You can guide diffusion models without computing gradients or scores—just reweight trajectories and resample periodically, making inference-time improvements cheaper and easier to implement.
This paper introduces URGE, a gradient-free method for improving diffusion model outputs at inference time. Instead of computing expensive gradients, URGE reweights and resamples trajectories using a mathematical technique called Girsanov estimation, making guidance simpler and faster while maintaining theoretical guarantees.