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Main Authors: Imamura, Yasunobu, Shinohara, Takeshi, Higuchi, Naoya, Hirata, Kouichi, Kuboyama, Tetsuji
Format: Preprint
Published: 2025
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Online Access:https://arxiv.org/abs/2508.21682
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author Imamura, Yasunobu
Shinohara, Takeshi
Higuchi, Naoya
Hirata, Kouichi
Kuboyama, Tetsuji
author_facet Imamura, Yasunobu
Shinohara, Takeshi
Higuchi, Naoya
Hirata, Kouichi
Kuboyama, Tetsuji
contents We report our participation in the SISAP 2025 Indexing Challenge using a novel indexing technique called the Hilbert forest. The method is based on the fast Hilbert sort algorithm, which efficiently orders high-dimensional points along a Hilbert space-filling curve, and constructs multiple Hilbert trees to support approximate nearest neighbor search. We submitted implementations to both Task 1 (approximate search on the PUBMED23 dataset) and Task 2 (k-nearest neighbor graph construction on the GOOAQ dataset) under the official resource constraints of 16 GB RAM and 8 CPU cores. The Hilbert forest demonstrated competitive performance in Task 1 and achieved the fastest construction time in Task 2 while satisfying the required recall levels. These results highlight the practical effectiveness of Hilbert order-based indexing under strict memory limitations.
format Preprint
id arxiv_https___arxiv_org_abs_2508_21682
institution arXiv
publishDate 2025
record_format arxiv
spellingShingle Hilbert Forest in the SISAP 2025 Indexing Challenge
Imamura, Yasunobu
Shinohara, Takeshi
Higuchi, Naoya
Hirata, Kouichi
Kuboyama, Tetsuji
Databases
Data Structures and Algorithms
We report our participation in the SISAP 2025 Indexing Challenge using a novel indexing technique called the Hilbert forest. The method is based on the fast Hilbert sort algorithm, which efficiently orders high-dimensional points along a Hilbert space-filling curve, and constructs multiple Hilbert trees to support approximate nearest neighbor search. We submitted implementations to both Task 1 (approximate search on the PUBMED23 dataset) and Task 2 (k-nearest neighbor graph construction on the GOOAQ dataset) under the official resource constraints of 16 GB RAM and 8 CPU cores. The Hilbert forest demonstrated competitive performance in Task 1 and achieved the fastest construction time in Task 2 while satisfying the required recall levels. These results highlight the practical effectiveness of Hilbert order-based indexing under strict memory limitations.
title Hilbert Forest in the SISAP 2025 Indexing Challenge
topic Databases
Data Structures and Algorithms
url https://arxiv.org/abs/2508.21682