| --- |
| license: mit |
| library_name: transformers |
| pipeline_tag: text-generation |
| tags: |
| - dflash |
| - speculative-decoding |
| - block-diffusion |
| - draft-model |
| - efficiency |
| - qwen |
| - diffusion-language-model |
| --- |
| |
| # Qwen3.6-35B-A3B-DFlash |
|
|
| [**Paper**](https://arxiv.org/abs/2602.06036) | [**GitHub**](https://github.com/z-lab/dflash) | [**Blog**](https://z-lab.ai/projects/dflash/) |
|
|
| **DFlash** is a speculative decoding method that uses a lightweight **block diffusion** model to draft multiple tokens in parallel. This is the drafter model, which must be paired with [Qwen/Qwen3.6-35B-A3B](https://huggingface.co/Qwen/Qwen3.6-35B-A3B). |
|
|
| <div align="center"> |
| <img src="assets/dflash_system.png" alt="DFlash Architecture" width="85%"> |
| </div> |
|
|
| ## Quick Start |
|
|
| ### Installation |
|
|
| vLLM: |
| ```bash |
| uv pip install vllm |
| uv pip install -U vllm --torch-backend=auto --extra-index-url https://wheels.vllm.ai/nightly |
| ``` |
|
|
| SGLang: |
| ```bash |
| uv pip install "git+https://github.com/sgl-project/sglang.git@refs/pull/20547/head#subdirectory=python" |
| ``` |
|
|
| ### Launch Server |
|
|
| vLLM: |
| ```bash |
| vllm serve Qwen/Qwen3.6-35B-A3B \ |
| --speculative-config '{"method": "dflash", "model": "z-lab/Qwen3.6-35B-A3B-DFlash", "num_speculative_tokens": 15}' \ |
| --attention-backend flash_attn \ |
| --max-num-batched-tokens 32768 |
| ``` |
|
|
| SGLang: |
| ```bash |
| # Optional: enable schedule overlapping (experimental, may not be stable) |
| # export SGLANG_ENABLE_SPEC_V2=1 |
| # export SGLANG_ENABLE_DFLASH_SPEC_V2=1 |
| # export SGLANG_ENABLE_OVERLAP_PLAN_STREAM=1 |
| |
| python -m sglang.launch_server \ |
| --model-path Qwen/Qwen3.6-35B-A3B \ |
| --speculative-algorithm DFLASH \ |
| --speculative-draft-model-path z-lab/Qwen3.6-35B-A3B-DFlash \ |
| --speculative-num-draft-tokens 16 \ |
| --tp-size 1 \ |
| --attention-backend fa3 \ |
| --mem-fraction-static 0.75 \ |
| --mamba-scheduler-strategy extra_buffer \ |
| --trust-remote-code |
| ``` |
| > **Tip:** For long-context or agentic workloads, add `--speculative-dflash-draft-window-size WINDOW_SIZE` to enable sliding-window attention for the drafter. |
| |
| ### Usage |
| |
| ```python |
| from openai import OpenAI |
| |
| client = OpenAI(base_url="http://localhost:30000/v1", api_key="EMPTY") |
| |
| response = client.chat.completions.create( |
| model="Qwen/Qwen3.6-35B-A3B", |
| messages=[{"role": "user", "content": "Write a quicksort in Python."}], |
| max_tokens=4096, |
| temperature=0.0 |
| ) |
| print(response.choices[0].message.content) |
| ``` |
| |
| ## Benchmark Results |
|
|
| **Setup:** Single NVIDIA B200, SGLang, thinking enabled, max output length 4096. We report end-to-end throughput, including prefill time. See our [GitHub repository](https://github.com/z-lab/dflash) for reproduction scripts. |
|
|
| ### Throughput and Speedup |
|
|
| DFlash achieves up to **2.9x** speedup at concurrency 1. |
|
|
| _Tokens/sec (speedup vs. autoregressive baseline)_ |
|
|
| **Block Size = 16** |
| | Task | Concurrency | AR | **DFlash** | |
| |---|---:|---:|---:| |
| | Math500 | 1 | 234 | **682 (2.9x)** | |
| | | 8 | 1266 | **3138 (2.5x)** | |
| | | 16 | 1954 | **4813 (2.5x)** | |
| | | 32 | 2755 | **6520 (2.4x)** | |
| | GSM8K | 1 | 235 | **556 (2.4x)** | |
| | | 8 | 1236 | **2564 (2.1x)** | |
| | | 16 | 1886 | **3821 (2.0x)** | |
| | | 32 | 2699 | **5239 (1.9x)** | |
| | HumanEval | 1 | 238 | **603 (2.5x)** | |
| | | 8 | 1255 | **2800 (2.2x)** | |
| | | 16 | 1944 | **4208 (2.2x)** | |
| | | 32 | 2767 | **5782 (2.1x)** | |
| | MBPP | 1 | 235 | **559 (2.4x)** | |
| | | 8 | 1224 | **2538 (2.1x)** | |
| | | 16 | 1948 | **3816 (2.0x)** | |
| | | 32 | 2780 | **5378 (1.9x)** | |
| | MT-Bench | 1 | 233 | **442 (1.9x)** | |
| | | 8 | 1238 | **2028 (1.6x)** | |
| | | 16 | 1885 | **2997 (1.6x)** | |
| | | 32 | 2633 | **4034 (1.5x)** | |
| | Alpaca | 1 | 235 | **393 (1.7x)** | |
| | | 8 | 1221 | **1782 (1.5x)** | |
| | | 16 | 1844 | **2567 (1.4x)** | |
| | | 32 | 2579 | **3689 (1.4x)** | |
|
|
| **Block Size = 8** |
| | Task | Concurrency | AR | **DFlash** | |
| |---|---:|---:|---:| |
| | Math500 | 1 | 234 | **617 (2.6x)** | |
| | | 8 | 1266 | **2839 (2.2x)** | |
| | | 16 | 1954 | **4465 (2.3x)** | |
| | | 32 | 2755 | **6614 (2.4x)** | |
| | GSM8K | 1 | 235 | **540 (2.3x)** | |
| | | 8 | 1236 | **2466 (2.0x)** | |
| | | 16 | 1886 | **3899 (2.1x)** | |
| | | 32 | 2699 | **5713 (2.1x)** | |
| | HumanEval | 1 | 238 | **561 (2.4x)** | |
| | | 8 | 1255 | **2655 (2.1x)** | |
| | | 16 | 1944 | **4135 (2.1x)** | |
| | | 32 | 2767 | **6059 (2.2x)** | |
| | MBPP | 1 | 235 | **497 (2.1x)** | |
| | | 8 | 1224 | **2324 (1.9x)** | |
| | | 16 | 1948 | **3636 (1.9x)** | |
| | | 32 | 2780 | **4884 (1.8x)** | |
| | MT-Bench | 1 | 233 | **438 (1.9x)** | |
| | | 8 | 1238 | **2060 (1.7x)** | |
| | | 16 | 1885 | **3182 (1.7x)** | |
| | | 32 | 2633 | **4720 (1.8x)** | |
| | Alpaca | 1 | 235 | **407 (1.7x)** | |
| | | 8 | 1221 | **1880 (1.5x)** | |
| | | 16 | 1844 | **2903 (1.6x)** | |
| | | 32 | 2579 | **4115 (1.6x)** | |
|
|
| ### Acceptance Length |
|
|
| | Task | B8 | B16 | |
| |---|---:|---:| |
| | Math500 | 5.56 | 7.35 | |
| | GSM8K | 5.21 | 6.73 | |
| | HumanEval | 5.09 | 6.44 | |
| | MBPP | 4.78 | 5.83 | |
| | MT-Bench | 4.20 | 5.14 | |
| | Alpaca | 3.94 | 4.62 | |
|
|
|
|
| ## Acknowledgements |
|
|
| Special thanks to [David Wang](https://davidwa.ng/) for his outstanding engineering support on this project. We are also grateful to [Modal](https://modal.com/), [InnoMatrix](https://innomatrix.ai), and [Yotta Labs](https://www.yottalabs.ai/) for providing the compute resources used to train this draft model. |
|
|
| ## Citation |
|
|
| If you find DFlash useful, please cite our work. To share feedback on DFlash or request new model support, please fill out this form: [DFlash Feedback](https://forms.gle/4YNwfqb4nJdqn6hq9). |
|
|
| ```bibtex |
| @article{chen2026dflash, |
| title = {{DFlash: Block Diffusion for Flash Speculative Decoding}}, |
| author = {Chen, Jian and Liang, Yesheng and Liu, Zhijian}, |
| journal = {arXiv preprint arXiv:2602.06036}, |
| year = {2026} |
| } |
| ``` |