Measuring Software: From Data to Actionable Knowledge

Measuring Software:
From Data to Actionable Knowledge
16 May 2015
International Workshop on Software Architecture and Metrics
Radu Marinescu
radumarinescu@me.com
@radu_marinescu

ogo
lori
Culoare pentru o institu]ie unic - clar, curat, u[or de recunoscut - culoarea
este elementul cel mai u[or de recunoscut, albastru indigo reflect personalitatea
institu]ieide<nv]m>ntsuperiortehnic-ferm,puternic,darintrospectiv,valorizator.
Este o combina]ie de albastru [i ro[u, <n care dominant este albastrul cu atributele
sale introspective. Griul neutru pune <n valoare albastrul, accentu>nd valorile sale.

ogo
ulori

Logo
culori

Michele Lanza
Radu Marinescu
Object-Oriented
Metrics
in Practice
Using Software Metrics to
Characterize, Evaluate, and Improve
the Design of Object-Oriented Systems
Foreword by Stéphane Ducasse
1 3
1000+reprinted2010/2015
MIPICSME’14

tens of
“mayﬂy”
prototypes

180.9
(12 subsystems)
(17 methods)
(3 subsystems)
NOW6 months ago
(1 class)
(22
(10 methods)
(32 classes)
(16 classes)
(28 classes)
(120 methods)

!This is not an
isolated story

use of metrics
(and other code analyses) in

use of metrics
(and other code analyses) in
misuse

12 Person-Years
http://nemo.sonarqube.org/

12 Person-Years
1 issues / 8 LOC

12 Person-Years
1 issues / 8 LOC1 “key” issue / 140 LOC

12 Person-Years
1 issues / 8 LOC1 “key” issue / 140 LOC
OMG! How is an “E”?!

Picture from http://www.savvykidsofarkansas.com/event/the-boy-who-cried-wolf/

The most efﬁcient 7 weeks in the
history of software development…

The most efﬁcient 7 weeks in the
history of software development…
16.5 Person-Years of Technical Debt vanished!

are these separate problems?

who “authorized”
these thresholds?

reducing CYCLO takes
only 1 min / branch ?

reducing CYCLO takes
only 1 min / branch ?
reducing CYCLO for class
is easier (137’) than for
methods (285’)

never knew it’s so easy
to change a signature!

solving duplication
does only depend on
the number of blocks?

…are these 2 cases equally easy?

Image from http://imgur.com/gallery/iWKad22

1 Irrelevant Warnings
2 Misleading Debt Quantiﬁcation

3 Toxic/Stupid Refactoring Advices

3 Toxic/Stupid Refactoring Advices
4 Phony Thresholds

The ﬁrst scary things was bugs

http://www.google.com/imgres?imgurl=http://micheltriana.com/
wp-content/uploads/2010/12/
resharper-8x6.png&imgrefurl=http://micheltriana.com/
2010/12/01/conﬁguring-resharper-code-analysis/
&h=459&w=640&tbnid=MFJydOmaXXj3xM:&zoom=1&docid=e0
dqbvDRdbGVSM&ei=xOEcVaXfOsiWaoa6gJAI&tbm=isch&client
=safari&ved=0CBwQMygAMAA

Most maintenance effort goes into
understanding
messy code
47%
19%
6%
28%
Testing Documenting
Coding Understanding
M. Ben-Menachem and G. S. Marliss. Software quality: Producing practical, consistent software. International Thomson Computer Press, 1997

Bugs
Time
hard to maintain
error-prone

… and bugs also usually hide in
messy code

!We missed
an essential distinction

Strategic Flaws
Tactical Flaws
Execution Flaws
…system
…statements
…classes
and functions
How do I
design the…

Execution ﬂaws Tactical ﬂaws

public class TarHeader{
/**
* The entry's name.
*/
public StringBuffer name;
/**
* The entry's permission mode.
*/
public int mode;
/**
* The entry's user id.
*/
public int userId;
/**
* The entry's group id.
*/
public int groupId;
}

public
/**
* The entry's name.
*/
/**
*/
int
/**
*/
/**
*/
int
}
public
public
public
public

public
/**
* The entry's name.
*/
/**
*/
int
/**
*/
/**
*/
int
}
public
public
public
public
Data
Class

public
/**
* The entry's name.
*/
/**
*/
/**
*/
/**
*/
int
}

public
/**
* The entry's name.
*/
/**
*/
/**
*/
/**
*/
int
}
private
private
private
private

public
/**
* The entry's name.
*/
/**
*/
/**
*/
/**
*/
int
}
private
private
private
private
Encapsulate public data
(in TarHeader)1

public class {
public void parseTarHeader( TarHeader hdr, byte[] header ){
int offset = 0;
hdr.name = TarHeader.parseName( header, offset,
TarHeader.NAMELEN );
offset += TarHeader.NAMELEN;
hdr.mode = (int)TarHeader.parseOctal( header, offset,
TarHeader.MODELEN );
offset += TarHeader.MODELEN;
hdr.userId = (int)TarHeader.parseOctal( header, offset,
TarHeader.UIDLEN );
offset += TarHeader.UIDLEN;
hdr.groupId = (int)TarHeader.parseOctal( header, offset,
TarHeader.GIDLEN );
}
TarEntry

public
public
hdr.
TarHeader.
offset += TarHeader.
hdr.
TarHeader.
hdr.
TarHeader.
hdr.
TarHeader
}
TarEntry
TarHeader hdr
hdr.name
hdr.mode
hdr.userId
hdr.groupId
parseTarHeader

public
public
hdr.
TarHeader.
hdr.
TarHeader.
hdr.
TarHeader.
hdr.
TarHeader
}
TarEntry
TarHeader hdr
hdr.name
hdr.mode
hdr.userId
hdr.groupId
parseTarHeader
Move the method
(TarEntry > TarHeader)1

public
public
hdr.
TarHeader.
hdr.
TarHeader.
hdr.
TarHeader.
hdr.
TarHeader
}
TarEntry
TarHeader hdr
hdr.name
hdr.mode
hdr.userId
hdr.groupId
parseTarHeader
(in TarHeader)2
Move the method
(TarEntry > TarHeader)1

public
public
int
hdr.
header, offset, TarHeader.
hdr.
offset, TarHeader.
hdr.
offset, TarHeader.
hdr.
offset, TarHeader
}
public
int
hdr.
offset, TarHeader.
hdr.
offset, TarHeader.
long
offset = TarHeader.getLongOctalBytes
( size, outbuf, offset, TarHeader.
}
hdr.mode = (int)TarHeader.parseOctal( header,
offset, TarHeader.MODELEN );
hdr.userId = (int)TarHeader.parseOctal( header,
offset, TarHeader.UIDLEN );
parseTarHeader
writeEntryHeader

public
public
int
hdr.
hdr.
offset, TarHeader.
hdr.
offset, TarHeader.
hdr.
offset, TarHeader
}
public
int
hdr.
offset, TarHeader.
hdr.
offset, TarHeader.
long
}
parseTarHeader
writeEntryHeader
Duplicated
Code

public
public
int
hdr.
hdr.
offset, TarHeader.
hdr.
offset, TarHeader.
hdr.
offset, TarHeader
}
public
int
hdr.
offset, TarHeader.
hdr.
offset, TarHeader.
long
}
hdr.mode
hdr.mode
offset, TarHeader.
offset, TarHeader.
hdr.userId
hdr.userId
offset, TarHeader.
offset, TarHeader.
parseTarHeader
writeEntryHeader
Extract method
(by factoring out the duplicated code)1

public
public
int
hdr.
hdr.
offset, TarHeader.
hdr.
offset, TarHeader.
hdr.
offset, TarHeader
}
public
int
hdr.
offset, TarHeader.
hdr.
offset, TarHeader.
long
}
hdr.mode
hdr.mode
offset, TarHeader.
offset, TarHeader.
hdr.userId
hdr.userId
offset, TarHeader.
offset, TarHeader.
parseTarHeader
writeEntryHeader
Extract method
Move the newly created method
(in TarHeader)2

public
public
int
hdr.
hdr.
offset, TarHeader.
hdr.
offset, TarHeader.
hdr.
offset, TarHeader
}
public
int
hdr.
offset, TarHeader.
hdr.
offset, TarHeader.
long
}
hdr.mode
hdr.mode
offset, TarHeader.
offset, TarHeader.
hdr.userId
hdr.userId
offset, TarHeader.
offset, TarHeader.
parseTarHeader
writeEntryHeader
Extract method
(in TarHeader)2
(in TarHeader)3

yet, there is an alternative solution…

Move data
(TarHeader > TarEntry)1

Move data
(in TarEntry)2

vs.
Extract method
(out of the duplicated code)1
(in TarHeader)2
(in TarHeader)3
Move data
(in TarEntry)2

vs.
Which solution is best?
Extract method
(out of the duplicated code)1
(in TarHeader)2
(in TarHeader)3
Move data
(in TarEntry)2

Only the developer
who knows the context
can decide!

?How to dealwith
tactical ﬂaws

start with
symptom indicators
Checkstyle

Lorenz, Kidd, 1994
Chidamber, Kemerer, 1994
LOC - number of lines of code
CYCLO - cyclomatic complexity of a function
NOF - number of functions
FANOUT - outgoing coupling
NOA - number of attributes
DIT - depth of inheritance tree
TCC - tight class cohesion
…

Image from pickywallpapers.com

!Tactical ﬂaws must be treated as
ﬁrst-class entities

!…and symptoms must be
aggregated

from S.Demeyer, S.Ducasse, O.Nierstrasz - Object-Oriented Reengineering Patterns, 2003

God Classes
use data from small data-classes,
centralize the intelligence of the system,
and do everything.
A.Riel, 1996

God Classes
break encapsulation, and
are complex, and
are not cohesive.
A.Riel, 1996

ATFD > FEW
Class uses directly more than a
few attributes of other classes
WMC ≥ VERY HIGH
Functional complexity of the
class is very high
TCC < ONE THIRD
Class cohesion is low
AND GodClass
from M.Lanza, R.Marinescu - Object-Oriented Metrics in Prac

but there is
one more problem
when dealing with metrics…

who “authorized”
these thresholds?

Experts, right?
Image from http://www.dilbert.com

5 projects?!?!
< 100 classes?!?!

Michele Lanza
Radu Marinescu
Object-Oriented
Metrics
in Practice
1 3

Michele Lanza
Radu Marinescu
Object-Oriented
Metrics
in Practice
1 3
37/45 projects…

4800 projects(SourceForge)
300.000.000 lines of code

4800 projects(SourceForge)
300.000.000 lines of code inFusion

#1
Distinguish tactical ﬂaws
from execution ﬂaws

#2
Don’t correct tactical ﬂaws
by ﬁxing isolated symptoms

#3
Correcting tactical ﬂaws
requires exploration tools

#3
Correcting tactical ﬂaws
requires exploration tools
powerful

Flaw Summary
Visualization
Metrics
Related ﬂaws
Source Highlighter
Dependency Breakout

#4
Improve
technical debt calculators

#5
Build massive collection of
curated measurement data

“ ”
A single arrow is easily broken, but not ten in a bundle.
Japanese proverb

Measuring Software: From Data to Actionable Knowledge

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