Hajimu Iida

Who should review my code? A file location-based code-reviewer recommendation approach for Modern Code Review

Software code review is an inspection of a code change by an independent third-party developer in order to identify and fix defects before an integration. Effectively performing code review can improve the overall software quality. In recent years, Modern Code Review (MCR), a lightweight and tool-based code inspection, has been widely adopted in both proprietary and open-source software systems. Finding appropriate code-reviewers in MCR is a necessary step of reviewing a code change. However, little research is known the difficulty of finding code-reviewers in a distributed software development and its impact on reviewing time. In this paper, we investigate the impact of reviews with code-reviewer assignment problem has on reviewing time. We find that reviews with code-reviewer assignment problem take 12 days longer to approve a code change. To help developers find appropriate code-reviewers, we propose RevFinder, a file location-based code-reviewer recommendation approach. We leverage a similarity of previously reviewed file path to recommend an appropriate code-reviewer. The intuition is that files that are located in similar file paths would be managed and reviewed by similar experienced code-reviewers. Through an empirical evaluation on a case study of 42,045 reviews of Android Open Source Project (AOSP), OpenStack, Qt and LibreOffice projects, we find that RevFinder accurately recommended 79% of reviews with a top 10 recommendation. RevFinder also correctly recommended the code-reviewers with a median rank of 4. The overall ranking of RevFinder is 3 times better than that of a baseline approach. We believe that RevFinder could be applied to MCR in order to help developers find appropriate code-reviewers and speed up the overall code review process.

SHINOBI: A Tool for Automatic Code Clone Detection in the IDE

Recent research has acknowledged that code clones decrease the maintainability and reliability of software programs, thus it is being regarded as one of the major factors to increase development/maintenance cost. We introduce SHINOBI, a novel code clone detection/modification tool that is designed to aid in recognizing and highlighting code clones during software maintenance tasks. SHINOBI is implemented as an add-in of Microsoft Visual Studio that automatically reports clones of modified snippets in real time.

Investigating code review practices in defective files: an empirical study of the Qt system

Software code review is a well-established software quality practice. Recently, Modern Code Review (MCR) has been widely adopted in both open source and proprietary projects. To evaluate the impact that characteristics of MCR practices have on software quality, this paper comparatively studies MCR practices in defective and clean source code files. We investigate defective files along two perspectives: 1) files that will eventually have defects (i.e., Future-defective files) and 2) files that have historically been defective (i.e., Risky files). Through an empirical study of 11,736 reviews of changes to 24,486 files from the Qt open source project, we find that both future-defective files and risky files tend to be reviewed less rigorously than their clean counterparts. We also find that the concerns addressed during the code reviews of both defective and clean files tend to enhance evolvability, i.e., Ease future maintenance (like documentation), rather than focus on functional issues (like incorrect program logic). Our findings suggest that although functionality concerns are rarely addressed during code review, the rigor of the reviewing process that is applied to a source code file throughout a development cycle shares a link with its defect proneness.

Improving code review effectiveness through reviewer recommendations

Effectively performing code review increases the quality of software and reduces occurrence of defects. However, this requires reviewers with experiences and deep understandings of system code. Manual selection of such reviewers can be a costly and time-consuming task. To reduce this cost, we propose a reviewer recommendation algorithm determining file path similarity called FPS algorithm. Using three OSS projects as case studies, FPS algorithm was accurate up to 77.97%, which significantly outperformed the previous approach.

Who does what during a code review? Datasets of OSS peer review repositories

We present four datasets that are focused on the general roles of OSS peer review members. With data mined from both an integrated peer review system and code source repositories, our rich datasets comprise of peer review data that was automatically recorded. Using the Android project as a case study, we describe our extraction methodology, the datasets and their application used for three separate studies. Our datasets are available online at http://sdlab.naist.jp/reviewmining/.

Revisiting code ownership and its relationship with software quality in the scope of modern code review

Code ownership establishes a chain of responsibility for modules in large software systems. Although prior work uncovers a link between code ownership heuristics and software quality, these heuristics rely solely on the authorship of code changes. In addition to authoring code changes, developers also make important contributions to a module by reviewing code changes. Indeed, recent work shows that reviewers are highly active in modern code review processes, often suggesting alternative solutions or providing updates to the code changes. In this paper, we complement traditional code ownership heuristics using code review activity. Through a case study of six releases of the large Qt and OpenStack systems, we find that: (1) 67%-86% of developers did not author any code changes for a module, but still actively contributed by reviewing 21%-39% of the code changes, (2) code ownership heuristics that are aware of reviewing activity share a relationship with software quality, and (3) the proportion of reviewers without expertise shares a strong, increasing relationship with the likelihood of having post-release defects. Our results suggest that reviewing activity captures an important aspect of code ownership, and should be included in approximations of it in future studies.

Review participation in modern code review

Software code review is a well-established software quality practice. Recently, Modern Code Review (MCR) has been widely adopted in both open source and proprietary projects. Our prior work shows that review participation plays an important role in MCR practices, since the amount of review participation shares a relationship with software quality. However, little is known about which factors influence review participation in the MCR process. Hence, in this study, we set out to investigate the characteristics of patches that: (1) do not attract reviewers, (2) are not discussed, and (3) receive slow initial feedback. Through a case study of 196,712 reviews spread across the Android, Qt, and OpenStack open source projects, we find that the amount of review participation in the past is a significant indicator of patches that will suffer from poor review participation. Moreover, we find that the description length of a patch shares a relationship with the likelihood of receiving poor reviewer participation or discussion, while the purpose of introducing new features can increase the likelihood of receiving slow initial feedback. Our findings suggest that the patches with these characteristics should be given more attention in order to increase review participation, which will likely lead to a more responsive review process.

A Multipath Controller for Accelerating GridFTP Transfer over SDN

A large amount of scientific data needs to be transferred from one site to another as fast as possible in the computational science fields. High-speed data transfer between sites is very important, especially in the Grid computing field, GridFTP has been widely used for bulk data transfer over a wide area network. GridFTP achieves greater performance by supporting parallel TCP streams. Using parallel TCP streams improves the throughput of slow-start algorithms and lossy networks even on a single path. This research proposes a traffic engineering technique that increases the data transfer performance by using multiple paths simultaneously for the parallel TCP streams. For this purpose, we use Software-Defined Network (SDN) technology and its implementation, OpenFlow. This paper presents the design and implementation of the proposed system. Our performance evaluation demonstrates that our proposed system can accelerate GridFTP Transfer in both virtual and real global-scale environments.

ReDA: A Web-Based Visualization Tool for Analyzing Modern Code Review Dataset

ReDA (http://reda.naist.jp/) is a web-based visualization tool for analyzing Modern Code Review (MCR) datasets for large Open Source Software (OSS) projects. MCR is a commonly practiced and lightweight inspection of source code using a support tool such as Gerrit system. Recently, mining code review history of such systems has received attention as a potentially effective method of ensuring software quality. However, due to increasing size and complexity of softwares being developed, these datasets are becoming unmanageable. ReDA aims to assist researchers of mining code review data by enabling better understand of dataset context and identifying abnormalities. Through real-time data interaction, users can quickly gain insight into the data and hone in on interesting areas to investigate. A video highlighting the main features can be found at: http://youtu.be/ fEoTRRas0U.

Using Profiling Metrics to Categorise Peer Review Types in the Android Project

Profiling of open source software (OSS) peer reviewers have many potential benefits related to quality assurance at both software and project levels. In this paper, we investigate its benefits such as identifying hidden experts, identify inactive or disinterested members to gauge the health of the OSS project and assisting aspiring members to monitor performance, identifying opportunities for career improvement. Preliminary results are promising, proving that our categories are practical and opening many avenues for future work. Recent improvements of data repositories mining tools and techniques make this research timely in able to provide quantitative insights for OSS peer review projects.