4) Here, sim(m i , m j ) denotes the similarity between the i th and j th molecules. Any metric can be used here. We use Tanimoto similarity, which has shown to be a good measure for molecules . The standard fingerprints from RDKIT 2019 were used for this step. As this metric depends on the set size, standardizing the plot with a set size is important. Each set used for SSD computation has 300 molecules unless specified otherwise. We were now able to quantify the possible variation in our molecules mathematically. Figure shows self-similarity distribution (SSD) of a set in the vacuum with no training, thus forming the baseline.