Xavier Blanc

Xavier Blanc, Eric Cancès, Mi-Song Dupuy

In Kohn-Sham electronic structure computations, wave functions have singularities at nuclear positions. Because of these singularities, plane-wave expansions give a poor approximation of the eigenfunctions. In conjunction with the use of pseudo-potentials, the PAW (projector augmented-wave) method circumvents this issue by replacing the original eigenvalue problem by a new one with the same eigenvalues but smoother eigenvectors. Here a slightly different method, called VPAW (variational PAW), is proposed and analyzed. This new method allows for a better convergence with respect to the number of plane-waves. Some numerical tests on an idealized case corroborate this efficiency.

Cédric Teyton, Jean-Rémy Falleri, Marc Palyart et al.

Software intensively depends on external libraries whose relevance may change during its life cycle. As a consequence, software developers must periodically reconsider the libraries they depend on, and must think about \textit{library migration}. To our knowledge, no existing study has been done to understand library migration although it is known to be an expensive maintenance task. Are library migrations frequent? For which software are they performed and when? For which libraries? For what reasons? The purpose of this paper is to answer these questions with the intent to help software developers that have to replace their libraries. To that extent, we have performed a statistical analysis of a large set of open source software to mine their library migration. To perform this analysis we have defined an approach that identifies library migrations in a pseudo-automatic fashion by analyzing the source code of the software. We have implemented this approach for the Java programming language and applied it on Java Open Source Software stored in large hosting services. The main result of our study is that library migration is not a frequent practice but depends a lot on the nature of the software as well as the nature of the libraries.

Matthieu Foucault, Xavier Blanc, Margaret-Anne Storey et al.

Context: Technical debt management is challenging for software engineers due to poor tool support and a lack of knowledge on how to prioritize technical debt repayment and prevention activities. Furthermore, when there is a large backlog of debt, developers often lack the motivation to address it. Objective: In this paper, we describe a design study to investigate how gamification can support Technical Debt Management in a large legacy software system of an industrial company. Our study leads to a novel tool (named Themis) that combines technical debt support, version control, and gamification features. In addition to gamification features, Themis provides suggestions for developers on where to focus their effort, and visualizations for managers to track technical debt activities. Method: We describe how Themis was refined and validated in an iterative deployment with the company, finally conducting a qualitative study to investigate how the features of Themis affect technical debt management behavior. We consider the impact on both developers and managers. Results: Our results show that it achieves increased developer motivation, and supports managers in monitoring and influencing developer behaviors. We show how our findings may be transferable to other contexts by proposing guidelines on how to apply gamification. Conclusions: With this case, gamification appears as a promising solution to help technical debt management, although it needs to be carefully designed and implemented to avoid its possible negative effects.

Jean-Rémy Falleri, Cédric Teyton, Matthieu Foucault et al.

According to Wikipedia, The Mining Software Repositories (MSR) field analyzes the rich data available in software repositories, such as version control repositories, mailing list archives, bug tracking systems, issue tracking systems, etc. to uncover interesting and actionable information about software systems, projects and software engineering. The MSR field has received a great deal of attention and has now its own research conference : http://www.msrconf.org/. However performing MSR studies is still a technical challenge. Indeed, data sources (such as version control system or bug tracking systems) are highly heterogeneous. Moreover performing a study on a lot of data sources is very expensive in terms of execution time. Surprisingly, there are not so many tools able to help researchers in their MSR quests. This is why we created the Harmony platform, as a mean to assist researchers in performing MSR studies.