不靠残差连接也能稳定训练Transformer,首次实现无跳接高效训练
Cutting the Skip: Training Residual-Free Transformers
- 基于雅可比分析设计新初始化策略,恢复无残差时的优化稳定性
- 在监督与自监督设置下,无残差ViT超越含残差基线模型性能
- 适合关注模型架构简化与层次表征学习的研究者
Transformer在众多应用中取得显著成功,常归因于其可扩展性。然而,去除残差连接后训练极为困难。虽然残差连接能稳定优化过程,但会破坏表征的层次结构,长期引发疑问:Transformer是否必须依赖残差连接才能高效训练?本文通过分析无残差Transformer块的雅可比矩阵,揭示了残差连接改善条件数的原因,并提出一种可恢复其稳定优势的合理初始化方法。基于此,我们首次实现无需修改标准架构即可稳定高效训练无残差Transformer。我们在视觉Transformer(ViTs)上验证该方法,在监督与自监督设置下,无残差ViT克服了常规优化障碍,学习到更丰富的层次化表征,并在密集预测任务上优于包含残差连接的强基线模型。结果表明,残差连接并非训练ViT的必要条件,为视觉模型中的层次表征学习开辟新路径。
原文摘要 · Abstract (English)
Transformers have achieved remarkable success across a wide range of applications, a feat often attributed to their scalability. Yet training them without skip (residual) connections remains notoriously difficult. While skips stabilize optimization, they also disrupt the hierarchical structure of representations, raising the long-standing question of whether transformers can be trained efficiently without them. In this work, we address this problem by analyzing the Jacobian of a skipless transformer block, showing why skips improve conditioning and revealing that their stabilization benefits can be recovered through a principled initialization strategy. Building on this insight, we introduce the first method that enables stable and efficient training of skipless transformers without altering the standard architecture. We validate our approach on Vision Transformers (ViTs) in both supervised and self-supervised settings, demonstrating that skipless ViTs trained with our initialization overcome the usual optimization barriers, learn richer hierarchical representations, and outperform strong baselines, that incorporate skip connections, on dense prediction benchmarks. These results show that skip connections are not a fundamental requirement for training ViTs and open new avenues for hierarchical representation learning in vision models.
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