首次实现对大模型权重算法复杂度的可扩展测量,揭示学习过程中的信息压缩规律。
Characterizing Learning in Deep Neural Networks using Tractable Algorithmic Complexity Analysis

- 提出QuBD方法,将权重量化后分位平面分析,实现非二值化模型的算法复杂度估算
- 发现模型训练中复杂度下降,过拟合时上升,与泛化性能正相关
- 关键信息集中在高位比特平面,可指导训练后量化策略
大规模深度神经网络训练资源消耗巨大,模型压缩成为必要。广为接受的“学习即压缩”假说认为,训练会赋予网络权重结构,从而实现压缩。通过科莫戈罗夫-蔡廷-索洛莫诺夫(KCS)复杂度衡量这种结构具有吸引力,但现有的基于编码定理法(CTM)和块分解法(BDM)的估计器仅适用于小规模二值对象,无法扩展到现代深层网络。本文提出量化块分解法(QuBD),将任意k元对象的算法复杂度估计拓展至大型非二值化模型。QuBD首先将网络权重量化为有限字母表,再通过聚合各比特平面的CTM估计值来计算整体KCS复杂度。理论上证明,相比二值化方法,QuBD在真实KCS复杂度估计上具有更紧的误差界。利用QuBD研究权重算法复杂度在训练中的演化,发现其随学习而降低,随数据量增加而上升,在过拟合阶段升高,遵循‘格洛克’现象中的延迟泛化模式,并与泛化性能显著相关。进一步表明,算法信息主要存在于最高有效比特平面,可作为训练后量化级别选择的实际诊断工具。本工作首次为大型非二值化对象如神经网络权重提供了可扩展、可操作的KCS复杂度估计,深化了对深度学习机制的理解。
原文摘要 · Abstract (English)
Training large-scale deep neural networks (DNNs) is resource-intensive, making model compression a practical necessity. The widely accepted ''learning as compression'' hypothesis posits that training induces structure in network weights, which enables compression. Measuring this structure through Kolmogorov-Chaitin-Solomonoff (KCS) complexity is appealing, but existing estimators based on the Coding Theorem Method (CTM) and the Block Decomposition Method (BDM) are limited to small binary objects and do not scale to modern DNNs. We introduce the Quantized Block Decomposition method (QuBD), which extends algorithmic complexity estimation to any $k$-ary object. QuBD first quantizes the network weights to a finite alphabet, then estimates the KCS complexity by aggregating per bit-plane CTM estimates. We show theoretically that QuBD yields a strictly tighter estimation gap with respect to true KCS complexity than binarization-based methods. Using QuBD, we study how the algorithmic complexity of neural network weights evolves during training, showing that it decreases as models learn, scales with data budget, increases during overfitting, follows the delayed generalization observed during grokking, and correlates with generalization performance. We further show that algorithmic information resides predominantly in the most significant bit-planes, which can serve as a practical diagnostic for determining appropriate post-training quantization levels. This work offers novel insights into learning mechanisms in DNNs by providing the first scalable, tractable estimates of KCS complexity for large, non-binary objects such as DNN weights.
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