NL4Py: Agent-Based Modeling in Python with Parallelizable NetLogo Workspaces

NL4Py is a NetLogo controller software for Python, for the rapid, parallel execution of NetLogo models. NL4Py provides both headless (no graphical user interface) and GUI NetLogo workspace control through Python. Spurred on by the increasing availability of open-source computation and machine learning libraries on the Python package index, there is an increasing demand for such rapid, parallel execution of agent-based models through Python. NetLogo, being the language of choice for a majority of agent-based modeling driven research projects, requires an integration to Python for researchers looking to perform statistical analyses of agent-based model output using these libraries. Unfortunately, until the recent introduction of PyNetLogo, and now NL4Py, such a controller was unavailable. This article provides a detailed introduction into the usage of NL4Py and explains its client-server software architecture, highlighting architectural differences to PyNetLogo. A step-by-step demonstration of global sensitivity analysis and parameter calibration of the Wolf Sheep Predation model is then performed through NL4Py. Finally, NL4Py's performance is benchmarked against PyNetLogo and its combination with IPyParallel, and shown to provide significant savings in execution time over both configurations

Achieving Quality through Software Maintenance and Evolution: on the role of Agile Methodologies and Open Source Software

Agile methodologies, open source software development, and emerging new technologies are at the base of disruptive changes in software engineering. Being effort estimation pivotal for effective project management in the agile context, in the first part of the thesis we contribute to improve effort estimation by devising a real-time story point classifier, designed with the collaboration of an industrial partner and by exploiting publicly available data on open source projects. We demonstrate that, after an initial training on at least 300 issue reports, the classifier estimates a new issue in less than 15 seconds with a mean magnitude of relative error between 0.16 and 0.61. In addition, issue type, summary, description, and related components prove to be project-dependent features pivotal for story point estimation. Since story points are the most popular effort estimation metric in the agile context, in the second study presented in the thesis we investigate the role of agile methodologies in software maintenance and evolution, and prove its undoubted influence on the refactoring research field over the last 15 years. In the later part of the thesis, we focus on recent technologies to understand their impact on software engineering. We start by proposing a specialized blockchain-oriented software engineering, on the basis of the peculiar challenges the blockchain sector must confront with and statistical data retrieved from a corpus of open source blockchain-oriented software repositories, identified relying upon the 2016 Moody’s Blockchain Report. We advocate the need for new professional roles, enhanced security and reliability, novel modeling languages, and specialized metrics, along with new research directions focusing on collaboration among large teams, testing, and specialized tools for the creation of smart contracts. Along with the blockchain, in the later part of this work we also study the growing mobile sector. More specifically, we focus on the relationships between software defects and the use of the underlying system API, proving that our findings are aligned with those in the literature, namely, that the applications which are more connected to API classes are also more defect-prone. Finally, in the last work presented in the dissertation, we conducted a statistical analysis of 20 open source object-oriented systems, 10 written in the highly popular language Java and 10 in the rising language Python. We leveraged two statistical distribution functions–the log-normal and the double Pareto distributions–to provide good fits, both in Java and Python, for three metrics, namely, the NOLM, NOM, and NOS metrics. The study, among other findings, revealed that the variability of the number of methods used in Python classes is lower than in Java classes, and that Java classes, on average, feature fewer lines of code than Python classes

Code Structure Guided Transformer for Source Code Summarization

Code summaries help developers comprehend programs and reduce their time to infer the program functionalities during software maintenance. Recent efforts resort to deep learning techniques such as sequence-to-sequence models for generating accurate code summaries, among which Transformer-based approaches have achieved promising performance. However, effectively integrating the code structure information into the Transformer is under-explored in this task domain. In this paper, we propose a novel approach named SG-Trans to incorporate code structural properties into Transformer. Specifically, we inject the local symbolic information (e.g., code tokens and statements) and global syntactic structure (e.g., data flow graph) into the self-attention module of Transformer as inductive bias. To further capture the hierarchical characteristics of code, the local information and global structure are designed to distribute in the attention heads of lower layers and high layers of Transformer. Extensive evaluation shows the superior performance of SG-Trans over the state-of-the-art approaches. Compared with the best-performing baseline, SG-Trans still improves 1.4% and 2.0% in terms of METEOR score, a metric widely used for measuring generation quality, respectively on two benchmark datasets