通过双梯度匹配学习归一化图像概率密度,提升生成模型的稳定性与泛化性。
Learning normalized image densities via dual score matching
- 设计能量网络,利用去噪目标和噪声水平梯度实现双重得分匹配
- 在ImageNet64上达到与顶尖方法相当的负对数似然(cross-entropy)
- 模型对非重叠数据训练仍具强泛化能力,揭示图像内容影响局部维度
从数据中学习概率模型是机器学习的核心挑战,常因维度灾难而困难。本文提出一种受扩散生成模型启发的新框架,用于学习归一化的能量(对数概率)模型。通过修改得分网络结构,在保持其归纳偏置的同时计算能量,其输入图像的梯度即为所学密度的得分,可通过去噪目标优化。关键创新在于:对噪声水平的梯度提供额外得分,结合新提出的二次目标,确保不同噪声水平下能量的一致性与归一性。我们在ImageNet64上训练该能量网络,获得的交叉熵(负对数似然)接近当前最优水平。进一步验证显示,两个在不重叠数据子集上训练的网络,其估计的对数概率几乎一致,表明模型具有强泛化性。最后发现,图像概率及局部邻域维度随图像内容显著变化,与传统假设如测度集中或低维流形支撑相悖。
原文摘要 · Abstract (English)
Learning probability models from data is at the heart of many machine learning endeavors, but is notoriously difficult due to the curse of dimensionality. We introduce a new framework for learning \emph{normalized} energy (log probability) models that is inspired by diffusion generative models, which rely on networks optimized to estimate the score. We modify a score network architecture to compute an energy while preserving its inductive biases. The gradient of this energy network with respect to its input image is the score of the learned density, which can be optimized using a denoising objective. Importantly, the gradient with respect to the noise level provides an additional score that can be optimized with a novel secondary objective, ensuring consistent and normalized energies across noise levels. We train an energy network with this \emph{dual} score matching objective on the ImageNet64 dataset, and obtain a cross-entropy (negative log likelihood) value comparable to the state of the art. We further validate our approach by showing that our energy model \emph{strongly generalizes}: log probabilities estimated with two networks trained on non-overlapping data subsets are nearly identical. Finally, we demonstrate that both image probability and dimensionality of local neighborhoods vary substantially depending on image content, in contrast with conventional assumptions such as concentration of measure or support on a low-dimensional manifold.
Thank you to arXiv for use of its open access interoperability. PaperDance 不是 arXiv 官方产品;中文卡片由大模型生成,请以原文为准。