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arXiv 2602.22271cs.LGmath.PRmath.STstat.TH

支持标记、稳定性边距与鲁棒大语言模型的新基础

Support Tokens, Stability Margins, and a New Foundation for Robust LLMs

LinkedIn

Deepak Agarwal, Dhyey Dharmendrakumar Mavani, Suyash Gupta, Karthik Sethuraman, Tejas Dharamsi

AI总结:

本文通过概率框架重新解释因果自注意力变换器,揭示参数约束和退化边界,提出支持标记概念,并通过贝叶斯MAP训练目标提升模型鲁棒性。

摘要:

自注意力通常被描述为一种灵活的内容自适应方式来混合标记与过去信息。我们通过概率框架重新解释因果自注意力变换器,类似于经典PCA扩展到概率PCA。这种重新表述揭示了底层变量变换的关键结构后果:自注意力参数出现屏障约束。由此几何结构暴露了退化边界,其中注意力诱导的映射局部退化,产生类似于支持向量机中的边距解释。这进一步表明因果变换器在无限标记序列上定义了一致的随机过程,为序列建模提供严谨的概率基础。基于此观点,我们推导出一种贝叶斯MAP训练目标,仅需对标准LLM训练进行最小修改:在通常的交叉熵损失中添加平滑对数屏障惩罚。经验上,所得训练目标提高了对输入扰动的鲁棒性,同时不牺牲外推准确性。

英文摘要:

Self-attention is usually described as a flexible, content-adaptive way to mix a token with information from its past. We reinterpret causal self-attention transformers, the backbone of modern foundation models, within a probabilistic framework, much as classical PCA is extended to probabilistic PCA. This reformulation reveals a key structural consequence of the underlying change of variables: a barrier constraint emerges on the parameters of self-attention. The resulting geometry exposes a degeneracy boundary where the attention-induced mapping becomes locally ill-conditioned, yielding a stability-margin interpretation analogous to the margin in support vector machines. This, in turn, naturally gives rise to the concept of support tokens. We further show that causal transformers define a consistent stochastic process over infinite token sequences, providing a rigorous probabilistic foundation for sequence modeling. Building on this view, we derive a Bayesian MAP training objective that requires only a minimal modification to standard LLM training: adding a smooth log-barrier penalty to the usual cross-entropy loss. Empirically, the resulting training objective improves robustness to input perturbations and sharpens the margin geometry of the learned representations without sacrificing out-of-sample accuracy.

机构、总结、中文摘要均由AI分析而来,可能存在错误,请以论文正文为准。

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