@inproceedings{
bu2024provably,
title={Provably Transformers Harness Multi-Concept Word Semantics for Efficient In-Context Learning},
author={Dake Bu and Wei Huang and Andi Han and Atsushi Nitanda and Taiji Suzuki and Qingfu Zhang and Hau-San Wong},
booktitle={The Thirty-eighth Annual Conference on Neural Information Processing Systems},
year={2024},
url={https://openreview.net/forum?id=57C9mszjj3}
}
Transformer-based large language models (LLMs) have displayed remarkable creative prowess and emergence capabilities. Existing empirical studies have revealed a strong connection between these LLMs' impressive emergence abilities and their in-context learning (ICL) capacity, allowing them to solve new tasks using only task-specific prompts without further fine-tuning. On the other hand, existing empirical and theoretical studies also show that there is a regularity of the multi-concept encoded semantic representation behind transformer-based LLMs. However, existing theoretical work fail to build up an understanding of the connection between this semantic regularity and the innovative power of ICL. Additionally, prior work often focuses on simplified, unrealistic scenarios with linear transformers or unrealistic loss functions, and due to their technical limitations, they come up with results exhibiting only linear or sub-linear convergence rates. In contrast, this work provides a fine-grained mathematical analysis to show how transformers leverage the multi-concept semantics of words to enable powerful ICL and excellent out-of-distribution ICL abilities, offering insights into how transformers innovate solutions for new unseen tasks encoded with multiple cross-concept semantics. Inspired by empirical studies on the latent geometry of LLMs, the analysis is based on a concept-based low-noise sparse coding prompt model. Leveraging advanced techniques, this work showcases the exponential 0-1 loss convergence over the highly non-convex training dynamics, which pioneeringly incorporates the challenges of softmax self-attention, ReLU-activated MLPs, and cross-entropy loss. Empirical simulations corroborate the theoretical findings.
Provably Transformers Harness Multi-Concept Word Semantics for Efficient In-Context Learning
Dake Bu Wei Huang Andi Han Atsushi Nitanda Taiji Suzuki Qingfu Zhang Hau-San Wong