1#include <iostream>
2#include <Eigen/Dense>
3
4using namespace std;
5using namespace Eigen;
6
7int main()
8{
9   MatrixXd A = MatrixXd::Random(100,100);
10   MatrixXd b = MatrixXd::Random(100,50);
11   MatrixXd x = A.fullPivLu().solve(b);
12   double relative_error = (A*x - b).norm() / b.norm(); // norm() is L2 norm
13   cout << "The relative error is:\n" << relative_error << endl;
14}
15