Augmented tour construction heuristics for the travelling salesman problem

Tour construction heuristics serve as fundamental techniques in optimizing the routes of a traveling salesman. These heuristics remain significant as foundational methods for generating initial solutions to the Traveling Salesman Problem (TSP), facilitating subsequent applications of tour improvement heuristics. These heuristics effectively comprise the iterative application of city node selection and insertion. However, thus far, no attempts have been made to enhance the basic structure of tour construction heuristics to bring a better initial solution for the advanced heuristics. This study aims to enhance tour construction heuristics without compromising their theoretical complexity. Specifically, an iterative step of partial tour deconstruction has been introduced to the existing heuristics. This additional step has been implemented and evaluated with three highly performing tour construction heuristics: the farthest insertion heuristic, the max difference insertion heuristic, and the fast max difference insertion heuristic. The results demonstrate that augmenting these heuristics with the partial tour deconstruction step improves the best, worst, and average solutions while preserving their theoretical complexit

Об одной задаче маршрутизации перемещений инструмента при листовой резке деталей

For the routing problem of tool permutations under the thermal cutting of parts from sheet material realized on CNC machines, questions connected with constructing precise (optimal) and heuristic algorithms used on the stage of mathematical simulation of route elements under sequential megalopolises circuit are investigated. Cutting points and points of tool cut-off are items (cities) of the above-mentioned megalopolises. In each megalopolis, interior works are provided. These works are connected with motion to the equidistant curve of the cut contour of a part from the cutting point and (with cutting completed) with motion from the equidistant curve to the tool cut-off (we keep in mind a working run). The problem about the time-optimal process of cutting which is a special variant of the generalized courier problem is investigated (the problem of the routing on the megalopolises with precedence conditions). An optimal procedure based on the dynamic programming and an effective heuristic algorithm realized on a multicore computer are proposed. A dynamic programming based procedure uses a special extension of the main problem. This extension provides the replacement of admissibility by precedence with the admissibility by deletion (from the list of tasks). Precedence conditions are used for decreasing computational complexity: it excludes the building of the whole array of the Bellman function values (this function is replaced by the layers system).Для задачи маршрутизации перемещений инструмента при термической резке деталей из листового материала на машинах с числовым программным управлением (ЧПУ) исследуются вопросы, связанные с построением точных (оптимальных) и эвристических алгоритмов, используемых на этапе математического моделирования элементов маршрутизации последовательного обхода мегаполисов. Пунктами (городами) упомянутых мегаполисов являются точки врезки (пробивки) материала и точки выключения инструмента. В каждом из мегаполисов предусматриваются внутренние работы, состоящие в продвижении к эквидистанте "вырезаемого" контура детали от точки врезки и в продвижении (по завершении резки) от эквидистанты к точке выключения инструмента (имеется в виду рабочий ход). Исследуется задача быстродействия процесса резки, являющаяся специальным случаем обобщенной задачи курьера (задача последовательного обхода мегаполисов с условиями предшествования). Предлагается оптимальная процедура на основе динамического программирования, а также эффективный эвристический алгоритм, реализованный на многоядерной ПЭВМ. Процедура на основе динамического программиро- вания использует специальное расширение основной задачи, при котором допустимость по предшествованию заменяется допустимостью по вычеркиванию (заданий из списка). Условия предшествования используются для снижения сложности вычислений: не осуществляется построение всего массива значений функции Беллмана (последняя заменяется в процедуре системой слоев)

Auto Carrier Transporter Loading and Unloading Improvement

Thousands of vehicles (cars, trucks and vans) are transported every day from one location to another. These vehicles are moved around the country on Auto Carrier Transports (ACTs). Delivering these vehicles involves large quantities of time, money and energy. Any reduction in time and energy will result in a significant savings of money. The intent of this research is to develop an algorithm to solve the Auto Carrier Transport Pickup and Delivery Problem. In doing so, the focus is to limit the total times vehicles are placed on and taken off the carrier, otherwise known as the number of loads, and to minimize distance driven. Loadings involve unloading a vehicle from a carrier, loading a vehicle onto a carrier, or reloading a vehicle onto a carrier that was removed to gain access to vehicles deeper on the carrier. Increases in either distance driven or loads result in the expenditure of more time and money. Furthermore, increases in loadings increase the risk of damage to vehicles resulting in lower resale values. Results show that it is possible to either modify the routing or the position of the vehicles on the carrier to limit the loads. Which process is used depends on the distances the carrier is traveling and how many vehicles are awaiting pickup

Heuristic for the preemptive asymmetric stacker crane problem

International audienceIn this paper, we deal with the preemptive asymmetric stacker crane problem in an heuristic way. We first present some theoretical results which allow us to turn this problem into a specific tree design problem. We next derive from this new representation a simple, efficient local search heuristic, as well as an original LIP model. We conclude by presenting experimental results which aim at both testing the efficiency of our heuristic and at evaluating the impact of the preemption hypothesis

Ant colony optimization for the ordered cutting stock problem

Orientadores: Antonio Carlos Moretti, Luis Leduino de Salles NetoDissertação (mestrado) - Universidade Estadual de Campinas, Instituto de Matematica, Estatistica e Computação CientificaResumo: O problema de corte de estoque ordenado, um problema relativamente novo na literatura, e uma adaptação do problema de corte de estoque tradicional onde algumas restrições quanto a limitação do numero de ordens de produção em processamento são adicionadas. Esta dissertação tem como objetivo estudar uma nova abordagem deste problema utilizando uma aplicação da metaheurística colônia de formigas. Esta metaheurística utiliza os princípios de auto-organização de uma população de formigas visando a resolução de problemas de otimização combinatorialAbstract: The Ordered Cutting Stock Problem (OCSP), a relatively recent problem in technical literarture, is a variant of the more well-known Cutting Stock Problem (CSP). This variant includes some new constraints in the mathematical formulation, regarding the number of production orders being processed simultaneously. This work studies a new approach to solve the OCSP, applying the Ant Colony Optimization (ACO) metaheurisitic. This metaheuristic is based in the self-organizing principles that govern ant population's behaviour, solving combinatorial optimization problemsMestradoPesquisa OperacionalMestre em Matemática Aplicad

An Adaptive Tabu Search Heuristic for the Location Routing Pickup and Delivery Problem with Time Windows with a Theater Distribution Application

The time constrained pickup and delivery problem (PDPTW) is a problem of finding a set of routes for a fleet of vehicles in order to satisfy a set of transportation requests. Each request represents a user-specified pickup and delivery location. The PDPTW may be used to model many problems in logistics and public transportation. The location routing problem (LRP) is an extension of the vehicle routing problem where the solution identifies the optimal location of the depots and provides the vehicle schedules and distribution routes. This dissertation seeks to blend the PDPTW and LRP areas of research and formulate a location scheduling pickup and delivery problem with time windows (LPDPTW) in order to model the theater distribution problem and find excellent solutions. This research utilizes advanced tabu search techniques, including reactive tabu search and group theory applications, to develop a heuristic procedure for solving the LPDPTW. Tabu search is a metaheuristic that performs an intelligent search of the solution space. Group theory provides the structural foundation that supports the efficient search of the neighborhoods and movement through the solution space