NNB: An efficient nearest neighbor search method for hierarchical clustering on large datasets

Author(s):  
Wei Zhang ◽  
Gongxuan Zhang ◽  
Yongli Wang ◽  
Zhaomeng Zhu ◽  
Tao Li
2015 ◽  
Vol 09 (03) ◽  
pp. 307-331 ◽  
Author(s):  
Wei Zhang ◽  
Gongxuan Zhang ◽  
Yongli Wang ◽  
Zhaomeng Zhu ◽  
Tao Li

Nearest neighbor search is a key technique used in hierarchical clustering and its computing complexity decides the performance of the hierarchical clustering algorithm. The time complexity of standard agglomerative hierarchical clustering is O(n3), while the time complexity of more advanced hierarchical clustering algorithms (such as nearest neighbor chain, SLINK and CLINK) is O(n2). This paper presents a new nearest neighbor search method called nearest neighbor boundary (NNB), which first divides a large dataset into independent subset and then finds nearest neighbor of each point in subset. When NNB is used, the time complexity of hierarchical clustering can be reduced to O(n log 2n). Based on NNB, we propose a fast hierarchical clustering algorithm called nearest-neighbor boundary clustering (NBC), and the proposed algorithm can be adapted to the parallel and distributed computing framework. The experimental results demonstrate that our algorithm is practical for large datasets.


Author(s):  
Federico Tombari ◽  
Samuele Salti ◽  
Luca Puglia ◽  
Giancarlo Raiconi ◽  
Luigi Di Stefano

Fractals ◽  
1997 ◽  
Vol 05 (supp01) ◽  
pp. 231-241
Author(s):  
Leszek Ciepliński ◽  
Czesław Jȩdrzejek ◽  
Tomasz Major

In this paper we investigate the effect of fast nearest neighbor search method on acceleration of fractal image compression. First we follow the Saupe1 encoding step of fractal image compression that uses the multi-dimensional nearest neighbor search in a projected space. Then we investigate performance of a method for finding the nearest vector called partial distortion elimination. We also propose some supplementary accelerating concepts. For all inspected methods the impact of the tolerance criterion for mean square error of block matching is examined.


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