A User-Centric Perspective on Parallel Programming with Focus on OpenMP

The process of developing software that takes advantage of multiple processors is commonly referred to as parallel programming. For various reasons, this process is much harder than the sequential case. For decades, parallel programming has been a problem for a small niche only: engineers working on parallelizing mostly numerical applications in High Performance Computing. This has changed with the advent of multi-core processors in mainstream computer architectures. Parallel programming in our days becomes a problem for a much larger group of developers. The main objective of this thesis was to find ways to make parallel programming easier for them. Different aims were identified in order to reach the objective: research the state of the art of parallel programming today, improve the education of software developers about the topic, and provide programmers with powerful abstractions to make their work easier. To reach these aims, several key steps were taken. To start with, a survey was conducted among parallel programmers to find out about the state of the art. More than 250 people participated, yielding results about the parallel programming systems and languages in use, as well as about common problems with these systems. Furthermore, a study was conducted in university classes on parallel programming. It resulted in a list of frequently made mistakes that were analyzed and used to create a programmers' checklist to avoid them in the future. For programmers' education, an online resource was setup to collect experiences and knowledge in the field of parallel programming - called the Parawiki. Another key step in this direction was the creation of the Thinking Parallel weblog, where more than 50.000 readers to date have read essays on the topic. For the third aim (powerful abstractions), it was decided to concentrate on one parallel programming system: OpenMP. Its ease of use and high level of abstraction were the most important reasons for this decision. Two different research directions were pursued. The first one resulted in a parallel library called AthenaMP. It contains so-called generic components, derived from design patterns for parallel programming. These include functionality to enhance the locks provided by OpenMP, to perform operations on large amounts of data (data-parallel programming), and to enable the implementation of irregular algorithms using task pools. AthenaMP itself serves a triple role: the components are well-documented and can be used directly in programs, it enables developers to study the source code and learn from it, and it is possible for compiler writers to use it as a testing ground for their OpenMP compilers. The second research direction was targeted at changing the OpenMP specification to make the system more powerful. The main contributions here were a proposal to enable thread-cancellation and a proposal to avoid busy waiting. Both were implemented in a research compiler, shown to be useful in example applications, and proposed to the OpenMP Language Committee.

Universität und solidarische Ökonomie

RESUMO: A economia solidária é aqui apresentada como um movimento social emancipatório e como uma das formas de resistências das trabalhadoras e trabalhadores ao modelo de desenvolvimento capitalista. O movimento contemporâneo de economia solidária abrange o processo de produção, comercialização e finanças. A economia solidária é caracterizada pela posse coletiva dos meios de produção e pelo controle dos trabalhadores dos empreendimentos através de autogestão, cooperação e solidariedade. Os empreendimentos econômicos solidários se organizam sob a forma de cooperativas, associações e grupos informais. Um dos maiores desafios da economia solidária está no campo educativo, porque impõe a desconstrução dos princípios individualistas e privatistas preponderantes na maioria das relações econômicas, e exige a construção de outra cultura pautada na solidariedade. Nesse sentido, a pesquisa realizada, tem como objeto de estudo as metodologias de incubação fomentadas pelas universidades nas ações de economia solidária. Para isso, analisamos as experiências da Incubadora de Economia Solidária da Universidade Federal da Paraíba - Brasil e da Incubadora na Universidade de Kassel- Alemanha – Verein für Solidarische Ökonomie e.V. A pesquisa buscou conhecer e analisar as práticas de incubagem das universidades na economia solidária, como processos de mudança social. A coleta de informações foi realizada, tendo por base, uma revisão bibliográfica, relatórios das Incubadoras, registros fotográficos, observação participante e entrevistas semi-estruturadas. Os resultados da análise indicam que as metodologias de incubação na economia solidaria, por terem um caráter aberto e participativo, por considerarem os condicionamentos históricos e as diferentes culturas, fazem-nas portadoras de mudanças sociais. Esta metodologia pode ser utilizada por diferentes atores, em lugares e situações distintas. A pesquisa indica ainda, a centralidade da questão ecológica como elemento que poderá unificar o movimento internacional de economia solidária.