#include <iostream>
#include <Eigen/Dense>
using namespace std;
using namespace Eigen;
int main()
{
Matrix2d A;
A << 2, 1,
2, 0.9999999999;
FullPivLU<Matrix2d> lu(A);
cout << "By default, the rank of A is found to be " << lu.rank() << endl;
lu.setThreshold(1e-5);
cout << "With threshold 1e-5, the rank of A is found to be " << lu.rank() << endl;
}