/* nag_dgtrfs (f07chc) 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;

  /* 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_dgtrfs (f07chc) 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)) ||
      !(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_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_dgttrf (f07cdc).
   */
  nag_dgttrf(n, dlf, df, duf, du2, ipiv, &fail);
  if (fail.code != NE_NOERROR)
    {
      printf("Error from nag_dgttrf (f07cdc).\n%s\n", fail.message);
      exit_status = 1;
      goto END;
    }

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

  /* Improve the solution and compute error estimates using
   * nag_dgtrfs (f07chc).
   */
  nag_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_dgtrfs (f07chc).\n%s\n", fail.message);
      exit_status = 1;
      goto END;
    }

  /* Print the solution 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;
    }

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

  return exit_status;
}

#undef B