LUTS: A lightweight user-level transaction scheduler

Software Transactional Memory (STM) systems have poor performance under high contention scenarios. Since many transactions compete for the same data, most of them are aborted, wasting processor runtime. Contention management policies are typically used to avoid that, but they are passive approaches as they wait for an abort to happen so they can take action. More proactive approaches have emerged, trying to predict when a transaction is likely to abort so its execution can be delayed. Such techniques are limited, as they do not replace the doomed transaction by another or, when they do, they rely on the operating system for that, having little or no control on which transaction should run. In this paper we propose LUTS, a Lightweight User-Level Transaction Scheduler, which is based on an execution context record mechanism. Unlike other techniques, LUTS provides the means for selecting another transaction to run in parallel, thus improving system throughput. Moreover, it avoids most of the issues caused by pseudo parallelism, as it only launches as many system-level threads as the number of available processor cores. We discuss LUTS design and present three conflict-avoidance heuristics built around LUTS scheduling capabilities. Experimental results, conducted with STMBench7 and STAMP benchmark suites, show LUTS efficiency when running high contention applications and how conflict-avoidance heuristics can improve STM performance even more. In fact, our transaction scheduling techniques are capable of improving program performance even in overloaded scenarios. © 2011 Springer-Verlag.

Comparative study of algorithms for mining association rules: Traditional approach versus multi-relational approach

The multi-relational Data Mining approach has emerged as alternative to the analysis of structured data, such as relational databases. Unlike traditional algorithms, the multi-relational proposals allow mining directly multiple tables, avoiding the costly join operations. In this paper, is presented a comparative study involving the traditional Patricia Mine algorithm and its corresponding multi-relational proposed, MR-Radix in order to evaluate the performance of two approaches for mining association rules are used for relational databases. This study presents two original contributions: the proposition of an algorithm multi-relational MR-Radix, which is efficient for use in relational databases, both in terms of execution time and in relation to memory usage and the presentation of the empirical approach multirelational advantage in performance over several tables, which avoids the costly join operations from multiple tables. © 2011 IEEE.

Transaction scheduling using dynamic conflict avoidance

Software transaction memory (STM) systems have been used as an approach to improve performance, by allowing the concurrent execution of atomic blocks. However, under high-contention workloads, STM-based systems can considerably degrade performance, as transaction conflict rate increases. Contention management policies have been used as a way to select which transaction to abort when a conflict occurs. In general, contention managers are not capable of avoiding conflicts, as they can only select which transaction to abort and the moment it should restart. Since contention managers act only after a conflict is detected, it becomes harder to effectively increase transaction throughput. More proactive approaches have emerged, aiming at predicting when a transaction is likely to abort, postponing its execution. Nevertheless, most of the proposed proactive techniques are limited, as they do not replace the doomed transaction by another or, when they do, they rely on the operating system for that, having little or no control on which transaction to run. This article proposes LUTS, a lightweight user-level transaction scheduler. Unlike other techniques, LUTS provides the means for selecting another transaction to run in parallel, thus improving system throughput. We discuss LUTS design and propose a dynamic conflict-avoidance heuristic built around its scheduling capabilities. Experimental results, conducted with the STAMP and STMBench7 benchmark suites, running on TinySTM and SwissTM, show how our conflict-avoidance heuristic can effectively improve STM performance on high contention applications. © 2012 Springer Science+Business Media, LLC.

Genetic associations among average annual productivity, growth traits, and stayability: A parallel between Nelore and composite beef cattle

This study was conducted to examine the relationship among average annual productivity of the cow (PRODAM), yearling weight (YW), postweaning BW gain (PWG), scrotal circumference (SC), and stayability in the herd for at least 6 yr (STAY) of Nelore and composite beef cattle. Measurements were taken on animals born between 1980 and 2010 on 70 farms located in 7 Brazilian states. Estimates of heritability and genetic and environmental correlations were obtained by Bayesian approach with 5-trait animal models. Genetic trends were estimated by regressing means of estimated breeding values by year of birth. The heritability estimates were between 0.14 and 0.47. Estimates of genetic correlation among female traits (PRODAM and STAY) and growth traits ranged from-0.02 to 0.30. Estimates of genetic correlations ranged from 0.23 to 0.94 among growth traits indicating that selection for these traits could be successful in tropical breeding programs. Genetic correlations among all traits were favorable and simultaneous selection for growth, productivity, and stayability is therefore possible. Genetic correlation between PRODAM and STAY was 0.99 and 0.85 for Nelore and composite cattle, respectively. Therefore, PRODAM and STAY might be influenced by many of the same genes. The inclusion of PRODAM instead of STAY as a selection criterion seems to be more advantageous for tropical breeding programs because the generation interval required to obtain accurate estimates of genetic merit for PRODAM is shorter. Average annual genetic changes were greater in Nelore than in composite cattle. This was not unexpected because the breeding program of composite cattle included a large number of farms, different production environments, and genetic level of the herds and breeds. Thus, the selection process has become more difficult in this population. © 2013 American Society of Animal Science. All rights reserved.

Algoritmos de alinhamento múltiplo e técnicas de otimização para esses algoritmos utilizando Ant Colony

Pós-graduação em Ciência da Computação - IBILCE

Precisão de projetos de uma represa segundo diferentes bases cartográficas

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Sequenciamento de lotes em prensas de alta capacidade com tempo de setup dependente da sequência

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Métodos de solução para um problema de sequenciamento da produção com sincronismo de execução de tarefas

Pós-graduação em Engenharia Mecânica - FEG

Integral transform solution for the forced convection of herschel-bulkley fluids in circular tubes and parallel-plates ducts

ABSTRACT: The thermal entry region in laminar forced convection of Herschel-Bulkley fluids is solved analytically through the integral transform technique, for both circular and parallel-plates ducts, which are maintained at a prescribed wall temperature or at a prescribed wall heat flux. The local Nusselt numbers are obtained with high accuracy in both developing and fully-developed thermal regions, and critical comparisons with previously reported numerical results are performed.

Modelagem numérica de dados MCSEM 3D usando computação paralela

Desenvolvemos a modelagem numérica de dados sintéticos Marine Controlled Source Electromagnetic (MCSEM) usada na exploração de hidrocarbonetos para simples modelos tridimensionais usando computação paralela. Os modelos são constituidos de duas camadas estrati cadas: o mar e o sedimentos encaixantes de um delgado reservatório tridimensional, sobrepostas pelo semi-espaço correspondente ao ar. Neste Trabalho apresentamos uma abordagem tridimensional da técnica dos elementos nitos aplicada ao método MCSEM, usando a formulação da decomposição primária e secundária dos potenciais acoplados magnético e elétrico. Num pós-processamento, os campos eletromagnéticos são calculados a partir dos potenciais espalhados via diferenciação numérica. Exploramos o paralelismo dos dados MCSEM 3D em um levantamento multitransmissor, em que para cada posição do transmissor temos o mesmo processo de cálculos com dados diferentes. Para isso, usamos a biblioteca Message Passing Interface (MPI) e o modelo servidor cliente, onde o processador administrador envia os dados de entradas para os processadores clientes computar a modelagem. Os dados de entrada são formados pelos parâmetros da malha de elementos nitos, dos transmissores e do modelo geoelétrico do reservatório. Esse possui geometria prismática que representa lentes de reservatórios de hidrocarbonetos em águas profundas. Observamos que quando a largura e o comprimento horizontais desses reservatório têm a mesma ordem de grandeza, as resposta in-line são muito semelhantes e conseqüentemente o efeito tridimensional não é detectado. Por sua vez, quando a diferença nos tamanhos da largura e do comprimento do reservatório é signi cativa o efeito 3D é facilmente detectado em medidas in-line na maior dimensão horizontal do reservatório. Para medidas na menor dimensão esse efeito não é detectável, pois, nesse caso o modelo 3D se aproxima de um modelo bidimensional. O paralelismo dos dados é de rápida implementação e processamento. O tempo de execução para a modelagem multitransmissor em ambiente paralelo é equivalente ao tempo de processamento da modelagem para um único transmissor em uma máquina seqüêncial, com o acréscimo do tempo de latência na transmissão de dados entre os nós do cluster, o que justi ca o uso desta metodologia na modelagem e interpretação de dados MCSEM. Devido a reduzida memória (2 Gbytes) em cada processador do cluster do departamento de geofísica da UFPA, apenas modelos muito simples foram executados.

Contribuições da implantação da tecnologia de informação MES - Manufacturing Execution System - para a melhoria das dimensões competitivas da manufatura: estudo de caso Novelis Brasil Ltda

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Stress analysis in oral obturator prostheses over parallel and tilted implants: photoelastic imaging

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Reformulation and a Lagrangian heuristic for lot sizing problem on parallel machines

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)