提出可生成贴近真实数据的敏感性分析方法,提升决策树集成模型的可信度。
Data-Aware and Scalable Sensitivity Analysis for Decision Tree Ensembles
- 结合MILP与SMT编码,约束敏感样本接近训练数据分布。
- 支持深度达8、最多800棵树的集成模型,性能远超现有方法。
- 适用于高风险场景下模型公平性与可靠性评估,实用性强。
决策树集成广泛应用于关键领域,其鲁棒性与敏感性分析对可信度至关重要。本文研究特征敏感性问题:即模型是否对特定特征(如受保护属性)敏感,其微小变动可能改变预测结果。现有方法产生的敏感样本常偏离训练数据分布,缺乏可解释性与实用性。为此,我们提出一种数据感知的敏感性分析框架,将敏感样本限制在贴近训练数据的范围内,从而生成真实且可理解的模型弱点证据。为此,我们开发了结合混合整数线性规划(MILP)与满足模理论(SMT)编码的新技术。主要贡献有四点:第一,强化了敏感性验证的NP难性结果,证明即使深度为1的树也成立;第二,提出MILP优化方法,显著加速单个集成的敏感性验证,并首次实现对多分类树集成的支持;第三,构建数据感知框架,生成贴近训练分布的合理敏感实例;第四,在大规模树集成上进行广泛实验,验证其可扩展性,支持最多800棵树、深度达8的集成,相较当前最优方法有显著提升。该框架为高风险应用中树模型的可靠性与公平性分析提供了实用基础。
原文摘要 · Abstract (English)
Decision tree ensembles are widely used in critical domains, making robustness and sensitivity analysis essential to their trustworthiness. We study the feature sensitivity problem, which asks whether an ensemble is sensitive to a specified subset of features -- such as protected attributes -- whose manipulation can alter model predictions. Existing approaches often yield examples of sensitivity that lie far from the training distribution, limiting their interpretability and practical value. We propose a data-aware sensitivity framework that constrains the sensitive examples to remain close to the dataset, thereby producing realistic and interpretable evidence of model weaknesses. To this end, we develop novel techniques for data-aware search using a combination of mixed-integer linear programming (MILP) and satisfiability modulo theories (SMT) encodings. Our contributions are fourfold. First, we strengthen the NP-hardness result for sensitivity verification, showing it holds even for trees of depth 1. Second, we develop MILP-optimizations that significantly speed up sensitivity verification for single ensembles and for the first time can also handle multiclass tree ensembles. Third, we introduce a data-aware framework generating realistic examples close to the training distribution. Finally, we conduct an extensive experimental evaluation on large tree ensembles, demonstrating scalability to ensembles with up to 800 trees of depth 8, achieving substantial improvements over the state of the art. This framework provides a practical foundation for analyzing the reliability and fairness of tree-based models in high-stakes applications.
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