Inter-package conflicts require the presence of two or more packages in a particular configuration, and thus tend to be harder to detect and localize than conventional (intra-package) defects. Hundreds of such inter-package conflicts go undetected by the normal testing and distribution process until they are later reported by a user. The reason for this is that current meta-data is not fine-grained and accurate enough to cover all common types of conflicts. A case study of inter-package conflicts in Debian has shown that with more detailed package meta-data, at least one third of all package conflicts could be prevented relatively easily, while another one third could be found by targeted testing of packages that share common resources or characteristics. This paper reports the case study and proposes ideas to detect inter-package conflicts in the future.
Seminal work by Mancinelli et. al @cite_1 has shown how to encode the installability problem for software packages as a SAT problem, established the (NP-Hard) complexity of the problem, and shown applications of the encoding to improve the quality of package repositories by avoiding non installable packages. Based on the same formalization, various quality metrics have been established, such as strong dependency and sensitivity @cite_15 (to evaluate the importance'' of a package in a given repository) and strong conflicts @cite_7 (to pinpoint packages which might hinder the installation of several other packages). In the same vein, package meta-data have also been used to predict future (non) installability of software packages @cite_3 . The abundance of studies that rely on package meta-data testifies the importance of the correctness of those meta-data.
@cite_15 @cite_3 @cite_1 @cite_7
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There are lots of different software metrics discovered and used for defect prediction in the literature. Instead of dealing with so many metrics, it would be practical and easy if we could determine the set of metrics that are most important and focus on them more to predict defectiveness. We use Bayesian networks to determine the probabilistic influential relationships among software metrics and defect proneness. In addition to the metrics used in Promise data repository, we define two more metrics, i.e. NOD for the number of developers and LOCQ for the source code quality. We extract these metrics by inspecting the source code repositories of the selected Promise data repository data sets. At the end of our modeling, we learn the marginal defect proneness probability of the whole software system, the set of most effective metrics, and the influential relationships among metrics and defectiveness. Our experiments on nine open source Promise data repository data sets show that response for class (RFC), lines of code (LOC), and lack of coding quality (LOCQ) are the most effective metrics whereas coupling between objects (CBO), weighted method per class (WMC), and lack of cohesion of methods (LCOM) are less effective metrics on defect proneness. Furthermore, number of children (NOC) and depth of inheritance tree (DIT) have very limited effect and are untrustworthy. On the other hand, based on the experiments on Poi, Tomcat, and Xalan data sets, we observe that there is a positive correlation between the number of developers (NOD) and the level of defectiveness. However, further investigation involving a greater number of projects is needed to confirm our findings. Software testing of applications in fields like scientific computing, simulation, machine learning, etc. is particularly challenging because many applications in these domains have no reliable “test oracle” to indicate whether the program’s output is correct when given arbitrary input. A common approach to testing such applications has been to use a “pseudo-oracle”, in which multiple independently-developed implementations of an algorithm process an input and the results are compared: if the results are not the same, then at least one of the implementations contains a defect. Other approaches include the use of program invariants, formal specification languages, trace and log file analysis, and metamorphic testing. In this paper, we present the results of two empirical studies in which we compare the effectiveness of some of these approaches, including metamorphic testing and runtime assertion checking. These results demonstrate that metamorphic testing is generally more effective at revealing defects in applications without test oracles in various application domains, including non-deterministic programs. We also analyze the results in terms of the software development process, and discuss suggestions for both practitioners and researchers who need to test software without the help of a test oracle. Software defect prediction, which predicts defective code regions, can help developers find bugs and prioritize their testing efforts. To build accurate prediction models, previous studies focus on manually designing features that encode the characteristics of programs and exploring different machine learning algorithms. Existing traditional features often fail to capture the semantic differences of programs, and such a capability is needed for building accurate prediction models. To bridge the gap between programs' semantics and defect prediction features, this paper proposes to leverage a powerful representation-learning algorithm, deep learning, to learn semantic representation of programs automatically from source code. Specifically, we leverage Deep Belief Network (DBN) to automatically learn semantic features from token vectors extracted from programs' Abstract Syntax Trees (ASTs). Our evaluation on ten open source projects shows that our automatically learned semantic features significantly improve both within-project defect prediction (WPDP) and cross-project defect prediction (CPDP) compared to traditional features. Our semantic features improve WPDP on average by 14.7 in precision, 11.5 in recall, and 14.2 in F1. For CPDP, our semantic features based approach outperforms the state-of-the-art technique TCA+ with traditional features by 8.9 in F1. Software and systems traceability is widely accepted as an essential element for supporting many software development tasks. Today's version control systems provide inbuilt features that allow developers to tag each commit with one or more issue ID, thereby providing the building blocks from which project-wide traceability can be established between feature requests, bug fixes, commits, source code, and specific developers. However, our analysis of six open source projects showed that on average only 60 of the commits were linked to specific issues. Without these fundamental links the entire set of project-wide links will be incomplete, and therefore not trustworthy. In this paper we address the fundamental problem of missing links between commits and issues. Our approach leverages a combination of process and text-related features characterizing issues and code changes to train a classifier to identify missing issue tags in commit messages, thereby generating the missing links. We conducted a series of experiments to evaluate our approach against six open source projects and showed that it was able to effectively recommend links for tagging issues at an average of 96 recall and 33 precision. In a related task for augmenting a set of existing trace links, the classifier returned precision at levels greater than 89 in all projects and recall of 50 . SUMMARY Substantial research in software engineering focuses on understanding the dynamic nature of software systems in order to improve software maintenance and program comprehension. This research typically makes use of automated instrumentation and profiling techniques after the fact, that is, without considering domain knowledge. In this paper, we examine another source of dynamic information that is generated from statements that have been inserted into the code base during development to draw the system administrators' attention to important run-time phenomena. We call this source communicated information (CI). Examples of CI include execution logs and system events. The availability of CI has sparked the development of an ecosystem of Log Processing Apps (LPAs) that surround the software system under analysis to monitor and document various run-time constraints. The dependence of LPAs on the timeliness, accuracy and granularity of the CI means that it is important to understand the nature of CI and how it evolves over time, both qualitatively and quantitatively. Yet, to our knowledge, little empirical analysis has been performed on CI and its evolution. In a case study on two large open source and one industrial software systems, we explore the evolution of CI by mining the execution logs of these systems and the logging statements in the source code. Our study illustrates the need for better traceability between CI and the LPAs that analyze the CI. In particular, we find that the CI changes at a high rate across versions, which could lead to fragile LPAs. We found that up to 70 of these changes could have been avoided and the impact of 15 to 80 of the changes can be controlled through the use of robust analysis techniques by LPAs. We also found that LPAs that track implementation-level CI (e.g. performance analysis) and the LPAs that monitor error messages (system health monitoring) are more fragile than LPAs that track domain-level CI (e.g. workload modelling), because the latter CI tends to be long-lived. Copyright © 2013 John Wiley & Sons, Ltd. Much of the software we use for everyday purposes incorporates elements developed and maintained by someone other than the developer. These elements include not only code and databases but also dynamic data feeds from online data sources. Although everyday software is not mission critical, it must be dependable enough for practical use. This is limited by the dependability of the incorporated elements. It is particularly difficult to evaluate the dependability of dynamic data feeds, because they may be changed by their proprietors as they are used. Further, the specifications of these data feeds are often even sketchier than the specifications of software components. We demonstrate a method of inferring invariants about the normal behavior of dynamic data feeds. We use these invariants as proxies for specifications to perform on-going detection of anomalies in the data feed. We show the feasibility of our approach and demonstrate its usefulness for semantic anomaly detection: identifying occasions when a dynamic data feed is delivering unreasonable values, even though its behavior may be superficially acceptable (i.e., it is delivering parsable results in a timely fashion). Software repositories with defect logs are main resource for defect prediction. In recent years, researchers have used the vast amount of data that is contained by software repositories to predict the location of defect in the code that caused problems. In this paper we evaluate the effectiveness of software fault prediction with Naive-Bayes classifiers and J48 classifier by integrating with supervised discretization algorithm developed by Fayyad and Irani. Public datasets from the promise repository have been explored for this purpose. The repository contains software metric data and error data at the function method level. Our experiment shows that integration of discretization method improves the software fault prediction accuracy when integrated with Naive-Bayes and J48 classifiers Published software quality models either provide abstract quality attributes or concrete quality assessments. There are no models that seamlessly integrate both aspects. In the project Quamoco, we built a comprehensive approach with the aim to close this gap. For this, we developed in several iterations a meta quality model specifying general concepts, a quality base model covering the most important quality factors and a quality assessment approach. The meta model introduces the new concept of a product factor, which bridges the gap between concrete measurements and abstract quality aspects. Product factors have measures and instruments to operationalise quality by measurements from manual inspection and tool analysis. The base model uses the ISO 25010 quality attributes, which we refine by 200 factors and 600 measures for Java and C# systems. We found in several empirical validations that the assessment results fit to the expectations of experts for the corresponding systems. The empirical analyses also showed that several of the correlations are statistically significant and that the maintainability part of the base model has the highest correlation, which fits to the fact that this part is the most comprehensive. Although we still see room for extending and improving the base model, it shows a high correspondence with expert opinions and hence is able to form the basis for repeatable and understandable quality assessments in practice. I describe and study the 'support encoding' of binary constraint satisfaction problems (CSP's) into boolean satisfiability (SAT). This is based on work by Kasif in 1990, in which clauses encode support information, rather than the encoding of conflicts in the standard 'direct encoding'. This enables arc consistency in the original CSP to be established by propagation in the translated SAT instance, providing an optimal worst case time algorithm for arc consistency [14]. I prove that the DP algorithm in SAT applied to the suport encoding behaves exactly like the MAC algorithm in CSP's. Using the SAT solver Chaff, I show that the support encoding can be used effectively to solve hard instances of random binary CSP's, and more effectively than the direct encoding on hard instances. Finally, I show that the local search algorithm WalkSAT can perform many times better on the support encoding than on the direct encoding. A case study is presented using thirteen releases of a large industrial inventory tracking system. Several types of questions are addressed in this study. The first involved examining how faults are distributed over the different files. This included making a distinction between the release during which they were discovered, the lifecycle stage at which they were first detected, and the severity of the fault. The second category of questions we considered involved studying how the size of modules affected their fault density. This included looking at questions like whether or not files with high fault densities at early stages of the lifecycle also had high fault densities during later stages. A third type of question we considered was whether files that contained large numbers of faults during early stages of development, also had large numbers of faults during later stages, and whether faultiness persisted from release to release. Finally, we examined whether newly written files were more fault-prone than ones that were written for earlier releases of the product. The ultimate goal of this study is to help identify characteristics of files that can be used as predictors of fault-proneness, thereby helping organizations determine how best to use their testing resources. We consider the problem of scheduling a number of jobs on a single machine against a restrictive common due date. The paper consists of two parts: firstly a new and appropriate problem representation is developed. As the restrictive common due date problem is known to be intractable we decided, secondly, to apply meta-heuristics, namely evolutionary strategies, simulated annealing and threshold accepting. We demonstrate that our application of these meta-heuristics is efficient in obtaining near-optimal solutions by solving 140 benchmark problems with up to 1000 jobs. Furthermore, we compare their solution quality and find that a new variant of threshold accepting is superior to the other approaches. Empirical studies in software testing research may not be comparable, reproducible, or characteristic of practice. One reason is that real bugs are too infrequently used in software testing research. Extracting and reproducing real bugs is challenging and as a result hand-seeded faults or mutants are commonly used as a substitute. This paper presents Defects4J, a database and extensible framework providing real bugs to enable reproducible studies in software testing research. The initial version of Defects4J contains 357 real bugs from 5 real-world open source pro- grams. Each real bug is accompanied by a comprehensive test suite that can expose (demonstrate) that bug. Defects4J is extensible and builds on top of each program’s version con- trol system. Once a program is configured in Defects4J, new bugs can be added to the database with little or no effort. Defects4J features a framework to easily access faulty and fixed program versions and corresponding test suites. This framework also provides a high-level interface to common tasks in software testing research, making it easy to con- duct and reproduce empirical studies. Defects4J is publicly available at http: defects4j.org. The development of a complex system depends on the self-coordinated action of a large number of agents, often determining unexpected global behavior. The case of software evolution has great practical importance: knowledge of what is to be considered atypical can guide developers in recognizing and reacting to abnormal behavior. Although the initial framework of a theory of software exists, the current theoretical achievements do not fully capture existing quantitative data or predict future trends. Here we show that two elementary laws describe the evolution of package sizes in a Linux-based operating system: first, relative changes in size follow a random walk with non-Gaussian jumps; second, each size change is bounded by a limit that is dependent on the starting size, an intriguing behavior that we call “soft bound.” Our approach is based on data analysis and on a simple theoretical model, which is able to reproduce empirical details without relying on any adjustable parameter and generates definite predictions. The same analysis allows us to formulate and support the hypothesis that a similar mechanism is shaping the distribution of mammalian body sizes, via size-dependent constraints during cladogenesis. Whereas generally accepted approaches struggle to reproduce the large-mass shoulder displayed by the distribution of extant mammalian species, this is a natural consequence of the softly bounded nature of the process. Additionally, the hypothesis that this model is valid has the relevant implication that, contrary to a common assumption, mammalian masses are still evolving, albeit very slowly. The selection of software metrics for building software quality prediction models is a search-based software engineering problem. An exhaustive search for such metrics is usually not feasible due to limited project resources, especially if the number of available metrics is large. Defect prediction models are necessary in aiding project managers for better utilizing valuable project resources for software quality improvement. The efficacy and usefulness of a fault-proneness prediction model is only as good as the quality of the software measurement data. This study focuses on the problem of attribute selection in the context of software quality estimation. A comparative investigation is presented for evaluating our proposed hybrid attribute selection approach, in which feature ranking is first used to reduce the search space, followed by a feature subset selection. A total of seven different feature ranking techniques are evaluated, while four different feature subset selection approaches are considered. The models are trained using five commonly used classification algorithms. The case study is based on software metrics and defect data collected from multiple releases of a large real-world software system. The results demonstrate that while some feature ranking techniques performed similarly, the automatic hybrid search algorithm performed the best among the feature subset selection methods. Moreover, performances of the defect prediction models either improved or remained unchanged when over 85were eliminated. Copyright © 2011 John Wiley & Sons, Ltd. The tens of thousands of high-quality open source software projects on the Internet raise the exciting possibility of studying software development by finding patterns across truly large source code repositories. This could enable new tools for developing code, encouraging reuse, and navigating large projects. In this paper, we build the first giga-token probabilistic language model of source code, based on 352 million lines of Java. This is 100 times the scale of the pioneering work by The giga-token model is significantly better at the code suggestion task than previous models. More broadly, our approach provides a new “lens” for analyzing software projects, enabling new complexity metrics based on statistical analysis of large corpora. We call these metrics data-driven complexity metrics. We propose new metrics that measure the complexity of a code module and the topical centrality of a module to a software project. In particular, it is possible to distinguish reusable utility classes from classes that are part of a program's core logic based solely on general information theoretic criteria. The importance of software testing to quality assurance cannot be overemphasized. The estimation of a module's fault-proneness is important for minimizing cost and improving the effectiveness of the software testing process. Unfortunately, no general technique for estimating software fault-proneness is available. The observed correlation between some software metrics and fault-proneness has resulted in a variety of predictive models based on multiple metrics. Much work has concentrated on how to select the software metrics that are most likely to indicate fault-proneness. In this paper, we propose the use of machine learning for this purpose. Specifically, given historical data on software metric values and number of reported errors, an Artificial Neural Network (ANN) is trained. Then, in order to determine the importance of each software metric in predicting fault-proneness, a sensitivity analysis is performed on the trained ANN. The software metrics that are deemed to be the most critical are then used as the basis of an ANN-based predictive model of a continuous measure of fault-proneness. We also view fault-proneness prediction as a binary classification task (i.e., a module can either contain errors or be error-free) and use Support Vector Machines (SVM) as a state-of-the-art classification method. We perform a comparative experimental study of the effectiveness of ANNs and SVMs on a data set obtained from NASA's Metrics Data Program data repository. In this paper, we study the problem of sub-dataset analysis over distributed file systems, e.g., the Hadoop file system. Our experiments show that the sub-datasets distribution over HDFS blocks, which is hidden by HDFS, can often cause corresponding analyses to suffer from a seriously imbalanced or inefficient parallel execution. Specifically, the content clustering of sub-datasets results in some computational nodes carrying out much more workload than others; furthermore, it leads to inefficient sampling of sub-datasets, as analysis programs will often read large amounts of irrelevant data. We conduct a comprehensive analysis on how imbalanced computing patterns and inefficient sampling occur. We then propose a storage distribution aware method to optimize sub-dataset analysis over distributed storage systems referred to as DataNet. First, we propose an efficient algorithm to obtain the meta-data of sub-dataset distributions. Second, we design an elastic storage structure called ElasticMap based on the HashMap and BloomFilter techniques to store the meta-data. Third, we employ distribution-aware algorithms for sub-dataset applications to achieve balanced and efficient parallel execution. Our proposed method can benefit different sub-dataset analyses with various computational requirements. Experiments are conducted on PRObEs Marmot 128-node cluster testbed and the results show the performance benefits of DataNet. Systems software such as OS kernels, embedded systems, and libraries must obey many rules for both correctness and performance. Common examples include "accesses to variable A must be guarded by lock B," "system calls must check user pointers for validity before using them," and "message handlers should free their buffers as quickly as possible to allow greater parallelism." Unfortunately, adherence to these rules is largely unchecked. This paper attacks this problem by showing how system implementors can use meta-level compilation (MC) to write simple, system-specific compiler extensions that automatically check their code for rule violations. By melding domain-specific knowledge with the automatic machinery of compilers, MC brings the benefits of language-level checking and optimizing to the higher, "meta" level of the systems implemented in these languages. This paper demonstrates the effectiveness of the MC approach by applying it to four complex, real systems: Linux, OpenBSD, the Xok exokernel, and the FLASH machine's embedded software. MC extensions found roughly 500 errors in these systems and led to numerous kernel patches. Most extensions were less than a hundred lines of code and written by implementors who had a limited understanding of the systems checked. Software is a ubiquitous component of our daily life. We often depend on the correct working of software systems. Due to the difficulty and complexity of software systems, bugs and anomalies are prevalent. Bugs have caused billions of dollars loss, in addition to privacy and security threats. In this work, we address software reliability issues by proposing a novel method to classify software behaviors based on past history or runs. With the technique, it is possible to generalize past known errors and mistakes to capture failures and anomalies. Our technique first mines a set of discriminative features capturing repetitive series of events from program execution traces. It then performs feature selection to select the best features for classification. These features are then used to train a classifier to detect failures. Experiments and case studies on traces of several benchmark software systems and a real-life concurrency bug from MySQL server show the utility of the technique in capturing failures and anomalies. On average, our pattern-based classification technique outperforms the baseline approach by 24.68 in accuracy. Display Omitted ContextNumerous open source software projects are based on volunteers collaboration and require a continuous influx of newcomers for their continuity. Newcomers face barriers that can lead them to give up. These barriers hinder both developers willing to make a single contribution and those willing to become a project member. ObjectiveThis study aims to identify and classify the barriers that newcomers face when contributing to open source software projects. MethodWe conducted a systematic literature review of papers reporting empirical evidence regarding the barriers that newcomers face when contributing to open source software (OSS) projects. We retrieved 291 studies by querying 4 digital libraries. Twenty studies were identified as primary. We performed a backward snowballing approach, and searched for other papers published by the authors of the selected papers to identify potential studies. Then, we used a coding approach inspired by open coding and axial coding procedures from Grounded Theory to categorize the barriers reported by the selected studies. ResultsWe identified 20 studies providing empirical evidence of barriers faced by newcomers to OSS projects while making a contribution. From the analysis, we identified 15 different barriers, which we grouped into five categories: social interaction, newcomers' previous knowledge, finding a way to start, documentation, and technical hurdles. We also classified the problems with regard to their origin: newcomers, community, or product. ConclusionThe results are useful to researchers and OSS practitioners willing to investigate or to implement tools to support newcomers. We mapped technical and non-technical barriers that hinder newcomers' first contributions. The most evidenced barriers are related to socialization, appearing in 75 (15 out of 20) of the studies analyzed, with a high focus on interactions in mailing lists (receiving answers and socialization with other members). There is a lack of in-depth studies on technical issues, such as code issues. We also noticed that the majority of the studies relied on historical data gathered from software repositories and that there was a lack of experiments and qualitative studies in this area.