提出无需梯度的可解释性方法,让黑箱模型也能生成分布级反事实解释。
DISCOVER: A Solver for Distributional Counterfactual Explanations
- 用提议-选择搜索替代梯度优化,适配不可导模型
- 每行计算影响分,只改最关键样本,控制干预数量
- 适合真实表格数据中的黑箱模型可解释性需求
反事实解释通过修改输入来说明模型决策。现有方法多为实例级,而分布级反事实解释(DCE)通过最优传输目标平衡输入分布邻近性和输出分布对齐性,并用机会约束保证统计可靠性。但DCE依赖梯度优化,难以用于大量非可导的表格模型。本文提出DISCOVER,一种模型无关的分布级反事实求解器,保留原DCE目标与认证机制,将梯度下降替换为带预算的提议-选择搜索。它通过运输目标的逐行分解计算每行影响分,施加top-k干预预算,聚焦于最具影响力样本。为在无预测梯度情况下生成候选,引入基于输入侧传输几何的锥采样机制。多个表格数据集实验显示,输入与输出分布实现强联合对齐,使分布级反事实推理可扩展至现代黑箱学习流程。代码已开源:https://github.com/VALHALLA9/Discover。
原文摘要 · Abstract (English)
Counterfactual explanations (CE) explain model decisions by identifying input modifications that lead to different predictions. Most existing methods operate at the instance level. Distributional Counterfactual Explanations (DCE) extend this setting by optimizing an optimal transport objective that balances proximity to a factual input distribution and alignment to a target output distribution, with statistical certification via chance constrained bounds. However, DCE relies on gradient based optimization, while many real-world tabular pipelines are dominated by non-differentiable models. We propose DISCOVER, a model-agnostic solver for distributional counterfactual explanations. DISCOVER preserves the original DCE objective and certification while replacing gradient descent with a budgeted propose-and-select search paradigm. It exploits a sample-wise decomposition of the transport objective to compute per-row impact scores and enforce a top-k intervention budget, focusing edits on the most influential samples. To guide candidate generation without predictor gradients, DISCOVER introduces an OT-guided cone sampling primitive driven by input-side transport geometry. Experiments on multiple tabular datasets demonstrate strong joint alignment of input and output distributions, extending distributional counterfactual reasoning to modern black box learning pipelines. A code repository is available at: https://github.com/VALHALLA9/Discover.
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