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arXiv 2604.18580cs.LGcs.AIcs.CL

Sessa: 选择性状态空间注意力

Sessa: Selective State Space Attention

Liubomyr Horbatko

Liubomyr Horbatko

AI总结:

Sessa通过在递归反馈路径中引入注意力机制,实现对长上下文信息的选择性检索,理论证明其记忆衰减更慢,实验显示在长上下文任务中表现最佳。

摘要:

现代序列建模主要由两种机制主导:Transformer的自注意力机制和结构化状态空间模型。这两种机制在长上下文中面临挑战:当注意力扩散时,单个token的影响被稀释;而递归状态传播则需要主动保存信息以保持长程敏感性。本文提出Sessa,一种将注意力置于递归反馈路径中的解码器,通过创建多个注意力路径使过去token能影响未来状态,而非依赖单一注意力读取或递归链。在显式假设和匹配条件下,Sessa的内存尾部呈幂律衰减$O(\ell^{-β})$,其中$0 < β < 1$,比Transformer和Mamba式基线更慢。进一步给出了实现该幂律衰减的显式构造。在相同假设下,Sessa是唯一能实现灵活选择性检索的模型类别,包括影响不随距离衰减的轮廓。理论优势一致体现在实验中,Sessa在长上下文基准上表现最强,同时在短上下文语言建模中与Transformer和Mamba式基线竞争。

英文摘要:

Modern sequence modeling is dominated by two families: Transformers, whose self-attention can access arbitrary elements of the visible sequence, and structured state-space models, which propagate information through an explicit recurrent state. These mechanisms face different limitations on long contexts: when attention is diffuse, the influence of individual tokens is diluted across the effective support, while recurrent state propagation can lose long-range sensitivity unless information is actively preserved. As a result, both mechanisms face challenges in preserving and selectively retrieving information over long contexts. We propose Sessa, a decoder that places attention inside a recurrent feedback path. This creates many attention-based paths through which past tokens can influence future states, rather than relying on a single attention read or a single recurrent chain. We prove that, under explicit assumptions and matched regimes, Sessa admits power-law memory tails $O(\ell^{-β})$ for $0 < β< 1$, with slower decay than in the corresponding Transformer and Mamba-style baselines. We further give an explicit construction that achieves this power-law rate. Under the same assumptions, Sessa is the only model class among those considered that realizes flexible selective retrieval, including profiles whose influence does not decay with distance. Consistent with this theoretical advantage, across matched experiments, Sessa achieves the strongest performance on long-context benchmarks while remaining competitive with Transformer and Mamba-style baselines on short-context language modeling.

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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