/* nag_dptrfs (f07jhc) Example Program.
 *
 * Copyright 2004 Numerical Algorithms Group.
 *
 * Mark 23, 2011.
 */

#include <stdio.h>
#include <nag.h>
#include <nagx04.h>
#include <nag_stdlib.h>
#include <nagf07.h>
#include <nagf16.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_dptrfs (f07jhc) Example Program Results\n\n");

  /* Skip heading in data file */
  scanf("%*[^\n]");

  scanf("%ld%ld%*[^\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_dge_copy (f16qfc). */
  nag_dge_copy(order, Nag_NoTrans, n, nrhs, b, pdb, x, pdx, &fail);
  if (fail.code != NE_NOERROR)
    {
      printf("Error from nag_dge_copy (f16qfc).\n%s\n", fail.message);
      exit_status = 1;
      goto END;
    }

  /* Factorize the copy of the tridiagonal matrix A using 
   * nag_dpttrf (f07jdc).
   */
  nag_dpttrf(n, df, ef, &fail);
  if (fail.code != NE_NOERROR)
    {
      printf("Error from nag_dpttrf (f07jdc).\n%s\n", fail.message);
      exit_status = 1;
      goto END;
    }
  /* Solve the equations AX = B using nag_dpttrs (f07jec). */
  nag_dpttrs(order, n, nrhs, df, ef, x, pdx, &fail);
  if (fail.code != NE_NOERROR)
    {
      printf("Error from nag_dpttrs (f07jec).\n%s\n", fail.message);
      exit_status = 1;
      goto END;
    }

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

  /* Print the solution and the forward and backward error estimates 
   * using nag_gen_real_mat_print (x04cac).
   */
  fflush(stdout);
  nag_gen_real_mat_print(order, Nag_GeneralMatrix, Nag_NonUnitDiag, n, nrhs, x,
                         pdx, "Solution(s)", 0, &fail);
  if (fail.code != NE_NOERROR)
    {
      printf("Error from nag_gen_real_mat_print (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":" ");

 END:
  if (b)    NAG_FREE(b);
  if (berr) NAG_FREE(berr);
  if (d)    NAG_FREE(d);
  if (df)   NAG_FREE(df);
  if (e)    NAG_FREE(e);
  if (ef)   NAG_FREE(ef);
  if (ferr) NAG_FREE(ferr);
  if (x)    NAG_FREE(x);

  return exit_status;
}
#undef B