Showing papers on "Tardiness published in 1976"

A dual algorithm for the one-machine scheduling problem

Abstract: A branch and bound algorithm is presented for the problem of schedulingn jobs on a single machine to minimize tardiness. The algorithm uses a dual problem to obtain a good feasible solution and an extremely sharp lower bound on the optimal objective value. To derive the dual problem we regard the single machine as imposing a constraint for each time period. A dual variable is associated with each of these constraints and used to form a Lagrangian problem in which the dualized constraints appear in the objective function. A lower bound is obtained by solving the Lagrangian problem with fixed multiplier values. The major theoretical result of the paper is an algorithm which solves the Lagrangian problem in a number of steps proportional to the product ofn 2 and the average job processing time. The search for multiplier values which maximize the lower bound leads to the formulation and optimization of the dual problem. The bounds obtained are so sharp that very little enumeration or computer time is required to solve even large problems. Computational experience with 20-, 30-, and 50-job problems is presented.

A statistical comparison of the performance of simple dispatching rules for a particular set of job shops

Abstract: This research involves the development and analysis of a model of a particular set of real world job shops. The characteristics of the process include workers flexibility and job routings which may include assembly operations. An experimental design was used which allowed statistical comparisons to be made. Various control and staffing policies were considered, with mean flow time and mean job tardiness used as performance criteria. The shortest imminent operation time rule was found to provide the best performance in all but one situation. Workforce flexibility was observed to significantly improve both performance criteria for all dispatching rules considered.