Flowshop scheduling to minimize the sum of weighted tardiness cost and weighted flowtime cost by synergy of heuristics

Scheduling multi-job orders in a multi-machine environment is shown to be NP - Hard. The Flowshop scheduling to minimize the makespan as well as a complex cost function are extremely relevant in today's context of manufacturing. In this paper, synergy of heuristic methods which performed well for minimizing rnakespan as well as minimizing a complex cost function is reported. The flowshop scheduling that minimizes the sum of weighted tardiness cost and weighted flowtime cost has been solved by branch & bound method to obtain optimum solution. The computation time for solving the large size problem is reported to exponentially increase as the number of jobs and machines increases. Several heuristic methods have been developed to overcome these difficulties. These heuristic methods are on the basis of dynamic dispatching rules. Similarly both optimum and heuristic methods are developed for solving flowshop scheduling problem to minimize the makespan. The synergy of heuristics that perform well, aims to construct a good permutation sequence of jobs by adapting certain insertion approach. The flowshop scheduling problem to minimize the complex objective function is solved by existing heuristic methods as well as by the proposed synergy of heuristics. The extensive computational investigation reveals that the proposed synergy of heuristics out performed.