• Authors: Zhi Zheng, Wee Sun Lee
• Institutes: School of Computing, National University of Singapore, Singapore;
• Resources: [📖Paper] [🏠Twitter] [🤗Huggingface]

📧 Welcome to feedback

We greatly appreciate your feedback and questions regarding the current status of this work.

Please feel free to contact Zhi Zheng at zhi.zheng@u.nus.edu

💡 Highlights

• 🔥 The First Powerful RLVR Algorithm for Soft-Thinking Reasoning: We introduce SofT-GRPO, a novel and powerful policy optimization algorithm designed for reinforcing the soft-thinking reasoning paradigm in LLMs.

• ⚙️ Gumbel-Softmax Noise in Rollout: It integrates the Gumbel-Softmax technique into the group rollout process, actively obtaining diverse but valid soft-thinking reasoning paths.

• ⚙️ Gumbel Reparameterization: We propose an innovative gradient estimation approach via Gumbel reparameterization, enabling precise attribution of improvements to the LLM’s output probability distributions in policy optimization.

• 📝 Comprehensive Experiments and High Effectiveness: We conduct comprehensive experiments across LLMs of 1.5B–7B parameters on five benchmarks, demonstrating that SofT-GRPO consistently outperforms the discrete-token GRPO baselines, especially at higher sample rates (Pass@16 and Pass@32). SofT-GRPO can also improve the out-of-Domain generalization ability of LLMs.

• 🔥 Showing the Prospects of Soft-Thinking: Can Soft-Thinking be the Answer for Better Effectiveness?

📜 News

[2025/9/24] Code, Weight, and Paper are released!

👨‍💻 Todo

• SGLang & verl Code Modification (e.g., activate the overlap for efficiency).

🛠️ Usage

1. Clone the repository

git clone https://github.com/zz1358m/SofT-GRPO-master
cd SofT-GRPO-master

2. Install dependencies

Option 1: For inference only,

conda create -n soft_grpo python=3.11.13 -y && conda activate soft_grpo
pip install pip==25.2
pip install torch==2.6.0 transformers==4.51.1 tensorboard==2.20.0 sgl_kernel==0.1.1 accelerate==1.10.1 torch_memory_saver==0.0.8 uvloop==0.21.0 jsonlines math_verify openai
pip install flash_attn==2.7.3  --no-build-isolation # may take more time (20min). try `pip install flash_attn==2.7.3 --no-build-isolation` if find undefined symbol bug, or try downloading from its official github.

cd Soft-Thinking+noise+loss-main/sglang_soft_thinking_pkg
pip install -e "python[all]"
cd ../..

Option 2: For inference & SofT-GRPO fine-tuning,

building the verl-0.4.x after doing the Option1.

cd verl-0.4.x
pip3 install -e .
cd ..

or trying to install requirements. (not recommended)

pip install -r requirements.txt

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3. Evaluating SofT-GRPO fine-tuned LLMs with soft-thinking pattern

Step 1: Download the SofT-GRPO, GRPO, weights from [🤗Huggingface]

Step 2: Evaluating GRPO under the discrete-token CoT pattern.

./Soft-Thinking+noise+loss-main/run_sample_discrete-token_grpo.sh

Step 3: Evaluating GRPO under the soft-thinking reasoning pattern.

./Soft-Thinking+noise+loss-main/run_sample_gumbel_grpo.sh

Step 3: Evaluating SofT-GRPO under the soft-thinking reasoning pattern.

./Soft-Thinking+noise+loss-main/run_sample_gumbel.sh

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4. Training with SofT-GRPO

Option 1: Train the SofT-GRPO on DeepSeek-R1-Distill-Qwen-1.5B

./SofT-GRPO-deepscaler-8k.sh # change the LLM path, dataset path accordingly

Option 2: Train the SofT-GRPO on DeepSeek-R1-Distill-Qwen-7B

./SofT-GRPO-deepscaler-8k-qwen7.sh # change the LLM path, dataset path accordingly

Option 3: Train the SofT-GRPO on Llama-3.2-3B-Instruct

./SofT-GRPO-deepscaler-8k-llama3.sh # change the LLM path, dataset path accordingly

✒️ Citation

If you find our work helpful for your research, please consider giving a star ⭐ and citation 📝

@article{zheng2025soft,
  title={SofT-GRPO: Surpassing Discrete-Token LLM Reinforcement Learning via Gumbel-Reparameterized Soft-Thinking Policy Optimization},
  author={Zheng, Zhi and Lee, Wee Sun},
  journal={arXiv preprint arXiv:2511.06411},
  year={2025}
}

❤️ Acknowledgments

• Soft-Thinking: The codebase we built upon. Thanks for their wonderful work.
• verl-0.4.x: Our work is based on this codebase as well.
• SIM-CoT: We use their template for README.md!
• Yu Gu: Undergraduate student from Nanjing University, volunteer for helping in code re-organization!