Object-Oriented design and development dominates both commercial and open source software projects. One of the principal goals of object-oriented design is to aid reuse, and hence, reduce future maintenance efforts of software systems. However, the on-going maintenance of large-scale software systems (both changes and faults) continues to be a significant proportion of the lifecycle of the system and the total investment cost. Understanding and thus being able to predict - or even reduce - the impact of the contributing factors of future maintenance efforts of a software system is thus highly beneficial to software practitioners. In this Thesis we empirically study a large, commercial software system with the principal aim to determine the contributing factors to the change and fault propensity over a three-year period. We consider the object-oriented design context of the software, specifically its inheritance characteristics, coupling and cohesion properties, object-oriented design pattern participation, and size. We also explore the effect of refactoring and test classes in the software. Our results show that several aspects of the design context of a class have an impact to the change and fault-proneness of the software. Specifically, we show that classes with high afferent or efferent coupling are more change and fault-prone; we also identify a number of design patterns whose participants tend to have a higher change and fault propensity than non-participants and we identify a range of inheritance characteristics (in terms of depth of inheritance and number of children) that result in an increase to change and fault-proneness. Furthermore we show that refactoring is a commonly occurring maintenance activity, although it is largely limited to simpler types of refactorings. Finally, we provide some insight into the co-evolution of production and test code during refactoring.

As otimizações de um programa podem ser efetuadas no código intermediário gerado na fase de compilação, ou através da Performance Refactoring que consiste na inserção de otimizações diretamente no código fonte da aplicação. Na estrutura do código fonte, os laços de iteração possuem um importante impacto no desempenho da aplicação, pois consomem elevados tempos de execução, sendo assim, é fundamental que estes sejam alvo de otimizações. Uma das otimizações de laço é o Unroll and Jam, que aplica operações de reestruturação de laços aninhados, permitindo utilizar eficientemente a hierarquia de memória. Os passos desta otimização consistem em primeiramente desenrolar os laços a serem otimizados, e posteriormente fusioná-los formando um bloco único de instrução. Neste trabalho se propôs usar refatoração de código para automatizar o Unroll and Jam de laços em nível do código fonte, o que possibilita acumular os efeitos da otimização no programa original com as melhorias tradicionais propiciadas pelo compilador na fase de otimização do código intermediário. A implementação foi realizada com base nas estruturas da ferramenta Photran 7.0, que consiste em um ambiente de desenvolvimento integrado para a linguagem Fortran 77-2008. Os resultados de desempenho obtidos demonstraram que a utilização de Unroll and Jam através da Performance Refactoring, com diferentes níveis de otimização, obteve ganhos significativos de desempenho em comparação a otimização realizada pelo com- pilador da Intel. Deve-se destacar que a aplicação conjunta de ambas as técnicas de oti- mização, originou resultados melhores que a utilização de uma técnica somente. Como trabalhos futuros, é interessante que novas pesquisas possam ser realizadas na obtenção de índices de desenrolamento ótimos e na aplicação conjunta de outras abordagens de otimização. Também pode haver estudos que permitam que outras otimizações sejam aplicadas pela Performance Refactoring. / The optimizations of a program can be performed on the intermediate code, generated during compilation time, or through the Performance Refactoring that consists of insertion of optimizations directly in the source code of the application. In the source code structure, iteration loops have a major impact in the performance of the application because they are time-consuming code and, thus, an essential target of optimizations. One loop optimization is the Unroll and Jam that applies restructuring operations in nested loops allowing efficient usage of memory hierarchy. Its optimization steps are: to unroll the target loops, and to join them forming a single block of instruction. This work proposes the usage of refactoring to automate Unroll and Jam loops in source code level, allowing to accumulate the effects of optimization in the original pro- gram with the optimizations in the intermediate code by traditional compilers. The im- plementation was based on structures of Photran tool 7.0, which consists of an integrated development environment for Fortran 77-2008. The performance results using Unroll and Jam by Performance Refactoring with dif- ferent levels of unrolling, showed significant gains compared to the optimization per- formed by the Intel compiler. It should also be noted that the joint of both optimization techniques has led to better results than the use of an individual technique. As future works, new researches can be performed to obtain optimal rates of unrolling and to join the application of other optimization approaches. Furthermore, studies may search for optimizations to be applied by the Performance Refactoring.

Abstract not available

M. Tech. Information Networks / Code clone is a code portion in one source code fragment that is similar or identical to a code portion in another source code fragment. Clones in applications are inevitable within an organization's intranet. There are a great number of clone detection tools to help maintenance programmers to locate and refactor code clones where they exist. Currently clone detection process has not been explored fully to construct digital libraries to store clones for reuse and shareability. This is because most of clone detection techniques produce Indexed Statistical Reports as textual file showing related group of code fragments. Other techniques visualize clones to depict clones versions history as genealogies. Furthermore current techniques do not indicate the reusability and shareability worthiness of the detected clones in taxonomy. In this mini-dissertation a Clone Wrapper Detection Technique prototype is developed to detect and store commonly used structural clones into a Discoverable Digital Clone Library hosted in Fedora Repository. Stored clones metadata are then extracted to induce a Clone Family Tree Ontology of related class clones in a taxonomy based on Abstraction (inheritance and composition hierarchy) process.

No description available.

Software can be considered a live entity, as it undergoes many alterations throughout its lifecycle. Therefore, code can become rather complex and difficult to understand. More specifically in object-oriented systems, classes may become very large and less cohesive. In order to identify such problematic cases, existing approaches have proposed the use of cohesion metrics. While metrics can identify classes with low cohesion, they usually cannot identify new or independent concepts. In this work, we propose a class decomposition method using an clustering algorithm based on the Jaccard distance between class members. The methodology is able to identify new concepts and rank the solutions according to their impact on the design quality of the system. The methodology was evaluated in terms of assessment by designers, expert assessment and metrics. The evaluation showed the ability of the method to identify new recognizable concepts and improve the design quality of the underlying system.

Thesis (M.S.E.)--University of Wisconsin -- La Crosse, 2008. / Includes bibliographical references (p. 43).

Refactorings are structured changes to existing software that leave its externally observable behaviour unchanged. The intent is to improve readability, performance or other non-behavioural properties of a program. Agile software engineering processes stress the importance of refactoring to keep program code extensible and maintainable. Despite their apparent benefits, manual refactorings are time-consuming and prone to introducing unintended side effects. Research efforts seek to support and automate refactoring tasks to overcome these limitations. Current research in automatic refactoring, as well as state-of-the-art automated refactoring tools, frequently rely on syntax-driven approaches. They focus on transformations which can be safely performed using only syntactic information about a program or act overly conservative when knowledge about program semantics is required. In this thesis we explore semantics-driven refactoring, which enables much more sophisticated refactoring schemata. Our semantics-driven refactorings rely on formal verification algorithms to reason over a program's behaviour, and we conjecture they are more precise and can handle more complex code scenarios than syntax-driven ones. For this purpose, we present and implement a program synthesis algorithm based on the CEGIS paradigm and demonstrate that it can be applied to a diverse set of applications. Our synthesiser relies on the bounded model checker CBMC as an oracle and is based on an earlier research prototype called Kalashnikov. We further define our Java Stream Theory (JST) which allows us to reason over a set of interesting semantic refactorings. Both solutions are combined into an automated semantic refactoring decision procedure, reasoning over program behaviours, and searching the space of possible refactorings using program synthesis. We provide experimental evidence to support our conjecture that semanticsdriven refactorings exceed syntax-driven approaches in precision and scope.

As otimizações de um programa podem ser efetuadas no código intermediário gerado na fase de compilação, ou através da Performance Refactoring que consiste na inserção de otimizações diretamente no código fonte da aplicação. Na estrutura do código fonte, os laços de iteração possuem um importante impacto no desempenho da aplicação, pois consomem elevados tempos de execução, sendo assim, é fundamental que estes sejam alvo de otimizações. Uma das otimizações de laço é o Unroll and Jam, que aplica operações de reestruturação de laços aninhados, permitindo utilizar eficientemente a hierarquia de memória. Os passos desta otimização consistem em primeiramente desenrolar os laços a serem otimizados, e posteriormente fusioná-los formando um bloco único de instrução. Neste trabalho se propôs usar refatoração de código para automatizar o Unroll and Jam de laços em nível do código fonte, o que possibilita acumular os efeitos da otimização no programa original com as melhorias tradicionais propiciadas pelo compilador na fase de otimização do código intermediário. A implementação foi realizada com base nas estruturas da ferramenta Photran 7.0, que consiste em um ambiente de desenvolvimento integrado para a linguagem Fortran 77-2008. Os resultados de desempenho obtidos demonstraram que a utilização de Unroll and Jam através da Performance Refactoring, com diferentes níveis de otimização, obteve ganhos significativos de desempenho em comparação a otimização realizada pelo com- pilador da Intel. Deve-se destacar que a aplicação conjunta de ambas as técnicas de oti- mização, originou resultados melhores que a utilização de uma técnica somente. Como trabalhos futuros, é interessante que novas pesquisas possam ser realizadas na obtenção de índices de desenrolamento ótimos e na aplicação conjunta de outras abordagens de otimização. Também pode haver estudos que permitam que outras otimizações sejam aplicadas pela Performance Refactoring. / The optimizations of a program can be performed on the intermediate code, generated during compilation time, or through the Performance Refactoring that consists of insertion of optimizations directly in the source code of the application. In the source code structure, iteration loops have a major impact in the performance of the application because they are time-consuming code and, thus, an essential target of optimizations. One loop optimization is the Unroll and Jam that applies restructuring operations in nested loops allowing efficient usage of memory hierarchy. Its optimization steps are: to unroll the target loops, and to join them forming a single block of instruction. This work proposes the usage of refactoring to automate Unroll and Jam loops in source code level, allowing to accumulate the effects of optimization in the original pro- gram with the optimizations in the intermediate code by traditional compilers. The im- plementation was based on structures of Photran tool 7.0, which consists of an integrated development environment for Fortran 77-2008. The performance results using Unroll and Jam by Performance Refactoring with dif- ferent levels of unrolling, showed significant gains compared to the optimization per- formed by the Intel compiler. It should also be noted that the joint of both optimization techniques has led to better results than the use of an individual technique. As future works, new researches can be performed to obtain optimal rates of unrolling and to join the application of other optimization approaches. Furthermore, studies may search for optimizations to be applied by the Performance Refactoring.

As otimizações de um programa podem ser efetuadas no código intermediário gerado na fase de compilação, ou através da Performance Refactoring que consiste na inserção de otimizações diretamente no código fonte da aplicação. Na estrutura do código fonte, os laços de iteração possuem um importante impacto no desempenho da aplicação, pois consomem elevados tempos de execução, sendo assim, é fundamental que estes sejam alvo de otimizações. Uma das otimizações de laço é o Unroll and Jam, que aplica operações de reestruturação de laços aninhados, permitindo utilizar eficientemente a hierarquia de memória. Os passos desta otimização consistem em primeiramente desenrolar os laços a serem otimizados, e posteriormente fusioná-los formando um bloco único de instrução. Neste trabalho se propôs usar refatoração de código para automatizar o Unroll and Jam de laços em nível do código fonte, o que possibilita acumular os efeitos da otimização no programa original com as melhorias tradicionais propiciadas pelo compilador na fase de otimização do código intermediário. A implementação foi realizada com base nas estruturas da ferramenta Photran 7.0, que consiste em um ambiente de desenvolvimento integrado para a linguagem Fortran 77-2008. Os resultados de desempenho obtidos demonstraram que a utilização de Unroll and Jam através da Performance Refactoring, com diferentes níveis de otimização, obteve ganhos significativos de desempenho em comparação a otimização realizada pelo com- pilador da Intel. Deve-se destacar que a aplicação conjunta de ambas as técnicas de oti- mização, originou resultados melhores que a utilização de uma técnica somente. Como trabalhos futuros, é interessante que novas pesquisas possam ser realizadas na obtenção de índices de desenrolamento ótimos e na aplicação conjunta de outras abordagens de otimização. Também pode haver estudos que permitam que outras otimizações sejam aplicadas pela Performance Refactoring. / The optimizations of a program can be performed on the intermediate code, generated during compilation time, or through the Performance Refactoring that consists of insertion of optimizations directly in the source code of the application. In the source code structure, iteration loops have a major impact in the performance of the application because they are time-consuming code and, thus, an essential target of optimizations. One loop optimization is the Unroll and Jam that applies restructuring operations in nested loops allowing efficient usage of memory hierarchy. Its optimization steps are: to unroll the target loops, and to join them forming a single block of instruction. This work proposes the usage of refactoring to automate Unroll and Jam loops in source code level, allowing to accumulate the effects of optimization in the original pro- gram with the optimizations in the intermediate code by traditional compilers. The im- plementation was based on structures of Photran tool 7.0, which consists of an integrated development environment for Fortran 77-2008. The performance results using Unroll and Jam by Performance Refactoring with dif- ferent levels of unrolling, showed significant gains compared to the optimization per- formed by the Intel compiler. It should also be noted that the joint of both optimization techniques has led to better results than the use of an individual technique. As future works, new researches can be performed to obtain optimal rates of unrolling and to join the application of other optimization approaches. Furthermore, studies may search for optimizations to be applied by the Performance Refactoring.