Understanding Reinforcement Learning for Model Training, and future directions with GRAPE

Fuente: arXiv
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Auteur principal: Patel, Rohit
Format: Preprint
Publié: 2025
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author Patel, Rohit
author_facet Patel, Rohit
contents This paper provides a self-contained, from-scratch, exposition of key algorithms for instruction tuning of models: SFT, Rejection Sampling, REINFORCE, Trust Region Policy Optimization (TRPO), Proximal Policy Optimization (PPO), Group Relative Policy Optimization (GRPO), and Direct Preference Optimization (DPO). Explanations of these algorithms often assume prior knowledge, lack critical details, and/or are overly generalized and complex. Here, each method is discussed and developed step by step using simplified and explicit notation focused on LLMs, aiming to eliminate ambiguity and provide a clear and intuitive understanding of the concepts. By minimizing detours into the broader RL literature and connecting concepts to LLMs, we eliminate superfluous abstractions and reduce cognitive overhead. Following this exposition, we provide a literature review of new techniques and approaches beyond those detailed. Finally, new ideas for research and exploration in the form of GRAPE (Generalized Relative Advantage Policy Evolution) are presented.
format Preprint
id arxiv_https___arxiv_org_abs_2509_04501
institution arXiv
publishDate 2025
record_format arxiv
spellingShingle Understanding Reinforcement Learning for Model Training, and future directions with GRAPE
Patel, Rohit
Computation and Language
Artificial Intelligence
Machine Learning
68T07, 68T05, 62M45, 68T50, 90C40
I.2.6; I.2.7
This paper provides a self-contained, from-scratch, exposition of key algorithms for instruction tuning of models: SFT, Rejection Sampling, REINFORCE, Trust Region Policy Optimization (TRPO), Proximal Policy Optimization (PPO), Group Relative Policy Optimization (GRPO), and Direct Preference Optimization (DPO). Explanations of these algorithms often assume prior knowledge, lack critical details, and/or are overly generalized and complex. Here, each method is discussed and developed step by step using simplified and explicit notation focused on LLMs, aiming to eliminate ambiguity and provide a clear and intuitive understanding of the concepts. By minimizing detours into the broader RL literature and connecting concepts to LLMs, we eliminate superfluous abstractions and reduce cognitive overhead. Following this exposition, we provide a literature review of new techniques and approaches beyond those detailed. Finally, new ideas for research and exploration in the form of GRAPE (Generalized Relative Advantage Policy Evolution) are presented.
title Understanding Reinforcement Learning for Model Training, and future directions with GRAPE
topic Computation and Language
Artificial Intelligence
Machine Learning
68T07, 68T05, 62M45, 68T50, 90C40
I.2.6; I.2.7
url https://arxiv.org/abs/2509.04501