用数学方法让生成模型的每一步都可解释且能一键生成。
Unfolding Generative Flows with Koopman Operators: Trajectory-Preserving Linearization
- 将生成过程映射到高维空间,用一个线性算子完整保留动态轨迹。
- 采样只需一步完成,速度大幅提升,且中间状态可解释。
- 适合想理解生成细节、做可控编辑或逆向生成的研究者。
连续归一化流(CNFs)虽在生成建模上表现优雅,但因迭代采样耗时且中间状态难以解释而受限。现有加速方法通过拉直轨迹或蒸馏终点来提速,却将原生成过程视为黑箱,忽略中间动态。本文提出新思路:基于Koopman理论全局线性化流动态,实现轨迹保持的线性化。将预训练的条件流匹配(CFM)模型嵌入高维Koopman空间,用单一线性算子表示其演化。关键在于,不只对端点进行蒸馏,而是沿整个生成路径强制与教师向量场在无穷小尺度上一致。我们推导出无需仿真的实用训练目标,带来双重优势:采样变为单步且可并行;由于线性化忠实于动力学,该算子能揭示生成过程的独特信息。实验表明,该结构支持新应用,如发现语义连贯的编辑方向、用教师对齐的线性算子进行反演,以及生成类别条件的谱特征。实证中,样本质量具竞争力,同时支持全程轨迹的谱分析与控制。
原文摘要 · Abstract (English)
Continuous Normalizing Flows (CNFs) enable elegant generative modeling but remain bottlenecked by their iterative nature requiring costly sampling and lacking interpretability of the intermediate states. Recent approaches accelerate sampling by straightening trajectories or distilling endpoints, yet they treat the original generative process as a black box, discarding the teacher's intermediate dynamics. We propose a fundamentally different perspective: globally linearizing flow dynamics via Koopman theory to achieve trajectory-preserving linearization. By lifting a pre-trained Conditional Flow Matching (CFM) model into a higher-dimensional Koopman space, we represent its evolution with a single linear operator. Crucially, unlike boundary-only distillation, our method enforces infinitesimal consistency with the teacher's vector field along the full generative path. We derive a practical, simulation-free training objective that ensures this global alignment and yields two key benefits. First, sampling becomes one-step and parallelizable. Second, because the linearization is faithful to the dynamics, the Koopman operator provides unique insights on the generation. We demonstrate that this structure enables novel applications unavailable in prior approaches, including discovery of semantically coherent editing directions, inversion with a teacher-aligned linear operator and class-conditional spectral signatures. Empirically, our approach achieves competitive sample quality, while enabling spectral analysis and control of the entire trajectories of generative flows.
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