1 Matrix4d X = Matrix4d::Random(4,4); 2 Matrix4d A = X + X.transpose(); 3 cout << "Here is a random symmetric 4x4 matrix:" << endl << A << endl; 4 Tridiagonalization<Matrix4d> triOfA(A); 5 Matrix4d pm = triOfA.packedMatrix(); 6 cout << "The packed matrix M is:" << endl << pm << endl; 7 cout << "The diagonal and subdiagonal corresponds to the matrix T, which is:" 8 << endl << triOfA.matrixT() << endl; 9