This document summarizes research on transfer defect learning to improve cross-project defect prediction. It presents Transfer Component Analysis (TCA) as a state-of-the-art transfer learning technique that maps data from source and target projects into a shared feature space to make their distributions more similar. It then proposes TCA+ which augments TCA with data normalization and decision rules to select the optimal normalization method based on characteristics of the source and target datasets. Experimental results on two cross-project defect prediction datasets show that TCA+ significantly outperforms traditional cross-project prediction and basic TCA.

1. Transfer Defect Learning
Jaechang Nam
The Hong Kong University of Science and Technology, China
Sinno Jialian Pan
Institute for Infocomm Research, Singapore
Sunghun Kim
The Hong Kong University of Science and Technology, China

2. Defect Prediction
• Hassan et al.@ICSE`09, Predicting Faults Using the Complexity of Code
Changes
• D’Ambros et al.@MSR`10, An Extensive Comparison of Bug Prediction
Approaches
• Rahman et al.@ICSE`12, Recalling the Impression of Cross-Project Defect
Prediction
• Hata et al.@ICSE`12, Bug Prediction based on Fine-grained Module
histories
• …
2
Program Prediction Model
(Machine learning)
Future defects

3. Training prediction model
3
Test set
Training set

4. Training prediction model
3
Test set
Training set
M1 M2 … M19 M20 Class
11 5 … 53 78 Buggy
… … … … … …
1 1 … 3 9 Clean
M1 M2 … M19 M20 Class
2 1 … 2 8 ?
… … … … … …
13 6 … 45 69 ?

5. Cross prediction model
4
Target project (Test set)
Source project (Training set)

6. Cross-project Defect Prediction
5
“Training data is often not available, either
because a company is too small or it is the first
release of a product”
Zimmerman et al.@FSE`09, Cross-project Defect Prediction

7. Cross-project Defect Prediction
5
“Training data is often not available, either
because a company is too small or it is the first
release of a product”
Zimmerman et al.@FSE`09, Cross-project Defect Prediction
“For many new projects we may not have enough
historical data to train prediction models.”
Rahman, Posnett, and Devanbu @ICSE`12, Recalling the
“Imprecision” of Cross-project Defect Prediction

8. Cross-project defect prediction
• Zimmerman et al.@FSE`09
– “We ran 622 cross-project predictions and found
only 3.4% actually worked.”
6
Worked,
3.4%
Not
worked,
96.6%

9. Cross-company defect prediction
• Turhan and Menzies et al.@ESEJ`09
– “Within-company data models are still the best”
7
0
0.05
0.1
0.15
0.2
0.25
0.3
0.35
0.4
Cross Cross with a NN
filter
Within
Avg. F-measure

10. Cross-project defect prediction
• Rahman, Posnett, and Devanbu@FSE`12
8
0
0.1
0.2
0.3
0.4
0.5
0.6
Cross Within
Avg. F-measure

11. Cross prediction results
9
0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
F-measure
Cross Within Cross Within Cross Within
Equinox JDT Lucene

12. Approaches of Transfer Defect Learning
10
Normalization TCA
TCA+

13. 11
• Data preprocessing for training and test dataNormalization
• A state-of-the art transfer learning algorithm
• Transfer Component AnalysisTCA
• Adapted TCA for cross-project defect prediction
• Decision rules to select a suitable data normalization optionTCA+
Approaches of Transfer Defect Learning

14. Data Normalization
• Adjust all feature values in the same scale
– E.g., Make Mean = 0 and Std = 1
• Known to be helpful for classification
algorithms to improve prediction
performance [Han et al. 2012].
12

15. Normalization Options
• N1: Min-max Normalization (max=1, min=0)
[Han et al., 2012]
• N2: Z-score Normalization (mean=0, std=1)
[Han et al., 2012]
• N3: Z-score Normalization only using source
mean and standard deviation
• N4: Z-score Normalization only using target
mean and standard deviation
13

16. 14
• Data preprocessing for training and test dataNormalization
• A state-of-the art transfer learning algorithm
• Transfer Component Analysis
TCA
• Adapted TCA for cross-project defect prediction
• Decision rules to select a suitable data normalization optionTCA+
Approaches of Transfer Defect Learning

17. Transfer Learning
15

18. Transfer Learning
15
Traditional Machine Learning (ML)
Learning
System
Learning
System

19. Transfer Learning
15
Traditional Machine Learning (ML)
Learning
System
Learning
System
Transfer Learning
Learning
System
Learning
System
Knowledge
Transfer

20. Transfer Learning
15
Traditional Machine Learning (ML)
Learning
System
Learning
System
Transfer Learning
Learning
System
Learning
System
Knowledge
Transfer

21. A Common Assumption in
Traditional ML
16
Pan andYang@TKDE`10, Survey onTransfer Learning
• Same distribution

22. A Common Assumption in
Traditional ML
16
Pan andYang@TKDE`10, Survey onTransfer Learning
• Same distribution
Cross Prediction

23. A Common Assumption in
Traditional ML
16
Pan andYang@TKDE`10, Survey onTransfer Learning
• Same distribution
Transfer Learning

24. Transfer Component Analysis
• Unsupervised Transfer learning
– Target project labels are not known.
• Must have the same feature space
• Make distribution difference between
training and test datasets similar
17
Pan et al.@TNN`10, Domain Adaptation viaTransfer ComponentAnalysis

25. Transfer Component Analysis (cont.)
• Feature extraction approach
– Dimensionality reduction
– Projection
• Map original data
in a lower-dimensional feature space
18

26. Transfer Component Analysis (cont.)
• Feature extraction approach
– Dimensionality reduction
– Projection
• Map original data
in a lower-dimensional feature space
18
2-dimensional feature space

27. Transfer Component Analysis (cont.)
• Feature extraction approach
– Dimensionality reduction
– Projection
• Map original data
in a lower-dimensional feature space
18
1-dimensional feature space

28. Transfer Component Analysis (cont.)
• Feature extraction approach
– Dimensionality reduction
– Projection
• Map original data
in a lower-dimensional feature space
18
1-dimensional feature space

29. Transfer Component Analysis (cont.)
• Feature extraction approach
– Dimensionality reduction
– Projection
• Map original data
in a lower-dimensional feature space
18
1-dimensional feature space
2-dimensional feature space

30. Transfer Component Analysis (cont.)
• Feature extraction approach
– Dimensionality reduction
– Projection
• Map original data
in a lower-dimensional feature space
– C.f. Principal Component Analysis (PCA)
18
1-dimensional feature space

31. Transfer Component Analysis (cont.)
19
Pan et al.@TNN`10, Domain Adaptation viaTransfer ComponentAnalysis
Target domain data
Source domain data

32. Transfer Component Analysis (cont.)
20
PCA TCA
Pan et al.@TNN`10, Domain Adaptation viaTransfer ComponentAnalysis

33. Preliminary Results using TCA
0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
F-measure
21*Baseline: Cross-project defect prediction without TCA and normalization
Baseline NoN N1 N2 N3 N4 Baseline NoN N1 N2 N3 N4
Safe  Apache Apache  Safe

34. Preliminary Results using TCA
0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
F-measure
21*Baseline: Cross-project defect prediction without TCA and normalization
Prediction performance of TCA
varies according to different
normalization options!
Baseline NoN N1 N2 N3 N4 Baseline NoN N1 N2 N3 N4
Safe  Apache Apache  Safe

35. 22
• Data preprocessing for training and test dataNormalization
• A state-of-the art transfer learning algorithm
• Transfer Component Analysis
TCA
• Adapted TCA for cross-project defect prediction
• Decision rules to select a suitable data
normalization option
TCA+
Approaches of Transfer Defect Learning

36. TCA+: Decision rules
• Find a suitable normalization for TCA
• Steps
– #1: Characterize a dataset
– #2: Measure similarity
between source and target datasets
– #3: Decision rules
23

37. #1: Characterize a dataset
24
3
1
…
Dataset A Dataset B
2
4
5
8
9
6
11
d1,2
d1,5
d1,3
d3,11
3
1
…
2
4
5
8
9
6
11
d2,6
d1,2
d1,3
d3,11
DIST={dij : i,j, 1 ≤ i < n, 1 < j ≤ n, i < j}
A

38. #2: Measure Similarity between
source and target
• Minimum (min) and maximum (max) values of
DIST
• Mean and standard deviation (std) of DIST
• The number of instances
25

39. #3: Decision Rules
• Rule #1
– Mean and Std are same  NoN
• Rule #2
– Max and Min are different  N1 (max=1, min=0)
• Rule #3,#4
– Std and # of instances are different
 N3 or N4 (src/tgt mean=0, std=1)
• Rule #5
– Default  N2 (mean=0, std=1)
26

40. EVALUATION
27

41. Experimental Setup
• 8 software subjects
• Machine learning algorithm
– Logistic regression
28
ReLink (Wu et al.@FSE`11)
Projects
# of metrics
(features)
Apache
26
(Source code)
Safe
ZXing
AEEEM (D’Ambros et al.@MSR`10)
Projects
# of metrics
(features)
Apache Lucene (LC)
61
(Source code,
Churn,
Entropy,…)
Equinox (EQ)
Eclipse JDT
Eclipse PDE UI
Mylyn (ML)

42. Experimental Design
29
Test set
(50%)
Training set
(50%)
Within-project defect prediction

43. Experimental Design
30
Target project (Test set)
Source project (Training set)
Cross-project defect prediction

44. Experimental Design
31
Target project (Test set)
Source project (Training set)
Cross-project defect prediction with TCA/TCA+
TCA/TCA+

45. RESULTS
32

46. ReLink Result
33*Baseline: Cross-project defect prediction without TCA/TCA+
0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
F-measure
Baseline TCA TCA+ Within
Safe  Apache Apache  Safe Safe  ZXing
Baseline TCA TCA+ Within Baseline TCA TCA+ Within

47. ReLink Result
F-measure
34
Cross
Source  Target
Safe  Apache
Zxing  Apache
Apache  Safe
Zxing  Safe
Apache  ZXing
Safe  ZXing
Average
Baseline
0.52
0.69
0.49
0.59
0.46
0.10
0.49
TCA
0.64
0.64
0.72
0.70
0.45
0.42
0.59
TCA+
0.64
0.72
0.72
0.64
0.49
0.53
0.61
Within
Target  Target
0.64
0.62
0.33
0.53
*Baseline: Cross-project defect prediction without TCA/TCA+

48. AEEEM Result
35*Baseline: Cross-project defect prediction without TCA/TCA+
0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
F-measure
Baseline TCA TCA+ Within
JDT  EQ PDE  LC PDE  ML
Baseline TCA TCA+ Within Baseline TCA TCA+ Within

49. AEEEM Result
F-measure
36
Cross
Source  Target
JDT  EQ
LC  EQ
ML  EQ
…
PDE  LC
EQ  ML
JDT  ML
LC  ML
PDE ML
…
Average
Baseline
0.31
0.50
0.24
…
0.33
0.19
0.27
0.20
0.27
…
0.32
TCA
0.59
0.62
0.56
…
0.27
0.62
0.56
0.58
0.48
…
0.41
TCA+
0.60
0.62
0.56
…
0.33
0.62
0.56
0.60
0.54
…
0.41
Within
Source  Target
0.58
…
0.37
0.30
…
0.42

50. Threats to Validity
• Systems are open-source projects.
• Experimental results may not be
generalizable.
• Decision rules in TCA+ may not be
generalizable.
37

51. Future Work
• Transfer defect learning on different
feature space
– e.g., ReLink  AEEEM
AEEEM  ReLink
• Local models using Transfer Learning
• Adapt Transfer learning in other Software
Engineering (SE) problems
– e.g., Knowledge from mailing lists
 Bug triage problem
38

52. Conclusion
• TCA+
– TCA
• Make distributions of source and target similar
– Decision rules to improve TCA
– Significantly improved cross-project defect
prediction performance
• Transfer Learning in SE
– Transfer learning may benefit other
prediction and recommendation systems in
SE domains.
39