The bias metric is defined to compare the evolution of six species of interest. Four of them are the four most common molecules in the training set: CH 4 , H 2 , C 2 H 6 and C 4 H 10 . The two other species of interest are the number of carbon in the longest carbon chain and the H:C ratio in this longest carbon chain. Using these six species of interest, the following bias metric is computed to compare the KMC predictions and the MD simulation: