A parallel ordering problem in facilities layout

In this paper, we study a problem that occurs in the row layout of facilities. Among n facilities, suppose that there are t facilities with some characteristic in common so that they should be arranged along one row, leaving the remainder (n−t) facilities to be arranged on a parallel row. The objective is to order the facilities in the two rows such that some cost function is minimized. This problem is called the parallel row ordering problem (PROP). The PROP is a generalization of the single row facility layout problem (SRFLP). Here, a mixed integer programming (MIP) formulation of the PROP is presented which extends a MIP formulation of the SRFLP. We show that a PROP with n facilities may be solved faster than a SRFLP with n facilities. Theoretical and experimental comparisons of the SRFLP and the PROP formulations are presented.