Distributed RL Framework for Language Model Fine-Tuning

This repository implements a distributed Reinforcement Learning (RL) training framework designed to fine-tune large language models using algorithms such as GRPO and DAPO. It supports multi-node and multi-GPU setups, scalable rollout generation, and policy optimization using libraries like VLLM. Currently, we support two Reinforcement Learning with Verifiable Reward (RLVR) tasks: solving math problems and code generation.

Please note that we are still under intensive development, stay tuned.

🚀 Features

• Distributed Training with Ray: Scalable to multiple machines and GPUs.
• Support for GRPO and DAPO: Choose your preferred policy optimization algorithm.
• Model Backends: Support vllm as inference backends.
• Rollout and Policy Decoupling: Efficient generation and consumption of data through parallel inferencer-trainer architecture.
• Evaluation Integration: Easily plug in task-specific eval datasets.
• Checkpoints and Logging: Configurable intervals and directories.
• [New]: Zero Bubble training framework that supports GRPO and DAPO. (read more)

🛠 Installation

Prepare Develop Environment

Install Colossalai & ColossalChat

git clone https://github.com/hpcaitech/ColossalAI.git
git checkout grpo-latest
BUILD_EXT=1 pip install -e .

cd ./applications/ColossalChat
pip install -e .

Install vllm

pip install vllm==0.7.3

Install Ray.

pip install ray

Install Other Dependencies

pip install cupy-cuda12x
python -m cupyx.tools.install_library --cuda 12.x --library nccl

To support long input/output sequence length (e.g., 32K), you may need to manually change the default setting (180 seconds) for the timeout_s variable in your ray installation to a larger value as shown in the screenshot below.

Prepare Model & dataset

huggingface-cli download --local-dir-use-symlinks False Qwen/Qwen2.5-7B --local-dir /models/Qwen/Qwen2.5-7B

Architecture Design

• Producer: inference engine which rollouts out examples and saves them into a shared buffer.
• Consumer: training framework which takes training examples from the shared buffer and train the policy model.

Key features for Producer-Consumer Pattern:

• Buffer: Acts as a shared queue where the producer adds data and the consumer removes data.
• Concurrency: Rollout and training can work concurrently.

🧠 Data Format

Samples in the training or evaluation .jsonl file should follow the format specific to the type of task. We currently support two RLVR tasks: solving math problems and code generation.

Math Data Format

{
  "messages": {
    "role": "user",
    "content": "Simplify $\\sqrt[3]{1+8} \\cdot \\sqrt[3]{1+\\sqrt[3]{8}}$."
  },
  "gt_answer": "3"
}

Code Data Format

We support Prime code dataset format. Inputs and outputs in test cases should be two lists containing only strings and matching in the number of elements. Your prompt must properly instruct the LLM to generate code to read test cases from stdin and output results to stdout.

{
    "messages": {
        "role": "user",
        "content": "Solve the following coding problem using the programming language python:\n\nMikhail walks on a Cartesian plane. He starts at the point $(0, 0)$, and in one move he can go to any of eight adjacent points. For example, ..."
    },
    "test_cases": {
        "inputs": [
            "3\n2 2 3\n4 3 7\n10 1 9\n"
        ],
        "outputs": [
            "1\n6\n-1\n"
        ]
    }
}

⚙️ Hyperparameters & Arguments

Distributed Training

Sampling

GRPO Specific

Logging and Checkpointing

Miscellaneous

⚙️ GRPO Settings

In addition to the two default training settings provided—GRPO and DAPO—users can customize their training by changing the following hyperparameters in grpo_config in rl_example.py.

🔄 Constraints and Notes

• num_inferencer + num_trainer == NUM_GPUs

• num_inferencer % num_trainer == 0

• (num_inferencer * inference_batch_size) % (num_trainer * train_batch_size) == 0

• train_batch_size >= train_minibatch_size >= train_microbatch_size

• inference_batch_size >= inference_microbatch_size

• Set microbatch sizes based on VRAM capacity

• To use tensor parallelism on inferencer

  • set backend to vllm
  • change tensor_parallel_size in inference_model_config in rl_example.py
  • set num_inferencer = NUM_INFERENCE_GPUs / tensor_parallel_size

• To set tensor parallelism / pipeline parallelism / zero stage

  • change corresponding settings in plugin_config in rl_example.py

• Ensure rollout generation rate matches trainer consumption:

  Copy

  num_inferencer * inference_batch_size % (
    num_trainer * train_batch_size /
    train_pipeline_parallelism_size /
    train_tensor_parallelism_size
  ) == 0
  

• Model weights sync every:

  Copy

  (num_inferencer * inference_batch_size) /
  (num_trainer * train_batch_size /
    train_pipeline_parallelism_size /
    train_tensor_parallelism_size)
  

• Reward Type

  We currently support three reward types--- think_answer_tags, boxed, code, each varies in details such as how answer is extracted and the reward calculation process. Please select one from think_answer_tags, boxed for math problem solving and use code for code generation. The default system prompt for each reward type is as follows. Please make sure your system prompt provides information for the answer to be correctly extracted from model responses.

  • think_answer_tags

    Answer extraction: extract the content between the last <answer>, </answer> tags.

    Copy

    You are a helpful assistant. The assistant first thinks about the reasoning process in the mind and then provides the user with the answer. The reasoning process and answer are enclosed within <think> </think> and<answer> </answer> tags, respectively, i.e., <think> reasoning process here </think><answer> answer here </answer>. Now the user asks you to solve a math problem that involves reasoning. After thinking, when you finally reach a conclusion, clearly output the final answer without explanation within the <answer> </answer> tags, i.e., <answer> 123 </answer>.\n\n
    

  • boxed

    Answer extraction: extract the last content marked by \\boxed{}

    Copy

    Please reason step by step, and put your final answer within \\boxed{}.
    

  • code

    Answer extraction: extract code inside ```python\n...```

    Copy

    You are a helpful assistant.
    

🧪 Example: single machine 8-GPU Zero2 Strategy

python rl_example.py \
  --dataset /path/to/train_data.jsonl \
  --model /path/to/Qwen2.5-3B/ \
  -t 4 -i 4 \
  -b vllm \
  -ibs 2 -tbs 4 -tMbs 1 -tmbs 4 -imbs 1 \
  -rt boxed \
  -g 4 \
  -ibs 1 \
  -tbs 2 \
  -tMbs 1 \
  -tmbs 2 \
  -imbs 1 \
  -s "Please reason step by step, and put your final answer within \\boxed{}." \
  -tMbs 8 \
  -p GRPO-Train-Align-Debug \

🧪 Example: multi-machine TP+PP Strategy

Create ray cluster on multi-machine

For example, now we have 4 nodes and their IPs are 10.0.0.3, 10.0.0.4, 10.0.0.5, 10.0.0.6. We use 10.0.0.3 as master node. First we start a ray cluster on 10.0.0.3:

ray start --head --node-ip-address=10.0.0.3

Then, for each slave node (10.0.0.4/10.0.0.5/10.0.0.6), we add to the ray cluster by following code:

ray start --address='10.0.0.3:6379'

Modify plugin_config in ./applications/ColossalChat/rl_example.py

plugin_config={
  "tp_size": 4,
  "pp_size": 2,
  "microbatch_size": max(
    1, args.train_microbatch_size // 2
  ),  # microbatch size should be set to train_microbatch_size // pp_size
  "zero_stage": 1,
  "max_norm": 1.0,
  },  # for pp, tp

# Hint1: replace /models/Qwen/Qwen2.5-7B to your model path
#        replace /datasets/train-alignment.jsonl to your dataset path
python rl_example.py
  -m /path/to/Qwen2.5-Math-7B/ \
  -d /path/to/train_data.jsonl \
  --master_address '10.0.0.3'
  -t 16 \
  -i 16 \
  -p GRPO-Train-Align-Debug \
  -g 2 \
  -ibs 1 \
  -tbs 2 \
  -tMbs 1 \
  -tmbs 2 \
  -imbs 1 \
  -b vllm \
  -e 2 \
  -rt boxed \
  -s "Please reason step by step, and put your final answer within \\boxed{}."

Acknowledgement

Colossal-RL is a distributed version of ColossalChat and inspired by a few awesome open-source projects. We would like to express our gratitude to the following awesome open-source projects and algorithms: GRPO, DAPO, TRL, Verl, OpenRLHF, StreamRL, Qwen, Logic-RL.