S is the reward function assessing the desirability of a sampled molecule and σ is a hyperparameter that scales the reward. A higher σ places a greater contribution on the reward function and less on the Prior. The Prior is used to ensure generated SMILES are syntactically correct and has been empirically shown to enforce reasonable chemistry. The loss function is defined as the squared difference between the Augmented Likelihood and the Agent Likelihood for a given batch, B, of sampled SMILES constructed following the actions, a ∈ A * (Equation ):