/* F11BD_P0W_F C++ Header Example Program.
 *
 * Copyright 2021 Numerical Algorithms Group.
 * Mark 27.2, 2021.
 */

#include <iostream>
#include <nag.h>
#include <nagad.h>
#include <nagx04.h>
#include <stdio.h>
#include <string>
using namespace std;

int main(void)
{
  int     exit_status = 0;
  void *  ad_handle   = 0;
  Integer ifail       = 0;

  cout << "F11BD_P0W_F C++ Header Example Program Results\n\n";
  // Skip heading in data file
  string mystr;
  getline(cin, mystr);

  // Read problem size
  Integer n, m;
  double  alpha;
  cin >> n;
  cin >> m;
  cin >> alpha;

  // Allocate arrays containing A and its factorized form, B
  // and the solution X.
  double *b = 0, *x = 0, *work = 0;
  Integer lwork = 2 * m * n + 1000;

  b    = new double[n];
  x    = new double[n];
  work = new double[lwork];

  double bb, b1, a, c;

  b1 = 12.0;
  a  = 1.0;
  c  = 1.0;
  bb = b1 - 2.0;

  ifail = 0;
  for (int i = 0; i < n; ++i)
    {
      b[i] = b1 * (i + 1);
      x[i] = 3.0;
    }
  b[n - 1] = b[n - 1] - (n + 1);

  b[0] = b[0] + (b1 - 1.0) * alpha;
  for (int i = 1; i < n - 1; ++i)
    {
      b[i] = b[i] + b1 * alpha;
    }
  b[n - 1] = b[n - 1] + (b1 - 1.0) * alpha;

  // Initialize rthe solver
  Integer iterm = 2, maxitn = 800, monit = 0, lwreq = lwork;
  double  sigmax = 0.0, anorm;
  double  tol    = 1.0e-10;
  ifail          = 0;
  nag::ad::f11bd(ad_handle, "RGMRES", "P", "2", "N", iterm, n, m, tol, maxitn,
                 anorm, sigmax, monit, lwreq, work, lwork, ifail);

  // Reverse communication call of solver
  Integer irevcm = 0;
  double  wgt[1];

  while (irevcm != 4)
    {
      ifail = 0;
      nag::ad::f11be(ad_handle, irevcm, x, b, wgt, work, lwreq, ifail);
      if (irevcm != 4)
        {
          ifail = -1;
          if (irevcm == -1)
            {
              //  b = A^Tx
              b[0] = bb * x[0] + a * x[1];
              for (int i = 1; i < n - 1; ++i)
                {
                  b[i] = c * x[i - 1] + bb * x[i] + a * x[i + 1];
                }
              b[n - 1] = c * x[n - 2] + bb * x[n - 1];
            }
          if (irevcm == 1)
            {
              // b = Ax
              b[0] = bb * x[0] + c * x[1];
              for (int i = 1; i < n - 1; ++i)
                {
                  b[i] = a * x[i - 1] + bb * x[i] + c * x[i + 1];
                }
              b[n - 1] = a * x[n - 2] + bb * x[n - 1];
            }
          if (irevcm == 2)
            {
              for (int i = 0; i < n; ++i)
                {
                  b[i] = x[i] / bb;
                }
            }
        }
    }

  cout.setf(ios::scientific, ios::floatfield);
  cout.precision(2);

  cout << "  Solution vector   Residual vector\n";
  for (int i = 0; i < n; ++i)
    {
      cout.width(12);
      cout << x[i] << "     ";
      cout.width(13);
      cout << b[i] << endl;
    }

  delete[] b;
  delete[] x;
  delete[] work;

  return exit_status;
}