Implementation Matters in Deep Policy Gradients: A Case Study on PPO and TRPO
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Cited by 54 in LLM alignment / RLHF / preference optimisation, but placed by its own abstract, which didn’t fit.
Abstract (arXiv)
We study the roots of algorithmic progress in deep policy gradient algorithms through a case study on two popular algorithms: Proximal Policy Optimization (PPO) and Trust Region Policy Optimization (TRPO). Specifically, we investigate the consequences of "code-level optimizations:" algorithm augmentations found only in implementations or described as auxiliary details to the core algorithm. Seemingly of secondary importance, such optimizations turn out to have a major impact on agent behavior. Our results show that they (a) are responsible for most of PPO's gain in cumulative reward over TRPO, and (b) fundamentally change how RL methods function. These insights show the difficulty and importance of attributing performance gains in deep reinforcement learning. Code for reproducing our results is available at https://github.com/MadryLab/implementation-matters .
Key facts. Cited by 184 papers in the map (data through 7 Oct 2026). First posted on arXiv 25 May 2020.
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Citing papers per year: 2020: 1; 2021: 17; 2022: 16; 2023: 30; 2024: 42; 2025: 37; 2026: 41.
184 papers.
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