1SelfAdjointEigenSolver<MatrixXf> es(4); 2MatrixXf X = MatrixXf::Random(4,4); 3MatrixXf A = X + X.transpose(); 4es.compute(A); 5cout << "The eigenvalues of A are: " << es.eigenvalues().transpose() << endl; 6es.compute(A + MatrixXf::Identity(4,4)); // re-use es to compute eigenvalues of A+I 7cout << "The eigenvalues of A+I are: " << es.eigenvalues().transpose() << endl; 8