How much really changes? A case study of firefox version evolution using a clone detector

This paper focuses on the applicability of clone detectors for system evolution understanding. Specifically, it is a case study of Firefox for which the development release cycle changed from a slow release cycle to a fast release cycle two years ago. Since the transition of the release cycle, three times more versions of the software were deployed. To understand whether or not the changes between the newer versions are as significant as the changes in the older versions, we measured the similarity between consecutive versions.We analyzed 82MLOC of C/C++ code to compute the overall change distribution between all existing major versions of Firefox. The results indicate a significant decrease in the overall difference between many versions in the fast release cycle. We discuss the results and highlight how differently the versions have evolved in their respective release cycle. We also relate our results with other results assessing potential changes in the quality of Firefox. We conclude the paper by raising questions on the impact of a fast release cycle.