[Installation]: vllm-flash-attn's pytorch is not compatible with vllm 0.6.5's

[jfcherng]

Your current environment

As the title, vllm-flash-attn pins torch==2.4.0 but vllm 0.6.5 requires torch==2.5.1.

How you are installing vllm

$ uv pip install vllm==0.6.5 vllm-flash-attn
  × No solution found when resolving dependencies:
  ╰─▶ Because vllm==0.6.5 depends on torch{platform_machine != 'aarch64'}==2.5.1 and
      vllm-flash-attn>=2.6.1 depends on torch==2.4.0, we can conclude that vllm==0.6.5 and
      all of:
          vllm-flash-attn==2.6.1
          vllm-flash-attn==2.6.2
       are incompatible. (1)

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[noooop]

LOL

Turn to serious face:

from #8245

vllm-flash-attn is compiled together with vllm instead of separately.
So you do not need to install vllm-flash-attn separately.

Obviously, the subsequent cmake files in the vllm-flash-attn warehouse were not updated along with vllm,
so now there is no way to install vllm-flash-attn separately.

[jfcherng]

vllm-flash-attn is compiled together with vllm instead of separately.

Even better. Thank you @noooop :)

[jfcherng]

I guess my issue has been resolved/clarified.