Given a real unsymmetric $n\times n$ matrix $A=\left\{{a}_{ij}\right\}$, this routine uses Arnoldi based methods to calculate the $r$ eigenvalues ${\lambda}_{i},i=1,...,r$, that are of largest absolute value, or are right-most, or are of largest imaginary parts. The right-most eigenvalues are those with the most positive real part. There is an option to compute the associated eigenvectors ${y}_{i}$, $i=1,...,r$, where ${Ay}_{i}={\lambda}_{i}{y}_{i}$. The routine may be used to compute the left-most eigenvalues of $A$ by using $-A$ in place of $A$.
The Arnoldi methods oﬀered by EB13 are:
Each method is available in blocked and unblocked form.