[2603.01837] Constrained Particle Seeking: Solving Diffusion Inverse Problems with Just Forward Passes

Computer Science > Machine Learning arXiv:2603.01837 (cs) [Submitted on 2 Mar 2026] Title:Constrained Particle Seeking: Solving Diffusion Inverse Problems with Just Forward Passes Authors:Hongkun Dou, Zike Chen, Zeyu Li, Hongjue Li, Lijun Yang, Yue Deng View a PDF of the paper titled Constrained Particle Seeking: Solving Diffusion Inverse Problems with Just Forward Passes, by Hongkun Dou and 5 other authors View PDF HTML (experimental) Abstract:Diffusion models have gained prominence as powerful generative tools for solving inverse problems due to their ability to model complex data distributions. However, existing methods typically rely on complete knowledge of the forward observation process to compute gradients for guided sampling, limiting their applicability in scenarios where such information is unavailable. In this work, we introduce \textbf{\emph{Constrained Particle Seeking (CPS)}}, a novel gradient-free approach that leverages all candidate particle information to actively search for the optimal particle while incorporating constraints aligned with high-density regions of the unconditional prior. Unlike previous methods that passively select promising candidates, CPS reformulates the inverse problem as a constrained optimization task, enabling more flexible and efficient particle seeking. We demonstrate that CPS can effectively solve both image and scientific inverse problems, achieving results comparable to gradient-based methods while significantly outperformin...