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@MastersThesis{Costa:2020:ExOpMe,
               author = "Costa, Rhuan Edson Caldini",
                title = "Explora{\c{c}}{\~a}o de oportunidades de melhoria de desempenho 
                         em um modelo clim{\'a}tico",
               school = "Instituto Nacional de Pesquisas Espaciais (INPE)",
                 year = "2020",
              address = "S{\~a}o Jos{\'e} dos Campos",
                month = "2020-02-17",
             keywords = "modelos clim{\'a}ticos, otimiza{\c{c}}{\~a}o, processamento 
                         corrente, desempenho de sistemas computacionais, climate models, 
                         optimization, concurrent processing, cumputer systems 
                         performance.rmance.",
             abstract = "Modelos clim{\'a}ticos s{\~a}o programas complexos, que envolvem 
                         a implementa{\c{c}}{\~a}o computacional de in{\'u}meros 
                         c{\'a}lculos matem{\'a}ticos de forma a representar 
                         fen{\^o}menos f{\'{\i}}sicos que interagem entre si. Tais 
                         fen{\^o}menos geralmente s{\~a}o representados por m{\'o}dulos 
                         espec{\'{\i}}ficos (atmosf{\'e}rico, oce{\^a}nico, solo, etc.) 
                         que s{\~a}o executados de forma acoplada, isto {\'e}, realizam a 
                         simula{\c{c}}{\~a}o dos respectivos fen{\^o}menos para um certo 
                         intervalo de tempo, trocando informa{\c{c}}{\~o}es entre si 
                         quando necess{\'a}rio. Desta complexidade, surge a necessidade de 
                         paralelizar e otimizar sua execu{\c{c}}{\~a}o de modo a se obter 
                         resultados em tempo vi{\'a}vel. Al{\'e}m da 
                         paraleliza{\c{c}}{\~a}o do modelo, t{\'e}cnicas de 
                         otimiza{\c{c}}{\~a}o voltadas {\`a} arquitetura de hardware 
                         utilizada tamb{\'e}m podem ser aplicadas, tais como 
                         vetoriza{\c{c}}{\~a}o e blocagem de loops. Este trabalho tem 
                         como objetivo explorar oportunidades de otimiza{\c{c}}{\~a}o de 
                         desempenho em modelos clim{\'a}ticos globais, utilizando como 
                         estudo de caso o Brazilian Earth System Model (BESM), um modelo 
                         desenvolvido pelo CPTEC/INPE com o principal objetivo de simular o 
                         clima global de modo a entender as causas das mudan{\c{c}}as 
                         clim{\'a}ticas. Inicialmente, foi avaliado o desempenho original 
                         do BESM, verificando como o modelo estava sendo compilado, quais 
                         eram as t{\'e}cnicas de paraleliza{\c{c}}{\~a}o utilizadas, 
                         como seus m{\'o}dulos eram executados, e quais eram os pontos com 
                         maior consumo de CPU. Em seguida, baseado nas 
                         informa{\c{c}}{\~o}es encontradas na an{\'a}lise inicial, foram 
                         exploradas poss{\'{\i}}veis otimiza{\c{c}}{\~o}es de 
                         desempenho do modelo. Foram aplicadas melhorias no processo de 
                         compila{\c{c}}{\~a}o e execu{\c{c}}{\~a}o do modelo, e 
                         tamb{\'e}m foram realizadas as altera{\c{c}}{\~o}es 
                         necess{\'a}rias para permitir a execu{\c{c}}{\~a}o dos 
                         m{\'o}dulos atmosf{\'e}rico e oce{\^a}nico de forma 
                         concorrente, com diferentes quantidades de CPUs alocados para cada 
                         m{\'o}dulo. Ap{\'o}s todas as otimiza{\c{c}}{\~o}es aplicadas, 
                         foi obtida redu{\c{c}}{\~a}o no tempo de execu{\c{c}}{\~a}o de 
                         at{\'e} quatro vezes quando utilizados 24 processadores, e foi 
                         reduzido pela metade o tempo m{\'{\i}}nimo de 
                         execu{\c{c}}{\~a}o das simula{\c{c}}{\~o}es empregando 
                         centenas de processadores. Apesar dos resultados 
                         consider{\'a}veis alcan{\c{c}}ados, ainda h{\'a} espa{\c{c}}o 
                         para melhorias no BESM em trabalhos futuros, voltadas ao 
                         balanceamento de carga entre os processos MPI, especialmente no 
                         m{\'o}dulo atmosf{\'e}rico. ABSTRACT: Climate models are complex 
                         programs that involve the computational implementation of numerous 
                         mathematical calculations in order to represent physical phenomena 
                         that interact with each other. Such phenomena are usually 
                         represented by specific modules (atmospheric, oceanic, land, etc.) 
                         that operate in a coupled way, that is, they perform the 
                         simulation of the respective phenomena for a certain interval of 
                         time, exchanging information among them when necessary. Due to 
                         this complexity, the need arises to parallelize its execution in 
                         order to obtain results in a viable time. In addition to the model 
                         parallelization, optimization techniques aiming the employed 
                         hardware architecture can also be applied, such as vectorization 
                         and loop blocking. This work aims to explore opportunities of 
                         performance improvements in global climate models, using as case 
                         study the Brazilian Earth System Model (BESM), a model developed 
                         by CPTEC/INPE with the main goal of simulating the global climate 
                         in order to understand the causes of climate changes. The work 
                         started with an evaluation of the original BESMs performance, 
                         verifying how the model was being compiled, which parallelization 
                         techniques were applied, how its modules were executed, and which 
                         were the points with the highest CPU consumption. Then, based on 
                         the information found in the initial analysis, the models 
                         performance was optimized. Improvements were made in the process 
                         of compiling and executing the model, and the necessary changes 
                         were also made to allow the execution of the atmospheric and 
                         oceanic modules concurrently, with different amounts of CPUs 
                         allocated for each module. After all the applied optimizations, a 
                         reduction in the execution time of up to four times was obtained 
                         when 24 processors were used, and the minimum time for executions 
                         with hundreds of processors was reduced to half of the original 
                         time. Despite the substantial results achieved, there is still 
                         room for improvement in BESM in future works, aimed at load 
                         balancing between the MPI processes, especially in the atmospheric 
                         module.",
            committee = "Stephany, Stephan (presidente) and Mendes, Celso Luiz (orientador) 
                         and Andrade Neto, Pedro Ribeiro de and Fazenda, {\'A}lvaro Luiz",
         englishtitle = "Exploring opportunities for performance improvement in a global 
                         climate model",
             language = "pt",
                pages = "52",
                  ibi = "8JMKD3MGP3W34R/3UU6PU2",
                  url = "http://urlib.net/rep/8JMKD3MGP3W34R/3UU6PU2",
           targetfile = "publicacao.pdf",
        urlaccessdate = "07 ago. 2020"
}


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