Order release planning in a job shop using a bi-directional simulation algorithm

Order release is an important job shop scheduling function that plans and controls the release of jobs to the shop floor. Deterministic simulation has been proposed to determine order release times with either a forward or a reversed approach. We develop a bi-directional algorithm that always starts and ends with a forward simulation run, and the algorithm includes a number of additional reversed and forward runs in between the first and last runs. A reversed simulation run determines potential job release times, and these potential times become actual release times when they are all non-negative. When one or more potential release times are negative, the algorithm modifies them to specify job release times for the succeeding forward simulation run. The last forward simulation run determines the job completion times. Experimental results show that the bi-directional simulation algorithm produces a significantly improved mean flow time, and the algorithm can improve mean tardiness in some cases.