Model checking is a fully automatic technique for checking concurrent software properties in which the states of a concurrent system are explored in an explicit or implicit way. However, the state explosion problem limits the size of the models that are possible to check. Genetic Algorithms (GAs) are metaheuristic techniques that have obtained good results in problems in which exhaustive techniques fail due to the size of the search space. Unlike exact techniques, metaheuristic techniques can not be used to verify that a program satisfies a given property, but they can find errors on the software using a lower amount of resources than exact techniques. In this paper, we compare a GA against classical exact techniques and we propose a new operator for this problem, called memory operator, that allows the GA to explore even larger search spaces. We implemented our ideas in the Java Pathfinder (JPF) model checker to validate them and present our results. To the best of our knowledge, this is the first implementation of a Genetic Algorithm in this model checker.

Abstract. Model checking is a fully automatic technique for checking concurrent software properties in which the states of a concurrent system are explored in an explicit or implicit way. The main drawback of this technique is the high memory consumption, which limits the size of the programs that can be checked. In the last years, some researchers have focused on the application of guided non-complete stochastic techniques to the search of the state space of such concurrent programs. In this paper, we compare five metaheuristic algorithms for this problem. The algorithms are Simulated Annealing, Ant Colony Optimization, Particle Swarm Optimization and two variants of Genetic Algorithm. To the best of our knowledge, it is the first time that Simulated Annealing has been applied to the problem. We use in the comparison a benchmark composed of 17 Java concurrent programs. We also compare the results of these algorithms with the ones of deterministic algorithms.

Determining the indoor location is usually performed by using several sensors. Some of these sensors are fixed to a known location and either transmit or receive information that allows other sensors to estimate their own locations. The estimation of the location can use information such as the time-of-arrival of the transmitted signals, or the received signal strength, among others. Major problems of indoor location include the interferences caused by the many obstacles in such cases, causing among others the signal multipath problem and the variation of the signal strength due to the many transmission media in the path from the emitter to the receiver. In this paper, the creation and usage of perfect sequences that eliminate the signal multipath problem are presented. It also shows the influence of the positioning of the fixed sensors to the precision of the location estimation. Finally, genetic algorithms were used for searching the optimal location of these fixed sensors, therefore minimizing the location estimation error.

<p>Existem escassas evidências sobre a eficácia da intervenção em salas de Snoezelen na redução de estereotipias em adultos com deficiência intelectual. Neste sentido, o presente estudo pretendeu avaliar a relação entre esta estimulação multissensorial e a redução de estereotipias em adultos com deficiência intelectual. Por meio da metodologia de estudo de caso, analisou-se o comportamento de um sujeito antes, durante e após estimulação multissensorial em salas de Snoezelen, durante dez sessões bissemanais, com a duração de 1h30. A recolha de dados foi concretizada por entrevista semiestruturada aos cuidadores formais do sujeito e da observação direta participante e não participante com registo audiovisual das sessões. Após a análise dos dados, com a utilização do software WebQDA, foi possível concluir que a estimulação multissensorial em sala de Snoezelen contribuiu para a redução das estereotipias no sujeito em estudo, durante a sua realização como imediatamente após, num contexto distinto. Outra evidência do presente estudo sugere que existe uma redução da frequência de estereotipias a médio prazo bem como o aumento da interação e comunicação do sujeito com o terapeuta.</p>

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