Keystone species are widely distributed across aquatic and terrestrial ecosystems and are fundamental in preserving the structure, diversity, and stability of an ecological community due to its disproportionately large impact on its community relative to its biomass. As biodiversity of ecosystems becomes more threatened with urbanization and habitat destruction, it is imperative to understand a keystone species' role in maintaining ecosystem function. One of the ways to do so is by examining their significance and connection to the ecosystem food web. Within North American freshwater ecosystems is the pebble nest-building minnow, the bluehead chub (Nocomis leptocephalus; "chub"). Chubs provide spawning habitat for not only themselves, but for other minnows, collectively called "nest associates". In this work, I observe the predatory and potential mutualistic interactions between chubs, nest associates, and their predators. In Chapter 1, I observe spawning nests to identify the predators of adult chubs, nest associates, and embryos. I further investigate how nest visibility covariates including minnow activity, minnow abundance, nest size (area), and nest growth affect predator encounter rate to spawning nests. I found a total of 23 diverse taxa to prey on the adult minnows and minnow embryos on chub spawning nests, 14 predators of which had not been reported in literature. One of these predators was the common snapping turtle (Chelydra serpentina; "turtle"). Additionally, I found that activity, abundance, nest size (area), and nest growth had a significant effect on predator encounter rate, attracting predators to seek spawning nests for prey. In Chapter 2, I investigate the effect of ambient temperature on turtle epizoic coverage during the spawning season and provide preliminary evidence of a potential cleaning symbiotic mutualism between the turtle and minnows. I found that epizoic coverage decreases during the duration of a minnow spawning season after an initial increase with early summer warming, and my results also present unique and shared bacterial communities across three sources, the ambient environment, gut contents of minnows, and turtles. The results additionally revealed there to be bacterial communities unique between minnows and turtles that were not identified in the ambient environment. Overall, this study is first to systematically document predators of chub spawning nests and first to provide preliminary evidence of a cleaning symbiotic mutualism between a freshwater turtle and minnow species (or freshwater turtles and fish in general), which, thus far, has not been explored in freshwater ecosystems. This work demonstrates that chub spawning nests are a crucial entity of the freshwater food web structure across Nocomis' distribution range and reveals that chub spawning nests create an interconnection between a diversity of fauna in a freshwater ecosystem. / Master of Science / Ecological communities often include species that are essential in ensuring the overall stability and biodiversity of an ecosystem. These species, otherwise called keystone species, play a crucial role in facilitating interconnections within the ecosystem's food web. The bluehead chub (Nocomis leptocephalus; "chub") is an example of a keystone minnow found in North American freshwater streams. This minnow engages in a complex, distinguished act when it reproduces, making mounded, pebble nests using only its mouth. Chubs are not the only minnow species interested in this engineering complexity. Various minnow species called "nest associates" reproduce on the nests as well, providing an appearance of a mutualism: all species involved benefit from the interaction. While this interaction has been observed, there is limited research identifying predators of chub nests and if there are potential mutualisms with any of these predators. In this work, I identify predatory and mutualistic interactions between chubs, nest associates, and their predators. In Chapter 1, I identify predators of chub nests and observe variables that attract these predators to the nests. In Chapter 2, I explore a potential, mutualistic interaction between these minnows and an identified predator from this research, the common snapping turtle (Chelydra serpentina; "turtle"), whereby minnows feed on potentially harmful growth of algae and bacteria on turtles, while turtles benefit from the cleaning. For Chapter 1, my results revealed that a chub nest is a hotspot for predator diversity, showing 23 diverse taxa as predators, in which 14 of the identified taxa are novel for ecological literature. Additionally, variables that were observed to attract predators to chub nests were minnow activity, minnow abundance, nest size (area), and nest growth. Results for Chapter 2 demonstrated that there are unique bacterial communities between turtles and minnows that are not found in the stream environment, therefore providing preliminary evidence of mutualistic interaction between the coexisting species. Overall, this study is the first to systematically document predators of chub nests. This study is also first to investigate a mutualistic interaction between minnows and turtles in a freshwater ecosystem, an area that has not been previously explored, unlike similar interactions in marine ecosystems. Cohesively, the keystone species, the chub, and their reproductive nests, are important for the aquatic food web structure and the interconnectedness to their overall ecosystem function. This research further stewards scientific knowledge about how important Nocomis are to natural freshwater ecosystems.

Mycorrhizal networks (MNs), or the networks of fungal mycelia that connect plants to each other, are vital in contributing to the well-being of ecosystems. They not only assist in the transport of nutrients across an ecosystem, but also help protect an ecosystem from disease and adverse conditions. However, more research into these networks is needed and modelling these networks as graphs can help us achieve this. By applying centrality analysis and performing k-core partitioning on these networks, we are able to identify the trees that are most important and central to a MN and observe the effects of removing these trees. We also perform random partitioning on these networks and compare the results to the k-core partitioning results. We found that these networks are fairly resilient to the removal of a single keystone individual, but this can disrupt the interconnectedness of a MN in a dry (xeric) moisture regime. We also found that these networks are less resilient to k-core partitioning. In a network of trees divided up by age cohorts, the maximal k-core subgraph contained a mix of trees that mostly belonged to older cohorts and were linked to one specific fungal genet. This could influence conservation efforts for not only a few older trees, but also some younger trees and potentially specific fungal genets. When removing the maximal k-core subgraphs for networks in dry (xeric) and moist (mesic) moisture regimes, the network became disconnected for the xeric graph and still somewhat connected for the mesic graph. So, mycorrhizal networks could possibly be more resilient to this k-core partitioning in an area where the soil is moist rather than dry.

A Análise de Redes Sociais (Social Network Analysis, SNA) é uma ferramenta que vem se demonstrando muito útil para o estudo da estrutura social dos primatas, apresentando métricas que permitem quantificar vários aspectos das sociedades. Para compreender o padrão de associações de um grupo devemos atentar às diferenças individuais que existem entre os sujeitos, que promovem ou evitam o estabelecimento de relações sociais. Dentre essas diferenças individuais, tradicionalmente se estudam o sexo, a idade e a dominância, mas, ultimamente, tem sido destacada a importância da personalidade dos indivíduos, uma variável que pode ter um papel fundamental na construção da estrutura social, mas cujo estudo ainda apresenta um desafio metodológico, sobretudo com animais de vida livre. Alguns estudos demostram como alguns indivíduos chave podem ter uma relevância especial dentro da estrutura social do grupo. O objetivo do presente estudo é investigar a importância de características individuais, incluindo a personalidade, assim como o papel de indivíduos chave, sobre a estrutura social de um grupo de Sapajus xanthosternos na reserva ReBio Una no estado de Bahia / Social Network Analysis (SNA) is a tool that has proved very useful for the study of the social structure of primates, presenting metrics that allow quantification of various aspects of societies. In order to understand the pattern of associations of a group we must pay attention to the individual differences that exist between-subjects, that promote or avoid the establishment of social relations. Among these individual differences, sex, age and dominance have traditionally been studied, but recently the importance of individuals\' personality has been highlighted, a variable that may play a fundamental role in the construction of social structure, but whose study still presents a methodological challenge, especially with free-living animals. Some studies show how some key (keystone) individuals may have special relevance within the social structure of the group. The objective of the present study is to investigate the importance of individual characteristics, including personality, as well as the role of keystone individuals, on the social structure of a Sapajus xanthosternos group in Una Biological Reserve in the state of Bahia, Brazil

Ficus (Moraceae) é o gênero mais importante para animais frugívoros nas florestas tropicais, considerado um recurso-chave durante períodos de escassez de frutos. Esses animais dispersam suas sementes e contribuem para a manutenção das populações de figueiras. A perda de hábitat e a fragmentação da paisagem podem afetar a sobrevivência de populações e a composição de comunidades e suas interações. Os objetivos deste trabalho foram (1) comparar a frugivoria e a dispersão de sementes por aves frugívoras entre espécies de Ficus encontradas em remanescentes de Floresta Estacional Semidecidual e (2) testar se a perda de hábitat influencia a frugivoria e dispersão de sementes dessas árvores. Estudamos três áreas de reservas florestais no Estado de São Paulo, sudeste do Brasil, com diferentes áreas e nível de fragmentação da paisagem: Parque Estadual do Morro do Diabo (33.845 ha), Estação Ecológica dos Caetetus (2.176 ha) e Estação Ecológica de Ribeirão Preto (180 ha). Ao longo de 443 h de observação árvore-focal, registramos todas as espécies de aves frugívoras se alimentando de figos e estimamos a taxa de remoção de figos e sementes. Como nossos dados não se adequaram a métodos estatísticos tradicionais, utilizamos a reamostragem por bootstrap para estimar os intervalos de confiança das taxas de remoção e dispersão de sementes e testar as diferenças entre as espécies de figueira e as áreas de estudo. Trinta e duas espécies de aves foram observadas consumindo figos de seis espécies de Ficus. As figueiras que apresentam figos verdes, de tamanho médio ou grande, foram consumidas por uma boa variedade de espécies, mas apenas uma das aves de cada assembléia foi responsável pela remoção da maior parte dos figos. Ficus luschnathiana, com figos pequenos e vermelhos quando maduros, foi consumida de forma mais equitativa pelos seus visitantes, e apresentou taxa de dispersão de sementes significativamente maior que as demais espécies. A fragmentação reduziu a remoção de figos e sementes de F. citrifolia. Ficus eximia não demonstrou nenhum padrão claro, uma vez que só teve um consumo expressivo em um microhábitat específico, não incluído na análise da fragmentação. No fragmento menor, aves de grande porte, consideradas bons dispersores de sementes, não foram encontradas e as aves menores e generalistas não compensaram a perda do serviço de dispersão de sementes. Essas espécies de Ficus, no entanto, devem depender mais de morcegos e macacos-prego que das aves no processo de dispersão, e devem inclusive ser beneficiadas pelo aumento na extensão de bordas. Mesmo que essa comunidade de figueiras no fragmento menor não estabeleça uma interação forte com a avifauna, ainda é relevante testar se a baixa densidade de indivíduos de F. luschnathiana é consequencia da ausência de bons dispersores de sementes. / Ficus (Moraceae) is the most important plant genus for tropical frugivores and is considered a keystone resource during periods of general fruit scarcity. Frugivorous animals disperse their seeds and contribute for the maintenance of fig trees populations. Habitat loss and landscape fragmentation can affect species survival as well as community composition and their interactions. The goals of this study were (1) to compare the frugivory and seed dispersal by frugivorous birds among Ficus species found in Semideciduous Seasonal Forest remnants and (2) to assess whether habitat loss influences frugivory and seed dispersal of these trees. We studied three natural reserves in São Paulo State, southeastern Brazil, which differ in area and landscape fragmentation: Morro do Diabo State Park (33.845 ha), Caetetus Ecological Station (2.176 ha) and Ribeirão Preto Ecological Station (180 ha). During 443 h focal tree observation, we registered all frugivorous birds eating figs and estimated their fruit removal and seed dispersal. As traditional statistical methods were not suitable for our data, we used bootstrap data resampling to estimate confidence limits of fruit removal and seed dispersal and test for differences between fig trees and forest fragments. A total of 32 bird species were observed consuming figs of six Ficus species. Fig trees bearing green-fruited and medium or large figs were consumed by a great diversity of birds, but showed a dominance of only one species over the others on the fruit removal. Ficus luschnathiana, whose figs are small and red when ripe, was more equally consumed by all visitors and had significantly more seeds dispersed per hour than the other species. Fragmentation reduced fruit removal and seed dispersal of F. citrifolia. Ficus eximia did not show a clear pattern, once it was only highly consumed by birds in a specific microhabitat not included on the fragmentation analysis. The effect upon other Ficus species remains to be tested. In the smallest forest remnant, large-bodied birds, considered high quality seed dispersers, cannot be found anymore and small and generalist birds are not able to compensate for this loss on seed dispersal service. These Ficus species, however, may depend more upon bats and capuchin monkeys than on birds for seed dispersal, and may even benefit from the increase in extension of forest edges. Even if this Ficus community as a whole does not seem to interact with birds, it remains relevant, though, to test whether F. luschnathiana\'s low density in the smallest fragment is due to the absence of good seed dispersers.

The subject of this diploma thesis is an analysis of the historical existence of European bison in the Czech geographical region and an evaluation of the significance of its presence to the surrounding landscape. The goal of the thesis is to depict bison population changes in the Czech territory over time and the meaning of efforts to reintroduce the bison into its natural habitat. An important part of the work then will be the preparation, realization and evaluation of two excursions during which students go for European bison directly into the field.

L'objectif de cette thèse est de contribuer à une meilleure compréhension de la formulation et du renouvellement des stratégies à travers le temps. Nous avons pour ce faire choisi d'analyser les comportements stratégiques de trois entreprises face à un choc prévisible annoncé plusieurs années d'avance. Il s'agit de l'abolition des quotas à l'importation de vêtements décidée par l'Organisation Mondiale du Commerce en 1995, et qui devait prendre effet en 2005. La recherche a porté sur les deux questions suivantes : • Quels sont les facteurs qui peuvent nous aider à comprendre la réaction et le comportement d'une entreprise à la suite d'une rupture institutionnelle programmée? • Existe-t-il des régularités qui se dégagent de l'évolution du processus stratégique prenant place à la suite d'une rupture institutionnelle programmée? La recherche est exploratoire et qualitative. Elle a été guidée par un modèle interactif de type contextualiste construit à partir de la littérature, qui met en relation trois éléments centraux : la création de sens par les décideurs, le contexte de chaque entreprise et les ressources relationnelles liant les entreprises et leurs parties prenantes. Ce modèle est globalement validé par le terrain. Il nous a permis, d'une part, de saisir les logiques sous-jacentes aux réponses formulées par les entreprises face à la rupture annoncée et, d'autre part, de replacer ces logiques dans l'évolution générale de la stratégie de ces entreprises à travers le temps. L'analyse de nos résultats nous a révélé l'existence d'une forte cohérence entre les différents éléments de réponse aux questions posées. Nous proposons de les intégrer dans un modèle centré sur le concept de « maturité stratégique », défini comme l'acquisition par une entreprise de l'expertise nécessaire à la construction et au renouvellement de sa vision et de son action stratégiques. La maturité stratégique est faite à la fois de clairvoyance proactive et de capacité d'action. Elle s'enrichit dans le temps au cours d'un processus collectif d'apprentissage au contact des différentes problématiques internes et externes auxquelles les dirigeants sont appelés à se mesurer. La maturité stratégique expliquerait ainsi pourquoi les entreprises d'une même industrie ont su profiter mieux que d'autres du délai de dix ans dont elles disposaient avant l'abolition définitive des quotas à l'importation. ______________________________________________________________________________ MOTS-CLÉS DE L’AUTEUR : formation des stratégies, rupture institutionnelle programmée, dirigeant, contexte, ressources relationnelles, création de sens, industrie du vêtement, abolition des quotas.

Ficus (Moraceae) é o gênero mais importante para animais frugívoros nas florestas tropicais, considerado um recurso-chave durante períodos de escassez de frutos. Esses animais dispersam suas sementes e contribuem para a manutenção das populações de figueiras. A perda de hábitat e a fragmentação da paisagem podem afetar a sobrevivência de populações e a composição de comunidades e suas interações. Os objetivos deste trabalho foram (1) comparar a frugivoria e a dispersão de sementes por aves frugívoras entre espécies de Ficus encontradas em remanescentes de Floresta Estacional Semidecidual e (2) testar se a perda de hábitat influencia a frugivoria e dispersão de sementes dessas árvores. Estudamos três áreas de reservas florestais no Estado de São Paulo, sudeste do Brasil, com diferentes áreas e nível de fragmentação da paisagem: Parque Estadual do Morro do Diabo (33.845 ha), Estação Ecológica dos Caetetus (2.176 ha) e Estação Ecológica de Ribeirão Preto (180 ha). Ao longo de 443 h de observação árvore-focal, registramos todas as espécies de aves frugívoras se alimentando de figos e estimamos a taxa de remoção de figos e sementes. Como nossos dados não se adequaram a métodos estatísticos tradicionais, utilizamos a reamostragem por bootstrap para estimar os intervalos de confiança das taxas de remoção e dispersão de sementes e testar as diferenças entre as espécies de figueira e as áreas de estudo. Trinta e duas espécies de aves foram observadas consumindo figos de seis espécies de Ficus. As figueiras que apresentam figos verdes, de tamanho médio ou grande, foram consumidas por uma boa variedade de espécies, mas apenas uma das aves de cada assembléia foi responsável pela remoção da maior parte dos figos. Ficus luschnathiana, com figos pequenos e vermelhos quando maduros, foi consumida de forma mais equitativa pelos seus visitantes, e apresentou taxa de dispersão de sementes significativamente maior que as demais espécies. A fragmentação reduziu a remoção de figos e sementes de F. citrifolia. Ficus eximia não demonstrou nenhum padrão claro, uma vez que só teve um consumo expressivo em um microhábitat específico, não incluído na análise da fragmentação. No fragmento menor, aves de grande porte, consideradas bons dispersores de sementes, não foram encontradas e as aves menores e generalistas não compensaram a perda do serviço de dispersão de sementes. Essas espécies de Ficus, no entanto, devem depender mais de morcegos e macacos-prego que das aves no processo de dispersão, e devem inclusive ser beneficiadas pelo aumento na extensão de bordas. Mesmo que essa comunidade de figueiras no fragmento menor não estabeleça uma interação forte com a avifauna, ainda é relevante testar se a baixa densidade de indivíduos de F. luschnathiana é consequencia da ausência de bons dispersores de sementes. / Ficus (Moraceae) is the most important plant genus for tropical frugivores and is considered a keystone resource during periods of general fruit scarcity. Frugivorous animals disperse their seeds and contribute for the maintenance of fig trees populations. Habitat loss and landscape fragmentation can affect species survival as well as community composition and their interactions. The goals of this study were (1) to compare the frugivory and seed dispersal by frugivorous birds among Ficus species found in Semideciduous Seasonal Forest remnants and (2) to assess whether habitat loss influences frugivory and seed dispersal of these trees. We studied three natural reserves in São Paulo State, southeastern Brazil, which differ in area and landscape fragmentation: Morro do Diabo State Park (33.845 ha), Caetetus Ecological Station (2.176 ha) and Ribeirão Preto Ecological Station (180 ha). During 443 h focal tree observation, we registered all frugivorous birds eating figs and estimated their fruit removal and seed dispersal. As traditional statistical methods were not suitable for our data, we used bootstrap data resampling to estimate confidence limits of fruit removal and seed dispersal and test for differences between fig trees and forest fragments. A total of 32 bird species were observed consuming figs of six Ficus species. Fig trees bearing green-fruited and medium or large figs were consumed by a great diversity of birds, but showed a dominance of only one species over the others on the fruit removal. Ficus luschnathiana, whose figs are small and red when ripe, was more equally consumed by all visitors and had significantly more seeds dispersed per hour than the other species. Fragmentation reduced fruit removal and seed dispersal of F. citrifolia. Ficus eximia did not show a clear pattern, once it was only highly consumed by birds in a specific microhabitat not included on the fragmentation analysis. The effect upon other Ficus species remains to be tested. In the smallest forest remnant, large-bodied birds, considered high quality seed dispersers, cannot be found anymore and small and generalist birds are not able to compensate for this loss on seed dispersal service. These Ficus species, however, may depend more upon bats and capuchin monkeys than on birds for seed dispersal, and may even benefit from the increase in extension of forest edges. Even if this Ficus community as a whole does not seem to interact with birds, it remains relevant, though, to test whether F. luschnathiana\'s low density in the smallest fragment is due to the absence of good seed dispersers.

Coimbra-Filho’s titi monkey, Callicebus coimbrai, is an endemic primate of the Atlantic Forest of the Brazilian Northeast, found only in Sergipe and northern Bahia. The species has been the focus of research and conservation efforts over the past twelve years, which has integrated the region’s scientists and institutions. The study presented here provides continuity, with three distinct, but complementary approaches. The first approach was an ecological study in the Mata do Junco Wildlife Refuge, in the municipality of Capela, in the Brazilian state of Sergipe. The results of this study highlighted the ecological resilience of the species in the face of habitat fragmentation. The titi is relatively inactive, spending most of the day at rest, and is predominantly frugivorous, although the proportion of time spent foraging was higher than in most previous studies of the same group, which may be related to variation in observational procedures. While some significant variation was found in the composition of the diet, the behavior of the members of the study group changed very little between the different periods of the year, or even among years, in comparison with previous years. Two aspects of the behavior of the animals were highlighted, however. One was the breakdown in the dispersal mechanism from the natal group, which apparently resulted in an endogamous mating between the resident reproductive male and its mature daughter. This is the second case of endogamy recorded in C. coimbrai, which may result from the inflexible social organization of the species in the context of habitat fragmentation, and represents a potentially serious problem for the long-term conservation of the species. The second new behavior was the predation of termites (Nasutitermes sp.), which appears to reflect the behavioral flexibility of C. combrai, and may represent a positive feature of the capacity of the species to cope with habitat fragmentation. In the second theme, the ecological concept of keystone species/resources was reviewed through a systematic literature search, which aimed to evaluate the potential practical applications of the concept for the conservation of C. combrai. This review revealed an extensive literature, which has grown almost exponentially in recent years, although the concept has been applied relatively rarely in primate studies. Together with the data accumulated on the ecology of the species, the discussion of the concept indicated that the extension of forest is a keystone resource for the conservation of C. coimbrai. This conclusion supports the third approach, which was an evaluation of the potential for the implementation of a network of ecological corridors in the study area. The analysis identified three priorities for the formation of corridors, one in the buffer zone of the RVS Mata do Junco, the second to the south of the area, and the third linking the refuge to the AIE Mata do Cipó. The thesis provides valuable insights into the long-term conservation of the species, but emphasizes the need for integrated efforts in research and practical action by environmental organs, research institutions, and the local population. / O guigó-de-coimbra, Callicebus coimbrai, é uma espécie de primata endêmica da MataAtlântica do nordeste brasileiro, encontrada somente em Sergipe e no extremo nordeste da Bahia. A espécie tem sido o alvo de esforços de pesquisa e conservação ao longo dos últimos doze anos, integrando pesquisadores e instituições da região. A pesquisa apresentada nesta tese dá continuidade a estes esforços através de três abordagens distintas, mas complementares. A primeira abordagem foi o estudo ecológico no Refúgio de Vida Silvestre Mata do Junco, no município sergipano de Capela, cujos resultados refletem principalmente a resiliência ecológica da espécie frente à fragmentação de habitats. O guigó é uma espécie pouco ativa, que passa a maior parte de seu dia descansando, e predominantemente frugívora, embora a proporção de tempo gasto em forrageio foi maior que na maioria dos estudos anteriores do mesmo grupo, podendo ser relacionado a variação nos procedimentos observacionais. Apesar de alguma variação sazonal significativa na composição da dieta, o comportamento dos membros do grupo de estudo mudou muito pouco entre diferentes períodos do ano, ou mesmo entre anos, na comparação com estudos anteriores. Dois aspectos do comportamento dos animais se destacaram, entretanto. Um foi uma falha no mecanismo de dispersão do grupo natal, que resultou num acasalamento aparentemente endogâmico entre o macho reprodutor residente e sua filha, amadurecida. Este é o segundo caso de endogamia registrado em C. coimbrai, que parece resultar da inflexibilidade da organização social da espécie, frente à fragmentação de habitat, e representa um problema potencialmente grave para a conservação da espécie em longo prazo. Outra novidade foi a predação de cupins (Nasutitermes sp.), que parece refletir a flexibilidade do comportamento de C. combrai e pode representar um aspecto positivo de sua capacidade de lidar com a fragmentação de habitat. Na segunda abordagem, foi revisada o conceito ecológico de espécie/recurso chave, através de uma revisão sistemática da literatura, visando avaliar o potencial para aplicações práticas na conservação de C. combrai. A revisão revelou uma literatura extensa, com crescimento quase exponencial em anos recentes, embora o conceito tem sido aplicado relativamente raramente em estudos de primatas. Junto aos dados acumulados sobre a ecologia da espécie, a discussão do conceito apontou para a extensão de floresta como o recurso chave para a conservação de C. coimbrai. Esta conclusão apoiou a terceira abordagem, que foi uma avaliação do potencial para a implementação de uma rede de corredores ecológicos na área de estudo. A análise identificou três prioridades para a formação de corredores, uma no entorno do RVS Mata do Junco, a segunda no sul da área, e a terceira ligando o refúgio com a AIE Mata do Cipó. A tese oferece valiosos insights para a conservação da espécie em longo prazo, mas frisa a necessidade de esforços integrados de pesquisa e ação prática por parte de órgãos ambientais, instituições de pesquisa e a população local. / São Cristóvão, SE

The energy consumption of large-scale high-performance computer (HPC) systems has become one of the foremost concerns of both data-center operators and computer manufacturers. This has renewed interest in alternative computer architectures that could offer substantially better energy-efficiency.Yet, the for the evaluation of the potential of these architectures necessary well-optimized implementations of typical HPC benchmarks are often not available for these for the HPC industry novel architectures. The in this work presented LU factorization benchmark implementation aims to provide such a high-quality tool for the HPC industry standard high-performance LINPACK benchmark (HPL) for the eight-core Texas Instruments TMS320C6678 digitalsignal processor (DSP). The presented implementation could perform the LU factorization at up to 30.9 GF/s at 1.25 GHz core clock frequency by using all the eight DSP cores of the System-on-Chip (SoC). This is 77% of the attainable peak double-precision floating-point performance of the DSP, a level of efficiency that is comparable to the efficiency expected on traditional x86-based processor architectures. A presented detailed performance analysis shows that this is largely due to the optimized implementation of the embedded generalized matrix-matrix multiplication (GEMM). For this operation, the on-chip direct memory access (DMA) engines were used to transfer the necessary data from the external DDR3 memory to the core-private and shared scratchpad memory. This allowed to overlap the data transfer with computations on the DSP cores. The computations were in turn optimized by using software pipeline techniques and were partly implemented in assembly language. With these optimization the performance of the matrix multiplication reached up to 95% of attainable peak performance. A detailed description of these two key optimization techniques and their application to the LU factorization is included. Using a specially instrumented Advantech TMDXEVM6678L evaluation module, described in detail in related work, allowed to measure the SoC’s energy efficiency of up to 2.92 GF/J while executing the presented benchmark. Results from the verification of the benchmark execution using standard HPL correctness checks and an uncertainty analysis of the experimentally gathered data are also presented. / Energiförbrukningen av storskaliga högpresterande datorsystem (HPC) har blivit ett av de främsta problemen för såväl ägare av dessa system som datortillverkare. Det har lett till ett förnyat intresse för alternativa datorarkitekturer som kan vara betydligt mer effektiva ur energiförbrukningssynpunkt. För detaljerade analyser av prestanda och energiförbrukning av dessa för HPC-industrin nya arkitekturer krävs väloptimerade implementationer av standard HPC-bänkmärkningsproblem. Syftet med detta examensarbete är att tillhandhålla ett sådant högkvalitativt verktyg i form av en implementation av ett bänkmärkesprogram för LU-faktorisering för den åttakärniga digitala signalprocessorn (DSP) TMS320C6678 från Texas Instruments. Bänkmärkningsproblemet är samma som för det inom HPC-industrin välkända bänkmärket “high-performance LINPACK” (HPL). Den här presenterade implementationen nådde upp till en prestanda av 30,9 GF/s vid 1,25 GHz klockfrekvens genom att samtidigt använda alla åtta kärnor i DSP:n. Detta motsvarar 77% av den teoretiskt uppnåbara prestandan, vilket är jämförbart med förväntningar på effektivteten av mer traditionella x86-baserade system. En detaljerad prestandaanalys visar att detta tillstor del uppnås genom den högoptimerade implementationen av den ingående matris-matris-multiplikationen. Användandet av specialiserade “direct memory access” (DMA) hårdvaruenheter för kopieringen av data mellan det externa DDR3 minnet och det interna kärn-privata och delade arbetsminnet tillät att överlappa dessa operationer med beräkningar. Optimerade mjukvaruimplementationer av dessa beräkningar, delvis utförda i maskinspåk, tillät att utföra matris-multiplikationen med upp till 95% av den teoretiskt nåbara prestandan. I rapporten ges en detaljerad beskrivning av dessa två nyckeltekniker. Energiförbrukningen vid exekvering av det implementerade bänkmärket kunde med hjälp av en för ändamålet anpassad Advantech TMDXEVM6678L evalueringsmodul bestämmas till maximalt 2,92 GF/J. Resultat från verifikationen av bänkmärkesimplementationen och en uppskattning av mätosäkerheten vid de experimentella mätningarna presenteras också.

No description available.