/* nag_real_tridiag_lin_solve (f04bcc) Example Program.
 *
 * Copyright 2004 Numerical Algorithms Group.
 *
 * Mark 8, 2004.
 */

#include <stdio.h>
#include <nag.h>
#include <nag_stdlib.h>
#include <nagf04.h>
#include <nagx04.h>

int main(void)
{

  /* Scalars */
  double errbnd, rcond;
  Integer exit_status, i, j, n, nrhs, pdb;

  /* Arrays */
  double *b=0, *d=0, *dl=0, *du=0, *du2=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

  exit_status = 0;
  INIT_FAIL(fail);
  Vprintf("nag_real_tridiag_lin_solve (f04bcc) Example Program Results\n\n");

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

  Vscanf("%ld%ld%*[^\n] ",   &n,  &nrhs);
  if (n >=0 && nrhs >= 0)
    {
      /* Allocate memory */
      if ( !(b = NAG_ALLOC(n*nrhs, double)) ||
           !(d = NAG_ALLOC(n, double)) ||
           !(dl = NAG_ALLOC(n-1, double)) ||
           !(du = NAG_ALLOC(n-1, double)) ||
           !(du2 = NAG_ALLOC(n-2, double)) ||
           !(ipiv = NAG_ALLOC(n, Integer)) )
        {
          Vprintf("Allocation failure\n");
          exit_status = -1;
          goto END;
        }
#ifdef NAG_COLUMN_MAJOR
      pdb = n;
#else
      pdb = nrhs;
#endif
    }
  else
    {
      Vprintf("%s\n",   "n and/or nrhs too small");
      exit_status = 1;
      return exit_status;
    }
  /* Read A and B from data file */
  for (i = 1; i <= n-1; ++i)
    {
      Vscanf("%lf", &du[i-1]);
    }
  Vscanf("%*[^\n] ");

  for (i = 1; i <= n; ++i)
    {
      Vscanf("%lf", &d[i-1]);
    }
  Vscanf("%*[^\n] ");

  for (i = 1; i <= n-1; ++i)
    {
      Vscanf("%lf", &dl[i-1]);
    }
  Vscanf("%*[^\n] ");

  for (i = 1; i <= n; ++i)
    {
      for (j = 1; j <= nrhs; ++j)
        {
          Vscanf("%lf", &B(i,j));
        }
    }
  Vscanf("%*[^\n] ");

  /* Solve the equations AX = B for X */
  /* nag_real_tridiag_lin_solve (f04bcc).
   * Computes the solution and error-bound to a real
   * tridiagonal system of linear equations
   */
  nag_real_tridiag_lin_solve(order, n, nrhs, dl, d, du, du2, ipiv, b, pdb,
                             &rcond, &errbnd, &fail);
  if (fail.code == NE_NOERROR)
    {
      /* Print solution, estimate of condition number and approximate */
      /* error bound */
      /* nag_gen_real_mat_print (x04cac).
       * Print real general matrix (easy-to-use)
       */
      nag_gen_real_mat_print(order, Nag_GeneralMatrix, Nag_NonUnitDiag, n, nrhs,
                             b, pdb, "Solution", 0, &fail);
      if (fail.code != NE_NOERROR)
        {
          Vprintf("Error from nag_gen_real_mat_print (x04cac).\n%s\n",
                  fail.message);
          exit_status = 1;
          goto END;
        }
      Vprintf("\n");
      Vprintf("%s\n      %9.1e\n", "Estimate of condition number", 1.0/rcond);
      Vprintf("\n\n");

      Vprintf("%s\n      %9.1e\n\n",
              "Estimate of error bound for computed solutions", errbnd);
    }
  else if (fail.code == NE_RCOND)
    {

      /* Matrix A is numerically singular.  Print estimate of */
      /* reciprocal of condition number and solution */


      Vprintf("\n");
      Vprintf("%s\n%6s%9.1e\n", "Estimate of reciprocal of condition number",
              "", rcond);
      Vprintf("\n\n");
      /* nag_gen_real_mat_print (x04cac), see above. */
      nag_gen_real_mat_print(order, Nag_GeneralMatrix, Nag_NonUnitDiag, n, nrhs,
                             b, pdb, "Solution", 0, &fail);
      if (fail.code != NE_NOERROR)
        {
          Vprintf("Error from nag_gen_real_mat_print (x04cac).\n%s\n",
                  fail.message);
          exit_status = 1;
          goto END;
        }

    }
  else if (fail.code == NE_SINGULAR)
    {

      /* The upper triangular matrix U is exactly singular.  Print */
      /* details of factorization */


      Vprintf("%s\n\n",   "Details of factorization");
      Vprintf("%s\n",   " Second super-diagonal of U");

      for (i = 1; i <= n - 2; ++i)
        {
          Vprintf("%9.4f%s", du2[i-1], i%8 == 0 || i == n - 2 ?"\n":" ");
        }
      Vprintf("\n");

      Vprintf("\n%s\n",   " First super-diagonal of U");
      for (i = 1; i <= n-1; ++i)
        {
          Vprintf("%9.4f%s", du[i-1], i%8 == 0 || i == n-1 ?"\n":" ");
        }
      Vprintf("\n\n");

      Vprintf("%s\n",   " Main diagonal of U");
      for (i = 1; i <= n; ++i)
        {
          Vprintf("%9.4f%s", d[i-1], i%8 == 0 || i == n ?"\n":" ");
        }
      Vprintf("\n\n");

      Vprintf("%s\n",   " Multipliers");
      for (i = 1; i <= n-1; ++i)
        {
          Vprintf("%9.4f%s", dl[i-1], i%8 == 0 || i == n-1 ?"\n":" ");
        }
      Vprintf("\n\n");

      Vprintf("%s\n",   " Vector of interchanges");
      for (i = 1; i <= n; ++i)
        {
          Vprintf("%9ld%s", ipiv[i-1], i%8 == 0 || i  == n ?"\n":" ");
        }
      Vprintf("\n");
    }
 END:
  if (b) NAG_FREE(b);
  if (d) NAG_FREE(d);
  if (dl) NAG_FREE(dl);
  if (du) NAG_FREE(du);
  if (du2) NAG_FREE(du2);
  if (ipiv) NAG_FREE(ipiv);

  return exit_status;
}

#undef B