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arXiv 2108.08052stat.MLcs.AIcs.LG
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Moser Flow:流形上基于分歧的生成建模

Moser Flow: Divergence-based Generative Modeling on Manifolds

Weizmann Institute of Science(魏茨曼科学研究学院);Facebook AI Research(Facebook人工智能研究院);UCLA(加利福尼亚大学洛杉矶分校)

Noam Rozen, Aditya Grover, Maximilian Nickel, Yaron Lipman

摘要:

我们有兴趣学习生成模型,通过流形描述复杂的几何形状,如球体,环面和其他隐式表面。现有的(欧几里德)生成模型的当前扩展仅限于特定的几何形状,并且通常遭受高计算成本。我们介绍Moser流(MF),一类新的生成模型的连续规范化流(CNF)的家庭。MF还通过变量变化公式的解产生CNF,然而与其他CNF方法不同,其模型(学习)密度被参数化为源(先验)密度减去神经网络(NN)的发散。散度是一个局部的线性微分算子,易于在流形上近似和计算。因此,与其他CNF不同,MF不需要在训练期间通过ODE求解器调用或反向传播。此外,将模型密度显式表示为NN的散度而不是ODE的解有助于学习高保真度密度。理论上,我们证明了MF构成一个普遍的密度逼近适当的假设下。从经验上讲,我们第一次展示了使用流动模型从一般曲面采样,并在密度估计,样本质量和训练复杂性方面取得了显着改善,超过现有的CNFs对具有挑战性的合成几何形状和现实世界的基准,从地球和气候科学。

英文摘要:

We are interested in learning generative models for complex geometries described via manifolds, such as spheres, tori, and other implicit surfaces. Current extensions of existing (Euclidean) generative models are restricted to specific geometries and typically suffer from high computational costs. We introduce Moser Flow (MF), a new class of generative models within the family of continuous normalizing flows (CNF). MF also produces a CNF via a solution to the change-of-variable formula, however differently from other CNF methods, its model (learned) density is parameterized as the source (prior) density minus the divergence of a neural network (NN). The divergence is a local, linear differential operator, easy to approximate and calculate on manifolds. Therefore, unlike other CNFs, MF does not require invoking or backpropagating through an ODE solver during training. Furthermore, representing the model density explicitly as the divergence of a NN rather than as a solution of an ODE facilitates learning high fidelity densities. Theoretically, we prove that MF constitutes a universal density approximator under suitable assumptions. Empirically, we demonstrate for the first time the use of flow models for sampling from general curved surfaces and achieve significant improvements in density estimation, sample quality, and training complexity over existing CNFs on challenging synthetic geometries and real-world benchmarks from the earth and climate sciences.

机构、总结、中文摘要均由AI分析而来,可能存在错误,请以论文正文为准。

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