Heuristic:Hpcaitech ColossalAI Warning Deprecated Ray Detached PPO

Knowledge Sources	ColossalAI Ray README Warning
Domains	RLHF, Distributed_Training
Last Updated	2026-02-09 12:00 GMT

Overview

Deprecation warning for the legacy Ray-based detached PPO training pipeline in `coati/ray/`, which has been superseded by the `coati/distributed/` framework.

Description

The coati/ray/ module implements an older distributed PPO training architecture using Ray remote actors (DetachedTrainer, ExperienceMakerHolder, DetachedReplayBuffer). The module's own README explicitly warns: "This content may be outdated since the major update of Colossal Chat."

The newer coati/distributed/ module provides the current recommended approach with Producer/Consumer patterns, Zero Bubble pipeline parallelism, and GRPO support.

Usage

Be aware of this deprecation when encountering any of the legacy Ray detached PPO components. Prefer the coati/distributed/ module for new distributed RLHF training workflows. The legacy Ray module may still work but is not actively maintained.

The Insight (Rule of Thumb)

Action: Use `coati.distributed.launch` or `coati.distributed.launch_zero_bubble` instead of the legacy Ray-based detached trainers.
Value: The new distributed framework supports GRPO, Zero Bubble pipeline parallelism, and modern producer-consumer patterns.
Trade-off: The legacy Ray module may be needed for backward compatibility with existing setups, but new projects should adopt the distributed module.

Reasoning

The `coati/ray/README.md` explicitly marks its content as potentially outdated. The `coati/distributed/` module was developed as a replacement, offering improved performance through Zero Bubble scheduling and supporting newer algorithms like GRPO alongside PPO. The newer module uses Ray under the hood but with a modernized architecture.

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