A Comparison of Nearest Neighbor Search Algorithms for Generic Object Recognition

The nearest neighbor (NN) classifier is well suited for generic object recognition. However, it requires storing the complete training data, and classification time is linear in the amount of data. There are several approaches to improve runtime and/or memory requirements of nearest neighbor methods: Thinning methods select and store only part of the training data for the classifier. Efficient query structures reduce query times. In this paper, we present an experimental comparison and analysis of such methods using the ETH-80 database. We evaluate the following algorithms. Thinning: condensed nearest neighbor, reduced nearest neighbor, Baram’s algorithm, the Baram-RNN hybrid algorithm, Gabriel and GSASH thinning. Query structures: kd-tree and approximate nearest neighbor. For the first four thinning algorithms, we also present an extension to k-NN which allows tuning the trade-off between data reduction and classifier degradation. The experiments show that most of the above methods are well suited for generic object recognition.