A Generalized Polymatroid Approach to Stable Matchings with Lower Quotas

Classified stable matching, proposed by Huang, describes a matching model between academic institutes and applicants, in which each institute has upper and lower quotas on classes, i.e., subsets of applicants. Huang showed that the problem to decide whether there exists a stable matching or not is NP-hard in general. On the other hand, he showed that the problem is solvable if classes form a laminar family. For this case, Fleiner and Kamiyama gave a concise interpretation in terms of matroids and showed the lattice structure of stable matchings.

In this paper we introduce stable matchings on generalized matroids, extending the model of Fleiner and Kamiyama. We design a polynomial-time algorithm which finds a stable matching or reports the nonexistence. We also show that the set of stable matchings, if nonempty, forms a lattice with several significant properties. Furthermore, we extend this structural result to the polyhedral framework, which we call stable allocations on generalized polymatroids.