Linguistic Collapse: Neural Collapse in (Large) Language Models
Keywords: neural collapse, uniformity, large language models, LLM, GPT, language modeling, geometry, unconstrained features, generative model, transformer, attention, causal, autoregressive
TL;DR: Analysis of the development of neural collapse in (large) language models and its relationship with generalization.
Abstract: Neural collapse ($\mathcal{NC}$) is a phenomenon observed in classification tasks where top-layer representations collapse into their class means, which become equinorm, equiangular and aligned with the classifiers.
These behaviors -- associated with generalization and robustness -- would manifest under specific conditions: models are trained towards zero loss, with noise-free labels belonging to balanced classes, which do not outnumber the model's hidden dimension.
Recent studies have explored $\mathcal{NC}$ in the absence of one or more of these conditions to extend and capitalize on the associated benefits of ideal geometries.
Language modeling presents a curious frontier, as \textit{training by token prediction} constitutes a classification task where none of the conditions exist: the vocabulary is imbalanced and exceeds the embedding dimension; different tokens might correspond to similar contextual embeddings; and large language models (LLMs) in particular are typically only trained for a few epochs.
This paper empirically investigates the impact of scaling the architectures and training of causal language models (CLMs) on their progression towards $\mathcal{NC}$.
We find that $\mathcal{NC}$ properties that develop with scale (and regularization) are linked to generalization.
Moreover, there is evidence of some relationship between $\mathcal{NC}$ and generalization independent of scale.
Our work thereby underscores the generality of $\mathcal{NC}$ as it extends to the novel and more challenging setting of language modeling.
Downstream, we seek to inspire further research on the phenomenon to deepen our understanding of LLMs -- and neural networks at large -- and improve existing architectures based on $\mathcal{NC}$-related properties.
Our code is hosted on GitHub: [`https://github.com/rhubarbwu/linguistic-collapse`](https://github.com/rhubarbwu/linguistic-collapse).
Primary Area: Optimization for deep networks
Submission Number: 20482
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