where L denotes the number of tokens associated to t i , and [t iℓ ] denotes the index Figure : Two pairs of molecules (s 1 , t 1 ), (s 2 , t 2 ) with Tanimoto similarity 0.71 and 0.76, respectively are shown. In the left example NLL 2 > NLL 1 , therefore the regularization term Ω (see Equation ) is greater than 0. In the right example NLL 1 > NLL 2 . In this case, Ω = 0 as the similarities and NLLs have the same rank-order.