You can implement LoRA-based fine-tuning for a 7B-parameter model using PyTorch by injecting low-rank adapters into the attention layers and updating only those parameters during training.
Here is the code snippet below:

In the above code, we are using the following key points:
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LoRA is injected into linear layers within attention blocks by wrapping them with low-rank adapters.
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Original weights are frozen to reduce trainable parameter count.
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Scaling is used to balance low-rank updates with frozen base outputs.
Hence, LoRA fine-tuning enables efficient training of large models by updating only a small number of additional parameters.