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强调问题:为什么Softpick在初始化时失败

Underscoring the Problem: Why Softpick Fails at Initialization

Aryan Sood, Jaikaran Singh, Ishaan Bansal

arXiv 2610.05488首次发表:更新:

发表机构

IIT Roorkee(印度理工学院罗尔基分校)

机构由 AI 辅助整理,请以论文原文为准。

AI 中文总结

本文指出Softpick在初始化时因分母归一化问题而失败,通过分离正负分母并采用停止梯度变体,在2.3亿参数下实现同等量化性能、更少死头及更可靠的passkey检索。

AI 中文摘要

Softmax注意力机制赋予每个token非零权重,在训练好的模型中,这些权重会集中形成注意力汇聚点(attention sinks)和巨大的激活值,从而拓宽了低精度推理必须覆盖的动态范围。Softpick通过修正分数来消除这一约束,去除注意力汇聚点并降低隐藏状态的峰度,但其优势在规模增大时逐渐消失。我们将这一失败重新定义为归一化问题。Softpick的分母分为正偏移和负偏移的和$D^+$和$D^-$,在前向和反向传播中相同使用,导致无法隔离它们各自的作用。我们将它们分离为一组算子,每个算子独立选择各自的分母。失败源于初始化阶段:每一层都存在$D^+$恰好为零的行,而接近死亡的行产生的梯度范数超过$10^{12}$,无论反向分母如何。只有Softpick和一种停止梯度变体(在前向中保持$D^+ + D^-$,但仅通过$D^+$进行反向传播)能够从头训练。在2.3亿参数规模下,停止梯度算子在量化性能上与Softpick相当,具有更少的死亡注意力头,并且更可靠地检索passkeys,仅在峰值注意力权重峰度上略逊一筹。

英文摘要

Softmax attention gives every token a nonzero weight, which in trained models concentrates into attention sinks and massive activations that widen the dynamic range low-precision inference must cover. Softpick removes this constraint by rectifying scores, eliminating sinks and lowering hidden-state kurtosis, but its advantage fades at scale. We reframe this failure as a normalization problem. Softpick's denominator splits into positive- and negative-shifted sums $D^+$ and $D^-$, used identically in the forward and backward pass, preventing their roles from being isolated. We separate them into a family of operators that independently choose each denominator. The failure originates at initialization: every layer contains rows where $D^+$ is exactly zero, while near-dead rows produce gradient norms above $10^{12}$ regardless of the backward denominator. Only Softpick and a stop-gradient variant, which keeps $D^+ + D^-$ forward but backpropagates through $D^+$ alone, train from scratch. At 230M parameters, the stop-gradient operator matches Softpick on quantization, has fewer dead heads, and retrieves passkeys more reliably, trailing only on peak attention-weight kurtosis.

Comments23 pages, 4 Figures

论文原文

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