/* nag_lapacklin_dgbsv (f07bac) Example Program.
 *
 * Copyright 2024 Numerical Algorithms Group.
 *
 * Mark 30.3, 2024.
 */

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

int main(void) {

  /* Scalars */
  Integer exit_status = 0, i, j, kl, ku, n, nrhs, pdab, pdb;

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

  /* Nag Types */
  NagError fail;
  Nag_OrderType order;

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

  INIT_FAIL(fail);

  printf("nag_lapacklin_dgbsv (f07bac) Example Program Results\n\n");

  /* Skip heading in data file */
  scanf("%*[^\n]");
  scanf("%" NAG_IFMT "%" NAG_IFMT "%" NAG_IFMT "%*[^\n] ", &n, &kl, &ku);
  scanf("%" NAG_IFMT "%*[^\n] ", &nrhs);
  if (n < 0 || kl < 0 || ku < 0 || nrhs < 0) {
    printf("One or more of n, kl, ku or nrhs has illegal value\n");
    exit_status = 1;
    goto END;
  }

  pdab = 2 * kl + ku + 1;

#ifdef NAG_COLUMN_MAJOR
  pdb = n;
#else
  pdb = nrhs;
#endif

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

  /* Read the band matrix A and the right hand side b 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] ");

  for (i = 1; i <= n; ++i)
    for (j = 1; j <= nrhs; ++j)
      scanf("%lf", &B(i, j));
  scanf("%*[^\n] ");

  /* Solve the equations Ax = b for x using nag_lapacklin_dgbsv (f07bac). */
  nag_lapacklin_dgbsv(order, n, kl, ku, nrhs, ab, pdab, ipiv, b, pdb, &fail);
  if (fail.code != NE_NOERROR) {
    printf("Error from nag_lapacklin_dgbsv (f07bac).\n%s\n", fail.message);
    exit_status = 1;
    goto END;
  }

  /* Print solution */
  printf("Solution\n");
  for (i = 1; i <= n; ++i) {
    for (j = 1; j <= nrhs; ++j)
      printf("%11.4f%s", B(i, j), j % 7 == 0 ? "\n" : " ");
    printf("\n");
  }

  /* Print details of the factorization */
  printf("\n");
  fflush(stdout);
  nag_file_print_matrix_real_band(order, n, 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("\nPivot indices\n");
  for (i = 1; i <= n; ++i)
    printf("%11" NAG_IFMT "%s", ipiv[i - 1], i % 7 == 0 ? "\n" : " ");
  printf("\n");
END:
  NAG_FREE(ab);
  NAG_FREE(b);
  NAG_FREE(ipiv);

  return exit_status;
}

#undef AB
#undef B