Spherical k-means is a widely used clustering algorithm for sparse and high-dimensional data such as document vectors. While several improvements accelerations have been introduced the original algorithm, not all easily translate to spherical variant: Many acceleration techniques, algorithms of Elkan Hamerly, rely on triangle inequality Euclidean distances. However, uses Cosine similarities ins...

TAMPERE UNIVERSITY OF TECHNOLOGY Master’s Degree Program in Information Technology Ranganathan, Sindhuja: Improvements to k-means clustering Master’s thesis, 42 November 2013 Major Subject: Software Systems Examiner(s): Professor Tapio Elomaa

The -means algorithm is by far the most widely used method for discovering clusters in data. We show how to accelerate it dramatically, while still always computing exactly the same result as the standard algorithm. The accelerated algorithm avoids unnecessary distance calculations by applying the triangle inequality in two different ways, and by keeping track of lower and upper bounds for dist...