Memory savings

4-bit vs 16-bit base = 4x reduction. Adapter minimal. 65B fine-tune on single 48GB GPU. 7B on 12GB.

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NF4 quantization

Normal Float 4: quantile-based scheme optimized for normal-distributed weights. Better than uniform 4-bit.

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Double quantization

Also quantize quantization constants. Small additional saving. Standard in QLoRA.