Given a real unsymmetric matrix , this routine uses subspace iteration to calculate the eigenvalues , , that are right-most, left-most, or are of largest modulus. The right-most (respectively, left-most) eigenvalues are the eigenvalues with the most positive (respectively, negative) real part. A second entry will return the associated eigenvectors , , where . The routine may also be used to calculate a group of eigensolutions elsewhere in the spectrum.