Feedback of my Phd work in Hbase project

[Igor Wiese <ig...@gmail.com>]

Hi, Hbase 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 Hbase 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 8492 commits in which a pair of files changed
together and could correctly predict 71% commits. These were the most
useful information for predicting co-changes of files:

- sum of number of lines of code added, modified and removed,

- number of words used to describe and discuss the issues,

- median value of closeness, a social network measure  obtained from issue
comments,

- median value of effective size, a social network measure obtained from
issue comments, and

-  median value of hierarchy, a social network measure obtained from issue
comments.


To illustrate, consider the following example from our analysis. For
release 1.1, the files "util/HBaseFsck.java" and
"hbase/util/HBaseFsckRepair.java" changed together in 13 commits. In
another 40 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 9 commits in which both files
changed together in release 1.1, and we only issued two false positives and
two wrong predictions. For this pair of files, the most important
contextual information was the number of developers that commented in an
each issue and the social network metric (efficiency) 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:
http://flosscoach.com/index.php/17-cochanges/71-hbase

All the best,
Igor Wiese
Phd Candidate