Abstract

A recently proposed product quantization method is efficient for large scale approximate nearest neighbor search, however, its performance on unstructured vectors is limited. This paper introduces residual vector quantization based approaches that are appropriate for unstructured vectors. Database vectors are quantized by residual vector quantizer. The reproductions are represented by short codes composed of their quantization indices. Euclidean distance between query vector and database vector is approximated by asymmetric distance, i.e., the distance between the query vector and the reproduction of the database vector. An efficient exhaustive search approach is proposed by fast computing the asymmetric distance. A straight forward non-exhaustive search approach is proposed for large scale search. Our approaches are compared to two state-of-the-art methods, spectral hashing and product quantization, on both structured and unstructured datasets. Results show that our approaches obtain the best results in terms of the trade-off between search quality and memory usage.

Highlights

  • Approximate nearest neighbor search (ANN) is proposed to tackle the curse of the dimensionality problem [1,2] in exact nearest neighbor (NN) searching

  • In contrast with using an external coarse quantizer, we propose a straight forward non-exhaustive search approach based on the approximating sequence of database vector y that is generated by residual vector quantization: l

  • We have introduced residual vector quantization for approximate nearest neighbor search

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Summary

Introduction

Approximate nearest neighbor search (ANN) is proposed to tackle the curse of the dimensionality problem [1,2] in exact nearest neighbor (NN) searching. In many computer vision applications, the data-points are high-dimensional vectors that are embedded in Euclidean space, and the memory usage for storing and searching high-dimensional vectors is a key criterion for problems involving large amount of data. The state-of-the-art approaches such as tree-based methods (e.g., KD-tree [4], hierarchical k-means (HKM) [5], FLANN [6]) and hash-based methods (e.g., Exact Euclidean Locality-Sensitive Hashing (E2LSH) [7,8]) involve indexing structures to improve the performance. The memory usage of indexing structure may even be higher than the original data when processing large scale data

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