An approach to parallelize the simulation of AC-Radial Shipboard Power Systems (SPSs) using multicore computers is presented. Time domain simulations of SPSs are notoriously slow, due principally to the number of components, and the time-variance of the component models. A common approach to reduce the simulation run-time of power systems is to formulate the electrical network equations using modified nodal analysis, use Bergeron's travelling-wave transmission line model to create subsystems, and to parallelize the simulation using a distributed computer. In this work, an SPS was formulated using loop analysis, defining the subsystems using a diakoptics-based approach, and the simulation parallelized using a multicore computer. A program was developed in C# to conduct multithreaded parallel-sequential simulations of an SPS. The program first represents an SPS as a graph, and then partitions the graph. Each graph partition represents a SPS subsystem and is computationally balanced using iterative refinement heuristics. Once balanced subsystems are obtained, each SPS subsystem's electrical network equations are formulated using loop analysis. Each SPS subsystem is solved using a unique thread, and each thread is manually assigned to a core of a multicore computer. To validate the partitioning approach, performance metrics were created to assess the speed gain and accuracy of the partitioned SPS simulations. The simulation parameters swept for the performance metrics were the number of partitions, the number of cores used, and the time step increment. The results of the performance metrics showed adequate speed gains with negligible error. An increasing simulation speed gain was observed when the number of partitions and cores were augmented, obtaining maximum speed gains of <30x when using a quadcore computer. Results show that the speed gain is more sensitive to the number partitions than is to the number of cores. While multicore computers are suitable for parallel-sequential SPS simulations, increasing the number of cores does not contribute to the gain in speed as much as does partitioning. The simulation error increased with the simulation time step but did not influence the partitioned simulation results. The number of operations caused by protective devices was used to determine whether the simulation error introduced by partitioning SPS simulations produced a inconsistent system behavior. It is shown, for the time step sizes uses, that protective devices did not operate inadvertently, which indicates that the errors did not alter RMS measurement and, hence, were non-influential.

Orientadores: Roger Josef Zemp, Paulo de Carvalho Tofani / Tese (doutorado) - Universidade Estadual de Campinas, Faculdade de Engenharia Quimica / Made available in DSpace on 2018-08-03T15:26:11Z (GMT). No. of bitstreams: 1 Veloso_MarceloAntonio_D.pdf: 10344720 bytes, checksum: e173f03cd07f8090cdc60aacf528de23 (MD5) Previous issue date: 2003 / Resumo: O programa computacional P ANTERA-2 (Programa para Análise Termo-hidráulica de Reatores a Água, Versão 2), cujos fundamentos são descritos neste trabalho, efetua a análise por subcanais de feixes de varetas em conjunção com a simulação de múltiplos circuitos. O programa resolve simultaneamente as equações de conservação da massa, dos momentos axial e lateral e da energia para a geometria de subcanais acopladas com as equações de balanço que descrevem o escoamento de um fluido em um número arbitrário de circuitos de remgeração conectados a um vaso de pressão que contém o feixe. Atendo-se à formulação de subcanais, a estratégia computacional básica de P ANTERA-2 provém dos códigos COBRA, mas um método implícito alternativo de solução orientado para o campo de pressões é usado para resolver as aproximações de diferenças finitas das leis de balanço. Os resultados previstos pelo modelo de subcanais compreendem as distribuições de densidades, entalpias, vazões de massa e pressões nos subcanais. O modelo de circuitos prevê as vazões nos circuitos individuais, a vazão total através do vaso de pressão e as velocidades de rotação das bombas em função do tempo subseqüente à falha de qualquer número das bombas de circulação. Os transitórios de vazão nos circuitos podem ser ocasionados pelas perdas de potência elétrica, ruptura de eixos e travamento de rotores das bombas. As variações nas velocidades de rotação das bombas em função do tempo são determinadas através de um balanço de torques. A altura de recalque e o torque hidráulico das bombas são calculadas em função da velocidade e da vazão com duas curvas homólogas polares fornecidas ao programa na forma tabular. Para ilustrar a capacidade analítica de P ANTERA-2, três problemas-exemplo são apresentados e discutidos. Comparações entre resultados calculados e medidos indicam que o programa reproduz com boa precisão dados experimentais de temperaturas de saída de subcanais e de fluxos de calor críticos em feixes de 5x5 varetas. Observa-se támbém uma boa concordância entre as curvas teóricas previstas por P ANTERA-2 e valores medidos para as velocidades de rotação das bombas e vazões de massa nos circuitos primários da central nuclear Angra-2, quando suas quatro bombas principais são simultaneamente desligadas para simular o evento de declínio de vazão. Palavras-chave: análise por subcanais, código de subcanais, códigos cobra, análise de circuitos de escoamento, acidente de falha de bombas / Abstract: PANTERA-2 (from Programa para Análise Termo-hidráulica de Reatores a ÁguaProgram for Thermal-hydraulic Analysis of Water Reactors, Version 2), whose fundamentals are described in this work, is intended to carry out rod bundle subchannel analysis in conjunction with multiloop simulation. It solves simultaneously the conservation equations of mass, axial and lateral momentum, and energy for subchannel geometry coupled with the balance equations that describe the fluid flows in any number of coolant loops connected to A pressure vessel containing the rod bundle. As far as subchannel analysis is concemed, the basic computational strategy of P ANTERA-2 comes from COBRA codes, but an altemative implicit solution method oriented to the pressure field has been used to solve the finitedifference approximations for the balance laws. The results provided by the subchannel mode1 comprise the fluid density, enthalpy, flow rate, and pressure fields in the subchannels. The loop model predicts the individualloop flows, total flow through the pressure vessel, and pump rotational speeds as a function of time subsequent to the failure of any number of the coolant pumps. The flow transients in the loops may initiated by partial, total or sequentialloss of electric power to the operating pumps. Transient events caused by either shaft break or rotor locking may also be simulated. The changes in rotational speed of the pumps as a function of time are determined from a torque balance. Pump dynamic head and hydraulic torque are calculated as a function of rotational speed and volumetric flow from two polar homologous curves supplied to the code in the tabular form In order to illustrate the analytical capability of P ANTERA-2, three sample problems are presented and discussed. Comparisons between calculated and measured results indicate that the program reproduces with a good accuracy experimental data for subchannel exit temperatures and critical heat fluxes in 5x5 rod bundles. It is also observed a good correspondence between the theoretical curves predicted by P ANTERA-2 and measured values for pump rotational speeds and mass flow rates in the primary loops of Angra-2 nuclear power plant, when the four main coolant pumps are simultaneously switched off to simulate the flow decline evento / Doutorado / Sistemas de Processos Quimicos e Informatica / Doutor em Engenharia Química

La complexité des CPUs s’est accrue considérablement depuis leurs débuts, introduisant des mécanismes comme le renommage de registres, l’exécution dans le désordre, la vectorisation, les préfetchers et les environnements multi-coeurs pour améliorer les performances avec chaque nouvelle génération de processeurs. Cependant, la difficulté a suivi la même tendance pour ce qui est a) d’utiliser ces mêmes mécanismes à leur plein potentiel, b) d’évaluer si un programme utilise une machine correctement, ou c) de savoir si le design d’un processeur répond bien aux besoins des utilisateurs.Cette thèse porte sur l’amélioration de l’observabilité des facteurs limitants dans les boucles de calcul intensif, ainsi que leurs interactions au sein de microarchitectures modernes.Nous introduirons d’abord un framework combinant CQA et DECAN (des outils d’analyse respectivement statique et dynamique) pour obtenir des métriques détaillées de performance sur des petits codelets et dans divers scénarios d’exécution.Nous présenterons ensuite PAMDA, une méthodologie d’analyse de performance tirant partie de l’analyse de codelets pour détecter d’éventuels problèmes de performance dans des applications de calcul à haute performance et en guider la résolution.Un travail permettant au modèle linéaire Cape de couvrir la microarchitecture Sandy Bridge de façon détaillée sera décrit, lui donnant plus de flexibilité pour effectuer du codesign matériel / logiciel. Il sera mis en pratique dans VP3, un outil évaluant les gains de performance atteignables en vectorisant des boucles.Nous décrirons finalement UFS, une approche combinant analyse statique et simulation au cycle près pour permettre l’estimation rapide du temps d’exécution d’une boucle en prenant en compte certaines des limites de l’exécution en désordre dans des microarchitectures modernes / The complexity of CPUs has increased considerably since their beginnings, introducing mechanisms such as register renaming, out-of-order execution, vectorization,prefetchers and multi-core environments to keep performance rising with each product generation. However, so has the difficulty in making proper use of all these mechanisms, or even evaluating whether one’s program makes good use of a machine,whether users’ needs match a CPU’s design, or, for CPU architects, knowing how each feature really affects customers.This thesis focuses on increasing the observability of potential bottlenecks inHPC computational loops and how they relate to each other in modern microarchitectures.We will first introduce a framework combining CQA and DECAN (respectively static and dynamic analysis tools) to get detailed performance metrics on smallcodelets in various execution scenarios.We will then present PAMDA, a performance analysis methodology leveraging elements obtained from codelet analysis to detect potential performance problems in HPC applications and help resolve them. A work extending the Cape linear model to better cover Sandy Bridge and give it more flexibility for HW/SW codesign purposes will also be described. It will bedirectly used in VP3, a tool evaluating the performance gains vectorizing loops could provide.Finally, we will describe UFS, an approach combining static analysis and cycle accurate simulation to very quickly estimate a loop’s execution time while accounting for out-of-order limitations in modern CPUs

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