Event Stream Processing with Multiple Threads

Current runtime verification tools seldom make use of multi-threading to speed up the evaluation of a property on a large event trace. In this paper, we present an extension to the BeepBeep 3 event stream engine that allows the use of multiple threads during the evaluation of a query. Various parallelization strategies are presented and described on simple examples. The implementation of these strategies is then evaluated empirically on a sample of problems. Compared to the previous, single-threaded version of the BeepBeep engine, the allocation of just a few threads to specific portions of a query provides dramatic improvement in terms of running time

TAPIOCA: An I/O Library for Optimized Topology-Aware Data Aggregation on Large-Scale Supercomputers

International audienceReading and writing data efficiently from storage system is necessary for most scientific simulations to achieve good performance at scale. Many software solutions have been developed to decrease the I/O bottleneck. One well-known strategy, in the context of collective I/O operations, is the two-phase I/O scheme. This strategy consists of selecting a subset of processes to aggregate contiguous pieces of data before performing reads/writes. In this paper, we present TAPIOCA, an MPI-based library implementing an efficient topology-aware two-phase I/O algorithm. We show how TAPIOCA can take advantage of double-buffering and one-sided communication to reduce as much as possible the idle time during data aggregation. We also introduce our cost model leading to a topology-aware aggregator placement optimizing the movements of data. We validate our approach at large scale on two leadership-class supercomputers: Mira (IBM BG/Q) and Theta (Cray XC40). We present the results obtained with TAPIOCA on a micro-benchmark and the I/O kernel of a large-scale simulation. On both architectures, we show a substantial improvement of I/O performance compared with the default MPI I/O implementation. On BG/Q+GPFS, for instance, our algorithm leads to a performance improvement by a factor of twelve while on the Cray XC40 system associated with a Lustre filesystem, we achieve an improvement of four

Avaliação da transferência de calor e massa em reatores de chama de difusão acoplados a sistemas de lentes aerodinâmicas

Dissertação (mestrado) - Universidade Federal de Santa Catarina, Centro Tecnológico, Programa de Pós-Graduação em Engenharia Química, Florianópolis, 2016.A utilização de nanopartículas tem recebido especial atenção devido às suas propriedades físicas e químicas e diversas aplicações. No campo da engenharia química, os nanomateriais tem aplicação fundamental no desenvolvimento de catalisadores e em revestimentos nanoestruturados aplicados a sensores. Nesse sentido, a tecnologia de reatores de chama tem-se mostrado uma via atrativa e de alto rendimento para a síntese de nanopartículas com propriedades e funcionalidades sofisticadas. A fabricação de nanofilmes pela deposição das nanopartículas provenientes da fase gasosa é uma abordagem promissora e, nesse aspecto, técnicas de expansão do fluxo, em particular, o uso de lentes aerodinâmicas, apresentam uma série de vantagens que auxiliam no seu processo de deposição. Contudo, para promover uma elevada taxa de produção sem comprometer as características finais das nanopartículas, uma compreensão da sua dinâmica e síntese é necessária. Através da resolução numérica das equações que governam os fenômenos envolvidos na síntese e deposição das nanopartículas, pode-se obter muitas informações a respeito da distribuição e transporte das variáveis de interesse, bem como os parâmetros geométricos que afetam o funcionamento do reator e as características dos nanomateriais formados. Neste trabalho é apresentada a investigação numérica do comportamento fluidodinâmico do processo de formação e deposição de nanopartículas em reator de chama de difusão acoplado ao sistema de lentes aerodinâmicas. A performance do sistema foi investigada através da análise dos perfis de velocidade, temperatura e concentração das espécies químicas, a fim de validar os dados experimentais e fornecer informações sobre o processo. Através da alteração da geometria do sistema, diferentes configurações foram avaliadas com o objetivo de determinar o funcionamento ideal do reator para a deposição das partículas. Os resultados mostram que o sistema de lentes aerodinâmicas é capaz de restringir o fluxo principal a uma região muito estreita em comparação ao reator de chama sem lentes, sendo esta uma característica essencial para o controle da deposição das nanopartículas e para o desenvolvimento de nanomateriais com novas propriedades funcionais e estruturais.Abstract : The nanoparticles use has received particular attention due to their physical and chemical properties and various applications. In the chemical engineering field, the nanomaterials have an important application in the development of catalysts and nanostructured coatings applied to sensors. Thus, the flame reactor technology has shown to be an attractive route with high performance for the synthesis of nanoparticles with sophisticated properties and functions. The nanofilms manufacturing by the deposition of nanoparticles from a gas phase is a promising approach and, in this sense, the flow expansion technique, in particular the use of aerodynamic lenses, shows many advantages, which help their deposition process. However, to promote a high production rate without compromising the final characteristics of the nanoparticles, an understanding of their synthesis and dynamic is required. Through the numerical solution of the equations that govern the main phenomena involved in the nanoparticles synthesis and deposition, a lot of information about the distribution and transport of the interest variables can be obtained, as well the geometric parameters that affect the reactor operation and the nanomaterials characteristics. This paper presents the fluid dynamic numerical investigation of the nanoparticle formation and deposition process in a diffusion flame reactor coupled to an aerodynamic lens system. The system performance was investigated by the analysis of the velocity, temperature and chemical species concentration profiles to validate the experimental data and provide information about the process. Changing the system geometry, different configurations were evaluated in order to determine the optimal reactor operation mode for the nanoparticle deposition. The results show that the aerodynamic lens system is able to restrict the main flow to a much narrow region when compared to the flame reactor without lenses, being this an essential feature to control the deposition of the nanoparticles and to development of new nanomaterials with structural and functional properties