Mathieu Acher gave a course at EJCP (summer school for PhD students in computer science) about “Software Variability and Artificial Intelligence”. It was mainly a replay of 2018, but with some new examples and exercices. A lot of great questions from the audience and nice interactions. EJCP was also a very nice event spanning different topics (Coccinelle, Coq, frama-c, constraint programming, etc.)
Most modern software systems are subject to variation or come in many variants. Web browsers like Firefox or Chrome are available on different operating systems, in different languages, while users can configure 2000+ preferences or install numerous 3rd parties extensions (or plugins). Web servers like Apache, operating systems like the Linux kernel, or a video encoder like x264 are other examples of software systems that are highly configurable at compile-time or at run-time for delivering the expected functionality andmeeting the various desires of users. Variability (“the ability of a software system or artifact to be efficiently extended, changed, customized or configured for use in a particular context”) is therefore a crucial property of software systems. Organizations capable of mastering variability can deliver high-quality variants (or products) in a short amount of time and thus attract numerous customers, new use-cases or usage contexts. A hard problem for end-users or software developers is to master the combinatorial explosion induced by variability: Hundreds of configuration options can be combined, each potentially with distinct functionality and effects on execution time, memory footprint, quality of the result, etc. The first part of this course will introduce variability-intensive systems, their applications and challenges, in various software contexts. We will use intuitive examples (like a generator of LaTeX paper variants) and real-world systems (like the Linux kernel). A second objective of this course is to show the relevance of Artificial Intelligence (AI) techniques for exploring and taming such enormous variability spaces. In particular, we will introduce how (1) satisfiability and constraint programming solvers can be used to properly model and reason about variability; (2) how machine learning can be used to discover constraints and predict the variability behavior of configurable systems or software product lines.