Optimal parallel randomized algorithms for the Voronoi diagram of line segments in the plane and related problems

Abstract

In this paper, we present an optimal parallel randomized algorithm for the Voronoi diagram of a set of n non-intersecting (except possibly at endpoints) line segments in the plane. Our algorithm runs in O(logn) time with very high probability and uses O(n) processors on a CRCW PRAM. This algorithm is optimal in terms of P.T bounds since the sequential time bound for this problem is O(nlogn). Our algorithm improves by an O(logn) factor the previously best known deterministic parallel algorithm which runs in O(log2n) time using O(n) processors. We obtain this result by using random sampling at “two stages” of our algorithm and using efficient randomized search techniques. This technique gives a direct optimal algorithm for the Voronoi diagram of points as well (all other optimal parallel algorithms for this problem use reduction from the 3-d convex hull construction).