/* nag_lapacklin_dgbcon (f07bgc) Example Program.
 *
 * Copyright 2024 Numerical Algorithms Group.
 *
 * Mark 30.3, 2024.
 */

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

int main(void) {
  /* Scalars */
  Integer i, ipiv_len, j, kl, ku, n, pdab;
  Integer exit_status = 0;
  double anorm, rcond, sum;
  NagError fail;
  Nag_OrderType order;

  /* Arrays */
  double *ab = 0;
  Integer *ipiv = 0;

#ifdef NAG_COLUMN_MAJOR
#define AB(I, J) ab[(J - 1) * pdab + kl + ku + I - J]
  order = Nag_ColMajor;
#else
#define AB(I, J) ab[(I - 1) * pdab + kl + J - I]
  order = Nag_RowMajor;
#endif

  INIT_FAIL(fail);

  printf("nag_lapacklin_dgbcon (f07bgc) Example Program Results\n\n");

  /* Skip heading in data file */
  scanf("%*[^\n] ");
  scanf("%" NAG_IFMT "%" NAG_IFMT "%" NAG_IFMT "%*[^\n] ", &n, &kl, &ku);
  ipiv_len = n;
  pdab = 2 * kl + ku + 1;

  /* Allocate memory */
  if (!(ab = NAG_ALLOC((2 * kl + ku + 1) * n, double)) ||
      !(ipiv = NAG_ALLOC(ipiv_len, Integer))) {
    printf("Allocation failure\n");
    exit_status = -1;
    goto END;
  }

  /* Read AB from data file */
  for (i = 1; i <= n; ++i) {
    for (j = MAX(i - kl, 1); j <= MIN(i + ku, n); ++j)
      scanf("%lf", &AB(i, j));
  }
  scanf("%*[^\n] ");
  /* Compute norm of A */
  anorm = 0.0;
  for (j = 1; j <= n; ++j) {
    sum = 0.0;
    for (i = MAX(j - ku, 1); i <= MIN(j + kl, n); ++i)
      sum = sum + ABS(AB(i, j));
    anorm = MAX(anorm, sum);
  }
  /* Factorize A */
  /* nag_lapacklin_dgbtrf (f07bdc).
   * LU factorization of real m by n band matrix
   */
  nag_lapacklin_dgbtrf(order, n, n, kl, ku, ab, pdab, ipiv, &fail);
  if (fail.code != NE_NOERROR) {
    printf("Error from nag_lapacklin_dgbtrf (f07bdc).\n%s\n", fail.message);
    exit_status = 1;
    goto END;
  }
  /* Estimate condition number */
  /* nag_lapacklin_dgbcon (f07bgc).
   * Estimate condition number of real band matrix, matrix
   * already factorized by nag_lapacklin_dgbtrf (f07bdc)
   */
  nag_lapacklin_dgbcon(order, Nag_OneNorm, n, kl, ku, ab, pdab, ipiv, anorm,
                       &rcond, &fail);
  if (fail.code != NE_NOERROR) {
    printf("Error from nag_lapacklin_dgbcon (f07bgc).\n%s\n", fail.message);
    exit_status = 1;
    goto END;
  }
  /* Print condition number */
  /* 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(ab);
  NAG_FREE(ipiv);
  return exit_status;
}