提出NAG架构,让深层模型更新不被残差范数压制,提升深度扩展性。
Scaling Adaptive Depth with Norm-Agnostic Residual Networks

- 将残差流的幅度与方向解耦,避免后期层更新被抑制
- 深度增加时性能提升显著,20%-25%的跳层率可保持全深性能
- 适合追求深度扩展与算力效率平衡的研究者和工程师
残差网络在深度学习中广泛应用,但存在隐性结构缺陷:残差流的范数随深度快速增长,导致后期层更新相对于累积状态变得微小,削弱其对表征的影响,限制了模型深度的可扩展性。为此,本文提出NAG(Norm-Agnostic Residual Networks),通过将残差流中的幅度与方向信息分离,保留各层有意义的贡献,防止后期更新被残差范数增长系统性抑制。NAG仅引入极少量额外参数,且操作简单,支持高效内核融合,维持训练效率。实验表明,该架构优于基线Transformer,深度越大优势越明显,支持有效训练更深模型。此外,其范数无关设计还催生可解释的混合深度(Mixture-of-Depths, MoD)机制,可自适应跳过注意力与MLP层。该机制不仅可在推理时实现精度-算力权衡,还可作为预训练阶段的缩放策略:在固定总计算量下,通过减少每令牌前向传播开销,将节省的算力用于更多样本训练,同时保持参数量与键值缓存预算不变。实验显示,约20%-25%的跳跃率即可在同等训练算力下达到全深模型性能,显著降低执行参数量与前向计算浮点操作数。结果表明,深度稀疏性是固定算力训练下的新缩放维度,支持构建极深且算力高效的模型。
原文摘要 · Abstract (English)
Residual architectures are ubiquitous in deep learning, but they suffer from a subtle structural limitation: the norm of the residual stream can grow rapidly with depth. As a result, updates from later layers become small relative to the accumulated residual state. This reduces their impact on the representation and limits the benefits of scaling models in depth. To address this, we introduce NAG, a norm-agnostic residual architecture that separates magnitude from directional information in the residual stream, preserving meaningful layer contributions throughout depth and preventing later updates from being systematically suppressed by residual-norm growth. Importantly, NAG introduces only a negligible number of additional parameters and relies on simple operations that are easily kernel-fusible, preserving training efficiency in practice. We show that this architecture outperforms baseline Transformers, with gains that increase substantially as depth grows, enabling effective training of much deeper models. The norm-agnostic formulation also leads to an interpretable Mixture-of-Depths (MoD) mechanism that adaptively skips both attention and MLP layers. Beyond serving as a post-training accuracy-compute tradeoff, this mechanism can be used as a pretraining-time scaling strategy: under iso-FLOP training, compute saved by reducing per-token forward-pass cost can be reinvested into training on more tokens while keeping the total parameter count and KV-cache budget fixed. In our experiments, moderate Mixture-of-Depths rates of approximately 20%-25% match full-depth baseline performance under equal training compute while substantially reducing the number of executed layer parameters and forward-pass FLOPs. These results identify sparsity in depth as a new scaling axis for fixed-compute training, enabling very deep yet FLOP-efficient models.
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