one is used to generate pseudo-molecular coordinates; the other to generate pseudo-latent variables (Figure ). Compared to canonical GAN model, implementation of an additional GAN for generation of pseudo-latent variables greatly enhances the model's capability of estimating probability density. In the coordinate space 𝑿, the generator 𝑮 𝒁→𝑿 takes the latent space variable To test the BGAN-EPS method, we employed cyclopentadiene (CP) dimerization as the model reaction (Figure ). The reaction was previously used by our group to benchmark EPS method. The reaction involves a bispericyclic (later called ambimodal) transition state structure (TSS) with C2-symmetry. The TSS initiates a symmetric post-TS bifurcation, which leads to two identical dimerized products with different bonding connectivity (i.e., formation of Bond 2 or 3, Figure ). Notably, the reaction dynamics trajectories of CP dimerization were also studied by Singleton and coworkers to understand Newtonian kinetic isotope effects , and by Houk and coworkers to investigate the dynamic basis of "two-stage" mechanism 47 . Using BGAN-EPS method, we tested whether a few hundred trajectories of CP dimerization can generate entropic profiles that are sufficiently similar to the reference entropic profiles calculated from 2,480 reaction dynamics trajectories. Two metrics were examined, including: 1) the similarity between two entropic profiles that lead to formally identical dimerized products with different bonding connectivity (i.e., Bond 2 vs. Bond 3, Figure ), and 2) the depth of entropic trap (i.e., -0.7 kcal/mol based on the reference) along the dynamic reaction path. Figure shows the comparison of entropic profiles of CP dimerization calculated using two different methods: EPS (top, Figure ) and BGAN-EPS (bottom, Figure ). In both cases, the entropic profiles were derived from 124 randomly selected trajectories -they were compared against the reference entropic profiles calculated from 2,480 trajectories. Using 124 trajectories, the EPS-derived entropic profiles qualitatively preserve two general features shared by the reference entropic profiles: 1) the presence of entropic maxima along the post-TS pathway and 2)