arXiv:2605.17582cs.LGcs.CE2026-05被引 1

提出可缩放等变的生成模型,提升金融时间序列建模精度。

Scale-Equivariant Generative Forecasting: Weight-Tied Dilated Convolutions, Wavelet Scattering Inputs, and Spectral-Consistency Training for Self-Similar Time Series

  • 共享卷积核参数实现多尺度不变性,减少参数量
  • 在标普500数据上达到0.020的缩放对齐误差,优于基线
  • 适合处理具有自相似性的金融、气候等时间序列

许多自然与工程时间序列(如股价收益、气候异常、湍流速度、神经记录、网络流量)近似具有自相似性:其时域跨度为T的分布由跨度为1的分布通过单一指数H关联。标准深度生成序列模型(如Transformer、膨胀TCN、WaveNet系列)忽略此特性,其感受野虽宽,但各膨胀层级的卷积核参数独立,仅为多尺度结构而非缩放等变结构。本文提出三项贡献:第一,明确定义一维因果网络的离散缩放等变性,并证明当膨胀系数为二进制时,若卷积核权重在各级共享,则可实现缩放等变性(边界效应除外)。共享卷积核使参数量降低L倍(L为深度),并硬编码自相似性作为归纳偏置。第二,构建基于该结构的缩放等变WaveNet(SE-WaveNet)框架,包含三部分共用先验:一级Daubechies-4小波输入、暴露局部缩放指数的Hurst-FiLM模块、针对|f|^{-(2H+1)}幂律谱的谱一致性训练项。头部采用条件归一化流以保持等变性。第三,在30年标普500日对数收益率数据上,SE-WaveNet样本重现了全市场前25名的实证缩放坍缩诊断结果,中位缩放误差$\mathcal{C}^\star = 0.020$,而同容量普通WaveNet未达此效果(≥0.06)。负对数似然、KS校准及尾部能量距离均优于或持平基线,且卷积参数量减少L倍。

原文摘要 · Abstract (English)

Many natural and engineered time series -- equity returns, climate anomalies, turbulent velocities, neural recordings, packet-level network traffic -- are approximately self-similar: their horizon-$T$ distribution is tied to the horizon-$1$ distribution by one scaling exponent $H$. Standard deep generative sequence models (transformers, dilated TCNs, the WaveNet family) ignore this. Their receptive fields are wide, but kernel parameters live independently at every dilation level, yielding a multi-scale architecture, not a scale-equivariant one. We make three contributions. First, we give a precise definition of discrete scale equivariance for 1D causal networks and prove that dyadic dilation commutes (up to boundary effects) with any dilated-convolution stack whose kernel weights are shared across levels. Tying the kernel shrinks the convolutional parameter budget by an $L$-fold factor (where $L$ is depth) and hard-wires self-similarity in as an inductive bias. Second, we wrap this Scale-Equivariant WaveNet (SE-WaveNet) backbone in three components that carry the same prior: a one-level Daubechies-4 wavelet input, a Hurst-FiLM block exposing the local scaling exponent, and a spectral-consistency training term targeting the $|f|^{-(2H+1)}$ power-law spectrum. The head is a conditional normalising flow, chosen to preserve equivariance. Third, on 30 years of S&P 500 daily log-returns, SE-WaveNet samples reproduce the empirical scaling-collapse diagnostic on the Allan-Variance top-25 universe (median $\mathcal{C}^\star = 0.020$), while a vanilla WaveNet at matched capacity does not ($\geq 0.06$). NLL, KS-calibration, and tail energy distance tie or beat the baseline, with $L\times$ fewer convolutional parameters.

时间序列生成模型自相似性等变网络

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