Hi, Lucene and Solr Community. My name is Igor Wiese, phd Student from Brazil. In my research I am investigating two important questions: What makes two files change together? Can we predict when they are going to co-change again?
I've tried to investigate this question on the Lucene and Solr project. I've collected data from issue reports, discussions and commits and using some machine learning techniques to build a prediction model. I collected a total of 1382 commits in which a pair of files changed together and could correctly predict 66% commits in the Lucene Project. For the Solr Project I collected a total of 111 commits in which a pair of files changed together and could correctly predict 47% commits. These were the most useful information for predicting co-changes of files: - number of lines of code added, - number of lines of code removed, - sum of number of lines of code added, modified and removed, - number of words used to describe and discuss the issues, and - median value of closeness, a social network measure obtained from issue comments. To illustrate, consider the following example in Lucene Project from our analysis. For release 4.7, the files "lucene/index/IndexWriter.java" and "lucene/index/StandardDirectoryReader.java" changed together in 4 commits. In another 11 commits, only the first file changed, but not the second. Collecting contextual information for each commit made to first file in previous release, we were able to predict 3 commits in which both files changed together in release 4.7, and we issued 0 false positive, and one wrong prediction. For this pair of files, the most important contextual information was the number of lines of code added in each commit, the number of words used to describe and discuss the issues, the number of comments in each issue and the social network metric (closeness) obtained from issue comments. - Do these results surprise you? Can you think in any explanation for the results? - Do you think that our rate of prediction is good enough to be used for building tool support for the software community? - Do you have any suggestion on what can be done to improve the change recommendation? You can visit a webpage to inspect the results in details: Lucene Project: http://flosscoach.com/index.php/17-cochanges/73-lucene Solr Project: http://flosscoach.com/index.php/17-cochanges/74-solr All the best, Igor Wiese Phd Candidate
