A note on the MIR closure and basic relaxations of polyhedra

Anderson et al. (2005) 1] show that for a polyhedral mixed integer set defined by a constraint system Ax≥b, along with integrality restrictions on some of the variables, any split cut is in fact a split cut for a basic relaxation, i.e., one defined by a subset of linearly independent constraints. This result implies that any split cut can be obtained as an intersection cut. Equivalence between split cuts obtained from simple disjunctions of the form x_j≤0 or x_j≥1 and intersection cuts was shown earlier for 0/1-mixed integer sets by Balas and Perregaard (2002) 4]. We give a short proof of the result of Anderson, Cornuéjols and Li using the equivalence between mixed integer rounding (MIR) cuts and split cuts.