A Scalability and Performance Evaluation of Precomputed Flow FieldMaps for Multi-Agent Pathfinding

Abstract: Background. The A' algorithm is a well-established pathfinding technique frequently used in video game development. However, a disadvantage of the A' algorithm is that it becomes computationally inefficient and impractical to utilize whenthousands of agents demand an optimal path. A solution to mitigate this issue isthe use of the flow field algorithm. This algorithm employs a goal-based pathfindingstrategy, which allows for the movement of a large number of units through the useof a single direction map (flow field map) that indicates the direction units must take to progress toward their goal. Objectives. The main objective of this study is to examine the performance and scalability of precomputed flow field maps with regard to execution time and memory utilization, with the objective of determining the feasibility of precomputed maps as an alternative to maps generated at runtime. Furthermore, the study implements and investigates compression techniques to minimize the memory footprint of precomputed flow field maps. Methods. The study adopts an experimental research design to assess the performance of the two implementations under various conditions of grid size and movement system. Performance evaluation is accomplished through the measurement and comparison of execution time and memory consumption. Additionally, a directional accuracy test is performed to quantify the potential loss of accuracy in the vectors stored in the precomputed flow field maps. Results. The precomputed flow field maps provide constant access time, with a time complexity of O(1), regardless of the grid size and the type of movement system. The memory usage of these maps increases significantly with the growth of the grid size. A doubling of the grid size leads to a more than fifteen-fold increase in memory usage. The techniques proposed in the study significantly reduced the memory footprint by a factor of thirty-two and by a factor of eight, depending on the selected movement system. The average loss in accuracy was approximately 0.35 degrees for the proposed any-angle compression technique. Conclusions. The use of precomputed flow field maps has limitations, including being limited to static environments and having high memory requirements. On the other hand, they provide constant access time for pathfinding information, independent of the grid dimensions, movement system, and the number of target nodes. Whether precomputed flow field maps are better than the traditional runtime implementation depends on the intended use.