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Multi Expression Programming (MEP) is an evolutionary technique that may be used for solving computationally difficult problems. MEP uses a linear solution representation. Each MEP individual is a string encoding complex expressions (computer programs). A MEP individual may encode multiple solutions of the current problem. In this paper MEP is used for evolving a Traveling Salesman Problem (TSP) heuristic for graphs satisfying triangle inequality. Evolved MEP heuristic is compared with Nearest Neighbor Heuristic (NN) and Minimum Spanning Tree Heuristic (MST) on some difficult problems in TSPLIB. For most of the considered problems the evolved MEP heuristic outperforms NN and MST. The obtained algorithm was tested against some problems in TSPLIB. The results emphasizes that evolved MEP heuristic is a powerful tool for solving difficult TSP instances., Comment: International Conference on Computational Sciences, ICCS'04, 6-9 June, Krakow, Poland, Edited by M. Bubak, G.van Albada, P. Sloot, and J. Dongarra, Vol II, pp. 670-673, Springer-Verlag, Berlin, 2004. Source code available for download at: http://www.cs.ubbcluj.ro/~moltean/evolve_heuristics.html

Berge equilibrium in the sense of Zhukovskii (Berge-Zhukovskii) is an alternate solution concept in non-cooperative game theory that formalizes cooperation in a noncooperative setting. In this paper the epsilon-Berge-Zhukovskii equilibrium is introduced and characterized by using a generative relation. A computational method for detecting epsilon-Berge-Zhukovskii equilibrium based on evolutionary multiobjective optimization algorithms is presented. Numerical examples are used to illustrate the results obtained.

An heuristic approach to compute strong Nash (Aumann) equilibria is presented. The method is based on differential evolution and three variants of a generative relation for strong Nash equilibria characterization. Numerical experiments performed on the minimum effort game for up to 150 players illustrate the efficiency of the approach. The advantages and disadvantages of each variant is discussed in terms of precision and running time.

A new game theoretical solution concept for open spectrum sharing in cognitive radio (CR) environments is presented, the Lorenz equilibrium (LE). Both Nash and Pareto solution concepts have limitations when applied to real world problems. Nash equilibrium (NE) rarely ensures maximal payoff and it is frequently Pareto inefficient. The Pareto set is usually a large set of solutions, often too hard to process. The Lorenz equilibrium is a subset of Pareto efficient solutions that are equitable for all players and ensures a higher payoff than the Nash equilibrium. LE induces a selection criterion of NE, when several are present in a game (e.g. many-player discrete games) and when fairness is an issue. Besides being an effective NE selection criterion, the LE is an interesting game theoretical situation per se, useful for CR interaction analysis., Comment: 5 pages, 4 figures

The aim of this work is to asses simultaneous spectrum access situations that may occur in Cognitive Radio (CR) environments. The approach is that of one shot, noncooperative games describing CR interactions. Open spectrum access scenarios are modelled based on continuous and discrete reformulations of the Cournot game theoretical model. CR interaction situations are described by Nash and Pareto equilibria. Also, the heterogeneity of players is captured by the new concept of joint Nash-Pareto equilibrium, allowing CRs to be biased toward different types of equilibrium. Numerical simulations reveal equilibrium situations that may be reached in simultaneous access scenarios of two and three users., Comment: 6 double-column pages, 8 figures, CSNDSP 2012. arXiv admin note: substantial text overlap with arXiv:1207.3365, arXiv:1209.5387, arXiv:1209.5013

In order to assess TV whitespace access scenarios, three oligopoly game models are considered and reformulated in terms of radio access: Cournot, Stackelberg, and Bertrand. Besides revisiting the relevance of Nash and Pareto equilibria, a new equilibrium concept, the joint Nash-Pareto equilibrium, is considered. An evolutionary game equilibria detection method is used. The analysis of the simulation results brings relevant insights on the issue of autonomy vs. regulation in emerging cognitive radio environments., Comment: 5 double-column pages, 6 figures, CrownCom 2011. arXiv admin note: substantial text overlap with arXiv:1207.3365, arXiv:1209.5013

In this paper it is introduced a biobjective ant algorithm for constructing low cost routing networks. The new algorithm is called the Distributed Pharaoh System (DPS). DPS is based on AntNet algorithm. The algorithm is using Pharaoh Ant System (PAS) with an extra-exploration phase and a 'no-entry' condition in order to improve the solutions for the Low Cost Network Routing problem. Additionally it is used a cost model for overlay network construction that includes network traffic demands. The Pharaoh ants (Monomorium pharaonis) includes negative pheromones with signals concentrated at decision points where trails fork. The negative pheromones may complement positive pheromone or could help ants to escape from an unnecessarily long route to food that is being reinforced by attractive signals. Numerical experiments were made for a random 10-node network. The average node degree of the network tested was 4.0. The results are encouraging. The algorithm converges to the shortest path while converging on a low cost overlay routing network topology., Comment: 4 pages, 4 figures

Ant-based algorithms are successful tools for solving complex problems. One of these problems is the Linear Ordering Problem (LOP). The paper shows new results on some LOP instances, using Ant Colony System (ACS) and the Step-Back Sensitive Ant Model (SB-SAM)., Comment: 5 pages, 5 figures Zbl:06048718

The idea of sensitivity in ant colony systems has been exploited in hybrid ant-based models with promising results for many combinatorial optimization problems. Heterogeneity is induced in the ant population by endowing individual ants with a certain level of sensitivity to the pheromone trail. The variable pheromone sensitivity within the same population of ants can potentially intensify the search while in the same time inducing diversity for the exploration of the environment. The performance of sensitive ant models is investigated for solving the generalized vehicle routing problem. Numerical results and comparisons are discussed and analysed with a focus on emphasizing any particular aspects and potential benefits related to hybrid ant-based models., Comment: 5 pages

The aim of this paper is to explore the potential of Game Theory (GT) in extracting rules of behaviour for emerging Cognitive Radio environments. We revisit the commons approach to unlicensed spectrum and try to show that a commons can be basically regulated from the inside out. GT simulations of CR interactions reveal the emergence of certain equilibria mirroring behaviours/trends?. Once these ?trends identified, norms may be expressed and then embedded into machines (CRs). Internalized norms may thus become the alternative to external enforcement of rules. We call these emerging norms techno-social norms (TSNs). TSNs could eventually become a means of regulating the use of unlicensed spectrum and making open spectrum access feasible. Open spectrum access scenarios are considered and analysis is performed based on reformulations of two game theoretical models: Cournot and Bertrand. The standard oligopoly models are reformulated in terms of radio resource access in unlicensed bands. In order to capture the large variety of CR interaction situations, several GT equilibrium concepts are considered: Nash, Pareto, Berge-Zhukovskii, and Lorenz. In order to capture the heterogeneity of CR interactions, the standard GT model is enriched allowing players to be biased toward different types of equilibrium (or rationality). An evolutionary game-equilibrium detection method is used. Numerical simulations bring relevant insights on the problem of autonomy vs. regulation in emerging CR environments. Relying on extensive GT simulations, some rules of behaviour - to be expanded into techno-social norms - may be derived., Comment: ("This work has been submitted to the IEEE for possible publication")