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Optimize Weight Rounding via Signed Gradient Descent for the Quantization of LLMs (2309.05516v5)

Published 11 Sep 2023 in cs.CL, cs.AI, and cs.LG

Abstract: LLMs have demonstrated exceptional proficiency in language-related tasks, but their deployment poses significant challenges due to substantial memory and storage requirements. Weight-only quantization has emerged as a promising solution, significantly reducing memory and storage needs without sacrificing too much performance. In this study, we introduce SignRound, a method that leverages signed gradient descent (SignSGD) to optimize rounding values and weight clipping in just 200 steps. SignRound integrates the advantages of Quantization-Aware Training (QAT) and Post-Training Quantization (PTQ), delivering exceptional results across 2 to 4 bits while minimizing tuning costs and avoiding additional inference overhead. For example, SignRound achieved absolute average accuracy improvements ranging from 6.91% to 33.22% at 2bits, as measured by the average zero-shot accuracy across 11 tasks. It also demonstrates strong generalization in recent models, achieving near-lossless 4-bit quantization in most scenarios. The source code is publicly available at https://github.com/intel/auto-round.

Citations (17)

Summary

  • The paper introduces SignRound, which applies signed gradient descent to optimize weight rounding in LLM quantization by altering only about 5% of rounding values.
  • It demonstrates significant accuracy improvements over traditional methods like Rounding-to-Nearest and competes with techniques such as GPTQ in 3- and 4-bit settings.
  • Experiments on LLaMA, BLOOM, and OPT models validate the method's robustness and efficiency, offering practical solutions for reducing memory and storage constraints.

Overview of "Optimize Weight Rounding via Signed Gradient Descent for the Quantization of LLMs"

The paper "Optimize Weight Rounding via Signed Gradient Descent for the Quantization of LLMs" presents a novel approach to the quantization of LLMs, addressing the challenges associated with their memory and storage requirements. The focus is on enhancing weight-only quantization, particularly for 3 and 4-bit representations, which are crucial for efficient deployment.

Methodology and Novel Contributions

The authors introduce a new method called SignRound, which utilizes signed gradient descent for block-wise tuning of weight rounding. This approach is motivated by the limited and precise boundary conditions in the quantization process, where modifying the rounding value threshold is critical.

SignRound operates efficiently within 400 steps by directly optimizing the weight rounding task without additional inference overhead. Notably, it achieves superior performance by altering only about 5% of the rounding values, demonstrating significant accuracy improvements over traditional methods like Rounding-to-Nearest (RTN) and existing techniques such as GPTQ.

Key Contributions:

  • Proposal of a succinct and potent weight-rounding optimization method using minimal unlabeled data.
  • Demonstrated improvements in performance through minimal alterations in rounding values.
  • Empirical evidence of substantial enhancements compared to RTN and competitiveness against recent methods.

Experimental Validation

The research evaluates SignRound across various tasks and LLM architectures including LLaMA, BLOOM, and OPT models, with different parameter sizes. The evaluation spans common sense reasoning tasks, language understanding, and perplexity analyses on datasets such as C4 and Wikitext2.

The results underscore the efficacy of SignRound, particularly in low-bit quantization scenarios, where it outperforms RTN in most cases and rivals or surpasses GPTQ. Additionally, the method shows robustness across different models and tasks, although there are notable instances where hyperparameter tuning can further optimize outcomes.

Theoretical Implications and Future Directions

The paper reinforces the importance of optimized quantization techniques in deploying memory-intensive LLMs effectively. By integrating signed gradient descent, SignRound opens avenues for leveraging the structured solution space in quantization tasks, potentially influencing further advancements in model compression and efficient AI deployments.

Future research could explore extending this technique to more diverse LLM models, including those tailored for specific applications like code generation or conversational agents. Additionally, addressing the few outlier scenarios through refined hyperparameter adjustments remains an area for further enhancement.

Conclusion

"Optimize Weight Rounding via Signed Gradient Descent for the Quantization of LLMs" provides a significant contribution to the field of model quantization. By focusing on precision boundary optimization and introducing an efficient gradient-based approach, the authors offer a compelling solution that balances accuracy and resource constraints. As AI models continue to scale, such techniques will be instrumental in ensuring their practical deployment across diverse platforms.

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