“…When the event {φ(X) < T } is rare relatively to the available simulation budget (which is often the case in safety and reliability issues), dierent algorithms described in [Sobol, 1994], [Bucklew, 2004], [Rubinstein and Kroese, 2004], [Zhang, 1996], [Bjerager, 1991], [Botev and Kroese, 2012], [Cérou et al, 2012] have notably been proposed to estimate accurately its probability.…”