“…Since the ambiguity set in the two-stage DRO problem we are considering is only constrained by the fixed marginals, its inner maximization problem corresponds to a multi-marginal optimal transport problem, with the cost function being the optimal value of the second-stage decision problem. Most numerical methods for multi-marginal optimal transport and related problems with non-discrete marginals rely on discretization (see, e.g., (Carlier, Oberman, and Oudet 2015, Eckstein, Guo, Lim, and Ob lój 2021, Guo and Ob lój 2019, Neufeld and Sester 2021a) and/or regularization techniques (see, e.g., (Cohen, Arbel, and Deisenroth 2020, De Gennaro Aquino and Bernard 2020, De Gennaro Aquino and Eckstein 2020, Eckstein and Kupper 2019, Eckstein, Kupper, and Pohl 2020, Henry-Labordère 2019, Neufeld and Sester 2021b) and do not provide computable estimates of approximation errors. Recently, developed a numerical method that is capable of computing feasible and approximately optimal solutions of high-dimensional multi-marginal optimal transport problems.…”