        &lt; 0:  if INFO = -i, the i-th argument had an illegal
                value;
          &gt; 0:  if INFO = i, i &lt;= N, the QR algorithm failed to
                complete the reduction of the matrix Ac to Schur
                canonical form (see LAPACK Library routine DGEES);
                on exit, the matrix T(i+1:N,i+1:N) contains the
                partially converged Schur form, and DWORK(i+1:N) and
                DWORK(N+i+1:2*N) contain the real and imaginary
                parts, res