Search

Spanning trees are widely used in networks for broadcasting, fault-tolerance, and securely delivering messages. Hexagonal interconnection networks have a number of real life applications. Examples are cellular networks, computer graphics, and image processing. Eisenstein-Jacobi (EJ) networks are a generalization of hexagonal mesh topology. They have a wide range of potential applications, and thus they have received researchers' attention in different areas among which interconnection networks and coding theory. In this paper, we present two spanning trees' constructions for Eisenstein-Jacobi (EJ). The first constructs three edge-disjoint node-independent spanning trees, while the second constructs six node-independent spanning trees but not edge disjoint. Based on the constructed trees, we develop routing algorithms that can securely deliver a message and tolerate a number of faults in point-to-point or in broadcast communications. The proposed work is also applied on higher dimensional EJ networks.

Message broadcasting in networks could be carried over spanning trees. A set of spanning trees in the same network is node independent if two conditions are satisfied. First, all trees are rooted at node $r$. Second, for every node $u$ in the network, all trees' paths from $r$ to $u$ are node-disjoint, excluding the end nodes $r$ and $u$. Independent spanning trees have applications in fault-tolerant communications and secure message distributions. Gaussian networks and two-dimensional toroidal networks share similar topological characteristics. They are regular of degree four, symmetric, and node-transitive. Gaussian networks, however, have relatively lesser network diameter that could result in a better performance. This promotes Gaussian networks to be a potential alternative for two-dimensional toroidal networks. In this paper, we present constructions for node independent spanning trees in dense Gaussian networks. Based on these constructions, we design routing algorithms that can be used in fault-tolerant routing and secure message distribution. We also design fault-tolerant algorithms to construct these trees in parallel.

The p-median problem is a well-known NP-hard problem. Many heuristics have been proposed in the literature for this problem. In this paper, we exploit a GPGPU parallel computing platform to present a new genetic algorithm implemented in Cuda and based on a Pseudo Boolean formulation of the p-median problem. We have tested the effectiveness of our algorithm using a Tesla K40 (2880 Cuda cores) on 290 different benchmark instances obtained from OR-Library, discrete location problems benchmark library, and benchmarks introduced in recent publications. The algorithm succeeded in finding optimal solutions for all instances except for two OR-library instances, namely pmed30 and pmed40, where better than 99.9\% approximations were obtained.

There is a sizable literature on investigating the minimum and maximum numbers of cycles in a class of graphs. However, the answer is known only for special classes. This paper presents a result on the smallest number of cycles in hamiltonian 3-connected cubic graphs. Further, it describes a proof technique that could improve an upper bound of the largest number of cycles in a hamiltonian graph., Comment: Accepted for publication in Mathematica Slovaca

The Variable Sized Bin Packing Problem has a wide range of application areas including packing, scheduling, and manufacturing. Given a list of items and variable sized bin types, the objective is to minimize the total size of the used bins. This problem is known to be NP-hard. In this article, we present two new heuristics for solving the problem using a new variation of P systems with active membranes, which we call a hybrid P system, implemented in CUDA. Our hybrid P-system model allows using the polarity and labels of membranes to represent object properties which results in reducing the complexity of implementing the P-system. We examine the performance of the two heuristics, and compare the results with those of other known algorithms. The numerical results show that good solutions for large instances (10000 items) of this problem could be obtained in a very short time (seconds) using our CUDA simulator., Comment: 20 pages; This paper is extracted from M.Sc. Thesis: Solution of the Variable Sized Bin Packing Problem using the P System and Cuda Architecture, by Qadhaa Al-Enezi, submitted March 2015, Computer Sc. Dept. Kuwait University, Supervised by Hosam AboElFotoh and Bader AlBdaiwi

Independent trees are used in building secure and/or fault-tolerant network communication protocols. They have been investigated for different network topologies including tori. Dense Gaussian networks are potential alternatives for 2-dimensional tori. They have similar topological properties; however, they are superiors in carrying communications due to their node-distance distributions and smaller diameters. In this paper, we present constructions of edge-disjoint node-independent spanning trees in dense Gaussian networks. Based on the constructed trees, we design algorithms that could be used in fault-tolerant routing or secure message distribution.

Lee codes have been intensively studied for more than 40 years. Interest in these codes has been triggered by the Golomb-Welch conjecture on the existence of the perfect error-correcting Lee codes. In this paper we deal with the existence and enumeration of diameter perfect Lee codes. As main results we determine all $q$ for which there exists a linear diameter-4 perfect Lee code of word length $n$ over $Z_{q},$ and prove that for each $n\geq 3$ there are uncountable many diameter-4 perfect Lee codes of word length $n$ over $Z.$ This is in a strict contrast with perfect error-correcting Lee codes of word length $n$ over $Z\,$\ as there is a unique such code for $n=3,$ and its is conjectured that this is always the case when $2n+1$ is a prime. We produce diameter perfect Lee codes by an algebraic construction that is based on a group homomorphism. This will allow us to design an efficient algorithm for their decoding. We hope that this construction will turn out to be useful far beyond the scope of this paper.