/* nag_lapacklin_dgtrfs (f07chc) Example Program.
 *
 * Copyright 2024 Numerical Algorithms Group.
 *
 * Mark 30.0, 2024.
 */

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

int main(void) {
  /* Scalars */
  Integer exit_status = 0, i, j, n, nrhs, pdb, pdx;

  /* Arrays */
  double *b = 0, *berr = 0, *d = 0, *df = 0, *dl = 0, *dlf = 0, *du = 0;
  double *du2 = 0, *duf = 0, *ferr = 0, *x = 0;
  Integer *ipiv = 0;

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

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

  INIT_FAIL(fail);

  printf("nag_lapacklin_dgtrfs (f07chc) Example Program Results\n\n");
  /* Skip heading in data file */
  scanf("%*[^\n]");
  scanf("%" NAG_IFMT "%" NAG_IFMT "%*[^\n]", &n, &nrhs);
  if (n < 0 || nrhs < 0) {
    printf("Invalid n or nrhs\n");
    exit_status = 1;
    goto END;
  }
  /* Allocate memory */
  if (!(b = NAG_ALLOC(n * nrhs, double)) || !(berr = NAG_ALLOC(nrhs, double)) ||
      !(d = NAG_ALLOC(n, double)) || !(df = NAG_ALLOC(n, double)) ||
      !(dl = NAG_ALLOC(n - 1, double)) || !(dlf = NAG_ALLOC(n - 1, double)) ||
      !(du = NAG_ALLOC(n - 1, double)) || !(du2 = NAG_ALLOC(n - 2, double)) ||
      !(duf = NAG_ALLOC(n - 1, double)) || !(ferr = NAG_ALLOC(nrhs, double)) ||
      !(x = NAG_ALLOC(n * nrhs, double)) || !(ipiv = NAG_ALLOC(n, Integer))) {
    printf("Allocation failure\n");
    exit_status = -1;
    goto END;
  }

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

  /* Read the tridiagonal matrix A from data file */
  for (i = 0; i < n - 1; ++i)
    scanf("%lf", &du[i]);
  scanf("%*[^\n]");
  for (i = 0; i < n; ++i)
    scanf("%lf", &d[i]);
  scanf("%*[^\n]");
  for (i = 0; i < n - 1; ++i)
    scanf("%lf", &dl[i]);
  scanf("%*[^\n]");

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

  /* Copy A into arrays duf, df and dlf. */
  for (i = 0; i < n - 1; ++i) {
    duf[i] = du[i], df[i] = d[i], dlf[i] = dl[i];
  }
  df[n - 1] = d[n - 1];

  /* Copy B into X using nag_blast_dge_copy (f16qfc). */
  nag_blast_dge_copy(order, Nag_NoTrans, n, nrhs, b, pdb, x, pdx, &fail);
  if (fail.code != NE_NOERROR) {
    printf("Error from nag_blast_dge_copy (f16qfc).\n%s\n", fail.message);
    exit_status = 1;
    goto END;
  }

  /* Factorize the copy of the tridiagonal matrix A
   * using nag_lapacklin_dgttrf (f07cdc).
   */
  nag_lapacklin_dgttrf(n, dlf, df, duf, du2, ipiv, &fail);
  if (fail.code != NE_NOERROR) {
    printf("Error from nag_lapacklin_dgttrf (f07cdc).\n%s\n", fail.message);
    exit_status = 1;
    goto END;
  }

  /* Solve the equations AX = B using  nag_lapacklin_dgttrs (f07cec). */
  nag_lapacklin_dgttrs(order, Nag_NoTrans, n, nrhs, dlf, df, duf, du2, ipiv, x,
                       pdx, &fail);
  if (fail.code != NE_NOERROR) {
    printf("Error from nag_lapacklin_dgttrs (f07cec).\n%s\n", fail.message);
    exit_status = 1;
    goto END;
  }

  /* Improve the solution and compute error estimates using
   * nag_lapacklin_dgtrfs (f07chc).
   */
  nag_lapacklin_dgtrfs(order, Nag_NoTrans, n, nrhs, dl, d, du, dlf, df, duf,
                       du2, ipiv, b, pdb, x, pdx, ferr, berr, &fail);
  if (fail.code != NE_NOERROR) {
    printf("Error from nag_lapacklin_dgtrfs (f07chc).\n%s\n", fail.message);
    exit_status = 1;
    goto END;
  }

  /* Print the solution using nag_file_print_matrix_real_gen (x04cac). */
  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 the forward and backward error estimates */
  printf("\nBackward errors (machine-dependent)\n");
  for (j = 0; j < nrhs; ++j)
    printf("%11.1e%s", berr[j], j % 7 == 6 ? "\n" : " ");

  printf("\n\nEstimated forward error bounds (machine-dependent)\n");
  for (j = 0; j < nrhs; ++j)
    printf("%11.1e%s", ferr[j], j % 7 == 6 ? "\n" : " ");
  printf("\n");

END:
  NAG_FREE(b);
  NAG_FREE(berr);
  NAG_FREE(d);
  NAG_FREE(df);
  NAG_FREE(dl);
  NAG_FREE(dlf);
  NAG_FREE(du);
  NAG_FREE(du2);
  NAG_FREE(duf);
  NAG_FREE(ferr);
  NAG_FREE(x);
  NAG_FREE(ipiv);

  return exit_status;
}

#undef B