An Improved Branch-Cut-and-Price Algorithm for Parallel Machine Scheduling Problems

This work presents an improved branch-cut-and-price algorithm for the identical parallel machine scheduling problem minimizing a generic function of the job completion times. A new family of cuts is proposed to strengthen the arc-time-indexed formulation, along with an efficient separation algorithm. Also, the projection of the arc-time-indexed into a time-indexed formulation is introduced to take advantage of the variable fixings performed in the larger variable space. The improved algorithm was capable of solving 146 out of 150 instances in the literature, with 12 being solved for the first time. Also, the running time for the 134 previously solved instances decreased by 95.7% on the average.