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PromptKD: Distilling Student-Friendly Knowledge for Generative Language Models via Prompt Tuning<br/>(EMNLP 2024 Findings)

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Method

PromptKD: Distilling Student-Friendly Knowledge for Generative Language Models via Prompt Tuning<br> Gyeongman Kim, Doohyuk Jang, Eunho Yang <br>

Abstract: <br> Recent advancements in large language models (LLMs) have raised concerns about inference costs, increasing the need for research into model compression. While knowledge distillation (KD) is a prominent method for this, research on KD for generative language models like LLMs is relatively sparse, and the approach of distilling student-friendly knowledge, which has shown promising performance in KD for classification models, remains unexplored in generative language models. To explore this approach, we propose PromptKD, a simple yet effective method that utilizes prompt tuning - for the first time in KD - to enable generative language models to transfer student-friendly knowledge. Unlike previous works in classification that require fine-tuning the entire teacher model for extracting student-friendly knowledge, PromptKD achieves similar effects by adding a small number of prompt tokens and tuning only the prompt with student guidance. Extensive experiments on instruction-following datasets using the GPT-2 model family show that PromptKD achieves state-of-the-art performance while adding only 0.0007% of the teacher's parameters as prompts. Further analysis suggests that distilling student-friendly knowledge alleviates exposure bias effectively throughout the entire training process, leading to performance enhancements.

Requirements

See install.sh

conda create -n promptkd python=3.8
conda activate promptkd
bash install.sh

Pretrained models

In order to use this project you need to download pretrained models and datasets. (Many of them are from MiniLLM github repository)

Use the download_requirements.sh script

bash download_requirements.sh

This script downloads

Model(GPT-2, OPT, Llama) checkpoints for reproducibility in checkpoints folder.
- Here, we provide PromptKD checkpoints via huggingface hub (Link)
Data for training and evaluation in data and processed_data folder.

Evaluation

Reproduce the performance of the model checkpoint used in the paper.

bash scripts/{model}/eval/run_eval.sh . checkpoints/{model}/train/{method}/{model}-{size}

You can choose {model} in {gpt2, opt, llama}, and {method} in {sft, kd, seqkd, minillm, promptkd}.

For GPT-2, you can choose {size} in {base, medium, large}.
For OPT, you can choose {size} in {1.3B, 2.7B, 6.7B}.
For Llama, put 7B in {size}.

Training

Training scripts are as below.

bash scripts/{model}/{method}/{method}_{student_size}.sh # For training
bash scripts/{model}/eval/run_eval.sh . results/{model}/train/{method}/{model}-{student_size}-{teacher_size}/{your_exp_folder}/best_rougeL # For evaluation

You can choose {model} in {gpt2, opt, llama}, and {method} in {sft, kd, seqkd, minillm, promptkd}.

Determine {student_size} and {teacher_size} by checking the scripts folder.
Also, put your experiment output folder in {your_exp_folder} by checking the results/{model}/train folder.

We use 8x NVIDIA GeForce RTX 3090 GPUs for GPT-2, and 4x NVIDIA A100 80 GB (PCIe) GPUs for OPT and Llama model.

Change Model Parallel Size

You can increase/decrease the tensor parallel sizes with

python3 tools/convert_mp.py \
    --input_path checkpoints/llama/train/sft/llama-13B \
    --source_mp_size 4 \
    --target_mp_size 1 \
    --model_type llama # choose from opt and llama

Credits

MiniLLM implementation:
https://github.com/microsoft/LMOps/tree/main/minillm
License (MIT) https://github.com/microsoft/LMOps/blob/main/LICENSE

Acknowledgement

This work was supported by Institute for Information & communications Technology Promotion (IITP) grant funded by the Korea government (MSIT)
(No.RS-2019-II190075, Artificial Intelligence Graduate School Program(KAIST))

Citation

If you make use of our work, please cite our paper:

@inproceedings{kim-etal-2024-promptkd,
    title     = "PromptKD: Distilling Student-Friendly Knowledge for Generative Language Models via Prompt Tuning",
    author    = "Kim, Gyeongman and Jang, Doohyuk and Yang, Eunho",
    booktitle = "Findings of the Association for Computational Linguistics: EMNLP 2024",
    year      = "2024"
}