[Hardware][Intel-Gaudi] Enable LoRA support for Intel Gaudi (HPU)

[SanjuCSudhakaran]

This PR enables support for LoRA on Intel Gaudi by adding HPU specific kernels in GaudiPunicaWrapper to handle LoRA computations more efficiently on the hardware.

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[jeejeelee]

Can we do it like CustomOp, where the punicawrapper remains unchanged, and we decide which ops to call based on the hardware? I think if we do it this way, it might have better extensibility.

[SanjuCSudhakaran]

GaudiPunicaWrapper is a class inherited from PunicaWrapper which does the following.

1. Overrides the functions add_lora, add_lora_packed_nslice and add_lora_logits.
2. Adds add_lora_embedding instead of add_expand to handle LoRA B embedding computation.

I'd to get a little more clarity on CustomOp .

I see that classes like RotaryEmbedding using CustomOp to automatically handle the forward pass based on the backend device. Here RotaryEmbedding is inherited from torch.nn.Module and CustomOp handles which forward pass to call.

But here neither PunicaWrapper nor the ops in it are torch.nn.modules. So to use CustomOp the ops in PunicaWrapper would have to be rewritten to torch.nn.Modules which requires a lot of refactoring.

@jeejeelee Please correct if I am missing something here.

[jeejeelee]

@SanjuCSudhakaran Thanks for your feedback.
I'm mainly considering that other hardware may need to support LoRA in the future. If we support it in your current way, it might lead to a lot of redundant conditionals. IMHO, the main difference between different hardware should be in the implementation of the 6 LoRA ops.
BTW, I actually have ideas and plans for extending LoRA support to other hardware. If you're interested, we can discuss this on Slack.