URGE解决了扩散模型推理时引导的计算瓶颈，做生成模型优化或采样加速的研究者可以直接用这个梯度无关的轻量方案，值得关注。
URGE（Unbiased Resampling via Girsanov Estimation）是一种无偏、无梯度的推理时缩放算法，用于扩散生成模型。它通过Girsanov测度变换对模拟轨迹进行路径重要性重加权，并定期重采样，无需计算分数、Hessian或PDE。该方法避免了现有技术中的偏差和高计算开销，在合成测试和扩散模型基准上优于现有推理时引导方法，且实现更简单。URGE建立了路径与粒子级序贯蒙特卡洛之间的等价性，确保两种方案产生相同的无偏终端分布。
SURGE: Approximation-free Training Free Particle Filter for Diffusion Surrogate
Diffusion-based generative models increasingly rely on inference-time guidance, adding a drift term or reweighting mixture of experts, to improve sample quality on task-specific objectives. However, most existing techniques require repeated score or gradient evaluations, introducing bias, high computational overhead, or both. We introduce \texttt{URGE}, Unbiased Resampling via Girsanov Estimation, a derivative-free inference-time scaling algorithm that performs path-wise importance reweighting via a Girsanov change of measure. Instead of computing gradient-based particle weights in previous work, \texttt{URGE} attaches a simple multiplicative weight to each simulated trajectory and periodically resamples. No score, no Hessian, and no PDE evaluation is required. We establish an equivalence between path-wise and particle-wise SMC: the Girsanov path weight admits a backward conditional expectation that recovers the previous particle-level weights, guaranteeing that both schemes produce the same unbiased terminal law. Empirically, \texttt{URGE} outperforms existing inference-time guidance baselines on synthetic tests and diffusion-model benchmarks, achieving better generation quality, while being significantly simpler to implement and fully gradient-free.