Distributed simulation is an enabling concept to support the networked interaction of models and real world elements that are geographically distributed. This technology has brought a new set of challenging problems to solve, such as Data Distribution Management (DDM). The aim of DDM is to limit and control the volume of the data exchanged during a distributed simulation, and reduce the processing requirements of the simulation hosts by relaying events and state information only to those applications that require them. In this thesis, we propose a new DDM scheme, which we refer to as dynamic grid-based DDM. A lightweight UNT-RTI has been developed and implemented to investigate the performance of our DDM scheme. Our results clearly indicate that our scheme is scalable and it significantly reduces both the number of multicast groups used, and the message overhead, when compared to previous grid-based allocation schemes using large-scale and real-world scenarios.

Healthcare systems are traditionally characterised by complexity and heterogeneity. With the continuous increase in size and shrinkage of available resources, the healthcare sector faces the challenge of delivering high quality services with fewer resources. Healthcare organisations cannot be seen in isolation since the services of one such affects the performance of other healthcare organisations. Efficient management and forward planning, not only locally but rather across the whole system, could support healthcare sector to overcome the challenges. An example of closely interwoven organisations within the healthcare sector is the emergency medical services (EMS). EMS operate in a region and usually consist of one ambulance service and the available accident and emergency (A&E) departments within the coverage area. EMS provide, mainly, pre-hospital treatment and transport to the appropriate A&E units. The life-critical nature of EMS demands continuous systems improvement practices. Modelling and Simulation (M&S) has been used to analyse either the ambulance services or the A&E departments. However, the size and complexity of EMS systems constitute the conventional M&S techniques inadequate to model the system as a whole. This research adopts the approach of distributed simulation to model all the EMS components as individual and composable simulations that are able to run as standalone simulation, as well as federates in a distributed simulation (DS) model. Moreover, the hybrid approach connects agent-based simulation (ABS) and discrete event simulation (DES) models in order to accommodate the heterogeneity of the EMS components. The proposed FIELDS Framework for Integrated EMS Large-scale Distributed Simulation supports the re-use of existing, heterogeneous models that can be linked with the High Level Architecture (HLA) protocol for distributed simulation in order to compose large-scale simulation models. Based on FIELDS, a prototype ABS-DES distributed simulation EMS model was developed based on the London EMS. Experiments were conducted with the model and the system was tested in terms of performance and scalability measures to assess the feasibility of the proposed approach. The yielded results indicate that it is feasible to develop hybrid DS models of EMS that enables holistic analysis of the system and support model re-use. The main contributions of this thesis is a distributed simulation methodology that derived along the process of conducting this project, the FIELDS framework for hybrid EMS distributed simulation studies that support re-use of existing simulation models, and a prototype distributed simulation model that can be potentially used as a tool for EMS analysis and improvement.

Esta tese propõe um ambiente automático para desenvolvimento de simulação distribuída ASDA (Ambiente de Simulação Distribuída Automático), que tem como objetivo principal facilitar a utilização e desenvolvimento de simulação distribuída. As funcionalidades definidas no ASDA tornam-o diferente de todos os outros ambientes encontrados na literatura. A especificação do ASDA foi realizada através de um diagrama modular composto por sete módulos e também com o auxílio da ferramenta UML (Unified Modelling Language), através da utilização de três de seus diagramas: de casos de uso, de classes e de atividades. O ASDA permite aos usuários a utilização de simulação distribuída através da definição de uma nova simulação ou da replicação de um programa de simulação já desenvolvido. Se a opção for pelo desenvolvimento de um novo programa de simulação, o usuário deve fornecer o modelo e os parâmetros e o ambiente se encarrega de gerar o código do programa de simulação utilizando a abordagem que proporciona o melhor desempenho, levando em consideração as características do modelo e da plataforma. Além da especificação do ASDA, esta tese definiu um protótipo do ambiente com o objetivo de mostrar sua viabilidade de utilização. Neste protótipo, três módulos foram implementados, destacando-se o módulo Replicador, que utiliza a abordagem MRIP (Multiple Replication in Parallel). Esta tese contribui também com a definição de algumas diretrizes para a utilização da abordagem MRIP. A base para essa definição foram os resultados obtidos com a utilização do módulo Replicador / This thesis proposes an automatic environment for the development of distributed simulation ASDA (Ambiente de Simulação Distribuída Automático (in Portuguese), whose main goal is to make easier the use and development of distributed simulation. The ASDA functionality makes it different from all other environments found in the literature. The ASDA has been specified through a modular diagram, composed of seven modules built with the help of the UML (Unified Modelling Language) tool, using three of its diagrams: use case, class and activity. ASDA users can define the distributed simulation by means of the specification of a new simulation program or the replication of a simulation program already developed. If the user chooses to develop a new simulation program, he must only provide the model and the parameters. The environment will then generate the simulation program code using the approach that provides the best performance considering the model and platform characteristics. Besides the specification, this thesis presents a prototype of the ASDA environment with the goal of showing its viability. Three modules have been implemented for the prototype, highlighting the Replication module, which uses the MRIP (Multiple Replication in Parallel) approach. Another contribution of this thesis is the definition of a set of guidelines to the utilization of the MRIP approach. The basis to define these procedures was the results obtained with the utilization of the Replication module

Este trabalho analisa o impacto causado no desempenho de uma simulação distribuída quando técnicas de particionamento convencionais são empregadas. Essas técnicas não levam em conta informações inerentes ao estado da simulação. Pelo fato da execução de uma simulação também estar sujeita a sofrer interferências da plataforma, informações sobre a potência computacional de cada recurso utilizado e sobre o tipo de simulação, podem ser aplicadas em seu particionamento. Foram utilizadas informações estáticas, geradas através da avaliação da plataforma com benchmarks, e dinâmicas, obtidas através de índices de carga. Os resultados obtidos da utilização destas técnicas se mostram atrativos, principalmente quando o objetivo é a execução das simulações em ambientes que não disponibilizam políticas de escalonamento específicas e sim políticas convencionais. Nos estudos de casos avaliados, observaram-se ganhos satisfatórios, como a redução de até 24% do tempo de execução, um aumento de até 22% de eficiência e 79% menos rollbacks causados. Percebe-se que dependendo do tempo que se dispõe e dos objetivos pretendidos, as técnicas convencionais podem ser empregadas em simulações distribuídas. Este trabalho também contribui com o aperfeiçoamento das duas ferramentas utilizadas: WARPED e AMIGO. Uma interface de comunicação entre as duas ferramentas foi desenvolvida, ampliando assim seus campos de utilização. / This work analyses the impact caused on distributed simulation performance when conventional partitioning techniques are employed. These techniques do not take into account inherent information about the state of the simulation. Since a simulation execution is subject to platform interference, information about the type of simulations and about the computational power of resources may be applied to the partitioning process. Static performance information, generated from evaluating the platform with benchmarks has been employed, as well as dynamic load information provided by load indices. The results obtained with this approach are attractive, mainly when the objective is to execute simulations on environments which make conventional scheduling policies available, instead of specific policies. The evaluated case studies show satisfactory performance gains of up to 24% of reduction in execution time, 22% of improvement in efficiency and reduction of up to 79% in rollbacks. So, depending on the available time and the aimed objectives, it is worth using conventional techniques to assist distributed simulation partitioning. This work also contributes to the improvement of both tools used in it: Warped and AMIGO. A communication interface has been developed to integrate the tools, extending their capabilities.

Esta tese apresenta uma avaliação do desempenho de simulações distribuídas em tempo de execução. Baseando-se nos resultados obtidos nessa avaliação é proposto um mecanismo em que diferentes protocolos de sincronização coexistem em uma mesma simulação. Esse mecanismo tem por objetivo adequar a simulação em execução ao melhor protocolo de sincronização, para garantir melhor desempenho e, conseqüentemente, resultados mais rápidos. Todas as modificações que são necessárias nos protocolos e a definição da troca de mensagens entre os processos são detalhadas neste trabalho. Esta tese apresenta também os resultados dos testes realizados para identificar os casos onde é melhor manter o protocolo conservador ou onde uma troca de protocolo deve ser considerada. Os resultados obtidos são apresentados e mostram em que momento a troca deve ser considerada. Diferentes abordagens podem ser utilizadas para avaliar o desempenho da simulação, considerando cada processo individualmente ou todos os processos globalmente. De maneira análoga, a troca de protocolos pode ser realizada de forma local ou global. Essas considerações permitem a criação de uma taxonomia para a troca de protocolo que também é apresentada nesta tese. / This thesis presents a performance evaluation of distributed simulations during execution time. According to the results obtained in this evaluation, it is proposed a mechanism where different synchronization protocols can be used in the same simulation. This mechanism aims at tunning the simulation in execution to the best protocol in order to reach better performance. All modifications needed in the protocols and the definition of the exchanged messages between logical processes is presented in this work. This thesis also presents the results of the tests realized to identify the cases where it is better to keep the conservative protocol or it is better to swap the protocol. The results obtained are presented and shown when it is necessary to swap the protocol. Different approaches can be used to evaluate the simulation performance considering that it is possible to evaluate each logical process locally or all of them globally. The change of the protocol can also be applied in just one logical process or in all of them. These considerations allowed the definition of a taxonomy that is also presented in this thesis.

Um melhor escalonamento em simulação distribuída é fundamental para uma execução mais rápida e eficiente. O projeto desenvolvido tem como objetivo a avaliação de desempenho de políticas de escalonamento convencionais e específicas para Simulação Distribuída (SD), apresentando uma comparação do desempenho destas duas abordagens. Análises das pesquisas feitas na área mostram que não existe avaliação semelhante. Assim, este trabalho tem a importante contribuição de demonstrar as vantagens e desvantagens do uso de políticas tradicionais em relação às específicas em SD. Para execução das simulações foi utilizada a ferramenta Warped, que está descrita nesta dissertação. Foram desenvolvidas e implementadas novas técnicas de escalonamento que utilizam os resultados da simulação em execução, assim executam um melhor balanceamento de carga. Para o desenvolvimento deste projeto foi necessária uma revisão bibliográfica envolvendo conceitos de simulação distribuída com seus respectivos protocolos de sincronização, escalonamento de processos específicos para programas de SD e políticas tradicionais. Com este estudo soma-se como contribuição deste trabalho uma nova classificação das políticas específicas para SD que utilizam protocolo otimista / A bestter scheduling in distributed simulation is fundamental to a fast and efficient execution. The developed project has as objective the evaluation of performance of conventional and specific politics of scheduling for Distributed Simulation (DS), presenting a comparison of the performance of these two boardings. Analyses of the research done in the area show that similar evaluation does not exists. Thus, this work has the important contribution to demonstrate to the advantages and disadvantages of the use of traditional politics in relation to the specific ones in DS. For execution of the simulations the Warped tool was used, that is described in this work. They had been developed and implemented new techniques of scheduling that use the results of the simulation in execution, thus they execute one better load balancing. For the development of this project a bibliographical revision was necessary involving concepts of simulation distributed with its respective protocols of synchronization, traditional scheduling of specific processes for DS programs and politics. With this study a new classification of the specific politics for DS is added as contribution of this work that use optimistical protocol

Nos últimos anos Jogos Online Massivamente Multijogadores (MMOG) têm se expandido em popularidade e investimento, influenciado, especialmente, pela evolução da conexão residencial (conexões mais rápidas a preços mais baixos). Com o crescimento dessa demanda, surgem problemas na utilização da arquitetura cliente-servidor, normalmente utilizada em jogos comerciais. Entre as arquiteturas alternativas de suporte a MMOGs estão as arquiteturas peer-to-peer. Porém essas arquiteturas apresentam problemas relativos a segurança, problemas esses que possuem, muitas vezes, soluções de baixo desempenho, sendo impraticáveis em jogos reais. Entre os problemas de segurança mais significativos para MMOGs encontra-se o cheating, ou a ação que um ou mais jogador toma para burlar as regras em favor próprio. A preocupação com cheating agravase quando o efeito desse cheating pode causar danos irreversíveis à economia virtual e, potencialmente, afetar todos os jogadores. O presente trabalho faz uso de uma divisão celular do mundo virtual para restringir o impacto de um dado cheating a uma única célula, evitando que este se propague. Para tanto é realizada uma classificação do estado do jogador e utiliza-se uma técnica de detecção de cheating para cada uma das classificações. Foram realizados experimentos através de simulação para testes de aplicabilidade do modelo e análise de desempenho e acuracidade. Os testes indicam que o modelo proposto consegue, de forma eficaz, realizar a proteção da economia virtual, impedindo que a ocorrência de um cheating atinja todos os jogadores. / In the past few years, Massively Multiplayer Online Games (MMOG) grew in both popularity and investment. This growth has been influenced by the evolution of residential connection (faster and cheaper connections). With the demand, some limitations imposed by the client-server architecture becomes more significant. Peer-to-peer architectures aim to solve those problems by distributing the game among several computers. However, those solutions usually lack security, or presents low performance. Among the problems, cheating can be considered the most significant to MMOGs. Cheating can be defined as the action taken by a player when this action is against the rules. This may be aggravated when this action can cause irreversible damage to the virtual economy and, potentially, affect all players in the virtual world. This work’s goal is to restrict the cheating impact using a cellular world division. The proposal is to restrict the cheating in a limited virtual space, preventing the propagation. A state classification is presented, and different cheating detection techniques are presented to each element of this classification. Simulation is used to make the experiments aiming to test the performance and accuracy of the proposal. Results indicate that the proposed solution can efficiently protect the virtual economy, restraining the effects of a cheating occurrence to a small portion of the virtual world.

<p>The aim of this thesis is to exploit the technological capabilities of computer supported collaborative work (CSCW) in the field of collaborative Modelling and Simulation (M&S). The thesis focuses on addressing two main problems: (i) providing flexible means of consistency management in collaborative M&S, and (ii) the ability of providing platform and application independent services for collaborative M&S.</p><p>In this work, some CSCW technologies and how some of the concepts can be incorporated in a distributed collaborative M&S environment, have been studied. An environment for component based simulation development and visualization, which provides support for collaborative M&S, has been designed. Some consistency policies that can be used in conjunction with distributed simulation and the High Level Architecture (HLA) have been investigated. Furthermore, the efficient utilization of HLA and XML in combination, as the foundation of a CSCW infrastructure has been proved. Two consistency policies were implemented utilizing HLA, a strict and an optimistic, in the distributed collaborative environment. Their performance was compared to the performance of a totally relaxed policy, in various collaboration situations.</p>

Discrete-event simulation has become one of the most widely used analysis tools for large-scale, complex and dynamic systems such as supply chains as it can take randomness into account and address very detailed models. However, there are major challenges that are faced in simulating such systems, especially when they are used to support short-term decisions (e.g., operational decisions or maintenance and scheduling decisions considered in this research). First, a detailed simulation requires significant amounts of computation time. Second, given the enormous amount of dynamically-changing data that exists in the system, information needs to be updated wisely in the model in order to prevent unnecessary usage of computing and networking resources. Third, there is a lack of methods allowing dynamic data updates during the simulation execution. Overall, in a simulation-based planning and control framework, timely monitoring, analysis, and control is important not to disrupt a dynamically changing system. To meet this temporal requirement and address the above mentioned challenges, a Dynamic-Data-Driven Adaptive Multi-Scale Simulation (DDDAMS) paradigm is proposed to adaptively adjust the fidelity of a simulation model against available computational resources by incorporating dynamic data into the executing model, which then steers the measurement process for selective data update. To the best of our knowledge, the proposed DDDAMS methodology is one of the first efforts to present a coherent integrated decision making framework for timely planning and control of distributed manufacturing enterprises.To this end, comprehensive system architecture and methodologies are first proposed, where the components include 1) real time DDDAM-Simulation, 2) grid computing modules, 3) Web Service communication server, 4) database, 5) various sensors, and 6) real system. Four algorithms are then developed and embedded into a real-time simulator for enabling its DDDAMS capabilities such as abnormality detection, fidelity selection, fidelity assignment, and prediction and task generation. As part of the developed algorithms, improvements are made to the resampling techniques for sequential Bayesian inferencing, and their performance is benchmarked in terms of their resampling qualities and computational efficiencies. Grid computing and Web Services are used for computational resources management and inter-operable communications among distributed software components, respectively. A prototype of proposed DDDAM-Simulation was successfully implemented for preventive maintenance scheduling and part routing scheduling in a semiconductor manufacturing supply chain, where the results look quite promising.

No description available.