1#include <iostream>
2#include <Eigen/SVD>
3using namespace Eigen;
4using namespace std;
5
6float inv_cond(const Ref<const MatrixXf>& a)
7{
8  const VectorXf sing_vals = a.jacobiSvd().singularValues();
9  return sing_vals(sing_vals.size()-1) / sing_vals(0);
10}
11
12int main()
13{
14  Matrix4f m = Matrix4f::Random();
15  cout << "matrix m:" << endl << m << endl << endl;
16  cout << "inv_cond(m):          " << inv_cond(m)                      << endl;
17  cout << "inv_cond(m(1:3,1:3)): " << inv_cond(m.topLeftCorner(3,3))   << endl;
18  cout << "inv_cond(m+I):        " << inv_cond(m+Matrix4f::Identity()) << endl;
19}
20