共查询到19条相似文献,搜索用时 400 毫秒
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研究带批运输的两台同型机排序问题. 在该问题中,工件在两台同型机上加工,完工的工件由一辆容量为z的车运输到客户. 这里假设工件有不同的物理大小,目标是求一个时间表使得所有工件送达客户且车回到机器所在位置的时间最小,给出了一个(14/9+ε)-近似算法 相似文献
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本文考虑下述由多工类工件组成的订单的单机排序问题:每一个客户提供一个由若干工件组成的订单,总共n个工件又分成k个类.当机器从加工某类中的工件转向加工不同于它的第i类工件时,需一调整时间si.每一订单有一给定的应交工时间,订单的完工时间定义为该定单所含全部工件完工时的时间.我们希望适当排列这n个工件,使得订单的迟后范围最小.相应这一排序问题,文中依不同的背景给出了以下二种模式:同类工件一起连续加工,工件的完工时间为其所属类中全部工件完工时的时间,用GT,Ba来表示;同类工件一起连续加工,工件的完工时间为其本身的完工时间,用GT,Ja来表示.对于这两种模式的排序同题,我们均证明了其NP-hard性并给出了对应的分枝定界算法. 相似文献
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工件按加工长度不增序到达的最小化最大流程在线分批排序 总被引:1,自引:0,他引:1
研究单处理机工件按加工长度不增顺序到达的在线分批排序问题.工件按时在线到达,目标是最小化最大流程.流程时间是指工件的完工时间与到达时间的差值,它体现了工件在系统内的逗留时间.对于批容量有界的情形,给出了一个竞争比为1+√5/2的最好可能的在线算法;对于批容量无界的情形,给出了一个竞争比为√2的最好可能的在线算法. 相似文献
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We consider supply chain scheduling problems where customers release jobs to a manufacturer that has to process the jobs and deliver them to the customers. The jobs are released on-line, that is, at any time there is no information on the number, release and processing times of future jobs; the processing time of a job becomes known when the job is released. Preemption is allowed. To reduce the total costs, processed jobs are grouped into batches, which are delivered to customers as single shipments; we assume that the cost of delivering a batch does not depend on the number of jobs in the batch. The objective is to minimize the total cost, which is the sum of the total flow time and the total delivery cost. For the single-customer problem, we present an on-line two-competitive algorithm, and show that no other on-line algorithm can have a better competitive ratio. We also consider an extension of the algorithm for the case of m customers, and show that its competitive ratio is not greater than 2m if the delivery costs to different customers are equal. 相似文献
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研究了具有线性恶化工件的单机排序问题,其中线性恶化工件指的是工件的加工时间是开工时间的线性增长函数.在一般情况下,对目标函数为极小化完工时间平方和与极小化总误工数问题分别给出了最优算法.此外,在分段情况下,对目标函数为极小化最大完工时间问题也给出了最优算法. 相似文献
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本文研究线形网络上单台车辆分群调度问题:若干客户分布在一条直线上,它们被划分成若干个连续子集,其中每个子集称为一个群;每个客户有一个释放时间和一个服务时间;一台机器服务所有客户,且要求每个群内的客户连续服务;目标为极小化时间表长。该问题分两种形式:返回型和不返回型。返回型的时间表长定义为机器服务完所有客户后返回其初始位置的时间;不返回型的时间表长则定义为所有客户的最大完工时间。我们的结果是:对每个客户服务时间为零的情形,证明了两种形式均可在O(n2) 时间内解决;对每个客户服务时间任意的情形,就返回型和不返回型,分别给出了16/9和13/7近似算法。 相似文献
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In this paper, we study a single machine scheduling problem by simultaneously considering the processing method of serial-batching, learning effect, resource-dependent processing times, and setup operations. We consider minimizing the makespan as the objective of the studied problem under the constraint that the total resource consumption does not exceed a given limit. For the special case where the resource allocation is given, we first propose the structural properties for job batching policies and batching sequencing, and an optimal batching policy is derived based on these properties. Then, we develop a novel hybrid GSA–TS algorithm which combines the Gravitational Search Algorithm (GSA) and the Tabu Search (TS) algorithm to solve the general case. Computational experiments with different scales show the effectiveness and efficiency of the proposed algorithm. 相似文献
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We consider a finite-population queueing system with heterogeneous classes of customers and a single server. For the case
of nonpreemptive service, we fully characterize the structure of the server's optimal service policy that minimizes the total
average customer waiting costs. We show that the optimal service policy may never serve some classes of customers. For those
classes that are served, we show that the optimal service policy is a simple static priority policy. We also derive sufficient
conditions that determine the optimal priority sequence. 相似文献
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We consider the scheduling problem of minimizing the makespan on a single machine with step-improving job processing times around a common critical date. For this problem we give an NP-hardness proof, a fast pseudo-polynomial time algorithm, an FPTAS, and an on-line algorithm with best possible competitive ratio. 相似文献
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In this paper we consider the problem of scheduling n jobs on a single batch processing machine in which jobs are ordered by two customers. Jobs belonging to different customers are processed based on their individual criteria. The considered criteria are minimizing makespan and maximum lateness. A batching machine is able to process up to b jobs simultaneously. The processing time of each batch is equal to the longest processing time of jobs in the batch. This kind of batch processing is called parallel batch processing. Optimal methods for three cases are developed: unbounded batch capacity, b > n, with compatible job groups and bounded batch capacity, b n, with compatible and non compatible job groups. Each job group represents a different class of customers and the concept of being compatible means that jobs which are ordered by different customers are allowed to be processed in a same batch. We propose an optimal method for the problem with incompatible groups and unbounded batches. About the case when groups are incompatible and bounded batches, our proposed method is considered as optimal when the group with maximum lateness objective has identical processing times. We regard this method, however, as a heuristic when these processing times are different. When groups are compatible and batches are bounded we consider another problem by assuming the same processing times for the group which has the maximum lateness objective and propose an optimal method for this problem. 相似文献
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We consider a load-sharing problem for a multiprocessor system in which jobs have real-time constraints: if the waiting time of a job exceeds a given random amount (called the laxity of the job), then the job is considered lost. To minimize the steady-state probability of loss with respect to the load-sharing parameters, we propose to use the likelihood ratio derivative estimate approach, which has recently been studied for sensitivity analysis of stochastic systems. We formulate a recursive stochastic optimization algorithm using likelihood ratio estimates to solve the optimization problem and provide a proof for almost sure convergence of the algorithm. The algorithm can be used for on-line optimization of the real-time system and does not require a priori knowledge of the arrival rate of customers to the system or the service time and laxity distributions. To illustrate our results, we provide simulation examples.This research was partially supported by an IBM Graduate Fellowship and by the National Science Foundation through Grant No. ECS-87-15217. 相似文献