将嵌入模型转化为可验证的自动编码器,提升降维方法的可靠性。
MEDAL: Manifold Embedding Distillation via Autoencoder Learning

- 用约束自编码器复现已有嵌入结果,实现新样本映射与逆映射
- 支持留出数据验证,能选出最优降维参数和方法
- 适用于生物、科学等领域,帮助发现隐藏结构并检测分布偏移
低维嵌入广泛用于高维数据的视觉摘要及下游科学发现。然而,t-SNE、UMAP等主流非线性降维方法常仅凭视觉效果选择,缺乏严谨的定量验证。主要原因在于这些嵌入通常不提供新样本的映射能力,也无法反推回原始特征空间,导致留出验证(监督学习金标准)几乎无法实施。为此,我们提出MEDAL(基于自编码器学习的流形嵌入蒸馏)框架,将已训练的流形嵌入蒸馏为可复用的编码器-解码器模型。MEDAL训练一个瓶颈层精确匹配任意教师嵌入的约束自编码器,同时解码器重建原始输入;这生成了新样本的显式映射、近似逆映射,以及基于点级重构误差的流形空间畸变度量。该方法使静态嵌入变为可留出验证的模型,支持不同降维方法比较与超参数调优。在多个基准和科学案例研究中,MEDAL实现了留出验证以确定最优嵌入与超参数,揭示了难以在二维嵌入中保留的生物学一致区域,并在新样本映射到固定参考流形时检测出分布偏移。MEDAL为任何现有降维技术提供通用验证框架,可显著提升科学工作流中降维的严谨性与可靠性。
原文摘要 · Abstract (English)
Low-dimensional embeddings are widely used as visual summaries of high-dimensional data and to enable downstream scientific discoveries. Yet, popular nonlinear dimension reduction methods, such as t-SNE and UMAP, are often selected based on visual appeal alone and without rigorous quantitative validation. A major reason is that manifold embeddings typically do not provide an out-of-sample map nor an inverse back to the original feature space; this makes held-out validation, the gold standard in supervised learning, all but impossible. To address these challenges, we develop a novel framework, MEDAL (Manifold Embedding Distillation via Autoencoder Learning), which distills a fitted manifold embedding into a reusable encoder--decoder model. MEDAL trains a constrained autoencoder whose bottleneck exactly matches any teacher embedding while the decoder reconstructs the original input; this yields an explicit map for new samples, an approximate inverse, and a pointwise reconstruction-based measure of distortion in the manifold space. This converts static manifold embeddings into models that can be evaluated on held-out data, enabling quantitative validation including comparing different dimension reduction methods as well as hyperparameter tuning. Across multiple benchmark and scientific case studies, we show that MEDAL enables held-out validation to determine optimal manifold embeddings and hyperparameters, reveals biologically coherent regions that are difficult to preserve in two dimensional embeddings, and detects distribution shift when new samples are mapped into a fixed reference manifold. MEDAL provides a general validation wrapper to any existing dimension reduction technique that will improve the rigor and reliability of dimension reduction in scientific workflows.
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