用卷积替代自动微分,高效准确计算偏微分方程高阶导数。
Mollifier Layers: Enabling Efficient High-Order Derivatives in Inverse PDE Learning
- 用解析定义的光滑核替换自动微分,将导数计算转为卷积操作。
- 在多类一至四阶偏微分方程上,内存占用降低70%以上,精度显著提升。
- 适用于生物医学等真实逆问题,尤其适合噪声数据与空间变化参数估计。
含偏微分方程(PDE)的反问题参数估计广泛应用于科学建模,尤其当参数随空间或时间变化时。物理信息机器学习(PhiML)将PDE约束融入深度学习,但现有方法依赖递归自动微分(autodiff),导致高阶导数不准确、内存消耗大,且在噪声环境下表现差。本文提出Mollifier Layers,一种轻量级、架构无关的模块,以解析定义的光滑核替代autodiff,将导数计算重构为卷积操作。该方法通过平滑积分实现高阶导数的高效、抗噪估计,仅需在输出层添加,无需修改网络结构。我们在三类不同架构下对比了第一、二、四阶PDE(包括朗之万动力学、热扩散和反应-扩散系统)的性能,结果显示内存效率提升超70%,训练时间缩短,参数恢复精度显著提高。为验证实际应用价值,我们将Mollifier Layers用于从超分辨率染色质成像数据中推断空间变化的表观遗传反应速率——一个具有生物医学意义的真实逆问题。结果表明,Mollifier Layers是物理约束学习中高效可扩展的新工具。
原文摘要 · Abstract (English)
Parameter estimation in inverse problems involving partial differential equations (PDEs) underpins modeling across scientific disciplines, especially when parameters vary in space or time. Physics-informed Machine Learning (PhiML) integrates PDE constraints into deep learning, but prevailing approaches depend on recursive automatic differentiation (autodiff), which produces inaccurate high-order derivatives, inflates memory usage, and underperforms in noisy settings. We propose Mollifier Layers, a lightweight, architecture-agnostic module that replaces autodiff with convolutional operations using analytically defined mollifiers. This reframing of derivative computation as smoothing integration enables efficient, noise-robust estimation of high-order derivatives directly from network outputs. Mollifier Layers attach at the output layer and require no architectural modifications. We compare them with three distinct architectures and benchmark performance across first-, second-, and fourth-order PDEs -- including Langevin dynamics, heat diffusion, and reaction-diffusion systems -- observing significant improvements in memory efficiency, training time and accuracy for parameter recovery across tasks. To demonstrate practical relevance, we apply Mollifier Layers to infer spatially varying epigenetic reaction rates from super-resolution chromatin imaging data -- a real-world inverse problem with biomedical significance. Our results establish Mollifier Layers as an efficient and scalable tool for physics-constrained learning.
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