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Bibliographic Details
Main Authors: Imamura, Yasunobu, Shinohara, Takeshi, Higuchi, Naoya, Hirata, Kouichi, Kuboyama, Tetsuji
Format: Preprint
Published: 2025
Subjects:
Online Access:https://arxiv.org/abs/2508.21682
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Table of 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.