  We revisit the numerical calculation of generalized Lyapunov exponents,
$L$($q$), in deterministic dynamical systems. The standard method consists of
adding noise to the dynamics in order to use importance sampling algorithms.
Then $L$($q$) is obtained by taking the limit noise-amplitude $\to$0 after the
calculation. We focus on a particular method that involves periodic cloning and
pruning of a set of trajectories. However, instead of considering a noisy
dynamics, we implement an imperfect (noisy) cloning. This alternative method is
compared with the standard one and, when possible, with analytical results. As
a workbench, we use the asymmetric tent map, the standard map, and a system of
coupled symplectic maps. The general conclusion of this study is that the
imperfect-cloning method performs as well as the standard one, with the
advantage of preserving the deterministic dynamics.
