Browsing by Author "Lautanala, Atte"

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  • Performance Comparison of Metaheuristics for Solving Pickup and Delivery Problems
    (2024-08-19) Lautanala, Atte
     Perustieteiden korkeakoulu | Master's thesis
    Pickup and delivery problem is dynamic vehicle routing problem, which is a generalization of the well known travelling salesman problem. The problem is to find optimal routes for a fleet of vehicles, that must deliver a number of orders which involve picking up goods from one location and delivering them to another location. The problem may have some constraints, such as limits on vehicle capacities, and time windows for visiting locations. This thesis compares some methods that can solve these problems when the time for finding a solution is limited. Solution methods included in the comparison are local search, guided local search, tabu search, and simulated annealing, which all are metaheuristic optimization methods. These methods iteratively improve an initial solution by enumerating its neighbourhood obtained by minor modifications to the initial solution. A number of different problem instances were generated for the comparison with different amounts of orders and vehicles. The method which found a solution with the smallest objective was considered as the best. Simulated annealing and guided local search most frequently found the best solutions. When limiting the number of search iterations, and therefore time allowed for computation, guided local search found more frequently better solutions than other methods. However, simulated annealing seemed to perform better with problem instances which were larger or had fewer vehicles for each order.
  • Symboliset tila-avaruushakumenetelmät
    (2020-04-26) Lautanala, Atte
     Perustieteiden korkeakoulu | Bachelor's thesis