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vllm - 💡(How to fix) Fix [Bug]: FA4 causes `no module named 'flash_attn.ops'` [1 pull requests]

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Error Message

FA4 contains the module flash_attn but not flash_attn.ops.triton.rotary, causing the import error. A quick fix is to change the code to find_spec("flash_attn.ops.triton.rotary").

Fix Action

Fixed

Code Example

if not current_platform.is_cpu() and find_spec("flash_attn") is not None:
            from flash_attn.ops.triton.rotary import apply_rotary
RAW_BUFFERClick to expand / collapse

🐛 Describe the bug

vllm/model_executor/layers/rotary_embedding/common.py conditionally imports flash_attn.ops.triton.rotary by:

if not current_platform.is_cpu() and find_spec("flash_attn") is not None:
            from flash_attn.ops.triton.rotary import apply_rotary

FA4 contains the module flash_attn but not flash_attn.ops.triton.rotary, causing the import error. A quick fix is to change the code to find_spec("flash_attn.ops.triton.rotary").

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#memory optimization#batch processing#GPU compatibility#latency issue#model loading

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vllm - 💡(How to fix) Fix [Bug]: FA4 causes `no module named 'flash_attn.ops'` [1 pull requests]