Dynamic algorithms for geometric spanners of small diameter: Randomized solutions

Let S be a set of n points in R-d and let t > 1 be a real number. A t-spann er for S is a directed graph having the points of S as its vertices, such t hat for any pair p and q of points there is a path from p to q of length at most t times the Euclidean distance between p and q. Such a path is called a t-spanner path. The spanner diameter of such a spanner is defined as the smallest integer D such that for any pair p and q of points there is a t-s panner path from p to q containing at most D edges. A randomized algorithm is given for constructing a t-spanner that, with hig h probability, contains O(n) edges and has spanner diameter O(log n). A dat a structure of size O(n log(d) n) is given that maintains this t-spanner in O(log(d) n log log n) expected amortized time per insertion and deletion, in the model of random updates, as introduced by Mulmuley. (C) 1999 Elsevie r Science B.V. All rights reserved.