arXiv:2511.22177cs.LGcs.CV2025-11被引 1

通过智能调整采样时间表,让文生图模型生成更精准的图像。

Designing Instance-Level Sampling Schedules via REINFORCE with James-Stein Shrinkage

  • 为每张图定制采样时间表,根据提示词和噪声动态调整。
  • 5步采样器效果媲美专门优化的高效模型,文本对齐显著提升。
  • 适合希望不修改模型就能增强生成质量的研究者和开发者。

大多数文生图模型的后训练方法聚焦于模型权重:或微调主干网络以增强对齐,或进行知识蒸馏以实现少步高效生成。本文另辟蹊径:对冻结的采样器重设计采样时间表。不同于固定全局的时间表,我们通过单次遍历的狄利克雷策略学习实例级(提示词与噪声条件)的时间表。为在高维策略学习中获得精确梯度估计,提出一种基于严谨詹姆斯-斯坦因估计器的新型奖励基线;其可证明地比常用变体误差更低,带来更优性能。重设计的采样器在现代 Stable Diffusion 与 Flux 模型家族中持续提升文本-图像对齐能力,包括文本渲染与组合控制。此外,采用本方法的 5 步 Flux-Dev 采样器生成质量可媲美专门蒸馏的 Flux-Schnell。因此,我们的调度框架被视为一种新兴的、模型无关的后训练工具,能充分释放预训练采样器的生成潜力。

原文摘要 · Abstract (English)

Most post-training methods for text-to-image samplers focus on model weights: either fine-tuning the backbone for alignment or distilling it for few-step efficiency. We take a different route: rescheduling the sampling timeline of a frozen sampler. Instead of a fixed, global schedule, we learn instance-level (prompt- and noise-conditioned) schedules through a single-pass Dirichlet policy. To ensure accurate gradient estimates in high-dimensional policy learning, we introduce a novel reward baseline based on a principled James-Stein estimator; it provably achieves lower estimation errors than commonly used variants and leads to superior performance. Our rescheduled samplers consistently improve text-image alignment including text rendering and compositional control across modern Stable Diffusion and Flux model families. Additionally, a 5-step Flux-Dev sampler with our schedules can attain generation quality comparable to deliberately distilled samplers like Flux-Schnell. We thus position our scheduling framework as an emerging model-agnostic post-training lever that unlocks additional generative potential in pretrained samplers.

采样调度扩散模型生成质量后训练

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