where 𝑦 𝑡 𝑘 represents the model output for the k-th token at time t, and i iterates over the set K, which encompasses all tokens. The token sampling process is regulated by the temperature parameter T. In this study, the start and end tokens for SMILES strings were denoted by "G" and "E" respectively. The key difference between the pre-trained model and traditional RNNs is that the pre-trained model consists of two RNNs that estimate two conditional probability distributions for the forward and backward directions as follows