v0.2 release

Highlights

New algorithms and features

• GRPO
• ReMax
• REINFORCE++
• Checkpoint manager for FSDP backend
• Sandbox for reward verification and scoring in PRIME

Performance optimization:

• Remove padding tokens (i.e. sequence packing). Significant throughput increase expected for Llama, Mistral, Gemma, Qwen2 transformer models. Documentation

actor_rollout_ref.model.use_remove_padding=True
critic.model.use_remove_padding=True

• Dynamic batch size. Significant throughput increase for variable length sequences. Documentation and example

actor_rollout_ref.actor.ppo_max_token_len_per_gpu
actor_rollout_ref.rollout.log_prob_max_token_len_per_gpu
actor_rollout_ref.ref.log_prob_max_token_len_per_gpu
critic.ppo_max_token_len_per_gpu
critic.forward_micro_batch_size_per_gpu
reward_model.forward_micro_batch_size_per_gpu

• Sequence parallelism for long context training. Documentation and example

actor_rollout_ref.actor.ulysses_sequence_parallel_size
critic.ulysses_sequence_parallel_size
reward_model.ulysses_sequence_parallel_size

• vllm v0.7+ integration (preview). For the qwen2 ppo example, 25% time reduction in rollout compared to v0.6.3, and 45% time reduction when cuda graph is enabled. Documentation

actor_rollout_ref.rollout.enforce_eager=False
actor_rollout_ref.rollout.free_cache_engine=False

• Liger-kernel integration for SFT. Documentation

model.use_liger=True

Changelog

New Features

1. Algorithm Support:

   • Added support for GRPO algorithm (#124).
   • Implemented REINFORCE++ algorithm (#228).
   • Added ReMax algorithm (#234)

2. Performance Improvements:

   • Enabled dynamic batch size support (#118).
   • Added meta device initialization and parallel load for FSDP to avoid OOMs during init (#123).
   • Improved gradient accumulation in sequence balance (#141).
   • Added ref/RM offload support (#121).
   • Added LoRA support for SFT (#127).
   • feat: spport rmpad/data-packing in FSDP with transformers (#91)
   • Liger kernel integration (#133)

3. Experiment Tracking:

   • Integrated SwanLab for experiment tracking with online/offline mode and local dashboard support (#218).
   • Added Mlflow support (#74).

---

Bug Fixes

1. Critical Fixes:

   • Fixed checkpoint save with existing directories (#174).
   • Fixed incorrect response_attention_mask in vLLM rollout (#213).
   • Fixed gradient accumulation loss value (#102).
   • Fixed reward model issues with TokenClassification models (#99).

2. Code Fixes:

   • Fixed redundant non_zero_mask (#152).
   • Fixed validation dp_size (#90).
   • Fixed response_mask index (#60).

---

Improvements

1. Performance:

   • Improved memory efficiency in logprobs_from_logits_v2 (#220).
   • Enabled multiprocess dataloader in SFT trainer (#122).
   • Added MFU calculation support (#117).

2. Miscellaneous:

   • Added option to log validation generations to wandb (#177).

---

Deprecations and Breaking Changes

1. Breaking Changes:
   • Changed micro_batch_size to micro_batch_size_per_gpu (#136).
   • Removed @ray.remote on workers to allow inheritance (#61).
   • Refactored old_log_prob into a separate function (#129).

---

Contributors

A big thank you to all the contributors who made this release possible:
@zhanluxianshen @xingyaoww @fzyzcjy @emergenz @openhands-agent @ZSL98 @YSLIU627 @ZefanW @corbt @jaysonfrancis @hiyouga @Jiayi-Pan @hongpeng-guo @eltociear @chujiezheng @PanAndy @zwhe99 @pcmoritz @huiyeruzhou @VPeterV @uygnef @zhiqi-0 @ExtremeViscent @liziniu @nch0w @Cppowboy @TonyLianLong @4332001876 @tyler-romero @ShaohonChen @kinman0224 @willem-bd @bebetterest @WeiXiongUST @dignfei

---

Pypi package will be soon available! Please let us know on Github if there's a problem extending RL training recipe based on the pip installed version fo verl.

Full Changelog: v0.1...v0.2