Leverage the HF cache for models

[byjlw]

🚀 The feature, motivation and pitch

torchchat currently uses the hf hub which has it's own model cache, torchchat copies it into it's own model directory so you end up two copies of the same model.

We should leverage the hf hub cache but not force users to use that location if they're using their own models.

Alternatives

No response

Additional context

From r/localllama
"One annoying thing is that it uses huggingface_hub for downloading but doesn't use the HF cache - it uses it's own .torchtune folder to store models so you just end up having double of full models (grr). Just use the defaul HF cache location.”

RFC (Optional)

No response

[orionr]

Great job bringing these back as issues! Is this also a problem with torchtune given that we're using .torchtune for this? cc @kartikayk ?

[vmpuri]

Going to add that we can use hf_transfer to "potentially double the download speed"
https://huggingface.co/docs/hub/models-downloading
https://huggingface.co/docs/huggingface_hub/v0.25.1/package_reference/environment_variables#hfhubenablehftransfer

This is an option to use a rust-based downloader. HF claims it's production ready, but just has a slightly worse UX. The 80/20 of this is that a majority people should get much faster download speeds (super useful for LLMs), and those who run into errors could fallback to the Python implementation with a quick pip install