/* nag_lapacklin_dptrfs (f07jhc) Example Program.
 *
 * Copyright 2024 Numerical Algorithms Group.
 *
 * Mark 30.1, 2024.
 */

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

int main(void) {

  /* Scalars */
  Integer exit_status = 0, i, j, n, nrhs, pdb, pdx;
  Nag_OrderType order;

  /* Arrays */
  double *b = 0, *berr = 0, *d = 0, *df = 0, *e = 0, *ef = 0, *ferr = 0;
  double *x = 0;

  /* Nag Types */
  NagError fail;

#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_dptrfs (f07jhc) 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)) ||
      !(e = NAG_ALLOC(n - 1, double)) || !(ef = NAG_ALLOC(n - 1, double)) ||
      !(ferr = NAG_ALLOC(nrhs, double)) || !(x = NAG_ALLOC(n * nrhs, double))) {
    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 lower bidiagonal part of the tridiagonal matrix A from */
  /* data file */
  for (i = 0; i < n; ++i)
    scanf("%lf", &d[i]);
  scanf("%*[^\n]");
  for (i = 0; i < n - 1; ++i)
    scanf("%lf", &e[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 DF and EF */
  for (i = 0; i < n; ++i)
    df[i] = d[i];
  for (i = 0; i < n - 1; ++i)
    ef[i] = e[i];

  /* 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_dpttrf (f07jdc).
   */
  nag_lapacklin_dpttrf(n, df, ef, &fail);
  if (fail.code != NE_NOERROR) {
    printf("Error from nag_lapacklin_dpttrf (f07jdc).\n%s\n", fail.message);
    exit_status = 1;
    goto END;
  }
  /* Solve the equations AX = B using nag_lapacklin_dpttrs (f07jec). */
  nag_lapacklin_dpttrs(order, n, nrhs, df, ef, x, pdx, &fail);
  if (fail.code != NE_NOERROR) {
    printf("Error from nag_lapacklin_dpttrs (f07jec).\n%s\n", fail.message);
    exit_status = 1;
    goto END;
  }

  /* Improve the solution and compute error estimates
   * using nag_lapacklin_dptrfs (f07jhc).
   */
  nag_lapacklin_dptrfs(order, n, nrhs, d, e, df, ef, b, pdb, x, pdx, ferr, berr,
                       &fail);
  if (fail.code != NE_NOERROR) {
    printf("Error from nag_lapacklin_dptrfs (f07jhc).\n%s\n", fail.message);
    exit_status = 1;
    goto END;
  }

  /* Print the solution and the forward and backward error estimates
   * 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;
  }
  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(e);
  NAG_FREE(ef);
  NAG_FREE(ferr);
  NAG_FREE(x);

  return exit_status;
}

#undef B