CAPACITATED VEHICLE ROUTING PROBLEM WITH TIME WINDOWS FOR MILK COLLECTION AT KPBS PANGALENGAN

This research aims to solve a real-life problem faced by KPBS, a regional dairy company in Pangalengan Village of West Java that collects raw milk from farmers to the location of Milk Treatment. In the considered problem, a daily plan is needed to determine a heterogeneous fleet of vehicles that depart from a depot (the factory) and must visit a set of farmers for collection operations within given time window. This problem is known as the Capacitated Vehicle Routing Problem with Time Windows (CVRPTW) which is one of the classical areas of study in Operations Research. In this study the problem will be solved using heuristic method. Key words: Milk collection, CVRPTW, Operations Research, Heuristi

A review of the Tabu Search Literature on Traveling Salesman Problems

The Traveling Salesman Problem (TSP) is one of the most widely studied problems inrncombinatorial optimization. It has long been known to be NP-hard and hence research onrndeveloping algorithms for the TSP has focused on approximate methods in addition to exactrnmethods. Tabu search is one of the most widely applied metaheuristic for solving the TSP. Inrnthis paper, we review the tabu search literature on the TSP, point out trends in it, and bringrnout some interesting research gaps in this literature.

An Improved Whale Optimization Algorithm for Vehicle Routing Problem with Time Windows

The vehicle routing problem with time windows (VRPTW) is a pivotal problem in logistics operation management which attempts to establish routes for vehicles to deliver goods to customers. The objective of VRPTW is to find the optimal set of routes for a fleet of vehicles in order to serve a given set of customers within time window constraints. As the VRPTW is known to be NP-hard combinatorial problem, it is hard to be solved in reasonable computational time. Therefore, this paper proposes the modification of the whale optimization algorithm with local search to solve the VRPTW. The local search comprised 2-Operator and single insertion for solution improvement. Furthermore, the 2-Operator is used after the exploration phase and single insertion in the exploitation phase. The computational experiments were applied to Solomon’s instance that included small to large size problems. The experiment results show that the average gap of the total distance between the Best Known Solution (BKS) and the proposed solutions is within 5.82%. In addition, the best solution was found 29 out of 56 instances that is better than the PSO at 1.09%. This shows that this proposed provides a minimum value and outperforms other metaheuristics approaches.Keywords: Whale Optimization Algorithm; Vehicle Routing Problem; Time Constraint

Estado del arte para la resolución de enrutamiento de vehículos con restricciones de capacidad

[ESP] El propósito del presente documento es el de realizar una revisión e investigación en la literatura científica para conocer el estado del arte referente a un problema real de optimización. Dicho problema emana de un proyecto de investigación en el que se estudia la aplicación de métodos de Investigación Operativa para la optimización y mejora de los Sistemas de Transporte Intermodal1. Se pretende, en definitiva, evaluar el conocimiento científico, así como las técnicas y métodos que son investigados y empleados para problemas o situaciones que guarden relación con el problema objeto. Este consiste en la optimización de la operativa de una empresa logística que se dedica a la distribución de vehículos por carretera (transporte rodado). Dicha distribución, se realiza en base a una serie de pedidos que son recibidos en unos almacenes/depósitos repartidos por toda la geografía española. En función de una serie de objetivos y restricciones se configura la carga que deben contener los camiones disponibles y la planificación de la ruta a seguir. Una vez que estos camiones han repartido la carga, se encontrarán disponibles para volver a realizar una recogida de carga y comenzar un nuevo reparto. Por lo tanto, los camiones no siguen un esquema en el que se realiza un reparto de manera centralizada sino que, de manera descentralizada, los camiones viajan por toda la geografía recogiendo y entregando las cargas

Effectiveness of Selection Mechanisms on the efficiency of Multi Parent Crossover Operator

Multi-parent crossover has been proven its ability to address many of combinatorial optimization problems such as the traveling salesman problem and the vehicle routing problem with time windows. The successful use of multi-parent crossover arises from its abilities to enhance the search performance via utilizing information exchanged by more than two parents and inheriting by offspring. These parents are selected according to one of the selection mechanisms. Selecting the most appropriate parents for a crossover process might leads to improving the effectiveness of genetic algorithm. Therefore, this work investigates the effect of selection mechanism on the efficiency of multi-parent crossover. To test this, seven selection mechanisms have been used; random selection mechanism, roulette wheel mechanism, stochastic universal sampling mechanism, tournament selection mechanism, best selection mechanism, single best-couple random selection mechanism and couple best- single random selection mechanism. The performance of the proposed algorithm is tested using Solomon VRPTW benchmark. The experimental results show the superiority of multi-parent crossover that employs the selection mechanism which selects the outstanding individuals to form most of parents over multi-parent crossover that employ other selection mechanisms. This demonstrates the efficiency of employing best parents in a crossover process that can assist the search process to attain a better solution

Automated test data generation using a scatter search approach

The techniques for the automatic generation of test cases try to efficiently find a small set of cases that allow a given adequacy criterion to be fulfilled, thus contributing to a reduction in the cost of software testing. In this paper we present and analyze two versions of an approach based on the Scatter Search metaheuristic technique for the automatic generation of software test cases using a branch coverage adequacy criterion. The first test case generator, called TCSS, uses a diversity property to extend the search of test cases to all branches of the program under test in order to generate test cases that cover these. The second, called TCSS-LS, is an extension of the previous test case generator which combines the diversity property with a local search method that allows the intensification of the search for test cases that cover the difficult branches. We present the results obtained by our generators and carry out a detailed comparison with many other generators, showing a good performance of our approac

Revisiting the Evolution and Application of Assignment Problem: A Brief Overview

The assignment problem (AP) is incredibly challenging that can model many real-life problems. This paper provides a limited review of the recent developments that have appeared in the literature, meaning of assignment problem as well as solving techniques and will provide a review on   a lot of research studies on different types of assignment problem taking place in present day real life situation in order to capture the variations in different types of assignment techniques. Keywords: Assignment problem, Quadratic Assignment, Vehicle Routing, Exact Algorithm, Bound, Heuristic etc

Enhancement on the modified artificial bee colony algorithm to optimize the vehicle routing problem with time windows

The vehicle routing problem with time windows (VRPTW) is a non-deterministictime hard (NP-hard) with combinatorial optimization problem (COP). The Artificial Bee Colony (ABC) is a popular swarm intelligence algorithm for COP. In this study, existing Modified ABC (MABC) algorithm is revised to solve the VRPTW. While MABC has been reported to be successful, it does have some drawbacks, including a lack of neighbourhood structure selection during the intensification process, a lack of knowledge in population initialization, and occasional stops proceeding the global optimum. This study proposes an enhanced Modified ABC (E-MABC) algorithm which includes (i) N-MABC that overcomes the shortage of neighborhood selection by exchanging the neighborhood structure between two different routes in the solution; (ii) MABC-ACS that solves the issues of knowledge absence in MABC population initialization by incorporating ant colony system heuristics, and (iii) PMABC which addresses the occasional stops proceeding to the global optimum by introducing perturbation that accepts an abandoned solution and jumps out of a local optimum. The proposed algorithm was evaluated using benchmark datasets comprising 56 VRPTW instances and 56 Pickup and Delivery Problems with Time Windows (PDPTW). The performance has been measured using the travelled distance (TD) and the number of deployed vehicles (NV). The results showed that the proposed E-MABC has lower TD and NV than the benchmarked MABC and other algorithms. The E-MABC algorithm is better than the MABC by 96.62%, MOLNS by 87.5%, GAPSO by 53.57%, MODLEM by 76.78%, and RRGA by 42.85% in terms of TD. Additionally, the E-MABC algorithm is better than the MABC by 42.85%, MOLNS by 17.85%, GA-PSO and RRGA by 28.57%, and MODLEN by 46.42% in terms of NV. This indicates that the proposed E-MABC algorithm is promising and effective for the VRPTW and PDPTW, and thus can compete in other routing problems and COPs

A simulation-optimization approach for a service-constrained multi-echelon distribution network

Academic research on (s,S) inventory policies for multi-echelon distribution networks with deterministic lead times, backordering, and fill rate constraints is limited. Inspired by a real-life Dutch food retail case we develop a simulation-optimization approach to optimize (s,S) inventory policies in such a setting. We compare the performance of a Nested Bisection Search (NBS) and a novel Scatter Search (SS) metaheuristic using 1280 instances from literature and we derive managerial implications from a real-life case. Results show that the SS outperforms the NBS on solution quality. Additionally, supply chain costs can be saved by allowing lower fill rates at upstream echelons

Reducing the number of membership functions in linguistic variables

Dissertation presented at Universidade Nova de Lisboa, Faculdade de Ciências e Tecnologia in fulfilment of the requirements for the Masters degree in Mathematics and Applications, specialization in Actuarial Sciences, Statistics and Operations ResearchThe purpose of this thesis was to develop algorithms to reduce the number of membership functions in a fuzzy linguistic variable. Groups of similar membership functions to be merged were found using clustering algorithms. By “summarizing” the information given by a similar group of membership functions into a new membership function we obtain a smaller set of membership functions representing the same concept as the initial linguistic variable. The complexity of clustering problems makes it difficult for exact methods to solve them in practical time. Heuristic methods were therefore used to find good quality solutions. A Scatter Search clustering algorithm was implemented in Matlab and compared to a variation of the K-Means algorithm. Computational results on two data sets are discussed. A case study with linguistic variables belonging to a fuzzy inference system automatically constructed from data collected by sensors while drilling in different scenarios is also studied. With these systems already constructed, the task was to reduce the number of membership functions in its linguistic variables without losing performance. A hierarchical clustering algorithm relying on performance measures for the inference system was implemented in Matlab. It was possible not only to simplify the inference system by reducing the number of membership functions in each linguistic variable but also to improve its performance