Bibliographic record
Abstract
Just-in-time defect prediction, which is also known as change-level defect prediction, can be used to efficiently allocate resources and manage project schedules in the software testing and debugging process. Just-in-time defect prediction can reduce the amount of code to review and simplify the assignment of developers to bug fixes. This paper reports a replicated experiment and an extension comparing the prediction of defect-prone changes using traditional machine learning techniques and ensemble learning. Using datasets from six open source projects, namely Bugzilla, Columba, JDT, Platform, Mozilla, and PostgreSQL we replicate the original approach to verify the results of the original experiment and use them as a basis for comparison for alternatives in the approach. Our results from the replicated experiment are consistent with the original. The original approach uses a combination of data preprocessing and a two-layer ensemble of decision trees. The first layer uses bagging to form multiple random forests. The second layer stacks the forests together with equal weights. Generalizing the approach to allow the use of any arbitrary set of classifiers in the ensemble, optimizing the weights of the classifiers, and allowing additional layers, we apply a new deep ensemble approach, called deep super learner, to test the depth of the original study. The deep super learner achieves statistically significantly better results than the original approach on five of the six projects in predicting defects as measured by F1 score.
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How this classification was reachedexpand
Full frame machine prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. The Gemma side is a direct model label for every work in the frame, read from the title-only record. The Codex side is a classifier learned from the 10,348 direct Codex labels and calibrated to design-weighted sample rates; fields without enough sample support carry no Codex call. Candidate is the union of the two sides; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels.
Distilled classifier scores by category (both heads)
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.056 | 0.171 |
| Meta-epidemiology (narrow) | 0.002 | 0.001 |
| Meta-epidemiology (broad) | 0.002 | 0.004 |
| Bibliometrics | 0.001 | 0.002 |
| Science and technology studies | 0.003 | 0.002 |
| Scholarly communication | 0.003 | 0.004 |
| Open science | 0.003 | 0.003 |
| Research integrity | 0.003 | 0.005 |
| Insufficient payload (model declined to judge) | 0.013 | 0.006 |
Machine scores (provisional)
The two teacher heads of the student model, read on this work. A score orders the frame for review; it never asserts a category, and the validation status ships verbatim with every row.
Baseline scores from an immature model (maturity gate not passed, 7 training rounds). Scores rank; they never assert a category.
score_only:v0-immature-baseline · verbatim from the scoring run: score_only means the number may rank works, and no category label ships from itClassification
machine, unvalidatedMachine predicted; a candidate call from one source (direct Gemma or distilled Codex), not a consensus.
How this classification was reached, model by model and score by score, is at the end of the page under "How this classification was reached".