Based on the random numbers ρ 1 ∈ [0, 1], the process q, which meets the condition q-1 i=1 k i ≥ ρ 1 k tot ≥ q i=1 k i , is then extracted and executed. The average escape time of the selected process is computed based on the random number ρ 2 ∈ (0, 1] and the total reaction rate k tot to propagate the system time t following