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Une tendance importante dans le domaine de l’embarqué est l’intégration de plus en plus d’éléments de calcul dans les systèmes multiprocesseurs sur puce (MPSoC). Cette tendance est due en partie aux limitations des puissances individuelles de ces éléments causées par des considérations de consommation d’énergie. Dans le même temps, en raison de leur sophistication croissante, les applications de traitement du signal ont des besoins en puissance de calcul de plus en plus dynamique. Dans la conception et le développement d’applications de traitement de signal multicoeur, l’un des principaux défis consiste à répartir efficacement les différentes tâches sur les éléments de calcul disponibles, tout en tenant compte des changements dynamiques des fonctionnalités de l’application et des ressources disponibles. Une utilisation inefficace peut conduire à une durée de traitement plus longue et/ou une consommation d’énergie plus élevée, ce qui fait de la répartition des tâches sur un système multicoeur une tâche difficile à résoudre. Les modèles de calcul (MoC) flux de données sont communément utilisés dans la conception de systèmes de traitement du signal. Ils décomposent la fonctionnalité de l’application en acteurs qui communiquent exclusivement par l’intermédiaire de canaux. L’interconnexion des acteurs et des canaux de communication est modélisée et manipulée comme un graphe orienté, appelé un graphique de flux de données. Il existe différents MoCs de flux de données qui offrent différents compromis entre la prédictibilité et l’expressivité. Ces modèles de calculs sont communément utilisés dans la conception de systèmes de traitement du signal en raison de leur analysabilité et leur expressivité naturelle du parallélisme de l’application. Dans cette thèse, une nouvelle méthode de répartition de tâches est proposée afin de répondre au défi que propose la programmation multicoeur. Cette méthode de répartition de tâches prend ses décisions en temps réel afin d’optimiser le temps d’exécution global de l’application. Les applications sont décrites en utilisant le modèle paramétrée et interfacé flux de données (PiSDF). Ce modèle permet de décrire une application paramétrée en autorisant des changements dans ses besoins en ressources de calcul lors de l’exécution. A chaque exécution, le modèle de flux de données paramétré est déroulé en un modèle intermédiaire faisant apparaitre toute les tâches de l’application ainsi que leurs dépendances. Ce modèle est ensuite utilisé pour répartir efficacement les tâches de l’application. La méthode proposé a été testée et validé sur plusieurs applications des domaines de la vision par ordinateur, du traitement du signal et du multimédia. / An important trend in embedded processing is the integration of increasingly more processing elements into Multiprocessor Systemson- Chip (MPSoC). This trend is due in part to limitations in processing power of individual elements that are caused by power consumption considerations. At the same time, signal processing applications are becoming increasingly dynamic in terms of their hardware resource requirements due to the growing sophistication of algorithms to reach higher levels of performance. In design and implementation of multicore signal processing systems, one of the main challenges is to dispatch computational tasks efficiently onto the available processing elements while taking into account dynamic changes in application functionality and resource requirements. An inefficient use can lead to longer processing times and higher energy consumption, making multicore task scheduling a very difficult problem to solve. Dataflow process network Models of Computation (MoCs) are widely used in design of signal processing systems. It decomposes application functionality into actors that communicate data exclusively through channels. The interconnection of actors and communication channels is modeled and manipulated as a directed graph, called a dataflow graph. There are different dataflow MoCs which offer different trade-off between predictability and expressiveness. These MoCs are widely used in design of signal processing systems due to their analyzability and their natural parallel expressivity. In this thesis, we propose a novel scheduling method to address multicore scheduling challenge. This scheduling method determines scheduling decisions strategically at runtime to optimize the overall execution time of applications onto heterogeneous multicore processing resources. Applications are described using the Parameterized and Interfaced Synchronous DataFlow (PiSDF) MoC. The PiSDF model allows describing parameterized application, making possible changes in application’s resource requirement at runtime. At each execution, the parameterized dataflow is then transformed into a locally static one used to efficiently schedule the application with an a priori knowledge of its behavior. The proposed scheduling method have been tested and benchmarked on multiple state-of-the-art applications from computer vision, signal processing and multimedia domains.

O objetivo desta tese foi avaliar os impactos decorrentes das mudanças de uso da terra e da variabilidade climática nos recursos hídricos (vazão e fluxo de sedimentos), em mesoescala (bacia do rio Piracicaba) e em pequena escala (microbacia do Ribeirão das Posses), através de um estudo de modelagem numérica com o modelo SWAT (Soil and Water Assessment Tool). Foram utilizados dados de modelo numérico de terreno, mapas de solo e uso da terra, temperatura, precipitação, vento, radiação solar e umidade relativa para forçar o modelo SWAT. O modelo mostrou resultados satisfatórios de desempenho na comparação com dados observados, conforme mostram os índices estatísticos na bacia do rio Piracicaba (COE entre 0,97 e 0,99 para vazão e de 0,90 para fluxo de sedimentos) e no Ribeirão das Posses (COE de 0,53 para a vazão e 0,7 para fluxo de sedimentos). Nas simulações de modificações de uso da terra os resultados indicam que em ambas as bacias as maiores vazões ocorrem nos cenários de desflorestamento, sendo o cenário de pastagem o de valores mais expressivos. O modelo correspondeu às evidências de que as vazões máximas, por exemplo os eventos de inundações, podem ser mitigados com o reflorestamento e que o cenário de antropização com gramíneas, no caso das pastagens e cana-de-açúcar, os eventos extremos tendem a ser aumentados ainda mais. Na avaliação da simulação dos fluxos de sedimentos, o cenário de reflorestamento por eucalipto mostra redução na perda do solo, porém ainda abaixo do cenário de reflorestamento por vegetação nativa, que apresentou os menores valores de fluxo de sedimentos, em ambas as bacias. Na simulação levando-se em consideração as mudanças climáticas, os resultados mostram aumento de vazão para o futuro (2078-2098) e consequente aumento de fluxo de sedimento, sendo um aumento médio de 12 % nas vazões do Piracicaba e de 19 % no fluxo de sedimentos. No Ribeirão das Posses este padrão de resposta também ocorreu, com aumento de 46% na vazão e 40 % no fluxo de sedimentos. / The aim of this thesis was to evaluate the impacts of changes in land use and climate variability on water resources (discharge and sediment fluxes), into mesoscale (Piracicaba River basin) and small-scale (watershed Ribeirão das Posses) processes throughout a study of numerical modeling with SWAT model (Soil and Water Assessment Tool). Data of numerical model of terrain, soil maps and land use, temperature, precipitation, wind speed, solar radiation and relative humidity forced the SWAT model. The model showed a satisfactory performance in comparison with the observed data, as showed by the statistical indices of the Piracicaba River Basin (COE between 0.97 and 0.99 to 0.90 for flow and sediment fluxes) and Ribeirão das Posses (COE of 0.53 to 0.7 for flow and sediment fluxes). In simulations of changes in land use the results indicate that in both basins larger flows occur in the case of deforestation scenarios, being the scene of the pasture the highest values. The model corresponded to the evidence that peak flows, for example the events of flooding can be mitigated with reforestation and the scenario of anthropogenic with grasses for grazing land and sugar cane, extreme events tend to be further enhanced too. In assessing the simulation of sediment flows, the scenario of reforestation with eucalyptus shows reduction in soil loss, but still below the scenario reforestation with native vegetation, which presented the lowest values of sediment flux in both basins. In the simulation taking into account climate change, the results show increased flow to the future (2078-2098) and consequent increase in stream sediment, with an average 12% increase in the flows of Piracicaba and 19 % in the flow sediment. In Ribeirão das Posses this response pattern also occurred with a 46% increase in throughput and 40 % in the stream sediments.

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