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Developers often spend much of their valuable development time on software debugging and bug finding. In addition, software defects cost software industry as a whole hundreds or even a trillion of US dollars. As a result, many fault localization (FL) techniques for localizing bugs automatically, have been proposed. Despite its popularity, adopting FL in industrial environments has been impractical due to its undesirable accuracy and high runtime overhead cost. Motivated by the real-world challenges of FL applicability, this dissertation addresses these issues by proposing two main enhancements to the existing FL. First, it explores different strategies to combine a variety of program execution information with Information Retrieval-based fault localization (IRFL) techniques to increase FL's accuracy. Second, this dissertation research invents and experiments with the unconventional techniques of Instant Fault Localization (IFL) using the innovative concept of triggering modes. Our empirical evaluations of the proposed approaches on various types of bugs in a real software development environment shows that both FL's accuracy is increased and runtime is reduced significantly. We find that execution information helps increase IRFL's Top-10 by 17–33% at the class level, and 62–100% at the method level. Another finding is that IFL achieves as much as 100% runtime cost reduction while gaining comparable or better accuracy. For example, on single-location bugs, IFL scores 73% MAP, compared with 56% of the conventional approach. For multi-location bugs, IFL's Top-1 performance on real bugs is 22%, just right below 24% that of the existing FL approaches. We hope the results and findings from this dissertation help make the adaptation of FL in the real-world industry more practical and prevalent. / Doctor of Philosophy / In software engineering, fault localization (FL) is a popular technique to automatically find software bugs, which cost a huge loss of hundreds of billions of US dollars on the software industry. Despite its high demanding and popularity, adopting FL in industrial software companies remains impractical. To help resolve this applicability problem, this dissertation proposed enhanced techniques to localize bugs more accurately and with less overhead runtime expenses. As a result, FL becomes more practical and efficient for software companies.

Fault localization is the process of realizing the true source of a failure from a set of collected failure notifications. Isolating failure recovery within the network optical domain is necessary to resolve alarm storm problems. The introduction of the monitoring trail (m-trail) has been proven to deliver better performance by employing monitoring resources in a form of optical trails - a monitoring framework that generalizes all the previously reported counterparts. In this dissertation, the m-trail design is explored and a focus is given to the analysis on using m-trails with established lightpaths to achieve fault localization. This process saves network resources by reducing the number of the m-trails required for fault localization and therefore the number of wavelengths used in the network. A novel approach based on Geographic Midpoint Technique, an adapted version of the Chinese Postman’s Problem (CPP) solution and an adapted version of the Traveling Salesman’s Problem (TSP) solution algorithms is introduced. The desirable features of network architectures and the enabling of innovative technologies for delivering future millimeter-waveband (mm-WB) Radio-over-Fiber (RoF) systems for wireless services integrated in a Dense Wavelength Division Multiplexing (DWDM) is proposed in this dissertation. For the conceptual illustration, a DWDM RoF system with channel spacing of 12.5 GHz is considered. The mm-WB Radio Frequency (RF) signal is obtained at each Optical Network Unit (ONU) by simultaneously using optical heterodyning photo detection between two optical carriers. The generated RF modulated signal has a frequency of 12.5 GHz. This RoF system is easy, cost-effective, resistant to laser phase noise and also reduces maintenance needs, in principle. A revision of related RoF network proposals and experiments is also included. A number of models for Passive Optical Networks (PON)/ RoF-PON that combine both innovative and existing ideas along with a number of solutions for m-trail design problem of these models are proposed. The comparison between these models uses the expected survivability function which proved that these models are liable to be implemented in the new and existing PON/ RoF-PON systems. This dissertation is followed by recommendation of possible directions for future research in this area.

Debugging is one of the most time-consuming activities in software development. Several fault localization techniques have been proposed in the last years, aiming to reduce development costs. A promising approach, called Spectrum-based Fault localization (SFL), consists of techniques that provide a list of suspicious program elements (e.g., statements, basic blocks, methods) more likely to be faulty. Developers should inspect a suspiciousness list to search for faults. However, these fault localization techniques are not yet used in practice. These techniques are based on assumptions about the developer\'s behavior when inspecting such lists that may not hold in practice. A developer is supposed to inspect an SFL list from the most to the least suspicious program elements (e.g., statements) until reaching the faulty one. This assumption leads to some implications: the techniques are assessed only by the position of a bug in a list; a bug is deemed as found when the faulty element is reached. SFL techniques should pinpoint the faulty program elements among the first picks to be useful in practice. Most techniques use ranking metrics to assign suspiciousness values to program elements executed by the tests. These ranking metrics have presented similar modest results, which indicates the need for different strategies to improve the effectiveness of SFL. Moreover, most techniques use only control-flow spectra due to the high execution costs associated with other spectra, such as data-flow. Also, little research has investigated the use of SFL techniques by practitioners. Understanding how developers use SFL may help to clarify the theoretical assumptions about their behavior, which in turn can collaborate with the proposal of techniques more feasible for practical use. Therefore, user studies are a valuable tool for the development of the area. The goal of this thesis research was to propose strategies to improve spectrum-based fault localization, focusing on its practical use. This thesis presents the following contributions. First, we investigate strategies to provide contextual information for SFL. These strategies helped to reduce the amount of code to be inspected until reaching the faults. Second, we carried out a user study to understand how developers use SFL in practice. The results show that developers can benefit from SFL to locate bugs. Third, we explore the use of data-flow spectrum for SFL. Data-flow spectrum singles out faults significantly better than control-flow spectrum, improving the fault localization effectiveness. / Depuração é uma das atividades mais custosas durante o desenvolvimento de programas. Diversas técnicas de localização de defeitos têm sido propostas nos últimos anos com o objetivo de reduzir custos de desenvolvimento. Uma abordagem promissora, chamada Localização de Defeitos baseada em Espectro (LDE), é formada por técnicas que fornecem listas contendo elementos de código (comandos, blocos básicos, métodos) mais suspeitos de conter defeitos. Desenvolvedores deveriam inspecionar uma lista de suspeição para procurar por defeitos. No entanto, essas técnicas de localização de defeitos ainda não são usadas na prática. Essas técnicas baseiam-se em suposições sobre o comportamento de desenvolvedores durante a inspeção de tais listas que podem não ocorrer na prática. Um desenvolvedor supostamente inspeciona uma lista de LDE a partir do elemento mais suspeito para o menos suspeito até atingir o elemento defeituoso. Essa suposição leva a algumas implicações: as técnicas são avaliadas somente pela posição dos defeitos nas listas; um defeito é considerado como encontrado quando o elemento defeituoso é atingido. Técnicas de LDE deveriam posicionar os elementos de código defeituosos entre as primeiras posições para serem úteis na prática. A maioria das técnicas usa métricas de ranqueamento para atribuir valores de suspeição aos elementos executados pelos testes. Essas métricas de ranqueamento têm apresentado resultados semelhantes, o que indica a necessidade de estratégias diferentes para melhorar a eficácia de LDE. Além disso, a maioria das técnicas usa somente espectros de fluxo de controle devido ao alto custo de execução associado a outros espectros, tais como fluxo de dados. Também, poucas pesquisas têm investigado o uso de técnicas de LDE por programadores. Entender como desenvolvedores usam LDE pode ajudar a esclarecer as suposições teóricas sobre seu comportamento, o que por sua vez pode para colaborar para a proposição de técnicas mais viáveis para uso prático. Portanto, estudos com usuários são importantes para o desenvolvimento da área. O objetivo desta pesquisa de doutorado foi propor estratégias para melhorar a localização de defeitos baseada em espectro focando em seu uso prático. Esta tese apresenta as seguintes contribuições originais. Primeiro, nós investigamos estratégias para fornecer informação de contexto para LDE. Essas estratégias ajudaram a reduzir quantidade de código a ser inspecionado até atingir os defeitos. Segundo, nós realizamos um estudo com usuários para entender como desenvolvedores usam LDE na prática. Os resultados mostram que desenvolvedores podem beneficiar-se de LDE para localizar defeitos. Terceiro, nós exploramos o uso de espectros de fluxo de dados para LDE. Mostramos que o espectro de fluxo de dados seleciona defeitos significamente melhor que espectro de fluxo de controle, aumentando a eficácia de localização de defeitos.

Fault localization is the process of realizing the true source of a failure from a set of collected failure notifications. Isolating failure recovery within the network optical domain is necessary to resolve alarm storm problems. The introduction of the monitoring trail (m-trail) has been proven to deliver better performance by employing monitoring resources in a form of optical trails - a monitoring framework that generalizes all the previously reported counterparts. In this dissertation, the m-trail design is explored and a focus is given to the analysis on using m-trails with established lightpaths to achieve fault localization. This process saves network resources by reducing the number of the m-trails required for fault localization and therefore the number of wavelengths used in the network. A novel approach based on Geographic Midpoint Technique, an adapted version of the Chinese Postman’s Problem (CPP) solution and an adapted version of the Traveling Salesman’s Problem (TSP) solution algorithms is introduced. The desirable features of network architectures and the enabling of innovative technologies for delivering future millimeter-waveband (mm-WB) Radio-over-Fiber (RoF) systems for wireless services integrated in a Dense Wavelength Division Multiplexing (DWDM) is proposed in this dissertation. For the conceptual illustration, a DWDM RoF system with channel spacing of 12.5 GHz is considered. The mm-WB Radio Frequency (RF) signal is obtained at each Optical Network Unit (ONU) by simultaneously using optical heterodyning photo detection between two optical carriers. The generated RF modulated signal has a frequency of 12.5 GHz. This RoF system is easy, cost-effective, resistant to laser phase noise and also reduces maintenance needs, in principle. A revision of related RoF network proposals and experiments is also included. A number of models for Passive Optical Networks (PON)/ RoF-PON that combine both innovative and existing ideas along with a number of solutions for m-trail design problem of these models are proposed. The comparison between these models uses the expected survivability function which proved that these models are liable to be implemented in the new and existing PON/ RoF-PON systems. This dissertation is followed by recommendation of possible directions for future research in this area.

I samband med att mellanspänningsnätet kablifieras ökar också kraven vad gäller fellokalisering. För att hålla avbrottstiderna i nätet korta är effektiv felsökning erforderlig. Detta arbete syftar till att kartlägga och redogöra för begränsande faktorer som finns vid fellokalisering med fokus på pulsekometoden. Uppdraget utförs tillsammans med Vattenfall Eldistribution AB. Det har uppdagats problem gällande fellokalisering på mellanspänningskablar med pulsekometoden. Ett flertal faktorer bidrar till denna problematik. Resultatet från studien visar att kabelkonstruktionen är en betydande del i det som begränsar pulsekometodens användningsområden och funktionalitet. Rapporten redogör för grundläggande information kring konstruktion och typer av mellanspänningskablar. Kartläggningen uppvisar hur vattenträd påverkar en kabel negativt. Allmänt redogörs för vad som orsakar vattenträd samt vilka avhjälpande åtgärder som vidtas; trippelextrudering samt mantel- och isolationsprovning. Vidare beskrivs olika feltyper, kabeltyper, kabelgenerationer samt instrument- och metodtyper som alla är påverkande faktorer vid fellokalisering. Dokumentering är i högsta grad väsentligt för en lyckad felsökningsprocedur, vilket klarläggs i rapporten. Utöver dokumentation redogörs för hur kabelns kondition kan påverka felsökningsresultatet. Ett antal mätmetoder och mätinstrument finns till förfogande vid felsökning och provning. Alla har sina egna för- respektive nackdelar. De har även tillhörande användningsområden. Pulsekometerns grundfunktion studeras och förklaras. De övriga mätmetoderna, som används vid fellokalisering och provning, redogörs för endast generellt / As the medium voltage network cables in Sweden is buried down in the earth, the demand of fault localization expertise increases. To keep downtimes in the network short, the importance of effective fault localization is necessary. This work is aimed to map and visualize limiting factors within fault localization with focus on the TDR - Time Domain Reflectometry. This work is a collaboration with Vattenfall Eldistribution AB. Problems with fault localization on medium voltage cables with the TDR have been detected. A multiple factors are contributing to this problem. The results of this study show that the cable construction is a significant part in which extent the TDR can be used. The report are also accounting for basic information about construction and types. The mapping also illustrates water treeing and how it affects cables in a negative way. Visualization of what causes water treeing and several actions such as triple extrusion, jacket testing and insulation testing is included in the essay. Further information about fault types, cable types, cable generations, instrument types and method types is given. All of them are affecting factors within the area of fault localization. Documentation is highly important for a successful fault localization procedure, which is clarified in the report. Besides documentation the cable condition and the influence on it affecting the result of fault localization is stated. A number of measuring methods and instruments are available to use when fault localization and testing are occurring. Every instrument has their own advantages and disadvantages. They also have their own respective area of usage. The basic principle of TDR is studied and explained accordingly. The other measuring methods, which are used in fault localization and testing, are shown more generally

Souvent, dû à l'aspect cyclique des programmes embarqués, les traces de microcontrôleurs contiennent beaucoup de données. De plus, dans notre contexte de travail, pour l'analyse du comportement, une seule trace se terminant sur une défaillance est disponible. L'objectif du travail présenté dans cette thèse est d'aider à l'analyse de trace de microcontrôleurs. La première contribution de cette thèse concerne l'identification de cycles, ainsi que la génération d'une description pertinente de la trace. La détection de cycles repose sur l'identification du loop-header. La description proposée à l'ingénieur est produite en utilisant la compression basée sur la génération d'une grammaire. Cette dernière permet la détection de répétitions dans la trace. La seconde contribution concerne la localisation de faute(s). Elle est basée sur l'analogie entre les exécutions du programme et les cycles. Ainsi, pour aider dans l'analyse de la trace, nous avons adapté des techniques de localisation de faute(s) basée sur l'utilisation de spectres. Nous avons aussi défini un processus de filtrage permettant de réduire le nombre de cycles à utiliser pour la localisation de faute(s). Notre troisième contribution concerne l'aide à l'analyse des cas où les multiples cycles d'une même exécution interagissent entre eux. Ainsi, pour faire de la localisation de faute(s) pour ce type de cas, nous nous intéressons à la recherche de règles d'association. Le groupement des cycles en deux ensembles (cycles suspects et cycles corrects) pour la recherche de règles d'association, permet de définir les comportements jugés correctes et ceux jugés comme suspects. Ainsi, pour la localisation de faute(s), nous proposons à l'ingénieur un diagnostic basé sur l'analyse des règles d'association selon leurs degrés de suspicion. Cette thèse présente également les évaluations menées, permettant de mesurer l'efficacité de chacune des contributions discutées, et notre outil CoMET. Les résultats de ces évaluations montrent l'efficacité de notre travail d'aide à l'analyse de traces de microcontrôleurs. / The microcontroller traces contain a huge amount of information. This is mainly due to the cyclic aspect of embedded programs. In addition, in our context, a single trace that ends at the failure is used to analyze the behavior of the microcontroller . The work presented in this thesis aims to assit in analysis of microcontroller traces. The first contribution of this thesis concerns the identification of cycles and the generation of a relevant description of the trace. The detection of cycles is based on the identification of the loop-header. The description of the trace is generated using Grammar-Based Compression, which allows the detection of repetitions in the trace. The second contribution concerns the fault localization. Our approach is based on the analogy between executions and cycles. Thus, this contribution is an adaptation of some spectrum-based fault localization techniques. This second contribution also defines a filtering process, which aims to reduce the number of cycles used by the fault localization. The third contribution considers that the multiple cycles of a same execution can interact together. Our fault localization for this type of cases is based on the use of association rules. Grouping cycles in two sets (suspect cycles and correct cycles), and searching for association rules using those two sets, helps to define the behaviors considered as corrects and those considered as suspects. This thesis presents the experimental evaluations concerning our contributions, and our tool CoMET.

This paper addresses the question formulation “Is it possible to implement automated testing in an existing client-server game in order to pinpoint faults and achieve credibility to tests?” The gaming industry’s goal, in most cases, is to release games that appeal to both their financial goals and the enjoyment factor of the players. In order to fulfill these goals, the game will need to function properly and the process to assure this is testing the game to find possible faults. This process is time and cost consuming in an exponential rate in accordance to game extensiveness, which makes this problem a very important decision in the process of development. The problem is most commonly tackled by using massive manual testing session, called alpha or beta sessions. In these session the game is at an early stage of development and gets released to a set player base to test and report issues encountered. We believe that the process of testing games could be more effective by utilizing automated testing. This thesis will investigate the possibilities to our claim. The result is a visual representation of the tests we managed to apply, while focusing on the client-server connectivity of Quake 3 and a graph of measurements for our improvised fault localization. This paper describes a solution in form of automated tests within a existing client-server game and a start to what could be early stages of a pattern obtained throughout this project.

Fault localization is the process of realizing the true source of a failure from a set of collected failure notifications. Isolating failure recovery within the network optical domain is necessary to resolve alarm storm problems. The introduction of the monitoring trail (m-trail) has been proven to deliver better performance by employing monitoring resources in a form of optical trails - a monitoring framework that generalizes all the previously reported counterparts. In this dissertation, the m-trail design is explored and a focus is given to the analysis on using m-trails with established lightpaths to achieve fault localization. This process saves network resources by reducing the number of the m-trails required for fault localization and therefore the number of wavelengths used in the network. A novel approach based on Geographic Midpoint Technique, an adapted version of the Chinese Postman’s Problem (CPP) solution and an adapted version of the Traveling Salesman’s Problem (TSP) solution algorithms is introduced. The desirable features of network architectures and the enabling of innovative technologies for delivering future millimeter-waveband (mm-WB) Radio-over-Fiber (RoF) systems for wireless services integrated in a Dense Wavelength Division Multiplexing (DWDM) is proposed in this dissertation. For the conceptual illustration, a DWDM RoF system with channel spacing of 12.5 GHz is considered. The mm-WB Radio Frequency (RF) signal is obtained at each Optical Network Unit (ONU) by simultaneously using optical heterodyning photo detection between two optical carriers. The generated RF modulated signal has a frequency of 12.5 GHz. This RoF system is easy, cost-effective, resistant to laser phase noise and also reduces maintenance needs, in principle. A revision of related RoF network proposals and experiments is also included. A number of models for Passive Optical Networks (PON)/ RoF-PON that combine both innovative and existing ideas along with a number of solutions for m-trail design problem of these models are proposed. The comparison between these models uses the expected survivability function which proved that these models are liable to be implemented in the new and existing PON/ RoF-PON systems. This dissertation is followed by recommendation of possible directions for future research in this area.