Dear ALPS community, I am writing for a question on the algorithm for classical Monte Carlo simulation of spin models. From the simulations I performed on classical O(2), O(3) and O(4) models it turned out that the autocorrelation time is quite large, let's say of about 80 o 90, for the energy density observable. I just would like to understand better if there is a particular reason for such a big tau and which kind of algorithm is really used for the simulation: Swendsen-Wang , Wolff single cluster or even something else? This is also because the term ”sweep” is quite unusual when cluster algorithms are concerned. I really thank you all for your help. Best regards, Rachele Nerattini -- --------------------------------------------------------------------------------------------- Rachele Nerattini Dip. di Fisica e Astronomia, Università di Firenze Via G. Sansone, 1, 50019 Sesto Fiorentino (FI), Italy ---------------------------------------------------------------------------------------------