Now showing 1 - 4 of 4
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    A performance analysis of dispatching rules and a heuristic in static flowshops with missing operations of jobs
    (16-06-2001) ;
    Ziegler, Hans
    An experimental investigation of the performance of dispatching rules and a heuristic for scheduling in static flowshops with missing operations is undertaken in this study. The measure of performance is the minimization of total flow time of jobs. Permutation schedules are generated by using the heuristic for scheduling. General schedules, which can be permutation or non-permutation schedules, are obtained by using dispatching rules. Four dispatching rules, including a new dispatching rule, are considered. Two types of flowshops are studied: one with no missing operations of jobs and another with missing operations of jobs. In the latter type of flowshops, jobs with varying number of missing operations are considered. An extensive investigation of the performance of the dispatching rules and the heuristic is carried out. It is observed that the heuristic minimizes total flow time of jobs more than dispatching rules up to a certain level of missing operations of jobs in flowshops, after which dispatching rules perform better. The performance of the heuristic and the dispatching rules in terms of minimizing the makespan as a secondary measure is also reported. © 2001 Elsevier Science B.V.
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    Scheduling to minimize the sum of weighted flowtime and weighted tardiness of jobs in a flowshop with sequence-dependent setup times
    (16-09-2003) ;
    Ziegler, Hans
    Efficient heuristics for scheduling jobs in a static flowshop with sequence-dependent setup times of jobs are presented in this paper. The objective is to minimize the sum of weighted flowtime and weighted tardiness of jobs. Two heuristic preference relations are used to construct a good heuristic permutation sequence of jobs. Thereafter, an improvement scheme is implemented, once and twice, on the heuristic sequence to enhance the quality of the solution. An existing heuristic, a random search procedure and a greedy local search are used as benchmark methods for relatively evaluating the proposed heuristics. An extensive performance analysis has shown that the proposed heuristics are computationally faster and more effective in yielding solutions of better quality than the benchmark procedures. © 2002 Elsevier Science B.V. All rights reserved.
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    Ant-colony algorithms for permutation flowshop scheduling to minimize makespan/total flowtime of jobs
    (01-06-2004) ;
    Ziegler, Hans
    The problem of scheduling in permutation flowshops is considered with the objective of minimizing the makespan, followed by the consideration of minimization of total flowtime of jobs. Two ant-colony optimization algorithms are proposed and analyzed for solving the permutation flowshop scheduling problem. The first algorithm extends the ideas of the ant-colony algorithm by Stuetzle [Proceedings of the 6th European Congress on Intelligent Techniques and Soft Computing (EUFIT '98), vol. 3, Verlag Mainz, Aachen, Germany, 1998, p. 1560], called max-min ant system (MMAS), by incorporating the summation rule suggested by Merkle and Middendorf [Proceedings of the EvoWorkshops 2000, Lecture Notes in Computer Science No. 1803, Springer-Verlag, Berlin, 2000, p. 287] and a newly proposed local search technique. The second ant-colony algorithm is newly developed. The proposed ant-colony algorithms have been applied to 90 benchmark problems taken from Taillard [European Journal of Operational Research 64 (1993) 278]. First, a comparison of the solutions yielded by the MMAS and the two ant-colony algorithms developed in this paper, with the heuristic solutions given by Taillard [European Journal of Operational Research 64 (1993) 278] is undertaken with respect to the minimization of makespan. The comparison shows that the two proposed ant-colony algorithms perform better, on an average, than the MMAS. Subsequently, by considering the objective of minimizing the total flowtime of jobs, a comparison of solutions yielded by the proposed ant-colony algorithms with the best heuristic solutions known for the benchmark problems, as published in an extensive study by Liu and Reeves [European Journal of Operational Research 132 (2001) 439], is carried out. The comparison shows that the proposed ant-colony algorithms are clearly superior to the heuristics analyzed by Liu and Reeves. For 83 out of 90 problems considered, better solutions have been found by the two proposed ant-colony algorithms, as compared to the solutions reported by Liu and Reeves. © 2003 Elsevier B.V. All rights reserved.
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    A heuristic for scheduling to minimize the sum of weighted flowtime of jobs in a flowshop with sequence-dependent setup times of jobs
    (01-01-1997) ;
    Ziegler, H.
    The problem of scheduling in a static flowshop with sequence-dependent setup times of jobs (FSDS) is considered in this paper. A new heuristic to minimize the sum of weighted flowtime of jobs in a FSDS is proposed. An improvement scheme is supplemented to enhance the quality of the heuristic solution. An extensive computational performance analysis has shown that the proposed heuristic is computationally faster and more effective in yielding solutions of better quality than the existing heuristic. An interesting observation is that even though the proposed heuristic aims to minimize the sum of weighted flowtime of jobs (just like the existing heuristic), it fares much better than the existing heuristic in minimizing the maximum weighted flowtime of a job too. © 1997 Elsevier Science Ltd.