  &lt; 0:  if INFO = -i, the i-th argument had an illegal
                value;
          = 1:  a matrix is (numerically) singular or the Sylvester
                equation is very ill-conditioned, when computing the
                largest singular value of G(infinity) (for
                DICO = 'C'); the descriptor system is nearly
                singular; the L-infinity norm could be infinite;
          = 2:  the (periodic) QR (or QZ) algorithm for computing
                eigenvalues did not converg