/* nag_lapacklin_dgbtrf (f07bdc) Example Program.
 *
 * Copyright 2024 Numerical Algorithms Group.
 *
 * Mark 30.1, 2024.
 */

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

int main(void) {
  /* Scalars */
  Integer i, ipiv_len, j, kl, ku, m, n, pdab;
  Integer exit_status = 0;
  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_dgbtrf (f07bdc) Example Program Results\n\n");

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

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

  /* Read A from data file */
  for (i = 1; i <= m; ++i) {
    for (j = MAX(i - kl, 1); j <= MIN(i + ku, n); ++j)
      scanf("%lf", &AB(i, j));
  }
  scanf("%*[^\n] ");

  /* Factorize A */
  /* nag_lapacklin_dgbtrf (f07bdc).
   * LU factorization of real m by n band matrix
   */
  nag_lapacklin_dgbtrf(order, m, 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;
  }
  /* Print details of factorization */
  /* nag_file_print_matrix_real_band (x04cec).
   * Print real packed banded matrix (easy-to-use)
   */
  fflush(stdout);
  nag_file_print_matrix_real_band(order, m, n, kl, kl + ku, ab, pdab,
                                  "Details of factorization", 0, &fail);
  if (fail.code != NE_NOERROR) {
    printf("Error from nag_file_print_matrix_real_band (x04cec).\n%s\n",
           fail.message);
    exit_status = 1;
    goto END;
  }

  /* Print pivot indices */
  printf("\nipiv\n");
  for (i = 1; i <= MIN(m, n); ++i)
    printf("%10" NAG_IFMT "%s", ipiv[i - 1], i % 7 == 0 ? "\n" : " ");
  printf("\n");

END:
  NAG_FREE(ab);
  NAG_FREE(ipiv);
  return exit_status;
}