/* nag_lapacklin_dgbrfs (f07bhc) 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, n, nrhs, pdab, pdafb, pdb, pdx;
  Integer exit_status = 0;
  NagError fail;
  Nag_OrderType order;

  /* Arrays */
  double *ab = 0, *afb = 0, *b = 0, *berr = 0, *ferr = 0, *x = 0;
  Integer *ipiv = 0;

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

  INIT_FAIL(fail);

  printf("nag_lapacklin_dgbrfs (f07bhc) Example Program Results\n\n");

  /* Skip heading in data file */
  scanf("%*[^\n] ");
  scanf("%" NAG_IFMT "%" NAG_IFMT "%" NAG_IFMT "%" NAG_IFMT "%*[^\n] ", &n,
        &nrhs, &kl, &ku);
  ipiv_len = n;
  pdab = kl + ku + 1;
  pdafb = 2 * kl + ku + 1;
#ifdef NAG_COLUMN_MAJOR
  pdb = n;
  pdx = n;
#else
  pdb = nrhs;
  pdx = nrhs;
#endif

  /* Allocate memory */
  if (!(ab = NAG_ALLOC((kl + ku + 1) * n, double)) ||
      !(afb = NAG_ALLOC((2 * kl + ku + 1) * n, double)) ||
      !(b = NAG_ALLOC(nrhs * n, double)) ||
      !(x = NAG_ALLOC(nrhs * n, double)) || !(berr = NAG_ALLOC(nrhs, double)) ||
      !(ferr = NAG_ALLOC(nrhs, double)) ||
      !(ipiv = NAG_ALLOC(ipiv_len, Integer))) {
    printf("Allocation failure\n");
    exit_status = -1;
    goto END;
  }
  /* Set A to zero to avoid referencing unitialized elements */
  for (i = 0; i < n * (kl + ku + 1); ++i)
    ab[i] = 0.0;
  /* Read A 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] ");
  /* Read B from data file */
  for (i = 1; i <= n; ++i) {
    for (j = 1; j <= nrhs; ++j)
      scanf("%lf", &B(i, j));
  }
  scanf("%*[^\n] ");
  /* Copy A to AFB and B to X */
  for (i = 1; i <= n; ++i) {
    for (j = MAX(i - kl, 1); j <= MIN(i + ku, n); ++j)
      AFB(i, j) = AB(i, j);
  }
  for (i = 1; i <= n; ++i) {
    for (j = 1; j <= nrhs; ++j)
      X(i, j) = B(i, j);
  }
  /* Factorize A in the array AFB */
  /* nag_lapacklin_dgbtrf (f07bdc).
   * LU factorization of real m by n band matrix
   */
  nag_lapacklin_dgbtrf(order, n, n, kl, ku, afb, pdafb, ipiv, &fail);
  if (fail.code != NE_NOERROR) {
    printf("Error from nag_lapacklin_dgbtrf (f07bdc).\n%s\n", fail.message);
    exit_status = 1;
    goto END;
  }
  /* Compute solution in the array X */
  /* nag_lapacklin_dgbtrs (f07bec).
   * Solution of real band system of linear equations,
   * multiple right-hand sides, matrix already factorized by
   * nag_lapacklin_dgbtrf (f07bdc)
   */
  nag_lapacklin_dgbtrs(order, Nag_NoTrans, n, kl, ku, nrhs, afb, pdafb, ipiv, x,
                       pdx, &fail);
  if (fail.code != NE_NOERROR) {
    printf("Error from nag_lapacklin_dgbtrs (f07bec).\n%s\n", fail.message);
    exit_status = 1;
    goto END;
  }
  /* Improve solution, and compute backward errors and  */
  /* estimated bounds on the forward errors */
  /* nag_lapacklin_dgbrfs (f07bhc).
   * Refined solution with error bounds of real band system of
   * linear equations, multiple right-hand sides
   */
  nag_lapacklin_dgbrfs(order, Nag_NoTrans, n, kl, ku, nrhs, ab, pdab, afb,
                       pdafb, ipiv, b, pdb, x, pdx, ferr, berr, &fail);
  if (fail.code != NE_NOERROR) {
    printf("Error from nag_lapacklin_dgbrfs (f07bhc).\n%s\n", fail.message);
    exit_status = 1;
    goto END;
  }
  /* Print solution */
  /* nag_file_print_matrix_real_gen (x04cac).
   * Print real general matrix (easy-to-use)
   */
  fflush(stdout);
  nag_file_print_matrix_real_gen(order, Nag_GeneralMatrix, Nag_NonUnitDiag, n,
                                 nrhs, x, pdx, "Solution(s)", 0, &fail);
  if (fail.code != NE_NOERROR) {
    printf("Error from nag_file_print_matrix_real_gen (x04cac).\n%s\n",
           fail.message);
    exit_status = 1;
    goto END;
  }
  /* Print forward and backward errors */
  printf("\nBackward errors (machine-dependent)\n");

  for (j = 1; j <= nrhs; ++j)
    printf("%11.1e%s", berr[j - 1], j % 7 == 0 ? "\n" : " ");

  printf("\nEstimated forward error bounds (machine-dependent)\n");

  for (j = 1; j <= nrhs; ++j)
    printf("%11.1e%s", ferr[j - 1], j % 7 == 0 ? "\n" : " ");
  printf("\n");
END:
  NAG_FREE(ab);
  NAG_FREE(afb);
  NAG_FREE(b);
  NAG_FREE(x);
  NAG_FREE(berr);
  NAG_FREE(ferr);
  NAG_FREE(ipiv);
  return exit_status;
}