Memória Transacional tem se demonstrado um paradigma promissor na implementação de aplicações concorrentes sob memória compartilhada que busquem evitar um modelo de sincronização baseado em locks. Em vez de sujeitar a execução a um acesso exclusivo com base no valor de um lock que é compartilhado por threads concorrentes, uma aplicação sob Memória Transacional tenta executar seções críticas de modo otimista, desfazendo as modificações no caso de um conflito de acesso à memória. Entretanto, apesar de a abordagem baseada em locks ter adquirido um número significativo de ferramentas automatizadas para a depuração, profiling e otimização automatizados (por ser uma das técnicas de sincronização mais antigas e mais bem pesquisadas), o campo da Memória Transacional ainda é comparativamente recente, e programadores frequentemente precisam adaptar manualmente suas aplicações transacionais ao encontrar problemas de eficiência. Este trabalho propõe um sistema no qual o profiling de código em uma implementação de Memória Transacional simulada é utilizado para caracterizar uma aplicação transacional, formando a base para uma parametrização automatizada do respectivo sistema especulativo para uma execução eficiente do código em questão. Também é proposta uma abordagem de escalonamento de threads guiado por profiling em uma implementação de Memória Transacional baseada em software, usando dados coletados pelo profiler para prever a probabilidade de conflitos e determinar que thread escalonar com base nesta previsão. São apresentados os resultados de experimentos sob ambas as abordagens. / Transactional Memory has shown itself to be a promising paradigm for the implementation of shared-memory concurrent applications that eschew a lock-based model of data synchronization. Rather than conditioning exclusive access on the value of a lock that is shared across concurrent threads, Transactional Memory attempts to execute critical sections optimistically, rolling back the modifications in the event of a data access conflict. However, while the lock-based approach has acquired a significant body of debugging, profiling and automated optimization tools (as one of the oldest and most researched synchronization techniques), the field of Transactional Memory is still comparably recent, and programmers are usually tasked with an unguided manual tuning of their transactional applications when facing efficiency problems. We propose a system in which code profiling in a simulated hardware implementation of Transactional Memory is used to characterize a transactional application, which forms the basis for the automated tuning of the underlying speculative system for the efficient execution of that particular application. We also propose a profile-guided approach to the scheduling of threads in a software-based implementation of Transactional Memory, using collected data to predict the likelihood of conflicts and determine what thread to schedule based on this prediction. We present the results achieved under both designs.

A Memória Transacional (TM) surgiu nos últimos anos como uma nova solução para sincronização em sistemas multiprocessados de memória compartilhada, permitindo explorar melhor o paralelismo das aplicações ao evitar limitações inerentes ao mecanismo de locks. Neste modelo, o programador define regiões de código que devem executar de forma atômica. O sistema tenta executá-las de forma concorrente, e, em caso de conflito nos acessos à memória, toma as medidas necessárias para preservar a atomicidade e isolamento das transações, na maioria das vezes abortando e reexecutando uma das transações. Um dos modelos mais aceitos de memória transacional em hardware é o LogTM, implementado neste trabalho em um MPSoC embarcado que utiliza uma NoC para interconexão. Os experimentos fazem uma comparação desta implementação com locks, levando-se em consideração performance e energia do sistema. Além disso, este trabalho mostra que o tempo que uma transação espera para reiniciar sua execução após ter abortado (chamado de backoff delay on abort) tem impactos significativos na performance e energia. Uma análise deste impacto é feita utilizando-se de três políticas de backoff. Um mecanismo baseado em um handshake entre transações, chamado Abort handshake, é proposto como solução para o problema. Os resultados dos experimentos são dependentes da aplicação e configuração do sistema e indicam ganhos da TM na maioria dos casos em relação ao mecanismo de locks. Houve redução de até 30% no tempo de execução e de até 32% na energia de aplicações de baixa demanda de sincronização. Em um segundo momento, é feita uma análise do backoff delay on abort na performance e energia de aplicações utilizando três políticas de backoff em comparação com o mecanismo Abort handshake. Os resultados mostram que o mecanismo proposto apresenta redução de até 20% no tempo de execução e de até 53% na energia comparado à melhor política de backoff dentre as analisadas. Para aplicações com alta demanda de sincronização, a TM mostra redução no tempo de execução de até 63% e redução de energia de até 71% em comparação com o mecanismo de locks. / Transactional Memory (TM) has emerged in the last years as a new solution for synchronization on shared memory multiprocessor systems, allowing a better exploration of the parallelism of the applications by avoiding inherent limitations of the lock mechanism. In this model, the programmer defines regions of code, called transactions, to execute atomically. The system tries to execute transactions concurrently, but in case of conflict on memory accesses, it takes the appropriate measures to preserve the atomicity and isolation, usually aborting and re-executing one of the transactions. One of the most accepted hardware transactional memory model is LogTM, implemented in this work in an embedded MPSoC that uses an NoC as interconnection mechanism. The experiments compare this implementation with locks, considering performance and energy. Furthermore, this work shows that the time a transaction waits to restart after abort (called backoff delay on abort) has significant impact on performance and energy. An analysis of this impact is done using three backoff policies. A novel mechanism based on handshake of transactions, called Abort handshake, is proposed as a solution to this issue. The results of the experiments depends on application and system configuration and show TM benefits in most cases in comparison to the locks mechanism, reaching reduction on the execution time up to 30% and reduction on the energy consumption up to 32% on low contention workloads. After that, an analysis of the backoff delay on abort on the performance and energy is presented, comparing to the Abort handshake mechanism. The proposed mechanism shows reduction of up to 20% on the execution time and up to 53% on the energy, when compared to the best backoff policy. For applications with a high degree of synchronization, TM shows reduction on the execution time up to 63% and energy savings up to 71% compared to locks.

Orientador: Sandro Rigo / Dissertação (mestrado) - Universidade Estadual de Campinas, Instituto de Computação / Made available in DSpace on 2018-08-17T08:11:55Z (GMT). No. of bitstreams: 1 Moreira_JoaoBatistaCorreaGomes_M.pdf: 4664392 bytes, checksum: 9057389ff1b0a5e68e89f32ea1310090 (MD5) Previous issue date: 2010 / Resumo: O surgimento das novas arquiteturas multiprocessadas introduziu novos desafios ao desenvolvimento de software. Dentre estes desafios está a dificuldade de realizar a sincronização adequada entre os fluxos de execução. Para solucionar este problema, novos mecanismos de sincronização com abstrações mais simplificadas tem sido propostos. Seguindo esta corrente, as Memórias Transacionais surgem como uma promissora alternativa aos mecanismos de sincronização tradicionais. Por se tratar de uma alternativa recentemente proposta, pouco se conhece a respeito dos efeitos no consumo de energia devido ao uso de Memórias Transacionais. Este trabalho apresenta um estudo comparativo entre os consumos de energia observados na execução do benchmark STAMP com usos de um sistema STM (Memória Transacional em Software) e de sincronização baseada em locks. Os resultados obtidos demonstram que a STM apresentou um desempenho inferior aos locks no que diz respeito ao consumo de energia, apresentando um consumo médio três vezes maior. Também foi avaliada a influência das penalidades decorrentes do uso de locks no consumo de energia, mostrando que, em sistemas cujo custo de falha na aquisição de um lock supera dez mil ciclos, a aplicação de STMs passa a ser uma abordagem competitiva. Durante os testes com Memórias Transacionais tornou-se clara a necessidade de ferramentas de simulação que possibilitam projetos de hardware e testes de software de forma mais ágil. Este trabalho descreve a implementação de uma plataforma de simulação para estimar o consumo de energia com abstração híbrida obtida a partir da integração de processadores funcionais que são gerados através da linguagem ArchC com a plataforma MPARM (que possui precisão de ciclos). Esta implementação atingiu ganhos de desempenho médios de até 2.1 vezes, com um máximo de 2.9 vezes. Imprecisões obtidas nas estimativas de consumo de energia puderam ser estatisticamente corrigidas através da aplicação de métodos de regressão linear, apresentando erros médios de 5,85%, sendo o erro mínimo e máximo de 0,87% e 19,6%, respectivamente / Abstract: The advent of the contemporary multiprocessor architectures has challenged software development. In order to overcome the hurdle of properly ordering the execution and data flows, new synchronization methods with simplified abstraction have been proposed. In this context, Transactional Memories have emerged as an alternative to traditional synchronization methods. Little is known about the effects on power consumption due to the use of ransactional memories since it is a recently proposed alternative. This work compares the Power consumption of the STAMP benchmark execution when using a STM system and a lockbased implementation. The results show that the STM implementation presented a worse performance, consuming three times more energy in avarage. In addition, the penalties deriving from the employment of locks in power consumption were assessed, indicating that, in systems where a failure in lock acquisition costs more than ten thousand cycles, the use of STMs becomes a competitive approach. The experiments with Transactional Memories executed during the first stage of this research indicated that faster simulation tools for hardware design and software testing are needed. Hence, this work describes an implementation of a simulation platform, built using hybrid abstraction level, that is able to estimate power consumption. The platform is the result of integrating functional processors described in the ArchC language with the MPARM platform, which is cycle-based. The implementation displays an average performance speedup of 2.1 and a maximum of 2.9. Inaccuracies due to power consumption estimation could be statistically adjusted by applying corrections based on linear regression. The model carries an average error of 5.85% with a maximum of 19.6% and minimum of 0.86% / Mestrado / Arquitetura de Computadores / Mestre em Ciência da Computação

Orientador: Rodolfo Jardim de Azevedo / Dissertação (mestrado) - Universidade Estadual de Campinas, Instituto de Computação / Made available in DSpace on 2018-08-23T23:05:30Z (GMT). No. of bitstreams: 1 Garcia_LeonardoAugustoGuimaraes_M.pdf: 3415043 bytes, checksum: 9df4293802303aa68e123c48882f387f (MD5) Previous issue date: 2013 / Resumo: A evolução das arquiteturas de computadores nos últimos anos, com a considerável introdução de processadores com vários núcleos e computadores com vários processadores, inclusive em máquinas consideradas de baixo poder de processamento, faz com que seja primordial o desenvolvimento de novos paradigmas e modelos de programação paralela que sejam fáceis de usar e depurar pela grande maioria dos programadores de sistemas. Os modelos de programação paralela, atualmente disponíveis, são baseados em primitivas de implementação cujo uso é complexo, tedioso e altamente sujeito a erros como, por exemplo, locks, semáforos, sinais, mutexes, monitores e threads. Neste cenário, as Memórias Transacionais (TM) aparecem como uma alternativa promissora que promete ser eficiente e, ao mesmo tempo, fácil de programar. Muita pesquisa foi feita nos últimos anos em relação às Memórias Transacionais em Software (STM), a maior parte delas relacionada a seu desempenho, com pouca atenção dada a outras métricas importantes, como, por exemplo, o consumo energético e como este se relaciona com o tempo de execução - energy-delay product (EDP). Esta dissertação de mestrado faz uma avaliação destas métricas em uma STM configurada com diversas políticas de gerenciamento da TM e de utilização energética, sendo algumas destas combinações inéditas. É mostrado que os resultados para desempenho e EDP nem sempre seguem a mesma tendência e, portanto, pode ser apropriado escolher diferentes políticas de gerenciamento dependendo de qual é o foco da otimização que se deseja fazer, sendo que algumas vezes a execução sequencial pode ser melhor que qualquer execução paralela. De uma forma geral, a execução com o uso de TM foi mais rápida quando comparada com a execução sequencial em dois terços dos casos analisados e teve melhor EDP em um terço das execuções. Através desta análise foi possível derivar um conjunto mínimo de políticas de gerenciamento da TM que foram capazes de entregar melhor resultado para o conjunto de benchmarks estudados, além de identificar tendências sobre o comportamento dos sistemas de TM para grupos de benchmarks quando se varia o número de núcleos executando em paralelo e o tamanho da carga de trabalho / Abstract: The recent unveilings on the computer architecture area, with the massive introduction of multi-core processors and computers with many processors in the last years, even in embedded systems, has brought to light the necessity to develop new paradigms and models for parallel programming that could be leveraged and are easy to debug by the majority of the developers. The current parallel programming models are based on primitives whose use is complex, tedious and highly error prone, such as locks, semaphores, signals, mutexes, monitors and threads. In this scenario, the Transactional Memories (TM) appear as a promising alternative which aims to be efficient and, at the same time, easy to program. Lots of research have been made on the past years on Software Transactional Memories (STM), the majority of them interested on the performance of such systems, with little attention given to other metrics such as energy and the relationship between energy and performance, known as the energy-delay product (EDP). This work evaluates these metrics in an STM configured with a number of TM and energy management policies, some of them new. It is shown that performance and EDP do not always follow the same trend, and, because of that, it might be appropriate to choose different management policies depending on the optimization target. It is also important to never forget about the sequential execution, as it can be more advantageous than any parallel execution in some scenarios. Overall, the execution with TM has a better performance when compared to the sequential execution in two thirds of the analysed situations, and a better EDP in one third of the scenarios. Through the analysis made in this work, it was possible to derive a minimal set of TM management policies that were able to deliver the best results with the benchmarks analysed. It was also possible to identify behavioural trends on the TM systems in certain sets of benchmarks when changing the number of cores in the execution and the workload size / Mestrado / Ciência da Computação / Mestre em Ciência da Computação

The advent of multicore processors has put the performance of traditional parallel programming techniques in question. The traditional lock-based parallel programming techniques are error prone and suffer from various problems such as deadlocks, live-locks, priority inversion etc. In the last one and half decade, a considerable amount of the research has been carried out to achieve the synchronization among the parallel applications without using locking. One of most promising technique which has come out as a result of this research work is Transactional Memory (TM). Transactional Memory system commits the data in atomic code sequences called the transaction. Research has shown that Transactional Memory has the potential to out perform traditional locking mechanisms. In order to understand the design and implementation trade-offs of different implementations of the Software Transactional Memory, a comprehensive comparative study is required. Although some comparative studies have been carried out in the past, they were very focused in their scope and covered only few STM implementations. In this master thesis, a qualitative literature survey is conducted and the state of the art in Software Transactional Memory is presented, covering prominent approaches to date while discussing their design and implementation trade offs. / Cell. Number: 0046762600489 Address: c/o Muhammad Naveed Ahmed, G-Infartsvagen 3B, Appartment No. 683, 371 41 Karlkrona, Sweden

Transactional memory (TM), a new programming paradigm, is one of the latest approaches to write programs for next generation multicore and multiprocessor systems. TM is an alternative to lock-based programming. It is a promising solution to a hefty and mounting problem that programmers are facing in developing programs for Chip Multi-Processor (CMP) architectures by simplifying synchronization to shared data structures in a way that is scalable and compos-able. Software Transactional Memory (STM) a full software approach of TM systems can be defined as non-blocking synchronization mechanism where sequential objects are automatically converted into concurrent objects. In this thesis, we present performance comparison of four different STM implementations – RSTM of V. J. Marathe, et al., TL2 of D. Dice, et al., TinySTM of P. Felber, et al. and SwissTM of A. Dragojevic, et al. It helps us in deep understanding of potential tradeoffs involved. It further helps us in assessing, what are the design choices and configuration parameters that may provide better ways to build better and efficient STMs. In particular, suitability of an STM is analyzed against another STM. A literature study is carried out to sort out STM implementations for experimentation. An experiment is performed to measure performance tradeoffs between these STM implementations. The empirical evaluations done as part of this thesis conclude that SwissTM has significantly higher throughput than state-of-the-art STM implementations, namely RSTM, TL2, and TinySTM, as it outperforms consistently well while measuring execution time and aborts per commit parameters on STAMP benchmarks. The results taken in transaction retry rate measurements show that the performance of TL2 is better than RSTM, TinySTM and SwissTM.

Syftet med denna litteraturstudie är att granska och analysera forskning kring hur lärare kan tillämpa modellerna RT, TSI, CORI och QtA i läsförståelseundervisning för att utveckla elevers läsförståelse. Studien är riktad mot elever i årskurs 2 och 3. Metodinsamling för denna kvalitativa litteraturstudie har inneburit sökningar i databaser, men även manuell sökning. Sammantaget tolv vetenskapliga forskningsartiklar har legat till grund för denna studies resultat. Resultaten visar att undervisningsmodellerna; Reciprocal Teaching, Transactional Strategy Instruction, Questioning The Author samt Concept-Oriented Reading Instruction visar på goda effekter på elevers läsförståelse. Vi har kommit fram till att modellerna har flera gemensamma inslag, men det finns även några skillnader. Forskning visar att strategiundervisning som lärs ut i ”set” har god effekt på elevers läsförståelse. Vidare styrker forskningen att förståelse av en text ökar när frågor ställs på olika nivåer till textens innehåll för att få förståelse för textens budskap. Sammanfattningsvis betonar forskning att det krävs en planerad undervisning samt ett stort engagemang från läraren, för att utveckla elevers läsförståelse. Läraren bör dessutom formulera tydliga mål i elevundervisningen samt ge ett större elevinflytande, då detta enligt forskning resulterar i engagemang och motivation hos elever.

Pour la première fois dans l’histoire de l’écriture, plusieurs personnes peuvent modifier au même moment et à distance le même document. Cette nouvelle pratique d’écriture rendue possible par la technologie numérique est l’écriture numérique collaborative synchrone. La question que pose cette recherche est celle de savoir comment des textes cohérents et lisibles peuvent émerger de tels dispositifs. De plus, les textes qui résultent de ces pratiques semblent difficilement pouvoir être réduits à des intentions de communication qui préexisteraient « dans la tête » des participants. Le texte émerge au sein même des situations et cela soulève la question méthodologique de savoir comment rendre compte de ces émergences. Cette thèse propose par conséquent d’explorer une manière de l’aborder : une enquête de type pragmatiste, et plus spécifiquement, une approche transactionnelle. Elle se caractérise par l’exigence de penser la relation dans sa dimension constitutive en ne présupposant rien des entités avant leur mise en situation. Elle implique en outre de toujours tenir pour provisoires et révisables toutes les descriptions que l’on peut donner d’une situation. Il s’agit d’une approche philosophique dont une opérationnalisation en Sciences de l’Information et de la Communication est ici proposée. Elle est mise en œuvre pour deux catégories de terrains : des situations de production d’argumentation en contexte pédagogique et des situations de production de comptes-rendus collaboratifs présentiels. Cette mise à l’épreuve permet de conclure à l’intérêt de poursuivre cette enquête selon une approche transactionnelle et d’esquisser un modèle d’analyse destiné à faciliter sa poursuite. / For the first time in the history of writing, several people can edit the same document at the same time and from a distance. This new writing practice, made possible by digital technology, is called synchronous collaborative digital writing. The question posed by this research is how a consistent and readable text can emerge from such systems. In addition, the texts that result from these practices can hardly be reduced to communication intentions that pre-exist "in the head" of the participants. The text emerges within the situations. This raises the methodological question of how to account for this emergence. This thesis therefore offers to explore a way to tackle it: a pragmatist type of investigation, and more specifically, a transactional approach. It is characterized by the need to think the relationship in its constitutive dimension without presupposing any of the entities prior to their entry in situation. It also implies that all of the descriptions of a given situation always have to be considered as provisional and subject to revision. Here, an operationalization of this philosophical approach is proposed in the field of Information and Communication Sciences. It is implemented for two categories of case studies: situations of production of argumentation in an educational context and situations of collaborative production of meeting reports. This experimentation makes it possible to conclude that it would be interesting to continue this investigation in a transactional approach and it outlines an analysis model to facilitate this pursuit.

There is a general scarcity of empirical studies investigating the impact of leadership styles on e-Government use in the service industry. This is doubly true of styles such as transformational, transactional and servant leadership. Theorised models propose that leadership style forms the desired organisational culture for implementing e-services, organisational culture being the mediator and the national culture the moderator. This research fills the empirical gap by investigating how leadership forms the organisational culture that facilitates and enhances the implementation and use of e-government in organisations in Saudi Arabia. The research was conducted through the sampling of employees in private and public sectors. While the data for the leadership styles, organisational culture and national culture were collected through the use of questionnaires designed for employees, the e-services were measured through organizations’ official websites. All data were processed and analysed using computer software (WarPPLS) and SPSS. The results support the hypothesized relationships proposed in the theoretical model, wherein all constructs under study (except for the mediating effect of National Culture (NC) on the relationship between leadership styles and organisational culture) positively affect e-services implementation, including Individualized Influence (IINF), Intellectual Stimulation (ISTIM), Individualized Support (ISUP), Contingent Reward (CR), Management by Exception (MbE), Servant Leadership (SL), Bureaucratic Culture (BC), Involvement Culture (INVC), Mission Culture (MC), Innovative Culture (INC), Task Culture (TC) and Future Culture (FC) and the mediating effect of National Culture (NC) on the relationship between organisational culture and e-services implementation. The results also indicated that specific leadership styles have direct and positive impacts on e-services implementation and indirect influences through a mediating organisational culture and a moderating national culture. The empirical findings bring new evidence in support of this proposal, indicating that specific leadership styles play crucial roles in influencing processes and outcomes within organizations. According to these results, e-services differ from one organization to another, and these variations were correlated to leadership styles and organizational culture. It was found that there were positive and significant correlations between total leadership styles (hybrid) and total organizational cultures (hybrid) in the full sample and in e-services implementation. E-services implementation increases when the mean for leadership styles rises, but types of organizational culture were also crucial factors in achieving better e-services. The national culture variable, which was used as a moderator, did not have a significant influence on the relationship between leadership style and organisational culture. Therefore, the moderating role of national culture in the relationship between leadership styles and organisational culture did not have any level of statistical significance, which means that regardless of the national culture (power distance or uncertainty avoidance) the effect of leadership style on organisational culture in the model adopted in this study appeared to be quite consistent. The study links theory to practice by explaining the subject of modern leadership styles and shows their relevance to the Saudi organisations and business environment. As such, it opens up a domain for investigating the application of modern management theories in a different culture. Although a plethora of studies have investigated the effect of factors such as organisational culture and/or national culture on e-services implementation in Saudi’s organisations, no study (to the best of this writer's knowledge) has tackled the issue of e-services implementation and leadership styles in those organisations. Therefore, studying e-services implementation and leadership styles in Saudi’s organisations is a contribution to the literature on the service industry, adding to its knowledge with a case study from a different cultural setting. The study also opens up a horizon for future research on developing the business sector, as it uses standardized tools in terms of reliability and validity within the context of the e-services implementation. Therefore, this study contributes to existing knowledge in that leadership and organisational culture are revealed to be key contributors to e-services implementation. The three leadership styles - transformational, transactional, and servant leadership - were empirically found to be appropriate styles that work well in e-services implementation projects. These styles have direct and positive benefits to e-services implementation and an indirect impact through the mediating means of organisational culture, and empirical findings bring new evidence for this notion. Moreover, the six organisational cultural dimensions were judged to be appropriate supporters of e-services implementation, specifically: involvement, mission, innovation, task-orientation, bureaucracy, and future-orientation.

Purpose: While it is commonly accepted that organizational innovation is vital for organizations‘ sustainability and competitive advantage, existing literature has not fully determined the relationship between different types of leadership and organizational innovation. The purpose of this study is to seek how transformational and transactional leadership behaviors influence organizational innovation and further examine the moderating role of empowerment. Methodology: The authors collected data from surveying senior and middle level managers from the four largest organizations in Greek telecommunication industry. The data collected were analyzed via regression analysis and the results were compared to the findings of existing literature and studies. Findings: The empirical findings validate that both transformational leadership and transactional leadership positively influence organizational innovation. Additional evidence highlights the importance of specific leadership components, inspirational motivation and contingent reward, in pursuing organizational innovation. Moreover, the results indicate a plausible moderating role of empowerment in the relationship of organizational innovation with both leadership styles. Originality /value: This study contributes to organizational innovation literature by finding that both transformational and transactional leadership can promote organizational innovation even in organizations operating in dynamic environments. Combining and balancing the different characteristics of transformational and transactional leadership can help leaders enhance their follower‘s behaviors towards an innovation-oriented strategy, even in large and mature organizations.