REINVENT REINVENT is an AI-based tool for molecular design and optimization. It contains three main components: a molecular generative model, a scoring function which scores the generated molecules based on a set of user-specified scoring criteria and produces a combined score as reward, and RL as a search algorithm to steer the generated model towards the chemical space with high reward. Additionally, to reduce the risk of mode collapse and encourage the diversity of the generated molecules, REINVENT uses a molecular memory system called the diversity filter (DF) with different implemented strategies. The DF penalizes the generation of identical compounds or compounds sharing the same scaffold that have been generated too often. The generative model acts as agent and describes the joint probability of generating a molecule represented by a token sequence T = t 1 , t 2 , . . . , t l given an input molecule token sequence X as