A polyhedral study on 0-1 knapsack problems with disjoint cardinality constraints: Facet-defining inequalities by sequential lifting

In this paper, we study the polyhedral structure of the set of 01 integer solutions to a single knapsack constraint and multiple disjoint cardinality constraints (MCKP). This set is a generalization of the classical 01 knapsack polytope (KP) and the 01 knapsack polytope with generalized upper bounds (GUBKP). For MCKP, we extend the traditional concept of a cover to that of a generalized cover. We then introduce generalized cover inequalities and present a polynomial algorithm that can lift them into facet-defining inequalities of the convex hull of MCKP. For the case where the knapsack coefficients are non-negative, we derive strong bounds on the lifting coefficients and describe the maximal set of generalized cover inequalities. Finally, we show that the bound estimates we obtained strengthen or generalize the known results for KP and GUBKP.