An Accelerated Nearest Neighbor Search Method for the K-Means Clustering Algorithm

K-means is undoubtedly the most widely used partitional clustering algorithm. Unfortunately, the nearest neighbor search step of this algorithm can be computationally expensive, as the distance between each input vector and all cluster centers need to be calculated. To accelerate this step, a computationally inexpensive distance estimation method can be tried first, resulting in the rejection of candidate centers that cannot possibly be the nearest center to the input vector under consideration. This way, the computational requirements of the search can be reduced as most of the full distance computations become unnecessary. In this paper, a fast nearest neighbor search method that rejects impossible centers to accelerate the k-means clustering algorithm is presented. Our method uses geometrical relations among the input vectors and the cluster centers to reject many unlikely centers that are not typically rejected by similar approaches. Experimental results show that the method can reduce the number of distance computations significantly without degrading the clustering accuracy.