Guarding orthogonal galleries with rectangular rooms

Consider an orthogonal art gallery partitioned into n rectangular rooms. If two rooms are adjacent, there is a door connecting them and a guard positioned at this door will see both rooms. In Czyzowicz et al. [(1994) Guarding rectangular art galleries. Discrete Appl. Math., 50, 149–157], it is shown that any rectangular gallery can be guarded with ⌈n/2⌉ guards. We prove that the same bound holds for L-shape polygons. We extend it to staircases and prove that an orthogonal staircase with n rooms and r reflex vertices can be guarded with ⌈(n+⌊ r/2⌋)/2⌉ guards. Then we prove an upper bound on the number of guards for arbitrary orthogonal polygon with orthogonal holes. This result improves the previous bound by Czyzowicz et al. [(1994) Guarding rectangular art galleries. Discrete Appl. Math., 50, 149–157] (even in the case of polygon without holes)

Optimizing the Minimum Vertex Guard Set on Simple Polygons via a Genetic Algorithm

The problem of minimizing the number of vertex-guards necessary to cover a given simple polygon (MINIMUM VERTEX GUARD (MVG) problem) is NP-hard. This computational complexity opens two lines of investigation: the development of algorithms that establish approximate solutions and the determination of optimal solutions for special classes of simple polygons. In this paper we follow the first line of investigation and propose an approximation algorithm based on general metaheuristic genetic algorithms to solve the MVG problem. Based on our algorithm, we conclude that on average the minimum number of vertex-guards needed to cover an arbitrary and an orthogonal polygon with n vertices is n / 6.38 and n / 6.40 , respectively. We also conclude that this result is very satisfactory in the sense that it is always close to optimal (with an approximation ratio of 2, for arbitrary polygons; and with an approximation ratio of 1.9, for orthogonal polygons)

Connecting Red Cells in a Bicolour Voronoi Diagram

Let S be a set of n + m sites, of which n are red and have weight wR, and m are blue and weigh wB. The objective of this paper is to calculate the minimum value of the red sites’ weight such that the union of the red Voronoi cells in the weighted Voronoi diagram of S is a connected region. This problem is solved for the multiplicativelyweighted Voronoi diagram in O((n+m)2 log(nm)) time and for both the additively-weighted and power Voronoi diagram in O(nmlog(nm)) timePostprint (published version

Minimizing the range for k-covered paths on sensor networks

Coverage problems are a flourishing topic in optimization, thanks to the recent advances in the field of wireless sensor networks. The main coverage issue centres around critical conditions that require reliable monitoring and prohibit failures. This issue can be addressed by maximal-exposure paths, regarding which this article presents new results. Namely, it shows how to minimize the sensing range of a set of sensors in order to ensure the existence of a k-covered path between two points on a given region. Such a path’s coverage depends on k ≥ 2, which is fixed. The three types of regions studied are: a planar graph, the whole plane and a polygonal region.Peer Reviewe

Minimum Vertex Guard problem for orthogonal polygons: a genetic approach

Abstract: The problem of minimizing the number of guards placed on vertices needed to guard a given simple polygon (MINIMUM VERTEX GUARD problem) is NP-hard. This computational complexity opens two lines of investigation: the development of algorithms that determine approximate solutions and the determination of optimal solutions for special classes of simple polygons. In this paper we follow the first line of investigation proposing an approximation algorithm based on the general metaheuristic Genetic Algorithms to solve the MINIMUM VERTEX GUARD problem

Minimizing the range for k-covered paths on sensor networks

Coverage problems are a flourishing topic in optimization, thanks to the recent advances in the field of wireless sensor networks. The main coverage issue centres around critical conditions that require reliable monitoring and prohibit failures. This issue can be addressed by maximal-exposure paths, regarding which this article presents new results. Namely, it shows how to minimize the sensing range of a set of sensors in order to ensure the existence of a k-covered path between two points on a given region. Such a path’s coverage depends on k ≥ 2, which is fixed. The three types of regions studied are: a planar graph, the whole plane and a polygonal region.Peer Reviewe

Connecting Red Cells in a Bicolour Voronoi Diagram

Let S be a set of n + m sites, of which n are red and have weight wR, and m are blue and weigh wB. The objective of this paper is to calculate the minimum value of the red sites’ weight such that the union of the red Voronoi cells in the weighted Voronoi diagram of S is a connected region. This problem is solved for the multiplicativelyweighted Voronoi diagram in O((n+m)2 log(nm)) time and for both the additively-weighted and power Voronoi diagram in O(nmlog(nm)) tim