无需梯度,单次遍历即可构建满足严苛连接约束的瞬时放大网络。
DAGGER: Gradient-Free Construction of Transiently Amplifying Networks under Hard Connectivity Constraints

- 基于有向无环图引导边权重重分配,实现无梯度单次构造。
- 峰值放大能力可达10¹⁰,且保持符号、稀疏性与对角线约束不变。
- 适合生物神经图谱与结构化RNN初始化等需精确连接控制的场景。
许多网络不仅依赖于瞬时非正规放大——即系统活动在稳定状态下发生数量级增长——而且正是这种特性支撑其功能。然而,在符号、稀疏性和对角线等硬性约束下构建此类网络,此前要么依赖需数千次内层特征分解的梯度优化方法,要么采用抽象基下的舒尔分解直接构造,但在投影后会破坏约束。本文提出DAGGER(有向无环图引导边权重重分配),一种无梯度、单次遍历的算法。给定一个稳定的带符号稀疏矩阵,DAGGER输出结果保持相同的符号、稀疏性和对角线结构。单一标量β控制沃尔什-2预算,平滑地在精确多重集保持(β=0)与放大能力之间权衡;峰值放大能力随β近乎无界增长,实测达到10¹⁰前数值溢出。DAGGER在多重集保持上表现匹配或超越梯度方法,仅需一次前向传播,比典型梯度内层循环减少30–100倍特征分解次数;在中等β值下,更以完全保留连接性的优势,实现数量级性能提升。我们开发该算法,与现有方法对比,并在下游信号检测任务中验证其效果,同时分析诊断结果揭示DAGGER在结构上与其他放大网络的根本差异。
原文摘要 · Abstract (English)
Many networks not only support but also rely on transient non-normal amplification, an orders-of-magnitude increase in the activity of an otherwise stable system. Constructing such networks under hard sign/sparsity/diagonal constraints -- the regime relevant for biological connectomes and structured RNN initializations -- has so far required either gradient-based local search with thousands of inner-loop eigendecompositions or Schur-form direct construction in an abstract basis that breaks the constraints under projection. Here we introduce DAGGER (Directed Acyclic Graph Guided Edge Reweighting), a gradient-free single-pass algorithm. Given a stable signed sparse matrix, DAGGER produces an output with the same sign, sparsity, and diagonal. A single scalar $β$ controls a Wasserstein-2 budget that smoothly trades exact multiset preservation ($β= 0$) for amplification; peak amplification grows essentially without bound with $β$, empirically reaching $10^{10}$ before numerical overflow. DAGGER matches or exceeds gradient-based methods at multiset preservation in a single forward pass -- 30-100$\times$ fewer eigendecompositions than a typical gradient inner loop -- and at moderate $β$ beats them by orders of magnitude with connectivity exactly preserved. We develop the algorithm, compare it to the existing methods and on a downstream signal-detection task, and examine the diagnostics that show why DAGGER is structurally different from other amplifying networks.
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