NAG Library Manual, Mark 28.3
/* F11JC_P0W_F C++ Header Example Program.
*
* Copyright 2022 Numerical Algorithms Group.
* Mark 28.3, 2022.
*/
#include <dco.hpp>
#include <iostream>
#include <nag.h>
#include <nagx04.h>
#include <stdio.h>
using namespace std;

int main()
{
int               exit_status = 0;
Integer           ifail = 0;

cout << "F11JC_P0W_F C++ Header Example Program Results\n\n";
// Skip heading in data file
string mystr;
getline(cin, mystr);

// Read order of matrix and number of nonzero entries
Integer n, nnz;
cin >> n;
cin >> nnz;

Integer  la     = 3 * nnz;
Integer  liwork = 2 * la + 7 * n + 1;
Integer  lwork  = 6 * n + 120;
double * a = 0, *x = 0, *y = 0, *work = 0;
Integer *icol = 0, *ipiv = 0, *irow = 0, *istr = 0, *iwork = 0;

a     = new double[la];
x     = new double[n];
y     = new double[n];
work  = new double[lwork];
icol  = new Integer[la];
ipiv  = new Integer[n];
irow  = new Integer[la];
istr  = new Integer[n + 1];
iwork = new Integer[liwork];

double  dtol, dscale, tol;
Integer lfill, maxitn;
cin >> lfill >> dtol;
cin >> dscale;
cin >> tol >> maxitn;

for (int i = 0; i < nnz; i++)
{
cin >> a[i] >> irow[i] >> icol[i];
}

for (int i = 0; i < n; i++)
{
cin >> y[i];
}
for (int i = 0; i < n; i++)
{
cin >> x[i];
}
// Calculate incomplete Cholesky factorization
Integer nnzc, npivm;
ifail = 0;
"M", ipiv, istr, nnzc, npivm, iwork, liwork, ifail);

// Solve Ax = y
double  rnorm;
Integer itn;
ifail = 0;
nag::ad::f11jc(ad_handle, "CG", n, nnz, a, la, irow, icol, ipiv, istr, y, tol,
maxitn, x, rnorm, itn, work, lwork, ifail);

// Output results
cout << " Converged in " << itn << " iterations" << endl;
cout << " Final residual norm = " << rnorm << endl;
cout.setf(ios::scientific, ios::floatfield);
cout.precision(4);
cout << endl;
cout << "  Solution vector" << endl;
for (int i = 0; i < n; ++i)
{
cout.width(12);
cout << x[i] << endl;
}

delete[] a;
delete[] x;
delete[] y;
delete[] work;
delete[] icol;
delete[] ipiv;
delete[] irow;
delete[] istr;
delete[] iwork;

return exit_status;
}