不用概率模型的生成框架,让图像重建更清晰。
Likelihood-Free Variational Autoencoders
- 用确定性解码器+能量评分构建损失,无需假设数据分布
- 单样本训练,效率高,能直接接入现有VAE流程
- 在图像重建上优于传统方法,适合追求高保真生成的场景
变分自编码器(VAE)通常依赖预设的概率解码器(如各向同性高斯分布)来建模数据条件于隐变量。这种设定虽便于优化,但常导致似然误设,尤其在高维图像数据上出现模糊重建和低数据保真度。本文提出EnVAE,一种新颖的无似然生成框架:采用确定性解码器,并利用能量评分(一种合理的评分规则)构建重构损失,实现无需显式参数化密度函数的无似然推断。为克服能量评分计算效率低的问题,引入基于解码器局部平滑性和后验分布尖锐性的快速变体FEnVAE,获得高效的单样本训练目标,可无缝集成到现有VAE流程且开销极小。在标准基准上的实证结果表明,EnVAE在重建与生成质量上均优于基于似然的基线方法。该框架提供了一种通用、可扩展且统计上严谨的非参数分布学习方案,适用于灵活的生成建模。
原文摘要 · Abstract (English)
Variational Autoencoders (VAEs) typically rely on a probabilistic decoder with a predefined likelihood, most commonly an isotropic Gaussian, to model the data conditional on latent variables. While convenient for optimization, this choice often leads to likelihood misspecification, resulting in blurry reconstructions and poor data fidelity, especially for high-dimensional data such as images. In this work, we propose EnVAE, a novel likelihood-free generative framework that has a deterministic decoder and employs the energy score--a proper scoring rule--to build the reconstruction loss. This enables likelihood-free inference without requiring explicit parametric density functions. To address the computational inefficiency of the energy score, we introduce a fast variant, FEnVAE, based on the local smoothness of the decoder and the sharpness of the posterior distribution of latent variables. This yields an efficient single-sample training objective that integrates seamlessly into existing VAE pipelines with minimal overhead. Empirical results on standard benchmarks demonstrate that EnVAE achieves superior reconstruction and generation quality compared to likelihood-based baselines. Our framework offers a general, scalable, and statistically principled alternative for flexible and nonparametric distribution learning in generative modeling.
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