Hierarchical Variational Policies for Reward-Guided Diffusion
分层变分策略用于奖励引导的扩散
Kushagra Pandey, Farrin Marouf Sofian, Jan Niklas Groeneveld, Felix Draxler, Stephan Mandt
AI总结 本文提出了一种分层变分模型框架,通过将控制信息压缩到轻量级且表达能力强的随机策略中,实现了在降低推理成本的同时生成高质量的奖励对齐样本,该方法在4倍超分辨率任务中实现了比现有最佳基线快5倍的推理速度并具有更好的感知质量。
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适应预训练扩散模型以解决下游目标如逆问题通常需要昂贵的测试时间引导或优化。我们提出了一种系统框架,能够在大幅降低推理成本的同时生成高质量的奖励对齐样本。我们的方法将测试时间适应建模为分层变分模型,其中控制被压缩到一个轻量级但表达能力强的随机策略中。这种建模自然支持少量步扩散采样:大步长使推理快速,而学习的策略通过提供结构化的每步控制保持样本质量。所得到的完全压缩采样器实现了强大的质量-速度权衡,匹配或超过最近的测试时间扩展基线,同时需要显著更少的计算资源。例如,在4倍超分辨率任务中,我们的方法在比最佳表现基线快5倍的情况下实现了更好的感知质量。我们进一步将该方法扩展到半压缩的 regime,结合廉价的压缩提案和有限的测试时间优化,在多个具有挑战性的逆问题中实现了最先进的感知质量。
Adapting pretrained diffusion models to downstream objectives such as inverse problems often requires expensive test-time guidance or optimization. We propose a principled framework for generating high-quality reward-aligned samples at substantially reduced inference cost. Our approach formulates test-time adaptation as a hierarchical variational model, where control is amortized into a lightweight yet expressive stochastic policy. This formulation naturally supports few-step diffusion sampling: large step sizes enable fast inference, while the learned policy maintains sample quality by providing structured per-step control. The resulting fully amortized sampler achieves a strong quality--speed tradeoff, matching or exceeding recent test-time scaling baselines while requiring significantly less compute. For example, on 4x super-resolution, our method achieves better perceptual quality with more than 5x faster inference compared to the best-performing baseline. We further extend our approach to a semi-amortized regime that combines cheap amortized proposals with limited test-time optimization, achieving state-of-the-art perceptual quality across several challenging inverse problems.