - 1]
  order = Nag_RowMajor;
#endif

  INIT_FAIL(fail);

  printf("nag_lapacklin_dpbcon (f07hgc) Example Program Results\n\n");

  /* Skip heading in data file */
  scanf("%*[^\n] ");
  scanf("%" NAG_IFMT "%" NAG_IFMT "%*[^\n] ", &n, &kd);
  pdab = kd + 1;

  /* Allocate memory */
  if (!(ab = NAG_ALLOC((kd + 1) * 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);

  k = kd + 1;
  if (uplo == Nag_Upper) {
    for (i = 1; i <= n; ++i) {
      for (j = i; j <= MIN(i + kd, n); ++j)
        scanf("%lf", &AB_UPPER(i, j));
    }
    scanf("%*[^\n] ");
  } else {
    for (i = 1; i <= n; ++i) {
      for (j = MAX(1, i - kd); j <= i; ++j)
        scanf("%lf", &AB_LOWER(i, j));
    }
    scanf("%*[^\n] ");
  }
  /* Compute norm of A */
  /* nag_blast_dsb_norm (f16rec).
   * 1-norm, infinity-norm, Frobenius norm, largest absolute
   * element, real symmetric band matrix
   */
  nag_blast_dsb_norm(order, Nag_OneNorm, uplo, n, kd, ab, pdab, &anorm, &fail);
  if (fail.code != NE_NOERROR) {
    printf("Error from nag_blast_dsb_norm (f16rec).\n%s\n", fail.message);
    exit_status = 1;
    goto END;
  }
  /* Factorize A */
  /* nag_lapacklin_dpbtrf (f07hdc).
   * Cholesky factorization of real symmetric
   * positive-definite band matrix
   */
  nag_lapacklin_dpbtrf(order, uplo, n, kd, ab, pdab, &fail);
  if (fail.code != NE_NOERROR) {
    printf("Error from nag_lapacklin_dpbtrf (f07hdc).\n%s\n", fail.message);
    exit_status = 1;
    goto END;
  }
  /* Estimate condition number */
  /* nag_lapacklin_dpbcon (f07hgc).
   * Estimate condition number of real symmetric
   * positive-definite band matrix, matrix already factorized
   * by nag_lapacklin_dpbtrf (f07hdc)
   */
  nag_lapacklin_dpbcon(order, uplo, n, kd, ab, pdab, anorm, &rcond, &fail);
  if (fail.code != NE_NOERROR) {
    printf("Error from nag_lapacklin_dpbcon (f07hgc).\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(ab);
  return exit_status;
}