Multi-objective Search via Lazy and Efficient Dominance Checks

Multi-objective Search via Lazy and Efficient Dominance Checks

Carlos Hernández, William Yeoh, Jorge A. Baier, Ariel Felner, Oren Salzman, Han Zhang, Shao-Hung Chan, Sven Koenig

Proceedings of the Thirty-Second International Joint Conference on Artificial Intelligence
Main Track. Pages 7223-7230. https://doi.org/10.24963/ijcai.2023/850

Multi-objective search can be used to model many real-world problems that require finding Pareto optimal paths from a specified start state to a specified goal state, while considering different costmetrics such as distance, time, and fuel. The performance of multi-objective search can be improved by making dominance checking—an operation necessary to determine whether or not a path dominates another—more efficient. This was shown in practice by BOA*, a state-of-the-art bi-objective search algorithm, which outperforms previously existing bi-objective search algorithms in part because it adopts a lazy approach towards dominance checking. EMOA*, a recent multi-objective search algorithm, generalizes BOA* to more-than-two objectives using AVL trees for dominance checking. In this paper, we first propose Linear-Time Multi-Objective A* (LTMOA*), an multi-objective search algorithm that implements a more efficient dominance checking than EMOA* using simple data structures like arrays. We then propose an even lazier approach towards dominance checking, and the resulting algorithm, LazyLTMOA*, distinguishes from EMOA* and LTMOA* by removing the dominance checking during node generation. Our experimental results show that LazyLTMOA* outperforms EMOA* by up to an order of magnitude in terms of runtime.
Keywords:
Search: S: Heuristic search
Robotics: ROB: Motion and path planning
Search: S: Combinatorial search and optimisation