The DRD2 dataset consists of 275,768 molecules represented as SMILES strings. In the beginning, we sample randomly 𝑁 0 = 10 molecules to 𝐷 0 and acquire their scores from the simulated chemist (oracle in the noise-free case). The rest of the molecules are used as 𝒰 in the simulated experiments. For the experiment with a human chemist, we randomly sample 10,000 molecules to 𝒰 to speed up the method. We use the existing data set for 𝒰 rather than molecules generated at previous rounds, to avoid collapsing to a local minimum due to very small initial data. Therefore, only the inner loop of iterations 𝑡 = 1, … , 𝑇 is needed. During interaction, we query in total 200 molecules from the simulated chemist in batches of 5 (𝑇 = 40).