DAPO: An Open-Source LLM Reinforcement Learning System at Scale

It introduces DAPO, a fully open-source, large-scale RL system that boosts the chain-of-thought reasoning capabilities of LLMs. DAPO raises the upper clipping threshold (“Clip-Higher”) in PPO-style training, preventing entropy collapse and helping the policy explore more diverse tokens. By filtering out samples that are always correct or always wrong, DAPO focuses training on prompts with useful gradient signals, speeding up convergence in fewer updates. Instead of averaging losses at the sample level, DAPO applies policy gradients per token, making each reasoning step matter. This ensures both high-quality and length-appropriate outputs. The system masks or softly penalizes excessively long answers, preventing meaningless verbosity or repetitive text. DAPO achieves SOTA math performance on the AIME 2024 test set. Specifically, DAPO trained from a Qwen2.5-32B base achieves 50% accuracy, outperforming DeepSeek’s R1 with less training time, and showcasing open-source reproducibility at scale.