拓展扩散模型至泊松、二项等非高斯逆问题,实现复杂场景下的贝叶斯推断。
Diffusion Models for Inverse Problems in the Exponential Family
- 利用指数族共轭性质设计证据技巧,获得可计算的似然梯度
- 在图像级强度的非均匀泊松过程上实现精准贝叶斯推断
- 在撒哈拉以南非洲疟疾发病率预测中达到领先水平
扩散模型已成为解决逆问题的强大工具,但以往研究主要针对高斯测量噪声的观测,限制了其在真实场景中的应用。这一局限源于似然得分的不可计算性,此前仅在高斯似然情形下可近似。本文将扩散模型扩展至服从指数族分布(如泊松或二项分布)的逆问题。通过利用指数族分布的共轭性质,提出证据技巧,实现对似然得分的可计算近似。实验表明,该方法能有效对空间异质泊松过程进行贝叶斯推断,其强度分布复杂度可达ImageNet图像级别。此外,方法在撒哈拉以南非洲疟疾流行率预测任务中表现优异,性能媲美当前最先进水平。
原文摘要 · Abstract (English)
Diffusion models have emerged as powerful tools for solving inverse problems, yet prior work has primarily focused on observations with Gaussian measurement noise, restricting their use in real-world scenarios. This limitation persists due to the intractability of the likelihood score, which until now has only been approximated in the simpler case of Gaussian likelihoods. In this work, we extend diffusion models to handle inverse problems where the observations follow a distribution from the exponential family, such as a Poisson or a Binomial distribution. By leveraging the conjugacy properties of exponential family distributions, we introduce the evidence trick, a method that provides a tractable approximation to the likelihood score. In our experiments, we demonstrate that our methodology effectively performs Bayesian inference on spatially inhomogeneous Poisson processes with intensities as intricate as ImageNet images. Furthermore, we demonstrate the real-world impact of our methodology by showing that it performs competitively with the current state-of-the-art in predicting malaria prevalence estimates in Sub-Saharan Africa.
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