/* F11BF_P0W_F C++ Header Example Program.
*
* Copyright 2023 Numerical Algorithms Group.
* Mark 29.3, 2023.
*/
#include <iostream>
#include <nag.h>
#include <nagad.h>
#include <nagx04.h>
#include <stdio.h>
#include <string>
using namespace std;
int main()
{
int exit_status = 0;
nag::ad::handle_t ad_handle;
Integer ifail = 0;
cout << "F11BF_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 >> 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;
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 the solver
Integer iterm = 2, maxitn = 800, monit = 0, lwreq = lwork;
double sigmax = 0.0, anorm = 0.0;
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;
}
}
}
}
// Obtain information about the computation
double stplhs, stprhs;
Integer ifail1 = 0, itn;
nag::ad::f11bf(ad_handle, itn, stplhs, stprhs, anorm, sigmax, work, lwreq,
ifail1);
// Print the output data
cout.setf(ios::scientific, ios::floatfield);
cout.precision(2);
cout << " Final Results " << endl;
cout << " Number of iterations for convergence: " << itn << endl;
cout << " Residual norm: ";
cout << stplhs << endl;
cout << " Right-hand side of termination criterion:";
cout << stprhs << endl;
// for iterm=2 anorm is not calculated
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;
}