用激活匹配生成简洁可信的模型决策解释。
Activation Matching for Explanation Generation
- 通过自编码器学习二值掩码,使解释图像保留原图分类结果和中间激活。
- 生成的掩码小而清晰,能忠实还原模型决策过程。
- 适合需要理解模型推理逻辑的研究者与开发者。
本文提出一种基于激活匹配的解释生成方法,针对预训练分类器在任意输入图像上的决策行为,生成最小且忠实的解释。给定输入图像 $x$ 和冻结模型 $f$,通过训练轻量级自编码器输出二值掩码 $m$,使得解释 $e = m igodot x$ 同时保留模型预测结果与中间层激活分布。目标函数包含:(i) 多层激活匹配,使用 KL 散度对齐激活分布,交叉熵保持顶层类别一致;(ii) 掩码先验——L1 面积约束以实现最小化,二值化惩罚项确保掩码为 0/1 值,总变差正则增强紧凑性;(iii) 反向推理约束以保障解释的忠实性与必要性。该方法生成的小尺寸、可读性强的掩码,能有效保留分类器行为并剔除无关区域,为模型决策提供实用且可信的极简解释。
原文摘要 · Abstract (English)
In this paper we introduce an activation-matching--based approach to generate minimal, faithful explanations for the decision-making of a pretrained classifier on any given image. Given an input image $x$ and a frozen model $f$, we train a lightweight autoencoder to output a binary mask $m$ such that the explanation $e = m \odot x$ preserves both the model's prediction and the intermediate activations of \(x\). Our objective combines: (i) multi-layer activation matching with KL divergence to align distributions and cross-entropy to retain the top-1 label for both the image and the explanation; (ii) mask priors -- L1 area for minimality, a binarization penalty for crisp 0/1 masks, and total variation for compactness; and (iii) abductive constraints for faithfulness and necessity. Together, these objectives yield small, human-interpretable masks that retain classifier behavior while discarding irrelevant input regions, providing practical and faithful minimalist explanations for the decision making of the underlying model.
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