车辆数限制的多车型校车路径问题模型及算法研究

为适应校车路径规划中校车有多种车型且每种车型数量受限的需求,建立车辆数限制的多车型校车路径问题(HFSBRP)的数学模型,并提出一种迭代局部搜索算法进行求解。该算法借助邻域随机选择的变邻域下降搜索(VND)算法完成局部提升。局部提升过程中,首先调整车型,然后再混合使用缩减路径数和提高车辆利用率的邻域解接受策略以提高算法的寻优能力,为保证解的多样性,允许接受一定偏差范围内的邻域解。此外,为避免算法过早陷入局部最优,设计了多点交换和移动的扰动规则。基于国际基准测试案例进行模型验证和算法测试,实验结果表明了模型的正确性和算法的有效性。     

求解多车型校车路径问题的带参数选择机制的GRASP算法

考虑到校车路径安排过程中不同车型容量和成本的差异,建立了多车型校车路径问题(SBRP)模型,并提出了一种带参数选择机制的贪婪随机自适应(GRASP)算法进行求解。在初始解构造阶段,设计一组阈值参数控制受限候选列表(RCL)的大小,使用轮盘赌法选择阈值参数。完成初始解构造后,使用可变邻域搜索(VNS)进行邻域解改进,并记录所选择的参数和解的目标值。算法迭代过程中,先设置相同阈值参数的选择概率,每隔若干次迭代后,评估每个阈值参数的性能并修改其选择概率,使得算法能够得到更好的平均解。使用基准测试案例进行了测试,比较了基本GRASP算法与设计的GRASP算法的性能,并与现有求解多车型校车路径问题的算法进行对比,实验结果表明所设计的算法是有效的。     

一种求解多校多车型校车路径问题的元启发算法

针对多种车型可用的多校校车路径问题(SBRP),建立数学模型,并提出了一种迭代局部搜索(ILS)元启发算法进行求解。该算法引入并改进了带时间窗的装卸一体化问题(PDPTW)求解中的点对邻域算子,并使用可变邻域下降搜索(VND)完成局部提升。局部提升过程中,设计一种基于路径段的车型调整策略,尽可能地调整车型,降低成本,并允许接受一定偏差范围内的邻域解以保证搜索的多样性。对于局部提升得到的最好解,使用多点移动方法对其进行扰动,以避免算法过早陷入局部最优。在国际基准测试案例上分别测试多校混载和不混载模式下算法的性能,实验结果验证了设计算法的有效性。进一步使用提出的算法求解单车型多校SBRP问题,并与后启发算法、模拟退火算法和记录更新法等算法进行比较,实验结果表明该算法仍然能够获得较好的优化效果。     

TSP问题的一种改进的GRASP算法

本文对Marinakis等提出的扩展邻域GRASP算法进行改进。首先使用最近α值方法构造初始TSP回路,然后运用混合的局部搜索即2-opt算法、双桥策略和3-opt算法来改进初始回路,并且引进α-nearness候选集和don’t-lookbit技术来提高搜索速度。实验结果表明,本文提出的GRASP能够在合理的时间内得到很好的解,并且解的质量优于M~rinakis等提出的扩展邻域GRASP算法得到的解。     

基于分段混合蛙跳算法的旅行商问题求解

针对旅行商问题(TSP)在搜索后期解的多样性和精度下降的问题,提出一种解决TSP问题的分段混合蛙跳算法(S-SFLA)。该算法在搜索初期利用逆转变异算子减少交叉路径,在搜索的后期引入邻域搜索(个体邻域,局部最优领域,全局最优邻域)增加种群多样性。在整个搜索过程中记忆全局历史最优解与局部历史最优解,进行全局更新和局部更新,避免迂回搜索。在局部更新中,每一个青蛙都有机会得到更新。实验结果表明,与遗传算法、蚁群算法、基本蛙跳算法相比,S-SFLA算法在求解中等规模的TSP问题上具有更快的搜索速度和更高的求解精度。     

基于混合平衡优化算法的疫苗配送路径优化

针对疫苗配送路径优化问题,在同时考虑固定成本、运输成本、制冷成本、碳排放成本和惩罚成本的情况下,提出以疫苗配送成本最小化为目标的车辆路径优化模型。为求解模型,在平衡优化器算法中引入模拟退火算法,改进平衡优化器算法容易陷入局部最优的不足,通过加入可变参数,提升算法平衡全局搜索和局部寻优的能力,得到一个能够稳定求出较高质量解的混合平衡优化算法。对2种不同规模的算例分别进行20次实验,将混合平衡优化算法与并行平衡优化算法、知识型蚁群算法、混合变邻域搜索算法、改进混合粒子群算法和平衡优化器算法进行对比。实验结果表明,混合平衡优化算法在小规模算例和大规模算例下得到的最小配送成本和配送成本的标准差都小于其他5种算法,其中,在小规模算例下进行实验后得到的最小配送成本分别为其他5种算法的73.5%、53.9%、69.1%、64.1%和33.4%。     

改进蚁群算法求解绿色周期性车辆路径问题北大核心CSCD

针对带时间窗的绿色周期性车辆路径问题(GPVRPTW),同时以最小化运输时间和总能耗为优化目标,提出一种改进蚁群算法(IACO)进行求解。首先,IACO采用三维概率矩阵记录不同配送日期的车辆路径子问题的优质解信息,并设计基于信息熵的信息素更新机制进行合理地学习和积累,从而增强算法全局搜索的引导性;其次,引入基于5种邻域操作的变邻域搜索以提高算法的局部搜索能力;最后,在不同规模问题上进行仿真实验与算法对比,结果验证了IACO的有效性。     

求解模糊Job Shop调度的遗传算法与蚁群算法融合研究

提出一种算法融合策略,解决单一算法求解模糊Job Shop调度问题存在的不足,提高这类问题的求解质量.算法融合策略中,采用遗传算法和蚁群算法进行并行搜索;根据模糊Job Shop调度问题解的特征,提出基于关键工序的邻域选择方法,并将基于这种邻域选择方法的禁忌搜索算法作为局部搜索算法,加强了遗传算法和蚁群算法的局部搜索能力.采用算法融合策略的混合优化算法对以13个难的benchmarks问题经模糊化得到实例进行求解,在较短的时间内,得到的平均满意度较并行遗传算法(PGA)提高5.24%、较TSAB算法提高8.40% .采用算法融合策略构造的混合算法具有较强的搜索能力,说明提出的混合搜索策略是有效的.     

基于邻域搜索的改进最大最小蚁群算法

针对蚁群算法求解旅行商问题时易陷入局部最优的问题,提出一个改进的混合最大最小蚁群算法,并应用于求解旅行商问题.上述算法设计了一种新的信息素更新模型,单个蚂蚁每走一步就进行信息素局部更新,在所有的蚂蚁搜索一周后,最优路径蚂蚁进行全局信息素更新.提出一种新的邻域搜索模型,将邻域大小设置为原来的一半,提高了计算的效率.在每个蚂蚁的一个周期循环后,使用邻域搜索算法优化最优解的路径长度.仿真结果表明,改进算法具有较高的求解精度和收敛速度.     

求解Job Shop调度问题的混合蚁群算法研究

为了解决单一算法求解Job Shop调度问题存在的不足，该文提出了一种混合算法，将蚁群算法用于全局搜索。针对蚁群算法易于陷入局部最优的情况，提出了一种基于关键工序的邻域搜索方法，将使用此邻域搜索方法的TS算法作为局部搜索策略。利用TS算法较强的局部搜索能力，提高了蚁群算法的优化能力，达到改善Job Shop调度问题解的质量。实验结果表明，混合算法在较短的时间内，找到了FT10、LA24、LA36等典型benchmarks问题的最优解，得到的makespan的平均值较并行遗传算法(PGA)和TSAB算法均有所提高。     

A multiobjective GRASP–VND algorithm to solve the waste collection problem

In this paper, the waste collection problem (WCP) of a city in the south of Spain is addressed as a multiobjective routing problem that considers three objectives. From the company's perspective, the minimization of the travel cost is desired as well as that of the total number of vehicles. Additionally, from the employee's point of view, a set of balanced routes is also sought. Four variants of a multiobjective hybrid algorithm are proposed. Specifically, a GRASP (greedy randomized adaptive search procedure) with a VND (variable neighborhood descent) is combined. The best GRASP–VND algorithm found is applied in order to solve the real‐world WCP of a city in the south of Spain.     

Solving Multitrip Pickup and Delivery Problem With Time Windows and Manpower Planning Using Multiobjective Algorithms

The multitrip pickup and delivery problem with time windows and manpower planning (MTPDPTW-MP) determines a set of ambulance routes and finds staff assignment for a hospital. It involves different stakeholders with diverse interests and objectives. This study firstly introduces a multiobjective MTPDPTW-MP (MO-MTPDPTWMP) with three objectives to better describe the real-world scenario. A multiobjective iterated local search algorithm with adaptive neighborhood selection (MOILS-ANS) is proposed to solve the problem. MOILS-ANS can generate a diverse set of alternative solutions for decision makers to meet their requirements. To better explore the search space, problem-specific neighborhood structures and an adaptive neighborhood selection strategy are carefully designed in MOILS-ANS. Experimental results show that the proposed MOILS-ANS significantly outperforms the other two multiobjective algorithms. Besides, the nature of objective functions and the properties of the problem are analyzed. Finally, the proposed MOILS-ANS is compared with the previous single-objective algorithm and the benefits of multiobjective optimization are discussed.      

A GRASP with adaptive large neighborhood search for pickup and delivery problems with transshipment

The pickup and delivery problem (PDP) has been studied extensively for applications ranging from courier, cargo and postal services, to public transportation. The work presented here was inspired by a daily route planning problem at a regional air carrier who was trying to determine the benefits of transshipment. Accordingly, a primary goal of this paper is identify the circumstances under which measurable cost saving can be achieved when one aircraft transports a request from its origin to an intermediate point and a second aircraft picks it up and delivers it to its final destination. In structuring the analysis, we describe a unique way to model this transshipment option on a directed graph and introduce a specialized two-route insertion heuristic that considers when to exploit this option. Based on the new representation, most existing heuristics for the PDP can be readily extended to handle transshipments.To find solutions, we developed a greedy randomized adaptive search procedure (GRASP) with several novel features. In the construction phase, shipment requests are inserted into routes until all demand is satisfied or no feasible insertion exists. In the improvement phase, an adaptive large neighborhood search algorithm is used to modify portions of the feasible routes. Specialized removal and insertion heuristics were designed for this purpose. In the absence of test cases in the literature, we also developed a procedure for randomly generating problem instances. Testing was done on 56 existing PDP instances which have 50 requests each, and on 50 new data sets with 25 requests each and one transshipment location. For the former, the performance and solution quality of the GRASP were comparable to the best known heuristics. For the latter, GRASP found the solutions within 1% of optimality on 88% of the instances.     

校车的线路选择及优化设计方法

以大学城教师接送车辆的线路优化为研究对象,针对大学教师接送站点分布分散的特点,建立多线路的校车调度方案,提出了一种利用K-means聚类算法对已有的站点位置进行区域划分,利用改进蚁群算法对每个区域的校车运行线路进行优化的方法。以杭州大学城某高校的校车线路优化为实例,验证在最适当的线路数下,得到最佳的目标值,能更好地提高校车效率。     

A hybrid particle swarm optimization algorithm for the vehicle routing problem

This paper introduces a new hybrid algorithmic nature inspired approach based on particle swarm optimization, for successfully solving one of the most popular supply chain management problems, the vehicle routing problem. The vehicle routing problem is considered one of the most well studied problems in operations research. The proposed algorithm for the solution of the vehicle routing problem, the hybrid particle swarm optimization (HybPSO), combines a particle swarm optimization (PSO) algorithm, the multiple phase neighborhood search–greedy randomized adaptive search procedure (MPNS–GRASP) algorithm, the expanding neighborhood search (ENS) strategy and a path relinking (PR) strategy. The algorithm is suitable for solving very large-scale vehicle routing problems as well as other, more difficult combinatorial optimization problems, within short computational time. It is tested on a set of benchmark instances and produced very satisfactory results. The algorithm is ranked in the fifth place among the 39 most known and effective algorithms in the literature and in the first place among all nature inspired methods that have ever been used for this set of instances.     

校车路径问题的改进迭代局部搜索算法

针对考虑站点服务时间、学生最大乘车时间约束的校车路径问题(SBRP),提出一种改进迭代局部搜索(ILS)算法以提升求解质量。该算法使用大规模邻域搜索(LNS)算法作为扰动算子;在解的破坏过程中,设计一组解的破坏因子并赋以一定的选择概率,每隔若干次迭代后根据解的质量自适应更改破坏因子的选择概率,进而调整解的破坏程度。为提升ILS解的多样性,算法采用了基于偏差系数的邻域解接受准则。在国际基准测试案例上进行了测试,测试结果表明在ILS算法中使用自适应调整破坏程度的LNS扰动比常规扰动和其他破坏扰动的求解质量有大幅提升;与蚁群算法的比较结果进一步验证了改进算法的有效性。     

An annotated bibliography of GRASP – Part I: Algorithms

A greedy randomized adaptive search procedure (GRASP) is a metaheuristic for combinatorial optimization. It is a multi-start or iterative process, in which each GRASP iteration consists of two phases, a construction phase, in which a feasible solution is produced, and a local search phase, in which a local optimum in the neighborhood of the constructed solution is sought. Since 1989, numerous papers on the basic aspects of GRASP, as well as enhancements to the basic metaheuristic have appeared in the literature. GRASP has been applied to a wide range of combinatorial optimization problems, ranging from scheduling and routing to drawing and turbine balancing. This is the first of two papers with an annotated bibliography of the GRASP literature from 1989 to 2008. This paper covers algorithmic aspects of GRASP.