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Dive into the research topics where Gerson Geraldo Homrich Cavalheiro is active.

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Featured researches published by Gerson Geraldo Homrich Cavalheiro.


middleware for grid computing | 2004

Towards a flexible security framework for peer-to-peer based grid computing

André Detsch; L. P. Gaspary; Marinho P. Barcellos; Gerson Geraldo Homrich Cavalheiro

The dynamic, multi-organization nature of large-scale grid computing introduces security issues that must be addressed before grid systems can become widely popular. This paper proposes P2PSLF (Peer-to-Peer Security Layer Framework), a flexible security framework for peer-to-peer based grid computing. P2PSLF provides a wide range of security mechanisms (e.g., authentication, confidentiality, integrity, authorization, and audit), and allows the creation of new ones. It is independent of the overlying application, which enables new systems to be implemented without having to deal with security issues within the application. In addition, the framework is modular and reconfigurable. The set of security requirements to be satisfied in communications is determined per peer, and can be changed without recompiling the application. The framework is exercised using OurGrid, a P2P-based middleware that enables the creation of a multi-organization grid computing environment for the execution of bag-of-tasks applications.


european conference on parallel processing | 1998

A General Modular Specification for Distributed Schedulers

Gerson Geraldo Homrich Cavalheiro; Yves Denneulin; Jean-Louis Roch

In parallel computing, performance is related both to algorithmic design choices at the application level and to the scheduling strategy. Concerning dynamic scheduling, general classifications have been proposed. They outline two fundamental units, related to control and information. In this paper, we propose a generic modular specification, based not on two but on four components. They and the interactions between them are precisely described. This specification has been used to implement various scheduling algorithms in two different parallel programming environments: PM2 (Espace) and Athapascan (Apache).


symposium on computer architecture and high performance computing | 2002

A framework for exploiting adaptation in high heterogeneous distributed processing

Adenauer C. Yamin; Jorge Luis Victória Barbosa; Iara Augustin; L. da Silva; Rodrigo Araújo Real; Cláudio Fernando Resin Geyer; Gerson Geraldo Homrich Cavalheiro

ISAM is a proposal directed to resource management in heterogeneous networks, supporting physical and logical mobility, dynamic adaptation and the execution of distributed applications based on components. In order to achieve its goals, ISAM uses, as strategy, an integrated environment that: (a) provides a programming paradigm and its execution environment; (b) handles the adaptation process through a multilevel collaborative model, in which both the system and the application contribute. In this paper we discuss the main mechanisms used to implement the ISAM features, and we also present a parallel application that explores some of this features.


symposium on computer architecture and high performance computing | 2017

A User-Level Scheduling Framework for BoT Applications on Private Clouds

Maicon Anca dos Santos; André Rauber Du Bois; Gerson Geraldo Homrich Cavalheiro

This paper presents a high level model to describe bag of tasks (BoT) applications and a framework to evaluate user level approaches to scheduler BoTs on coarser works units. The scheduler consolidates the load of the tasks in a given number of virtual machines (VMs) providing the estimated makespan. The framework allows to change the policy of tasks selection in order to compare the length of the scheduling produced giving a limited number of VMs. The framework has as input a BoT description and produces for each VM its trace of processing load. This paper validates the BoT model and the proposed framework with a performance assessment. In our case studies, the output of the framework is submitted to a real OpenStack based IaaS infrastructure. The results show that the makespan can be reduced by grouping tasks in coarse units of loads.


symposium on computer architecture and high performance computing | 2017

Comparing Performance of C Compilers Optimizations on Different Multicore Architectures

Roger da Silva Machado; Ricardo Borges Almeida; Andre D. Jardim; Ana Marilza Pernas; Adenauer C. Yamin; Gerson Geraldo Homrich Cavalheiro

Multithread programming tools become popular for exploitation of high performance processing with the dissemination of multicore processors. In this context, it is also popular to exploit compiler optimization to improve the performance at execution time. In this work, we evaluate the performance achieved by the use of flags -O1, -O2, and -O3 of two C compilers (GCC and ICC) associated with five different APIs: Pthreads, C++11, OpenMP, Cilk Plus, and TBB. The experiments were performed on two distinct but compatible architectures (Intel Xeon and AMD Opteron). In our experiments, the use of optimization improves the performance independently from the API. We observe that the application scheduling performed by the programming interfaces providing an application level scheduler has more impact on the final performance than the optimizations.


Proceeding Series of the Brazilian Society of Computational and Applied Mathematics | 2015

Casos de estudo com ferramentas de programação multithread felipe haertel

Lucas Xavier; Rodrigo Bazo; Gerson Geraldo Homrich Cavalheiro; Renata Reiser

Arquiteturas paralelas tem se tornado onipresentes como suporte computacional em funcao da popularidade da tecnologia multicore. Nestas arquiteturas, as ferramentas de programacao mais adequadas sao aquelas que implementam modelos de programacao multithread, permitindo que programas sejam descritos por multiplos fluxos de execucao concorrente capazes de ocupar as varias unidades de processamento de forma paralela. Existem dois modelos basicos para decomposicao do paralelismo de uma aplicacao: a decomposicao em termos de paralelismo de dados ou de tarefas. A opcao por um ou outro destes modelos se da em funcao da natureza do problema que esta sendo implementado, sendo que diferentes ferramentas de programacao multithread oferecem diferentes facilidades de desenvolvimento para cada caso. Este trabalho avalia a interface de programacao oferecida por quatro ferramentas multithread como suporte a implementacao de diferentes padroes de paralelismo expresso por problemas recorrentes em aplicacoes matematicas. Neste texto sao considerados quatro padroes de problemas: (i) trivialmente paralelizaveis, (ii) recursivos, (iii) programacao dinâmica, e (iv) com grande numero de dependencias entre as atividades paralelas. Estes padroes sao representados, respectivamente, pelas seguintes aplicacoes: (i) problema de Satisfatibilidade Booleana (denominado 3Sat no restante deste texto), (ii) calculo da serie de Fibonacci (Fibo), (iii) o algoritmo Smith-Waterman para o alinhamento de sequencias (S-W), e (iv) decomposicao LU de uma matriz (LU). O estudo e completado com uma analise do desempenho dos programas construidos para estas aplicacoes nas diferentes ferramentas considerando suas estrategias de escalonamento. Com este tipo de trabalho, interdisciplinar, entende-se obter avancos tanto na area de desenvolvimento de software matematico como aprimoramento nas tecnicas de execucao paralela, conforme discutido em [1] Este texto limita-se a caracterizar as ferramentas de programacao selecionadas nesta fase do trabalho, que sao a academica Athreads [2], e as comerciais Cilk, OpenMP e TBB, sumarizadas em [4], e exemplificar os resultados pela analise de um conjunto de resultados de desempenho. Um dos objetivos a ser atingido e identificar a usabilidade de ferramentas de programacao multithread [3] no desenvolvimento de diferentes padroes de problemas matematicos. Athreads, Cilk e TBB embutem um nucleo de escalonamento que explora informacoes sobre a ordem lexicografica definida entre os threads pelo programa em execucao. Destas dependencias sao inferidos os custos computacionais de cada thread, assumindo que quanto mais antigo um thread for, maior sera seu custo computacional. Esta informacao de custo e considerada nas tomadas de decisao sobre os recursos de processamento disponiveis. A diferenca entre estas ferramentas se da na interface de programacao. Enquanto Cilk restringe o modelo de programacao em uma estrutura de criacao e sincronizacao aninhada de threads (nested fork/join), Athreads permite a construcao de qualquer estrutura de dependencias. Como consequencia, a estrutura regular em Cilk pode ser explorada com uma eficiencia maior por uma heuristica simples de escalonamento que considere esta regularidade nas dependencias entre threads. Por outro lado, em Athreads cabe ao programador conhecer a estrategia de escalonamento e organizar a criacao de threads de forma a refletir a heuristica de escalonamento empregada. TBB tambem tem como padrao a criacao aninhada de threads, mas, para nao limitar tanto como Cilk o poder de expressao de paralelismo, esta ferramenta permite ao programador criar threads externas a esta estrutura aninhada. Com uma interface de programacao totalmente diversa das anteriores, OpenMP e voltado para problemas onde ocorre paralelismo de dados, sendo seus programas caracterizados pela criacao, tambem aninhada, de lotes de trabalho. Seu nucleo de escalonamento considera a distribuicao da carga de trabalho contida neste lote. Operando, portanto, em rodadas de lotes de trabalhos recebidos. Dependencias entre os trabalhos nao sao consideradas, apenas o programador pode indicar que diferentes trabalhos, em um mesmo lote, possuem cargas computacionais diferentes para auxiliar nas heuristicas de escalonamento. Na Figura 1 sao apresentados os desempenhos, em termos de speedup (relacao entre o tempo de execucao do problema com uma thread e seu tempo de execucao paralelo) em uma arquitetura com oito cores. Por questoes de espaco, o grafico reflete o speedup apenas para o caso de execucao paralela com tambem oito threads. Figura 1. Grafico de speedup para o caso de oito threads. Observamos que, para uma aplicacao trivialmente paralelizavel, como o 3Sat, nao houve grande impacto do mecanismo de escalonamento e tambem as interfaces de programacao oferecidas pelas ferramentas nao impuseram nenhuma restricao a sua implementacao. No outro extremo, em aplicacoes como LU, em que o numero de dependencias entre threads e alto, tambem observamos que o nucleo de escalonamento nao possui margem de trabalho que permita diferenciar as ferramentas. Neste tipo de problema tambem notou-se uma maior dificuldade de desenvolvimento do programa em ferramentas vocacionadas ao paralelismo de dados, como OpenMP. Ja em aplicacoes onde existe uma estrutura regular na criacao de tarefas, como no calculo recursivo de Fibonacci, a heuristica de escalonamento adotada por Athreads, Cilk e TBB reflete em ganho de desempenho. Note-se que, quanto maior for a restricao imposta pela ferramenta para expressao do paralelismo (como em Cilk e TBB), maiores as chances de sucesso do escalonamento. Por outro lado, em Athreads, pequenas variacoes na ordem de criacao de threads, o que e permitido pela ferramenta, ocasionam impacto no desempenho obtido. Finalmente, no caso de um algoritmo de programacao dinâmica, como o S-W, encontramos dificuldades em modelar o problema considerando as diferentes interfaces de programacao utilizadas. No grafico e traduzido o desempenho obtido na melhor implementacao realizada ate o momento pelo grupo.


international symposium on computers and communications | 2009

AGRADC: An architecture for autonomous deployment and configuration of grid computing applications

Luciano Paschoal Gaspary; Weverton Luis da Costa Cordeiro; Sidnei Roberto Selzler Franco; Marinho P. Barcellos; Gerson Geraldo Homrich Cavalheiro

Deployment and configuration of grid computing applications are exhaustive and error-prone tasks, and represent a weak link of the lifecycle of grid applications. To address the problem, this paper proposes AGRADC, an architecture to instantiate grid applications on demand, which incorporates features from the Autonomic Computing paradigm. This architecture improves the grid application development process, providing tools to define a deployment flow, configuration parameters, and actions to be executed when adverse situations like faults arise.


distributed systems operations and management | 2006

A WSDM-based architecture for global usage characterization of grid computing infrastructures

Glauco Antonio Ludwig; Luciano Paschoal Gaspary; Gerson Geraldo Homrich Cavalheiro; Walfredo Cirne

Current solutions to characterize grid computing usage are limited in three important aspects. First, they do not provide a global, uniform view of the use of infrastructures comprised of heterogeneous grid middleware. Second, they do not allow the specification of policies to publicize the collected information. Third, they do not generate statistics about the applications that are executed on the grid. To fill this gap, we propose an architecture based on the Web Services Distributed Management standard and on access control policies to characterize global usage of grid computing infrastructures, even when such grids are formed by heterogeneous middleware packages. We introduce this architecture and present preliminary results obtained with a prototype.


international conference on e-business and telecommunication networks | 2005

On the Evaluation of a Secure Solution to Access 802.11 Networks

Fernando da Costa; Luciano Paschoal Gaspary; Jorge Luis Victória Barbosa; Gerson Geraldo Homrich Cavalheiro; Luciano Pfitscher; José Dirceu G. Ramos

Despite offering the possibility to develop and distribute a new set of applications to its users, the widespread and unrestricted use of mobile computing depends on the provisioning of a secure network environment. Regarding the communication established from mobile devices such as PDAs (Personal Digital Assistants), one of the most currently used standards is the IEEE 802.11b, which presents known security flaws. To overcome them, some alternative setups are commonly deployed, based on link, network, transport or application-layer. In this paper we evaluate the impact on data reception rate and energy consumption of IPSec-based PDAs access to 802.11b (WiFi) wireless LANs. As a result of this work we identify the overhead imposed by the security mechanisms and the capacity of the device to run CPU and network-intensive applications.


Mobile Computing Handbook | 2004

ISAM, Joining Context-Awareness and Mobility to Building Pervasive Applications.

Iara Augustin; Adenauer Yamin; Jorge L. V. Barbosa; Luciano Cavalheiro da Silva; Rodrigo Araújo Real; Gustavo Frainer; Gerson Geraldo Homrich Cavalheiro; Cláudio Fernando Resin Geyer

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Dive into the Gerson Geraldo Homrich Cavalheiro's collaboration.

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Luciano Paschoal Gaspary

Universidade do Vale do Rio dos Sinos

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Adenauer C. Yamin

Universidade Católica de Pelotas

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Jorge Luis Victória Barbosa

Universidade do Vale do Rio dos Sinos

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Cláudio Fernando Resin Geyer

Universidade Federal do Rio Grande do Sul

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Iara Augustin

Universidade Federal de Santa Maria

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Maurício L. Pilla

Universidade Católica de Pelotas

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Philippe Olivier Alexandre Navaux

Universidade Federal do Rio Grande do Sul

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Renata Reiser

Universidade Federal de Pelotas

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André Rauber Du Bois

Universidade Federal de Pelotas

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Glauco Antonio Ludwig

Universidade do Vale do Rio dos Sinos

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