Software defect prediction: do different classifiers find the same defects?

Open Access: This article is distributed under the terms of the Creative Commons Attribution 4.0 International License CC BY 4.0 (http://creativecommons.org/licenses/by/4.0/), which permits unrestricted use, distribution, and reproduction in any medium, provided you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons license, and indicate if changes were made.During the last 10 years, hundreds of different defect prediction models have been published. The performance of the classifiers used in these models is reported to be similar with models rarely performing above the predictive performance ceiling of about 80% recall. We investigate the individual defects that four classifiers predict and analyse the level of prediction uncertainty produced by these classifiers. We perform a sensitivity analysis to compare the performance of Random Forest, Naïve Bayes, RPart and SVM classifiers when predicting defects in NASA, open source and commercial datasets. The defect predictions that each classifier makes is captured in a confusion matrix and the prediction uncertainty of each classifier is compared. Despite similar predictive performance values for these four classifiers, each detects different sets of defects. Some classifiers are more consistent in predicting defects than others. Our results confirm that a unique subset of defects can be detected by specific classifiers. However, while some classifiers are consistent in the predictions they make, other classifiers vary in their predictions. Given our results, we conclude that classifier ensembles with decision-making strategies not based on majority voting are likely to perform best in defect prediction.Peer reviewedFinal Published versio

Some changes of hydraulics conditions along a river engineered part of the Cedron Stream in the Beskid Sredni mountains

W pracy przedstawiono skutki zabudowy hydrotechnicznej potoku i jej wpływ na zmianę wybranych parametrów hydraulicznych koryta. Reżim przepływu w korytach jest charakteryzowany przez rozkład prędkości wody w pionach hydrometrycznych, wartość naprężeń stycznych na dno, wartość mocy strumienia oraz wartość mocy jednostkowej strumienia. Założono sześć przekrojów poprzecznych na potoku Cedron w Beskidzie Średnim, w których zostały wykonane pomiary prędkości na kilku głębokościach nad dnem przed i po regulacji, a następnie obliczono naprężenia styczne na dnie cieku, całkowite i jednostkowe moce strumienia i przeprowadzono analizę obliczonych parametrów.The paper presents the effects of applied river engineering works and its influence on the changes of chosen hydraulics parameters along a reach of the mountainous stream. It was done by presenting the regime of the stream before and after river engineering works. The key parameters used for the hydraulics analysis were: stream velocity, shear stresses, stream power and finally the unit stream power. The research area was located in Polish Carpathians in the Beskid Sredni Mountains. The research stream is called the Cedron and the research reach is located close to Radziszow municipality around 30 kilometers from Krakow. The research was carried out in 2003 (before the river engineering works, after the major flooding in the region) and in 2004 after finishing river training works, which were mostly targeted to stop the bottom of the river and its banks from erosion. To carry on the research 6 cross sections were chosen where detailed velocities of running water were measured in the velocity profiles. Later the rest of analyzed hydraulics parameters such as stream power and shear stresses were calculated. The results were presented in graphical manner (fig. 1-4) and analyzed. In final conclusions it was pointed out, that all river training works hale the inevitable influence on river regime changes, thus after river engineering works which had a place on the left bank of the Cedron river (where special river bank protection gabions were installed) the shear stresses acting on the river bed and banks were stabilized