Core Viewpoint - The article discusses the educational series on artificial intelligence initiated by Nando de Freitas, focusing on reinforcement learning (RL) and its applications in large language models (LLMs) [1][2]. Summary by Sections Introduction to AI Education - Nando de Freitas aims to educate readers on AI through a series of posts on X, starting with reinforcement learning and gradually covering diffusion and flow matching technologies [1][2]. Learning Types - The article highlights that there is no ultimate conclusion on unsupervised learning, supervised learning, and reinforcement learning [8][19]. - Supervised learning is described as basic imitation, requiring high-quality expert data for effective learning [9]. - Reinforcement learning focuses on selective imitation, allowing agents to learn from suboptimal experiences and improve their performance [10][11]. Distributed Reinforcement Learning Systems - Modern distributed RL systems consist of two main components: Actors and Learners, where Actors interact with the environment and collect data, while Learners update the policy network based on this data [23][24]. - The importance of measuring operational durations and communication bandwidth in such systems is emphasized [24][27]. Offline Reinforcement Learning - Offline RL has unique value in scenarios like post-training LLMs, where it can leverage historical data for learning [28][29]. Single-step and Multi-step RL - The article differentiates between single-step and multi-step RL problems, with single-step focusing on immediate actions and multi-step involving planning over a series of interactions [35][39]. - The complexity of multi-step RL is noted, particularly in credit assignment issues where multiple decisions affect outcomes [40][41]. Policy Gradient and Techniques - Policy gradient methods are discussed, including the use of baseline subtraction to reduce variance in reward signals [49][56]. - The article also covers the significance of KL divergence in maintaining proximity to supervised fine-tuning strategies during post-training [69]. Importance Sampling and PPO - Importance sampling is introduced as a method to correct off-policy sample bias, with Proximal Policy Optimization (PPO) being a key technique to manage policy updates [73][78]. - The integration of various techniques in training models like DeepSeek-R1 is highlighted, showcasing the complexity of modern RL systems [81]. Future Directions - Freitas plans to expand the discussion from single-step to multi-step RL, indicating ongoing developments in the field [82].