根据输入数据特点动态调整采样步数,提升生成质量。
Few-Step Diffusion Sampling Through Instance-Aware Discretizations
- 基于输入自适应调整采样步长分配,突破全局固定步数限制。
- 在图像、视频生成中显著提升质量,且推理开销几乎不变。
- 适合对生成质量要求高、需高效采样的实际应用者。
扩散模型和流匹配模型通过模拟常微分方程或随机微分方程定义的路径生成高质量数据,从一个可处理的先验分布开始。概率流常微分方程形式使高级数值求解器可用于加速采样。然而,求解器设计的关键在于离散化策略。早期方法依赖人工启发式,近期方法采用优化技术,但多数策略对所有样本采用全局统一的时间步调度。这种统一处理忽略了生成过程中实例特异性复杂度,可能制约性能。受合成数据上的受控实验启发,发现全局时间步在实例动态不同时存在次优性,我们提出一种实例感知的离散化框架。该方法学习根据输入相关的先验条件自适应分配时间步,将基于梯度的离散化搜索扩展至条件生成设置。在多种场景下的实证结果表明,包括合成数据、像素空间扩散、潜在空间图像和视频流匹配模型,本方法在仅需少量调参成本(相比训练)的情况下,持续提升生成质量,且推理开销可忽略。
原文摘要 · Abstract (English)
Diffusion and flow matching models generate high-fidelity data by simulating paths defined by Ordinary or Stochastic Differential Equations (ODEs/SDEs), starting from a tractable prior distribution. The probability flow ODE formulation enables the use of advanced numerical solvers to accelerate sampling. Orthogonal yet vital to solver design is the discretization strategy. While early approaches employed handcrafted heuristics and recent methods adopt optimization-based techniques, most existing strategies enforce a globally shared timestep schedule across all samples. This uniform treatment fails to account for instance-specific complexity in the generative process, potentially limiting performance. Motivated by controlled experiments on synthetic data, which reveals the suboptimality of global schedules under instance-specific dynamics, we propose an instance-aware discretization framework. Our method learns to adapt timestep allocations based on input-dependent priors, extending gradient-based discretization search to the conditional generative setting. Empirical results across diverse settings, including synthetic data, pixel-space diffusion, latent-space images and video flow matching models, demonstrate that our method consistently improves generation quality with marginal tuning cost compared to training and negligible inference overhead.
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