Changeable Message Signs (CMS) are commonly utilized by transportation agencies to inform motorists of traffic, roadway, and environmental conditions. They may be used to provide information, such as delay and alternate route guidance, in the event of an incident, construction or a roadway closure. The effectiveness of CMS in managing freeway traffic, however, is a function of many factors including the number of CMS installations, the location of CMS, the messages displayed, varied traffic network characteristics, and drivers' response to incident conditions and CMS information. The objective of this thesis is to develop a CMS location planning model that can be used by transportation agencies to develop a CMS location plan that could achieve the largest long-term benefit to the system. This research is mainly motivated by the lack of systematic, robust and practical methods for locating CMS. State-of-practice methods rely mostly on the practitioner's experience and judgement. Other methods fail to incorporate reasonable driver behaviour models, consider time-varying demand, allow for computational efficiency on large networks, or consider the spatial variation of incidents on a traffic network. A new CMS location optimization model has been developed that is unique in both model realism and computational efficiency. The model incorporates several components to estimate incident delay, predict driver response, estimate network-wide benefit, and choose those CMS locations that would provide the most benefit. Deterministic queuing methods are used in conjunction with historic incident characteristics to approximate the delay impact of an incident with and without CMS. A discrete choice model is used to predict the rate at which drivers would switch from the incident route to a less congested alternative under CMS information. A network traffic assignment model is then incorporated in an attempt to estimate the resulting traffic induced by incidents. Genetic algorithms are utilized as an optimization technique to choose a set of CMS that would provide the most benefit. An extensive computational analysis was performed on both a hypothetical network and a segment of Highway 401 through Toronto. A sensitivity analysis was performed to test the model's response to parameter and data estimation errors. The model was found to be most sensitive to the diversion model parameters. The model produced reasonable results with locations selected upstream of major freeway interchange diversion points. Considering the additional components included in the proposed model, and its ability to consider more location schemes, the proposed model may be considered superior to previous CMS location models.

Traffic signs are ubiquitous in the road environment, and are a crucial and cost-effective means of ensuring traffic safety. In Queensland, Australia, a class of temporary traffic signs is used for roadwork applications, and has recently been expanded to include Multiple-Message Signs: a novel, and as yet empirically untested system, which presents numerous advantages in terms of flexibility and economy. However, potential Human Factors problems surround aspects of the design of multiple message signs. In particular, the efficiency with which information is communication may be compromised relative to single message signs. The project involved a series of laboratory studies focussing on the behavioural requirements of temporary roadworks signs, beginning with the improvement of response characteristics of a sign used to communicate lane-closure. In the first empirical study, a proposed redesign of the Lane-Status sign based on principles of warning communication was found to be more effective than the original sign. The same sign was then examined in the context of multiple-message presentation, and significant cost s with respect to the speed and accuracy of responses relative to single-message presentation were found. A subsequent study investigated multiple-message presentation of speed limit information, which is more familiar and widely encountered than lane-closure information. Similar costs for multiple-message presentation were found. However, there were data to suggest that the additional information in multiple-message signs, if used correctly, may offer drivers and additional incentive to reduce speed. The next two studies were concerned with the effects of presentation, content type (e.g., speed-limit, symbolic and text-based) and visual clutter on recognition and visual search for traffic signs. The presentation of information via multiple message signs was compared with spatially distributed single message signs, with information matched with respect to message length and sign content. Overall advantages for multiple message presentation were found for recognition, which were particularly robust for speed limit information. The results for visual search indicated some benefits to multiple message presentation, but were less decisive than those for recognition. The final two studies investigated the possibility of improving response characteristics of single-message signs with sequential, rather then individual presentation. The role of the temporal interval between successive sign presentations was explored, which has implications for the feasibility of sequential presentation in practice. In addition, the nature of sign pairs presented in sequence – identical, or of the same meaning – was found to be important. Generally, benefits to sequential presentation diminished with increases in the temporal separation interval. In terms of practical implications, the viability of introducing the proposed design changes to the Lane Status sign is discussed. The results pertaining to multiple-message sign are evaluated in the context of published design guidelines, and theoretical and practical issues surrounding sequential sign presentation are reviewed. Finally, possibilities for future research, in part based on the limitations of the current work, are expounded.

Traffic signs are ubiquitous in the road environment, and are a crucial and cost-effective means of ensuring traffic safety. In Queensland, Australia, a class of temporary traffic signs is used for roadwork applications, and has recently been expanded to include Multiple-Message Signs: a novel, and as yet empirically untested system, which presents numerous advantages in terms of flexibility and economy. However, potential Human Factors problems surround aspects of the design of multiple message signs. In particular, the efficiency with which information is communication may be compromised relative to single message signs. The project involved a series of laboratory studies focussing on the behavioural requirements of temporary roadworks signs, beginning with the improvement of response characteristics of a sign used to communicate lane-closure. In the first empirical study, a proposed redesign of the Lane-Status sign based on principles of warning communication was found to be more effective than the original sign. The same sign was then examined in the context of multiple-message presentation, and significant cost s with respect to the speed and accuracy of responses relative to single-message presentation were found. A subsequent study investigated multiple-message presentation of speed limit information, which is more familiar and widely encountered than lane-closure information. Similar costs for multiple-message presentation were found. However, there were data to suggest that the additional information in multiple-message signs, if used correctly, may offer drivers and additional incentive to reduce speed. The next two studies were concerned with the effects of presentation, content type (e.g., speed-limit, symbolic and text-based) and visual clutter on recognition and visual search for traffic signs. The presentation of information via multiple message signs was compared with spatially distributed single message signs, with information matched with respect to message length and sign content. Overall advantages for multiple message presentation were found for recognition, which were particularly robust for speed limit information. The results for visual search indicated some benefits to multiple message presentation, but were less decisive than those for recognition. The final two studies investigated the possibility of improving response characteristics of single-message signs with sequential, rather then individual presentation. The role of the temporal interval between successive sign presentations was explored, which has implications for the feasibility of sequential presentation in practice. In addition, the nature of sign pairs presented in sequence – identical, or of the same meaning – was found to be important. Generally, benefits to sequential presentation diminished with increases in the temporal separation interval. In terms of practical implications, the viability of introducing the proposed design changes to the Lane Status sign is discussed. The results pertaining to multiple-message sign are evaluated in the context of published design guidelines, and theoretical and practical issues surrounding sequential sign presentation are reviewed. Finally, possibilities for future research, in part based on the limitations of the current work, are expounded.

O aumento crescente no número de processadores das arquiteturas paralelas que estão no topo dos rankings de desempenho, apesar de permitir uma maior capacidade de processamento, também traz consigo um aumento na taxa de falhas diretamente proporcional ao número de processadores. Atualmente, as técnicas de tolerância a falhas com recuperação retroativa são as mais empregadas em aplicações MPI, principalmente a técnica de checkpoint coordenado. No entanto, previsões afirmam que essa última técnica será inadequada para as arquiteturas emergentes. Em contrapartida, as técnicas de log de mensagens possuem características que as tornam mais apropriadas no novo cenário que se estabelece. O presente trabalho consiste em uma proposta de log de mensagens pessimista remoto com checkpoint não-coordenado e a avaliação de desempenho da comunicação MPI sobre Publish/Subscriber no qual se baseia o log de mensagens. O trabalho compreende: um estudo das técnicas de tolerância a falhas mais empregadas em ambientes de alto desempenho e a motivação para a escolha dessa variante de log de mensagens; a proposta de log de mensagens; uma implementação de comunicação Open MPI sobre OpenAMQ e sua respectiva avaliação de desempenho com comunicação tradicional TCP/IP e com o log de mensagens pessimista local da distribuição do Open MPI. Os benchmarks utilizados foram o NetPIPE, o NAS Parallel Benchmarks e a aplicação Virginia Hydrodynamics (VH-1). / The growing number of processors in parallel architectures at the top of performance rankings allows a higher processing capacity. However, it also brings an increase in the fault rate which is directly proportional to the number of processors. Nowadays, coordinated checkpoint is the most widely used rollback technique for system recovery in the occurrence of faults in MPI applications. Nevertheless, projections point that this technique will be inappropriate for the emerging architectures. On the other hand, message logging seems to be more appropriate to this new scenario. This work consists in a proposal of pessimistic message logging (remote based) with non-coordinated checkpoint and the performance evaluation of an MPI communication mechanism that works over Publish/Subscriber channels in which the proposed message logging is based. The work is organized as following: an study of fault tolerant techniques used in HPC and the motivation for choosing this variant of message logging; a message logging proposal; an implementation of Open MPI communication over OpenAMQ; performance evaluation and comparision with the tradicional TCP/IP communication and a pessimistic message logging (sender based) from Open MPI distribution. The benchmark set is composed of NetPIPE, NAS Parallel Benchmarks and Virginia Hydrodynamics (VH-1).

En algorithmique distribuée, le modèle asynchrone par envoi de messages et à pannes est connu et utilisé dans de nombreux articles de par son réalisme,par ailleurs il est suffisamment simple pour être utilisé et suffisamment complexe pour représenter des problèmes réels. Dans ce modèle, les n processus communiquent en s'échangeant des messages, mais sans borne sur les délais de communication, c'est-à-dire qu'un message peut mettre un temps arbitrairement long à atteindre sa destination. De plus, jusqu'à f processus peuvent tomber en panne, et ainsi arrêter définitivement de fonctionner. Ces pannes indétectables à cause de l'asynchronisme du système limitent les possibilités de ce modèle. Dans de nombreux cas, les résultats connus dans ces systèmes sont limités à une stricte minorité de pannes. C'est par exemple le cas de l'implémentation de registres atomiques et de la résolution du renommage. Cette barrière de la majorité de pannes, expliquée par le théorème CAP, s'applique à de nombreux problèmes, et fait que le modèle asynchrone par envoi de messages avec une majorité de pannes est peu étudié. Il est donc intéressant d'étudier ce qu'il est possible de faire dans ce cadre.Cette thèse cherche donc à mieux comprendre ce modèle à majorité de pannes, au travers de deux principaux problèmes. Dans un premier temps, on étudie l'implémentation d'objets partagés similaires aux registres habituels, en définissant les bancs de registres x-colorés et les α-registres. Dans un second temps, le problème du renommage est étendu en renommage k-redondant, dans ses versions à-un-coup et réutilisable, et de même pour les objets partagés diviseurs, étendus en k-diviseurs. / In distributed computing, asynchronous message-passing model with crashes is well-known and considered in many articles, because of its realism and it issimple enough to be used and complex enough to represent many real problems.In this model, n processes communicate by exchanging messages, but withoutany bound on communication delays, i.e. a message may take an arbitrarilylong time to reach its destination. Moreover, up to f among the n processesmay crash, and thus definitely stop working. Those crashes are undetectablebecause of the system asynchronism, and restrict the potential results in thismodel.In many cases, known results in those systems must verify the propertyof a strict minority of crashes. For example, this applies to implementationof atomic registers and solving of renaming. This barrier of a majority ofcrashes, explained by the CAP theorem, restricts numerous problems, and theasynchronous message-passing model with a majority of crashes is thus notwell-studied and rather unknown. Hence, studying what can be done in thiscase of a majority of crashes is interesting.This thesis tries to analyse this model, through two main problems. The first part studies the implementation of shared objects, similar to usual registers,by defining x-colored register banks, and α-registers. The second partextends the renaming problem into k-redundant renaming, for both one-shotand long-lived versions, and similarly for the shared objects called splitters intok-splitters.

Cette thèse aborde la résolution des problèmes d'interaction fluide-structure par un algorithme consistant en un couplage entre deux solveurs : un pour le fluide et un pour la structure. Pour assurer la cohérence entre les maillages fluide et structure, on considère également une discrétisation de chaque domaine par volumes finis. En raison des difficultés de décomposition du domaine en sous-domaines, nous considérons pour chaque environnement un algorithme parallèle de multi-splitting (ou multi-décomposition) qui correspond à une présentation unifiée des méthodes de sous-domaines avec ou sans recouvrement. Cette méthode combine plusieurs applications de points fixes contractantes et nous montrons que, sous des hypothèses appropriées, chaque application de points fixes est contractante dans des espaces de dimensions finies normés par des normes hilbertiennes et non-hilbertiennes. De plus, nous montrons qu'une telle étude est valable pour les résolutions parallèles synchrones et plus généralement asynchrones de grands systèmes linéaires apparaissant lors de la discrétisation des problèmes d'interaction fluide-structure et peut être étendue au cas où le déplacement de la structure est soumis à des contraintes. Par ailleurs, nous pouvons également considérer l’analyse de la convergence de ces méthodes de multi-splitting parallèles asynchrones par des techniques d’ordre partiel, lié au principe du maximum discret, aussi bien dans le cadre linéaire que dans celui obtenu lorsque les déplacements de la structure sont soumis à des contraintes. Nous réalisons des simulations parallèles pour divers cas test fluide-structure sur différents clusters, en considérant des communications bloquantes et non bloquantes. Dans ce dernier cas nous avons eu à résoudre une difficulté d'implémentation dans la mesure où une erreur irrécupérable survenait lors de l'exécution ; cette difficulté a été levée par introduction d’une méthode assurant la terminaison de toutes les communications non bloquantes avant la mise à jour du maillage. Les performances des simulations parallèles sont présentées et analysées. Enfin, nous appliquons la méthodologie présentée précédemment à divers contextes d'interaction fluide-structure de type industriel sur des maillages non structurés, ce qui constitue une difficulté supplémentaire. / This thesis deals with the solution of fluid-structure interaction problems by an algorithm consisting in the coupling between two solvers: one for the fluid and one for the structure. In order to ensure the consistency between fluid and structure meshes, we also consider a discretization of each domain by finite volumes. Due to the difficulties of decomposing the domain into sub-domains, we consider a parallel multi-splitting algorithm for each environment which represents a unified presentation of sub-domain methods with or without overlapping. This method combines several contracting fixed point mappings and we show that, under appropriate assumptions, each fixed point mapping is contracting in finite dimensional spaces normalized by Hilbertian and non-Hilbertian norms. In addition, we show that such a study is valid for synchronous parallel solutions and more generally asynchronous of large linear systems arising from the discretization of fluidstructure interaction problems and can be extended to cases where the displacement of the structure is subject to constraints. Moreover, we can also consider the analysis of the convergence of these asynchronous parallel multi-splitting methods by partial ordering techniques, linked to the discrete maximum principle, both in the linear frame and in the one obtained when the structure's displacements are subjected to constraints. We carry out parallel simulations for various fluidstructure test cases on different clusters considering blocking and non-blocking communications. In the latter case, we had to solve an implementation problem due to the fact that an unrecoverable error occurred during execution; this issue has been overcome by introducing a method to ensure the termination of all non-blocking communications prior to the mesh update. Performances of parallel simulations are presented ans analyzed. Finally, we apply the methodology presented above to various fluid-structure interaction cases on unstructured meshes, which represents an additional difficulty.

O aumento crescente no número de processadores das arquiteturas paralelas que estão no topo dos rankings de desempenho, apesar de permitir uma maior capacidade de processamento, também traz consigo um aumento na taxa de falhas diretamente proporcional ao número de processadores. Atualmente, as técnicas de tolerância a falhas com recuperação retroativa são as mais empregadas em aplicações MPI, principalmente a técnica de checkpoint coordenado. No entanto, previsões afirmam que essa última técnica será inadequada para as arquiteturas emergentes. Em contrapartida, as técnicas de log de mensagens possuem características que as tornam mais apropriadas no novo cenário que se estabelece. O presente trabalho consiste em uma proposta de log de mensagens pessimista remoto com checkpoint não-coordenado e a avaliação de desempenho da comunicação MPI sobre Publish/Subscriber no qual se baseia o log de mensagens. O trabalho compreende: um estudo das técnicas de tolerância a falhas mais empregadas em ambientes de alto desempenho e a motivação para a escolha dessa variante de log de mensagens; a proposta de log de mensagens; uma implementação de comunicação Open MPI sobre OpenAMQ e sua respectiva avaliação de desempenho com comunicação tradicional TCP/IP e com o log de mensagens pessimista local da distribuição do Open MPI. Os benchmarks utilizados foram o NetPIPE, o NAS Parallel Benchmarks e a aplicação Virginia Hydrodynamics (VH-1). / The growing number of processors in parallel architectures at the top of performance rankings allows a higher processing capacity. However, it also brings an increase in the fault rate which is directly proportional to the number of processors. Nowadays, coordinated checkpoint is the most widely used rollback technique for system recovery in the occurrence of faults in MPI applications. Nevertheless, projections point that this technique will be inappropriate for the emerging architectures. On the other hand, message logging seems to be more appropriate to this new scenario. This work consists in a proposal of pessimistic message logging (remote based) with non-coordinated checkpoint and the performance evaluation of an MPI communication mechanism that works over Publish/Subscriber channels in which the proposed message logging is based. The work is organized as following: an study of fault tolerant techniques used in HPC and the motivation for choosing this variant of message logging; a message logging proposal; an implementation of Open MPI communication over OpenAMQ; performance evaluation and comparision with the tradicional TCP/IP communication and a pessimistic message logging (sender based) from Open MPI distribution. The benchmark set is composed of NetPIPE, NAS Parallel Benchmarks and Virginia Hydrodynamics (VH-1).

Made available in DSpace on 2014-12-17T14:56:04Z (GMT). No. of bitstreams: 1 ClaudioACF.pdf: 1310703 bytes, checksum: 20942a00fb9b1da452758bbafaf1b59d (MD5) Previous issue date: 2003-09-23 / Coordena??o de Aperfei?oamento de Pessoal de N?vel Superior / The last years have presented an increase in the acceptance and adoption of the parallel processing, as much for scientific computation of high performance as for applications of general intention. This acceptance has been favored mainly for the development of environments with massive parallel processing (MPP - Massively Parallel Processing) and of the distributed computation. A common point between distributed systems and MPPs architectures is the notion of message exchange, that allows the communication between processes. An environment of message exchange consists basically of a communication library that, acting as an extension of the programming languages that allow to the elaboration of applications parallel, such as C, C++ and Fortran. In the development of applications parallel, a basic aspect is on to the analysis of performance of the same ones. Several can be the metric ones used in this analysis: time of execution, efficiency in the use of the processing elements, scalability of the application with respect to the increase in the number of processors or to the increase of the instance of the treat problem. The establishment of models or mechanisms that allow this analysis can be a task sufficiently complicated considering parameters and involved degrees of freedom in the implementation of the parallel application. An joined alternative has been the use of collection tools and visualization of performance data, that allow the user to identify to points of strangulation and sources of inefficiency in an application. For an efficient visualization one becomes necessary to identify and to collect given relative to the execution of the application, stage this called instrumentation. In this work it is presented, initially, a study of the main techniques used in the collection of the performance data, and after that a detailed analysis of the main available tools is made that can be used in architectures parallel of the type to cluster Beowulf with Linux on X86 platform being used libraries of communication based in applications MPI - Message Passing Interface, such as LAM and MPICH. This analysis is validated on applications parallel bars that deal with the problems of the training of neural nets of the type perceptrons using retro-propagation. The gotten conclusions show to the potentiality and easinesses of the analyzed tools. / Os ?ltimos anos t?m apresentado um aumento na aceita??o e ado??o do processamento paralelo, tanto para computa??o cient?fica de alto desempenho como para aplica??es de prop?sito geral. Essa aceita??o tem sido favorecida principalmente pelo desenvolvimento dos ambientes com processamento maci?amente paralelo (MPP - Massively Parallel Processing) e da computa??o distribu?da. Um ponto comum entre sistemas distribu?dos e arquiteturas MPPs ? a no??o de troca de mensagem, que permite a comunica??o entre processos. Um ambiente de troca de mensagem consiste basicamente de uma biblioteca de comunica??o que, atuando como uma extens?o das linguagens de programa??o, permite a elabora??o de aplica??es paralelas, tais como C, C++ e Fortran. No desenvolvimento de aplica??es paralelas, um aspecto fundamental esta ligado ? an?lise de desempenho das mesmas. V?rias podem ser as m?tricas utilizadas nesta an?lise: tempo de execu??o, efici?ncia na utiliza??o dos elementos de processamento, escalabilidade da aplica??o com respeito ao aumento no n?mero de processadores ou ao aumento da inst?ncia do problema tratado. O estabelecimento de modelos ou mecanismos que permitam esta an?lise pode ser uma tarefa bastante complicada considerando-se par?metros e graus de liberdade envolvidos na implementa??o da aplica??o paralela. Uma alternativa encontrada tem sido a utiliza??o de ferramentas de coleta e visualiza??o de dados de desempenho, que permitem ao usu?rio identificar pontos de estrangulamento e fontes de inefici?ncia em uma aplica??o. Para uma visualiza??o eficiente torna-se necess?rio identificar e coletar dados relativos ? execu??o da aplica??o, etapa esta denominada instrumenta??o. Neste trabalho ? apresentado, inicialmente, um estudo das principais t?cnicas utilizadas na coleta dos dados de desempenho, e em seguida ? feita uma an?lise detalhada das principais ferramentas dispon?veis que podem ser utilizadas em arquiteturas paralelas do tipo Cluster Beowulf com Linux sobre plataforma X86 utilizando bibliotecas de comunica??o baseadas em aplica??es MPI - Message Passing Interface, tais como LAM e MPICH . Esta an?lise ? validada sobre aplica??es paralelas que tratam do problema do treinamento de redes neurais do tipo perceptrons usando retropropaga??o. As conclus?es obtidas mostram as potencialidade e facilidades das ferramentas analisadas.

Denna studie handlar om huruvida livsstilsbudskap på Facebook påverkar unga kvinnor. Syftet har varit att stärka tidigare forskning som visar på att människor påverkas av reklam. Vidare har varit att på djupet ta reda på hur Facebook bidrar till hur unga kvinnor påverkas av livsstilsbudskap. För att uppfylla syftet med studien och svara på frågeställningen har empirisk data samlats in med hjälp av Små-N-studier. Det innefattade besöksintervjuer med sex medverkande unga kvinnor, där det togs reda på hur de upplevde reklam på Facebook, tankar kring normer och interaktionen med Facebook. Det togs även fram ett underlag till intervjuerna som bestod av att få en överblick över vilken reklam som dök upp på respondenternas nyhetsflöden på Facebook. Resultatet utifrån studiens teori och empiri visar på att livsstilsbudskap på Facebook påverkar unga kvinnor. Det är dock svårt att mäta på vilket sätt och i vilken grad livsstilsbudskap på Facebook påverkar eftersom det finns så många andra faktorer som påverkar människor. Det går att konstatera att Facebook är en alternativ verklighet för unga idag och att de spenderar mycket av sin tid där. Företag och vänner är de som skapar innehållet på Facebook och att de kan interagera med varandra är en faktor som gör Facebook till en kanal där reklamen har extra stor påverkan. Begränsningarna som studien hade var bland annat relationen till respondenterna eftersom det kan störa distanseringen. Det hade varit välbehövligt att använda sig av fler djupintervjuer för att kunna analysera mer data och stärka studien ännu mer, men på grund av tid-och resursbrist var det inte möjligt. Det hade varit önskvärt att studera mer djupgående i de olika teorierna som har tagits upp i studien samt även lägga mer tid på informationssökningen inom de digitala medierna och ungdomars användning av Facebook, eftersom det var svårt att hitta relevant forskning och teorier. / This study is about whether lifestyle message on Facebook affects young women. The purpose has been to reinforce previous research that shows that people are influenced by advertising. Moreover, has been to the depths to find out how this contributes to the young women affected by lifestyle message. In order to fulfill the purpose of the study and answer the question empirical data has been collected by using Small-N-studies. It included interviews with six participating young women, where it was taken out how they experienced advertising on Facebook, thoughts about the norms and interaction with Facebook. It was also prepared some basis for the interviews and it was to obtain an overview of the advertising that appeared on the respondents news feeds on Facebook. The findings of the study on the basis of theory and empirical evidence shows that lifestyle messages on Facebook affects young women. However, it is difficult to measure how and to what extent lifestyle message on Facebook influence because there are so many other factors that affect people. But one can say that this is an alternate reality for young people today and that they spend much of their time there. Businesses and friends are the ones who create the content on Facebook and that they can interact with each other is a factor that makes this a channel where advertising affect some extra. The limitations of the study was the relationship to the respondents because it can interfere with the distancing. It would have been desirable to do more of in-depth interviews to analyze more data and enhance the study even more, but because of time and lack of resources it was not possible. It would also have been desirable to study more in depth in the various theories that have been raised in the study, and also spend more time on the search for information within digital media and young people's use of Facebook, because it was difficult to find relevant research and theories.

O aumento crescente no número de processadores das arquiteturas paralelas que estão no topo dos rankings de desempenho, apesar de permitir uma maior capacidade de processamento, também traz consigo um aumento na taxa de falhas diretamente proporcional ao número de processadores. Atualmente, as técnicas de tolerância a falhas com recuperação retroativa são as mais empregadas em aplicações MPI, principalmente a técnica de checkpoint coordenado. No entanto, previsões afirmam que essa última técnica será inadequada para as arquiteturas emergentes. Em contrapartida, as técnicas de log de mensagens possuem características que as tornam mais apropriadas no novo cenário que se estabelece. O presente trabalho consiste em uma proposta de log de mensagens pessimista remoto com checkpoint não-coordenado e a avaliação de desempenho da comunicação MPI sobre Publish/Subscriber no qual se baseia o log de mensagens. O trabalho compreende: um estudo das técnicas de tolerância a falhas mais empregadas em ambientes de alto desempenho e a motivação para a escolha dessa variante de log de mensagens; a proposta de log de mensagens; uma implementação de comunicação Open MPI sobre OpenAMQ e sua respectiva avaliação de desempenho com comunicação tradicional TCP/IP e com o log de mensagens pessimista local da distribuição do Open MPI. Os benchmarks utilizados foram o NetPIPE, o NAS Parallel Benchmarks e a aplicação Virginia Hydrodynamics (VH-1). / The growing number of processors in parallel architectures at the top of performance rankings allows a higher processing capacity. However, it also brings an increase in the fault rate which is directly proportional to the number of processors. Nowadays, coordinated checkpoint is the most widely used rollback technique for system recovery in the occurrence of faults in MPI applications. Nevertheless, projections point that this technique will be inappropriate for the emerging architectures. On the other hand, message logging seems to be more appropriate to this new scenario. This work consists in a proposal of pessimistic message logging (remote based) with non-coordinated checkpoint and the performance evaluation of an MPI communication mechanism that works over Publish/Subscriber channels in which the proposed message logging is based. The work is organized as following: an study of fault tolerant techniques used in HPC and the motivation for choosing this variant of message logging; a message logging proposal; an implementation of Open MPI communication over OpenAMQ; performance evaluation and comparision with the tradicional TCP/IP communication and a pessimistic message logging (sender based) from Open MPI distribution. The benchmark set is composed of NetPIPE, NAS Parallel Benchmarks and Virginia Hydrodynamics (VH-1).