Slide 1
Slide 1 text
Will this clone be short-lived? Towards understanding
of the characteristics of short-lived clones
- Journal First Presentation -
Ahmed Hassan
Weiyi Shang
Patanamon (Pick)
Thongtanunam
patanamon.thongtanunam
@unimelb.edu.au
@patanamon
Slide 2
Slide 2 text
Code clone: a group of code fragments that are
nearly-identical
For lower maintenance effort, these clones should
be refactored to reduce code repetitiveness
Monopoly/IncomeTaxSquare.java
Monopoly/GoToJailSquare.java
“2,241 refactoring instances were detected
in 285 GitHub projects [Silva et al., 2016]”
!2
Slide 3
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Refactoring all clones may not be worthwhile
Released
Version
2 versions
2 versions
10 versions
!3
Slide 4
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Refactoring all clones may not be worthwhile
Released
Version
2 versions
2 versions
75% and 36% of volatile clones in the carol
and dnsjava systems lived for a short-duration
[Kim et al., 2005]
10 versions
!3
Slide 5
Slide 5 text
Refactoring all clones may not be worthwhile
Released
Version
2 versions
2 versions
75% and 36% of volatile clones in the carol
and dnsjava systems lived for a short-duration
[Kim et al., 2005]
Many of the long-lived clones cannot be
removed using standard refactoring techniques
[Kim et al., 2005]
10 versions
!3
Slide 6
Slide 6 text
Refactoring all clones may not be worthwhile
Released
Version
2 versions
2 versions
10 versions
!3
Determining the life expectancy of
clones in advance may be
beneficial when managing clones
Slide 7
Slide 7 text
Understanding clone genealogies and
their life expectancy
Apache Pig
17 Years
22 Releases
10 Years
35 Releases
13 Years
66 Releases
14 Years
36 Releases
8 Years
15 Releases
11 Years
43 Releases
(PQ1) How long do clones live
in a software system?
(PQ2) How were short-lived and long-lived
clones changed throughout their lifetime?
!4
Slide 8
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Identifying clone life expectancy
!5
Slide 9
Slide 9 text
Identifying clone life expectancy
!5
Code
Repository
Slide 10
Slide 10 text
Identifying clone life expectancy
!5
Code
Repository
Extract sequentially
developed versions
v2.17.1
v2.17.2
v2.17.3
v2.16.0
v2.17.0
v2.18.0
v2.18.1
v2.18.2
v2.18.3
v2.17.4
Using git commands
Slide 11
Slide 11 text
Identifying clone life expectancy
Extract clone
genealogies
2 versions
6 versions
Using iClones
[Göde and Koschke, 2009]
!5
Code
Repository
Extract sequentially
developed versions
v2.17.1
v2.17.2
v2.17.3
v2.16.0
v2.17.0
v2.18.0
v2.18.1
v2.18.2
v2.18.3
v2.17.4
Using git commands
Slide 12
Slide 12 text
Identifying clone life expectancy
Identify short-lived &
long-lived clones
2 versions
6 versions
Using a clustering technique
Short Long
Extract clone
genealogies
2 versions
6 versions
Using iClones
[Göde and Koschke, 2009]
!5
Code
Repository
Extract sequentially
developed versions
v2.17.1
v2.17.2
v2.17.3
v2.16.0
v2.17.0
v2.18.0
v2.18.1
v2.18.2
v2.18.3
v2.17.4
Using git commands
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Slide 13 text
30% (Maven) - 87% (Jackrabbit) of clones are
short-lived clones
Maven Pig Tomcat
Ant Camel Jackrabbit
1−2
(1.27) 3−5
(4.05) 6−8
(6.57)
12−13
(12.33)
14−16
(14.94)
19−20
(19.43) 1−2
(1.27) 3−4
(3.43) 5−5
(5) 6−7
(6.43)
8−11
(9.22)
12−14
(13.54) 1−7
(3.9)
9−19
(13.12)
21−38
(26.91)
1−2
(1.21) 3−4
(3.32) 6−7
(6.62) 8−9
(8.22)
10−11
(10.79)
12−14
(12.67) 1−6
(2.63)
7−25
(11.06) 1−9
(2.28)
10−28
(16.2)
35−56
(51.5)
0
200
400
0
20
40
60
80
0
200
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600
800
0
300
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1200
0
25
50
75
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0
5
10
15
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Number of versions
Number of clones
Short-lived Long-lived
!6
Identify short-lived &
long-lived clones
2 versions
6 versions
Using a clustering technique
Short Long
Slide 14
Slide 14 text
30% (Maven) - 87% (Jackrabbit) of clones are
short-lived clones
Maven Pig Tomcat
Ant Camel Jackrabbit
1−2
(1.27) 3−5
(4.05) 6−8
(6.57)
12−13
(12.33)
14−16
(14.94)
19−20
(19.43) 1−2
(1.27) 3−4
(3.43) 5−5
(5) 6−7
(6.43)
8−11
(9.22)
12−14
(13.54) 1−7
(3.9)
9−19
(13.12)
21−38
(26.91)
1−2
(1.21) 3−4
(3.32) 6−7
(6.62) 8−9
(8.22)
10−11
(10.79)
12−14
(12.67) 1−6
(2.63)
7−25
(11.06) 1−9
(2.28)
10−28
(16.2)
35−56
(51.5)
0
200
400
0
20
40
60
80
0
200
400
600
800
0
300
600
900
1200
0
25
50
75
100
0
5
10
15
20
Number of versions
Number of clones
Short-lived Long-lived
Short-lived
!6
Identify short-lived &
long-lived clones
2 versions
6 versions
Using a clustering technique
Short Long
Slide 15
Slide 15 text
30% (Maven) - 87% (Jackrabbit) of clones are
short-lived clones
Maven Pig Tomcat
Ant Camel Jackrabbit
1−2
(1.27) 3−5
(4.05) 6−8
(6.57)
12−13
(12.33)
14−16
(14.94)
19−20
(19.43) 1−2
(1.27) 3−4
(3.43) 5−5
(5) 6−7
(6.43)
8−11
(9.22)
12−14
(13.54) 1−7
(3.9)
9−19
(13.12)
21−38
(26.91)
1−2
(1.21) 3−4
(3.32) 6−7
(6.62) 8−9
(8.22)
10−11
(10.79)
12−14
(12.67) 1−6
(2.63)
7−25
(11.06) 1−9
(2.28)
10−28
(16.2)
35−56
(51.5)
0
200
400
0
20
40
60
80
0
200
400
600
800
0
300
600
900
1200
0
25
50
75
100
0
5
10
15
20
Number of versions
Number of clones
Short-lived Long-lived
Short-lived
Long-lived
!6
Identify short-lived &
long-lived clones
2 versions
6 versions
Using a clustering technique
Short Long
Slide 16
Slide 16 text
30% (Maven) - 87% (Jackrabbit) of clones are
short-lived clones
Maven Pig Tomcat
Ant Camel Jackrabbit
1−2
(1.27) 3−5
(4.05) 6−8
(6.57)
12−13
(12.33)
14−16
(14.94)
19−20
(19.43) 1−2
(1.27) 3−4
(3.43) 5−5
(5) 6−7
(6.43)
8−11
(9.22)
12−14
(13.54) 1−7
(3.9)
9−19
(13.12)
21−38
(26.91)
1−2
(1.21) 3−4
(3.32) 6−7
(6.62) 8−9
(8.22)
10−11
(10.79)
12−14
(12.67) 1−6
(2.63)
7−25
(11.06) 1−9
(2.28)
10−28
(16.2)
35−56
(51.5)
0
200
400
0
20
40
60
80
0
200
400
600
800
0
300
600
900
1200
0
25
50
75
100
0
5
10
15
20
Number of versions
Number of clones
Short-lived Long-lived
!6
Identify short-lived &
long-lived clones
2 versions
6 versions
Using a clustering technique
Short Long
The life expectancy of
short-lived clones
account for <17% of all
studied releases
Slide 17
Slide 17 text
!7
Consistent changes appear in the long-lived
clones more often than short-lived clones
Slide 18
Slide 18 text
Clones are
consistently changed
!7
Clones are
consistently changed
Consistent changes appear in the long-lived
clones more often than short-lived clones
Slide 19
Slide 19 text
!7
%clone genealogies
including consistently
changing patterns
Ant Camel Jackrabbit Maven Pig Tomcat
35%
25%
25%
26%
37%
31%
19%
9%
14%
15%
16%
10%
Short-lived Long-lived
Consistent changes appear in the long-lived
clones more often than short-lived clones
Slide 20
Slide 20 text
!7
The maintenance effort that is associated with short-lived clones is
smaller than the maintenance effort associated with long-lived clones
%clone genealogies
including consistently
changing patterns
Ant Camel Jackrabbit Maven Pig Tomcat
35%
25%
25%
26%
37%
31%
19%
9%
14%
15%
16%
10%
Short-lived Long-lived
Consistent changes appear in the long-lived
clones more often than short-lived clones
Slide 21
Slide 21 text
Understanding clone genealogies and
their life expectancy
Apache Pig
17 Years
22 Releases
10 Years
35 Releases
13 Years
66 Releases
14 Years
36 Releases
8 Years
15 Releases
11 Years
43 Releases
(PQ1) How long do clones live
in a software system?
(PQ2) How were short-lived and long-lived
clones changed throughout their lifetime?
!8
Slide 22
Slide 22 text
Understanding clone genealogies and
their life expectancy
(PQ1) How long do clones live
in a software system?
(PQ2) How were short-lived and long-lived
clones changed throughout their lifetime?
Many clones lived in the studied
systems for a short duration
The maintenance effort for short-
lived clones is smaller than that for
long-lived clones
It is important to determine in advance whether a clone will
be short-lived or long-lived to manage clones more efficiently
!9
Slide 23
Slide 23 text
Building a classifier to determine the life
expectancy of a newly-introduced clone
A clone at the time when
it was injected into the
source code
A classifier
(Random Forest)
Train
!10
Product metrics
Process metrics
Clone metrics
(Churn, #Developers)
(#Lines of Code)
(#Clone Siblings)
38 metrics
Slide 24
Slide 24 text
Towards understanding of the characteristics of
short-lived clones
(RQ1) How well can we determine whether an
introduced clone will be short-lived?
(RQ2) What are the most influential metrics for
determining the clone life expectancy?
A classifier
(Random Forest)
Short-lived?
Long-lived?
Product metrics
Process metrics
Clone metrics
(Churn, #Developers)
!11
(#Lines of Code)
(#Clone Siblings)
Slide 25
Slide 25 text
Towards understanding of the characteristics of
short-lived clones
(RQ1) How well can we determine whether an
introduced clone will be short-lived?
(RQ2) What are the most influential metrics for
determining the clone life expectancy?
A classifier
(Random Forest)
Process
metrics
Our random forest classifiers
achieve an average AUC of
0.63 to 0.92
Clones that are introduced with a
large amount of churn made into
their methods are more likely to be
short-lived
Our classifiers and metrics can be used to determine
whether a newly-introduced clone will be short-lived
!12
Slide 26
Slide 26 text
!13
Slide 27
Slide 27 text
Maven Pig Tomcat
Ant Camel Jackrabbit
1−2
(1.27) 3−5
(4.05) 6−8
(6.57)
12−13
(12.33)
14−16
(14.94)
19−20
(19.43) 1−2
(1.27) 3−4
(3.43) 5−5
(5) 6−7
(6.43)
8−11
(9.22)
12−14
(13.54) 1−7
(3.9)
9−19
(13.12)
21−38
(26.91)
1−2
(1.21) 3−4
(3.32) 6−7
(6.62) 8−9
(8.22)
10−11
(10.79)
12−14
(12.67) 1−6
(2.63)
7−25
(11.06) 1−9
(2.28)
10−28
(16.2)
35−56
(51.5)
0
200
400
0
20
40
60
80
0
200
400
600
800
0
300
600
900
1200
Number of versions
Long−lived
Short−lived
Short
Long
Less consistent
changes
More consistent
changes
!13
Slide 28
Slide 28 text
Maven Pig Tomcat
Ant Camel Jackrabbit
1−2
(1.27) 3−5
(4.05) 6−8
(6.57)
12−13
(12.33)
14−16
(14.94)
19−20
(19.43) 1−2
(1.27) 3−4
(3.43) 5−5
(5) 6−7
(6.43)
8−11
(9.22)
12−14
(13.54) 1−7
(3.9)
9−19
(13.12)
21−38
(26.91)
1−2
(1.21) 3−4
(3.32) 6−7
(6.62) 8−9
(8.22)
10−11
(10.79)
12−14
(12.67) 1−6
(2.63)
7−25
(11.06) 1−9
(2.28)
10−28
(16.2)
35−56
(51.5)
0
200
400
0
20
40
60
80
0
200
400
600
800
0
300
600
900
1200
Number of versions
Long−lived
Short−lived
Short
Long
Less consistent
changes
More consistent
changes
Clone metrics
Product metrics
Process metrics
A classifier
Building a classifier to determine
the life expectancy of clones
!13
Slide 29
Slide 29 text
Towards understanding of the characteristics of
short-lived clones
(RQ1) How well can we determine whether an
introduced clone will be short-lived?
(RQ2) What are the most influential metrics for
determining the clone life expectancy?
A classifier
(Random Forest)
Process
metrics
Our random forest classifiers
achieve an average AUC of
0.63 to 0.92
Clones that are introduced with a
large amount of churn made into
their methods are more likely to be
short-lived
Our classifiers and metrics can be used to determine
whether a newly-introduced clone will be short-lived
Maven Pig Tomcat
Ant Camel Jackrabbit
1−2
(1.27) 3−5
(4.05) 6−8
(6.57)
12−13
(12.33)
14−16
(14.94)
19−20
(19.43) 1−2
(1.27) 3−4
(3.43) 5−5
(5) 6−7
(6.43)
8−11
(9.22)
12−14
(13.54) 1−7
(3.9)
9−19
(13.12)
21−38
(26.91)
1−2
(1.21) 3−4
(3.32) 6−7
(6.62) 8−9
(8.22)
10−11
(10.79)
12−14
(12.67) 1−6
(2.63)
7−25
(11.06) 1−9
(2.28)
10−28
(16.2)
35−56
(51.5)
0
200
400
0
20
40
60
80
0
200
400
600
800
0
300
600
900
1200
Number of versions
Long−lived
Short−lived
Short
Long
Less consistent
changes
More consistent
changes
Clone metrics
Product metrics
Process metrics
A classifier
Building a classifier to determine
the life expectancy of clones
!13
Slide 30
Slide 30 text
Towards understanding of the characteristics of
short-lived clones
(RQ1) How well can we determine whether an
introduced clone will be short-lived?
(RQ2) What are the most influential metrics for
determining the clone life expectancy?
A classifier
(Random Forest)
Process
metrics
Our random forest classifiers
achieve an average AUC of
0.63 to 0.92
Clones that are introduced with a
large amount of churn made into
their methods are more likely to be
short-lived
Our classifiers and metrics can be used to determine
whether a newly-introduced clone will be short-lived
Maven Pig Tomcat
Ant Camel Jackrabbit
1−2
(1.27) 3−5
(4.05) 6−8
(6.57)
12−13
(12.33)
14−16
(14.94)
19−20
(19.43) 1−2
(1.27) 3−4
(3.43) 5−5
(5) 6−7
(6.43)
8−11
(9.22)
12−14
(13.54) 1−7
(3.9)
9−19
(13.12)
21−38
(26.91)
1−2
(1.21) 3−4
(3.32) 6−7
(6.62) 8−9
(8.22)
10−11
(10.79)
12−14
(12.67) 1−6
(2.63)
7−25
(11.06) 1−9
(2.28)
10−28
(16.2)
35−56
(51.5)
0
200
400
0
20
40
60
80
0
200
400
600
800
0
300
600
900
1200
Number of versions
Long−lived
Short−lived
Short
Long
Less consistent
changes
More consistent
changes
Clone metrics
Product metrics
Process metrics
A classifier
Building a classifier to determine
the life expectancy of clones
Our classifiers and insights can help teams to
plan the most effective use of the clone
management resources
patanamon.thongtanunam
@unimelb.edu.au
@patanamon
http://patanamon.com
!13