QLoRA

[cuichenx]

What does this PR do ?

Add QLoRA

Current Results

Convergence

Llama 7b, Squad, packed seq 2k, LoRA on all layers
gbs4, 2e-4, 2k iterations
exact_match 89.199 f1 94.791 rougeL 94.400 total 6064.000

Normal LoRA (qkv only)
exact_match 88.819 f1 94.415 rougeL 94.084 total 6064.000

Memory Usage

Llama 13b, Alpaca, seq len 512, LoRA on all layers, gbs256
Peak memory reserved (GB):

Batch Size	LoRA	QLoRA	% Reduction
2	37.5	18.3	51%
4	46.7	27.4	41%
8	65.4	46.4	29%

Performance

Llama 13b, Alpaca, seq len 512, LoRA on all layers, gbs256
Global batch step timing (s):

Batch Size	LoRA	QLoRA	% Increase
2	2.7	6.7	148%
4	2.3	4.4	91%
8	2.2	3.2	46%

Collection: NLP

Changelog

• Add specific line by line info of high level changes in this PR.

Usage

Set this flag in megatron_gpt_finetuning_config.yaml to enable QLoRA

model.peft.peft_scheme=qlora

To get the maximum memory savings, also set these flags

++model.dist_ckpt_load_on_device=False         # load checkpoint on CPU
++model.use_cpu_initialization=True            # initialize model on CPU
++model.peft.lora_tuning.target_modules=[all]  # quantize all linear layers in the model

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Additional Information

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[arendu]

LGTM! awesome PR!