10 research outputs found
Lower bounds on the dilation of plane spanners
(I) We exhibit a set of 23 points in the plane that has dilation at least
, improving the previously best lower bound of for the
worst-case dilation of plane spanners.
(II) For every integer , there exists an -element point set
such that the degree 3 dilation of denoted by in the domain of plane geometric spanners. In the
same domain, we show that for every integer , there exists a an
-element point set such that the degree 4 dilation of denoted by
The
previous best lower bound of holds for any degree.
(III) For every integer , there exists an -element point set
such that the stretch factor of the greedy triangulation of is at least
.Comment: Revised definitions in the introduction; 23 pages, 15 figures; 2
table
EMBEDDING POINT SETS INTO PLANE GRAPHS OF SMALL DILATION
Let S be a set of points in the plane. What is the minimum possible dilation of all plane graphs that contain S? Even for a set S as simple as five points evenly placed on the circle, this question seems hard to answer; it is not even clear if there exists a lower bound> 1. In this paper we provide the first upper and lower bounds for the embedding problem. 1. Each finite point set can be embedded into the vertex set of a finite triangulation of dilation ≤ 1.1247. 2. Each embedding of a closed convex curve has dilation ≥ 1.00157. 3. Let P be the plane graph that results from intersecting n infinite families of equidistant, parallel lines in general position. Then the vertex set of P has dilation ≥ 2 / √ 3 ≈ 1.1547
A fast algorithm for approximating the detour of a polygonal chain
Let C be a simple(1) polygonal chain of n edges in the plane, and let p and q be two arbitrary points on C. The detour of C on (p, q) is defined to be the length of the subchain of C that connects p with q, divided by the Euclidean distance between p and q. Given an epsilon >0, we compute in time O((1)/(epsilon) n log n) a pair of points on which the chain makes a detour at least 1/(1 + epsilon) times the maximum detour. (C) 2003 Elsevier B.V. All rights reserved
Computing the Maximum Detour of a Plane Graph in Subquadratic Time
Let G be a plane graph where each edge is a line segment. We consider the problem of computing the maximum detour of G, defined as the maximum over all pairs of distinct points p and q of G of the ratio between the distance between p and q in G and the distance |pq|. The fastest known algorithm for this problem has Θ(n 2) running time where n is the number of vertices. We show how to obtain O(n 3/2 log 3 n) expected running time. We also show that if G has bounded treewidth, its maximum detour can be computed in O(n log 3 n) expected time
On the Geometric Dilation of Finite Point Sets
Let G be an embedded planar graph whose edges may be curves. For two arbitrary points of G, we can compare the length of the shortest path in G connecting them against their Euclidean distance
Computing the detour and spanning ratio of paths, trees, and cycles in 2D and 3D
SCOPUS: cp.jinfo:eu-repo/semantics/publishe