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arXiv 2103.03404cs.LG
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Attention并非你所需要的全部:纯Attention的秩随深度以双重指数速度丢失

Attention is Not All You Need: Pure Attention Loses Rank Doubly Exponentially with Depth

Google(谷歌);EPFL(洛桑联邦理工学院)

Yihe Dong, Jean-Baptiste Cordonnier, Andreas Loukas

AI总结:

本工作提出一种分解方法证明纯self-attention网络对“token uniformity”具有强烈inductive bias,若无skip connections或MLPs,其输出会以双重指数速度收敛至rank-1矩阵,并通过实验验证了该收敛现象。

摘要:

基于attention的架构在机器学习中已变得无处不在,然而我们对其有效性的原因的理解仍然有限。本工作提出了一种理解self-attention网络的新方法:我们证明其输出可分解为更小项的总和,每项都涉及跨层的一系列attention head的操作。利用该分解,我们证明self-attention对“token uniformity”具有强烈的inductive bias。具体而言,如果没有skip connections或multi-layer perceptrons (MLPs),输出会以双重指数速度收敛至rank-1矩阵。另一方面,skip connections和MLPs能阻止输出退化。我们的实验在标准transformer架构的不同变体上验证了所识别的收敛现象。

英文摘要:

Attention-based architectures have become ubiquitous in machine learning, yet our understanding of the reasons for their effectiveness remains limited. This work proposes a new way to understand self-attention networks: we show that their output can be decomposed into a sum of smaller terms, each involving the operation of a sequence of attention heads across layers. Using this decomposition, we prove that self-attention possesses a strong inductive bias towards "token uniformity". Specifically, without skip connections or multi-layer perceptrons (MLPs), the output converges doubly exponentially to a rank-1 matrix. On the other hand, skip connections and MLPs stop the output from degeneration. Our experiments verify the identified convergence phenomena on different variants of standard transformer architectures.

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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