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arXiv · 2412.21104

On Parallel External-Memory Bidirectional Search

Lior Siag·Shahaf S. Shperberg·Ariel Felner·Nathan R. Sturtevant
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Abstract

Parallelization and External Memory (PEM) techniques have significantly enhanced the capabilities of search algorithms when solving large-scale problems. Previous research on PEM has primarily centered on unidirectional algorithms, with only one publication on bidirectional PEM that focuses on the meet-in-the-middle (MM) algorithm. Building upon this foundation, this paper presents a framework that integrates both uni- and bi-directional best-first search algorithms into this framework. We then develop a PEM variant of the state-of-the-art bidirectional heuristic search (BiHS) algorithm BAE* (PEM-BAE*). As previous work on BiHS did not focus on scaling problem sizes, this work enables us to evaluate bidirectional algorithms on hard problems. Empirical evaluation shows that PEM-BAE* outperforms the PEM variants of A* and the MM algorithm, as well as a parallel variant of IDA*. These findings mark a significant milestone, revealing that bidirectional search algorithms clearly outperform unidirectional search algorithms across several domains, even when equipped with state-of-the-art heuristics.

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Lior Siag, Shahaf S. Shperberg, Ariel Felner, Nathan R. Sturtevant. 2024-12-30. On Parallel External-Memory Bidirectional Search. https://doi.org/10.3233/faia240991

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