Efficient Fine-Tuning for Large Models: LoRA, CIAT, and QLoRA | CMU 11-868 Lecture 23
Lecture 23 of 11-868 treats fine-tuning as a memory problem. Full-parameter half-precision fine-tuning of LLaMA-8B needs about 80GB. LoRA brings that to about 33GB, and QLoRA, which stores the frozen weights in 4 bits, gets it to about 9.2GB. The lecture moves in three steps: train only two small low-rank matrices A and B (the slides credit CIAT as the first to do this); squeeze frozen weights to about 0.52 bytes per parameter with an NF4 lookup table and double quantization; and use a paged optimizer to push optimizer state to the CPU when the GPU is about to run out.