/* nag_lapacklin_dtbrfs (f07vhc) Example Program.
 *
 * Copyright 2024 Numerical Algorithms Group.
 *
 * Mark 30.3, 2024.
 */

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

int main(void) {
  /* Scalars */
  Integer i, j, k, kd, n, nrhs, pdab, pdb, pdx;
  Integer ferr_len, berr_len;
  Integer exit_status = 0;
  Nag_UploType uplo;
  NagError fail;
  Nag_OrderType order;
  /* Arrays */
  char nag_enum_arg[40];
  double *ab = 0, *b = 0, *berr = 0, *ferr = 0, *x = 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]
#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_UPPER(I, J) ab[(I - 1) * pdab + J - I]
#define AB_LOWER(I, J) ab[(I - 1) * pdab + k + J - I - 1]
#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_dtbrfs (f07vhc) Example Program Results\n\n");

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

  ferr_len = nrhs;
  berr_len = nrhs;

  /* Allocate memory */
  if (!(berr = NAG_ALLOC(berr_len, double)) ||
      !(ferr = NAG_ALLOC(ferr_len, double)) ||
      !(ab = NAG_ALLOC((kd + 1) * n, double)) ||
      !(b = NAG_ALLOC(n * nrhs, double)) ||
      !(x = NAG_ALLOC(n * nrhs, double))) {
    printf("Allocation failure\n");
    exit_status = -1;
    goto END;
  }

  /* Read A and B from data file, and copy B to X */
  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] ");
  }

  for (i = 1; i <= n; ++i) {
    for (j = 1; j <= nrhs; ++j)
      scanf("%lf", &B(i, j));
  }
  scanf("%*[^\n] ");
  /* Copy B to X */
  for (i = 1; i <= n; ++i) {
    for (j = 1; j <= nrhs; ++j)
      X(i, j) = B(i, j);
  }
  /* Compute solution in the array X */
  /* nag_lapacklin_dtbtrs (f07vec).
   * Solution of real band triangular system of linear
   * equations, multiple right-hand sides
   */
  nag_lapacklin_dtbtrs(order, uplo, Nag_NoTrans, Nag_NonUnitDiag, n, kd, nrhs,
                       ab, pdab, x, pdx, &fail);
  if (fail.code != NE_NOERROR) {
    printf("Error from nag_lapacklin_dtbtrs (f07vec).\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_dtbrfs (f07vhc).
   * Error bounds for solution of real band triangular system
   * of linear equations, multiple right-hand sides
   */
  nag_lapacklin_dtbrfs(order, uplo, Nag_NoTrans, Nag_NonUnitDiag, n, kd, nrhs,
                       ab, pdab, b, pdb, x, pdx, ferr, berr, &fail);
  if (fail.code != NE_NOERROR) {
    printf("Error from nag_lapacklin_dtbrfs (f07vhc).\n%s\n", fail.message);
    exit_status = 1;
    goto END;
  }
  /* Print details of 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;
  }
  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(berr);
  NAG_FREE(ferr);
  NAG_FREE(ab);
  NAG_FREE(b);
  NAG_FREE(x);
  return exit_status;
}