where is x and x ′ are binary fingerprint vectors, < •, • > is the Euclidean inner product, || • || 2 is the Euclidean norm and σ f is the scalar kernel signal amplitude hyperparameter. In accordance with the GAUCHE documentation, we initially applied the Tanimoto kernel to extended connectivity fingerprints (ECFP4, ECFP6) and bag-of-characters representations of SMILES and SELFIES strings. Note that the bag-of-characters representation was previously used in the SMILES string kernel .