The Dulmage-Mendelsohn Decomposition for $b$-Matchings

We establish the theory of the Dulmage-Mendelsohn decomposition for $b$-matchings. The original Dulmage-Mendelsohn decomposition is a classical canonical decomposition of bipartite graphs, which describes the structures of the maximum $1$-matchings and the dual optimizers, i.e., the minimum vertex covers. In this paper, we develop analogical properties, and thus obtain the structure of the maximum $b$-matchings and characterizes the family of $b$-verifying set.