Experimental Analysis of Locality Sensitive Hashing Techniques for High-Dimensional Approximate Nearest Neighbor Searches

Finding nearest neighbors in high-dimensional spaces is a fundamental operation in many multimedia retrieval applications. Exact tree-based approaches are known to suffer from the notorious curse of dimensionality for high-dimensional data. Approximate searching techniques sacrifice some accuracy while returning good enough results for faster performance. Locality Sensitive Hashing (LSH) is a popular technique for finding approximate nearest neighbors. There are two main benefits of LSH techniques: they provide theoretical guarantees on the query results, and they are highly scalable. The most dominant costs for existing external memory-based LSH techniques are algorithm time and index I/Os required to find candidate points. Existing works do not compare both of these costs in their evaluation. In this experimental survey paper, we show the impact of both these costs on the overall performance. We compare three state-of-the-art techniques on six real-world datasets, and show the importance of comparing these costs to achieve a more fair comparison.