1 #include <iostream>
2 #include <Eigen/SVD>
3 using namespace Eigen;
4 using namespace std;
5 
inv_cond(const Ref<const MatrixXf> & a)6 float 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 
main()12 int 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