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vllm/docs/features/speculative_decoding/mlp.md
2026-03-04 17:23:34 +00:00

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# MLP Draft Models
The following code configures vLLM to use speculative decoding where proposals are generated by draft models that condition draft predictions on both context vectors and sampled tokens. For more information see [The Hitchhiker's Guide to Speculative Decoding](https://pytorch.org/blog/hitchhikers-guide-speculative-decoding/) and [IBM Research's Technical Report](https://arxiv.org/abs/2404.19124).
## MLP Drafter Example
```python
from vllm import LLM, SamplingParams
prompts = ["The future of AI is"]
sampling_params = SamplingParams(temperature=0.8, top_p=0.95)
llm = LLM(
model="meta-llama/Meta-Llama-3.1-8B-Instruct",
tensor_parallel_size=1,
speculative_config={
"model": "ibm-ai-platform/llama3-8b-accelerator",
"draft_tensor_parallel_size": 1,
"method": "mlp_speculator",
},
)
outputs = llm.generate(prompts, sampling_params)
for output in outputs:
prompt = output.prompt
generated_text = output.outputs[0].text
print(f"Prompt: {prompt!r}, Generated text: {generated_text!r}")
```
!!! warning "Known issue"
`ibm-ai-platform/llama3-70b-accelerator` can fail with:
`AttributeError: 'MLPSpeculatorConfig' object has no attribute 'num_attention_heads'`.
Track status in [#34106](https://github.com/vllm-project/vllm/issues/34106)
and [#34163](https://github.com/vllm-project/vllm/pull/34163).
## Pre-Trained MLP Drafter Models
A variety of speculative models of this type are available on HF hub:
- [llama-13b-accelerator](https://huggingface.co/ibm-ai-platform/llama-13b-accelerator)
- [llama3-8b-accelerator](https://huggingface.co/ibm-ai-platform/llama3-8b-accelerator)
- [codellama-34b-accelerator](https://huggingface.co/ibm-ai-platform/codellama-34b-accelerator)
- [llama2-70b-accelerator](https://huggingface.co/ibm-ai-platform/llama2-70b-accelerator)
- [llama3-70b-accelerator](https://huggingface.co/ibm-ai-platform/llama3-70b-accelerator)
- [granite-3b-code-instruct-accelerator](https://huggingface.co/ibm-granite/granite-3b-code-instruct-accelerator)
- [granite-8b-code-instruct-accelerator](https://huggingface.co/ibm-granite/granite-8b-code-instruct-accelerator)
- [granite-7b-instruct-accelerator](https://huggingface.co/ibm-granite/granite-7b-instruct-accelerator)
- [granite-20b-code-instruct-accelerator](https://huggingface.co/ibm-granite/granite-20b-code-instruct-accelerator)