Distributionally robust optimization (DRO) provides a framework for training machine learning models that are able to perform well on a collection of related data distributions (the "uncertainty set"). This is done by solving a min-max game: the model is trained to minimize its maximum expected loss among all distributions in the uncertainty set. While careful design of the uncertainty set is critical to the success of the DRO procedure, previous work has been limited to relatively simple alternatives that keep the min-max optimization problem exactly tractable, such as $f$-divergence balls. In this paper, we argue instead for the use of neural generative models to characterize the worst-case distribution, allowing for more flexible and problem-specific selection of the uncertainty set. However, while simple conceptually, this approach poses a number of implementation and optimization challenges. To circumvent these issues, we propose a relaxation of the KL-constrained inner maximization objective that makes the DRO problem more amenable to gradient-based optimization of large scale generative models, and develop model selection heuristics to guide hyper-parameter search. On both toy settings and realistic NLP tasks, we find that the proposed approach yields models that are more robust than comparable baselines.

本文提出了一种基于神经生成模型的分布鲁棒优化(DRO)方法，通过对不确定集合中的分布进行建模，使得模型在不确定的分布中表现优异，并提出一种KL约束内部最大化目标的松弛优化方式，通过大规模生成模型的梯度优化来解决相应的实现和优化挑战，并且开发模型选择启发式方法来指导超参数搜索。实验结果表明提出的方法比当前基线模型更具鲁棒性。

分布鲁棒优化中第二玩家建模