verl is a distributed training system designed for large language model alignment and reinforcement learning. It provides a framework for executing post-training pipelines, including supervised fine-tuning and reinforcement learning from human feedback, to refine model behavior and agentic capabilities.
The system utilizes a hybrid training and inference engine that optimizes memory and communication when switching between model generation and gradient updates. It supports multi-modal reinforcement learning for models processing both image and text data, and implements algorithms such as PPO and GRPO to align models using reward signals.
The architecture focuses on distributed scaling through expert parallelism, device-aware placement mapping, and memory resharding. It further reduces resource overhead via low-rank adaptation and decoupled computation dataflows, while providing modular interfaces to integrate with various training and inference engines.
The project includes tools for experiment tracking to log training metrics and performance data to external monitoring platforms.