The Nearest Neighbor classifier is one of the most popular non-parametric classification methods. It is very simple, intuitive and accurate in a great variety of realworld applications. Despite its simplicity and effectiveness, practical use of this decision rule has been historically limited due to its high storage requirements and the computational costs involved. In order to overcome these drawbacks, it is possible either to employ fast search algorithms or to use a training set size

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... n scheme. The present paper provides a comparative analysis of fast search algorithms and data reduction techniques to assess their pros and cons from both theoretical and practical viewpoints.