Computing k Centers over Streaming Data for Small k

In this paper, we consider the k-center problem for streaming points in Rd. More precisely, we consider the single-pass streaming model, where each point in the stream is allowed to be examined only once and a small amount of information can be stored in a device. Since the size of memory is much smaller than the size of the data in the streaming model, it is important to develop an algorithm whose space complexity does not depend on the number of input data. We present an approximation algorithm for k = 2 that guarantees a (2 + ε)-factor using O(d/ε) space and update time in arbitrary dimensions for any metric. We show that our algorithm can be extended to approximate an optimal k-center within factor (2 + ε) for k > 2.