  The core is a central solution concept in cooperative game theory, defined as
the set of feasible allocations or payments such that no subset of agents has
incentive to break away and form their own subgroup or coalition. However, it
has long been known that the core (and approximations, such as the least-core)
are hard to compute. This limits our ability to analyze cooperative games in
general, and to fully embrace cooperative game theory contributions in domains
such as explainable AI (XAI), where the core can complement the Shapley values
to identify influential features or instances supporting predictions by
black-box models. We propose novel iterative algorithms for computing variants
of the core, which avoid the computational bottleneck of many other approaches;
namely solving large linear programs. As such, they scale better to very large
problems as we demonstrate across different classes of cooperative games,
including weighted voting games, induced subgraph games, and marginal
contribution networks. We also explore our algorithms in the context of XAI,
providing further evidence of the power of the core for such applications.
