Rethinking State-Machine Replication for Parallelism

State-machine replication, a fundamental approach to designing fault-tolerant services, requires commands to be executed in the same order by all replicas. Moreover, command execution must be deterministic: each replica must produce the same output upon executing the same sequence of commands. These requirements usually result in single-threaded replicas, which hinders service performance. This paper introduces Parallel State-Machine Replication (P-SMR), a new approach to parallelism in state-machine replication. P-SMR scales better than previous proposals since no component plays a centralizing role in the execution of independent commands---those that can be executed concurrently, as defined by the service. The paper introduces P-SMR, describes a "commodified architecture" to implement it, and compares its performance to other proposals using a key-value store and a networked file system

Improving reconfigurable systems reliability by combining periodical test and redundancy techniques: a case study

This paper revises and introduces to the field of reconfigurable computer systems, some traditional techniques used in the fields of fault-tolerance and testing of digital circuits. The target area is that of on-board spacecraft electronics, as this class of application is a good candidate for the use of reconfigurable computing technology. Fault tolerant strategies are used in order for the system to adapt itself to the severe conditions found in space. In addition, the paper describes some problems and possible solutions for the use of reconfigurable components, based on programmable logic, in space applications

Lazy State Determination for SQL databases

Transactional systems have seen various efforts to increase their throughput, mainly by making use of parallelism and efficient Concurrency Control techniques. Most approaches optimize the systems’ behaviour when under high contention. In this work, we strive towards reducing the system’s overall contention through Lazy State Determination (LSD). LSD is a new transactional API that leverages on futures to delay the accesses to the Database as much as possible, reducing the amount of time that transactions require to operate under isolation and, thus, reducing the contention window. LSD was shown to be a promising solution for Key-Value Stores. Now, our focus turns to Relational Database Management Systems, as we attempt to implement and evaluate LSD in this new setting. This implementation was done through a custom JDBC driver to minimize required modifications to any external platform. Results show that the reduction of the contention window effectively improves the success rate of transactional applications. However, our current implementation exhibits some performance issues that must be further investigated and addressed.Os sistemas transacionais têm sido alvo de esforços variados para aumentar a sua velocidade de processamento, principalmente através de paralelismo e de técnicas de controlo de concorrência mais eficazes. A maior parte das soluções propostas visam a otimização do comportamento destes sistemas em ambientes de elevada contenção. Neste trabalho, nós iremos reduzir a contenção no sistema recorrendo ao Lazy State Determination (LSD). O LSD é uma nova API transacional que promove a utilização de futuros para adiar o máximo os acessos à Base de Dados, reduzindo assim o tempo que cada transação requer para executar em isolamento e, por consequência, reduzindo também a janela de contenção. O LSD tem-se mostrado uma solução promissora para bases de dados Chave-Valor. O nosso foco foi agora redirecionado para Sistemas de Gestão de Bases de Dados Relacionais, com uma tentativa de implementação e avaliação do LSD neste novo contexto. Este objetivo foi concretizado através da implementação de um controlador JDBC para minimizar quaisquer alterações a plataformas externas. Os resultados mostram que a redução da janela de contenção efetivamente melhora a taxa de sucesso de aplicações transacionais. No entanto, a nossa implementação atual tem alguns problemas de desempenho que necessitam de ser investigados e endereçados

Theoretical impact of insecticide-impregnated school uniforms on dengue incidence in Thai children.

BACKGROUND: Children carry the main burden of morbidity and mortality caused by dengue. Children spend a considerable amount of their day at school; hence strategies that reduce human-mosquito contact to protect against the day-biting habits of Aedes mosquitoes at schools, such as insecticide-impregnated uniforms, could be an effective prevention strategy. METHODOLOGY: We used mathematical models to calculate the risk of dengue infection based on force of infection taking into account the estimated proportion of mosquito bites that occur in school and the proportion of school time that children wear the impregnated uniforms. PRINCIPAL FINDINGS: The use of insecticide-impregnated uniforms has efficacy varying from around 6% in the most pessimistic estimations, to 55% in the most optimistic scenarios simulated. CONCLUSIONS: Reducing contact between mosquito bites and human hosts via insecticide-treated uniforms during school time is theoretically effective in reducing dengue incidence and may be a valuable additional tool for dengue control in school-aged children. The efficacy of this strategy, however, is dependent on the compliance of the target population in terms of proper and consistent wearing of uniforms and, perhaps more importantly, the proportion of bites inflicted by the Aedes population during school time

The Impact of Child Labor and School Quality on Academic Achievement in Brazil

We analyze the impact of child labor on school achievement using Brazilian school achievement test data from the 2003 Sistema Nacional de Avaliação da Educação Básica (SAEB). We control for the endogeneity of child labor using instrumental variable techniques, where the instrumental variable is the average wage for unskilled male labor in the state. Using our preferred OLS estimates, we find that child labor causes a loss in students' school achievement. Children and adolescents who do not work have better school performance than students who work. Up to two hours of work per day do not have a statistically significant effect on school performance, but additional hours decrease student's achievement. Differences in work conditions affect school performance. For high school students in Portuguese, compared to students who have schooling as their only activity, students who work only at home score 4 percent lower on the tests. Those students who only work outside the house are worse off than those who only work within the house, with test scores decreasing by 5 percent. Students who work both inside and outside the house have the lowest test scores of all the working conditions, decreasing by up to 7 percent.child labor, school achievement, Brazil

A Population-based Hybrid Approach to Hyperparameter Optimization for Neural Networks

In recent years, large amounts of data have been generated, and computer power has kept growing. This scenario has led to a resurgence in the interest in artificial neural networks. One of the main challenges in training effective neural network models is finding the right combination of hyperparameters to be used. Indeed, the choice of an adequate approach to search the hyperparameter space directly influences the accuracy of the resulting neural network model. Common approaches for hyperparameter optimization are Grid Search, Random Search, and Bayesian Optimization. There are also population-based methods such as CMA-ES. In this paper, we present HBRKGA, a new population-based approach for hyperparameter optimization. HBRKGA is a hybrid approach that combines the Biased Random Key Genetic Algorithm with a Random Walk technique to search the hyperparameter space efficiently. Several computational experiments on eight different datasets were performed to assess the effectiveness of the proposed approach. Results showed that HBRKGA could find hyperparameter configurations that outperformed (in terms of predictive quality) the baseline methods in six out of eight datasets while showing a reasonable execution time.Comment: 28 pages, 7 figure

Health social organizations as a way of public/private management

O presente tem como objetivo analisar o processo de implementação das organizações sociais de saúde (OSS), no Estado de São Paulo, focalizando o papel desempenhado por fatores como autonomia administrativa e financeira, direcionamento proposto pelo contrato de gestão e o emprego de instrumentos e práticas gerenciais inovadoras, como fatores que condicionam o ganho de eficiência destas (OSS) frente às unidades da administração direta (AD). A abordagem adotada foi a do estudo comparativo, que propõe estabelecer possibilidades de, a partir da confrontação entre duas unidades (HOSS e HAD), identificar os elementos capazes de explicar esta diferença de desempenho entre os dois modelos de gestão. A investigação aponta para a influência positiva da autonomia administrativa e financeira, da direcionalidade imprimida aos processos de trabalho pelas metas estabelecidas no contrato de gestão e de tecnologias gerenciais inovadoras com uso intensivo da informação como base para a tomada de decisão. Este resultado, longe de indicar a completa conversão da AD para a publicização por meio do modelo OSS, aponta para as possibilidades e limites de desenvolvimento da AD, pela incorporação de tecnologias gerenciais implementadas no âmbito das OSS.This work has as objective to analyze the implementation process of the Health Social Organizations (OSS), in the State of São Paulo, focusing the role played by factors as administrative and financial autonomy, direction proposed by the Management Contract and the use of instruments and innovative management practices, as factors that give condition to the gain of efficiency of these OSS facing the Direct Administration units (AD). The adopted approach was the Comparative Study, which proposes the establishment of possibilities, from the confrontation between two units (HOSS and HAD), to identify the elements capable of explaining this difference of performance between the two models of management. The research points to the positive influence of the administrative and financial autonomy, to the direction given to the work processes by goals setting in the Management Contract and innovative management technologies with the intensive use of the information as base for taking decisions. This result, far from indicating the complete conversion of AD to the publicizing by the OSS model, points to the possibilities and limits of development of AD, by the incorporation of management technologies in the OSS environment