Magic
behind
the
numbers
So.ware
metrics
in
prac&ce
Sebas&an
Marek,
So.ware
Architect

• a
Pole
living
in
Sheffield
• over
12
years
in
development
• Pascal,
C++,
PHP,
perl,
python,
Java
• co-­‐author
of
2
PHP
books
• big
fan
of
process
automa&on
• TDD
and
CI
• occasionally
contributes
to
open
source
projects
• wants
to
be
a
knight
@proofek

• What
I
will
be
talking
about
• Code
metrics
• Design
metrics
• What
I
will
not
be
talking
about
• Project
metrics
Agenda

Most
effec&ve
code
quality
measure

“It is the mapping of
a particular
characteristic
of a measured entity
to a numerical value”
Source: Object-Oriented Metrics
in Practice
What
is
a
metric?

“Good design quality metrics are not
necessarily indicative of good designs.
Likewise, bad design quality metrics are
not necessarily indicative of bad
designs”
Source: Jdepend Docs
So.ware
design

• Obsolete
documenta&on
• Convoluted
design
• Intensive
patch
mechanism
(hacking)
• Large
size
• Severe
duplica&on
• Obsolete
parts
(dead
code)
• Long
build
&mes
• Loss
of
original
developers
System
maintenance

• CLOC
–
comment
lines
of
code
• ELOC
–
executable
lines
of
code
• LOC
–
lines
of
code
• NCLOC
–
non
comment
lines
of
code
• NOP
–
number
of
packages
• NOC
–
number
of
classes
• NOM
–
number
of
methods
Simple
metrics

Cyclomatic complexity measures
the amount of decision logic
in a single software module
Cycloma&c
Complexity
(CYCLO)

Condi3onal
statements:
• ?
• case
• elseif
• for
• foreach
• if
• while
Cycloma&c
Complexity
Number
(CCN)

Condi3onal
statements:
• ?
• &&
• case
• ||
• elseif
• for
• or
• foreach
• and
• if
• xor
• while
CCN2

Condi3onal
statements:
• ?
• &&
• case
• ||
• elseif
• for
• or
• foreach
• and
• if
• xor
• while
• catch
Cycloma&c
Complexity

class Foo {
public function example() {
if ($a == $b) {
if ($a1 == $b1) {
fiddle();
} elseif ($a2 == $b2) {
fiddle();
} else {
fiddle();
}
} elseif ($e == $f) {
for ($n = 0; $n < $h; $n++) {
fiddle();
}
} else {
fiddle();
}
}
}
Cycloma&c
complexity
-­‐
example

class Foo {
public function example() { 1
if ($a == $b) { 2
if ($a1 == $b1) { 3
fiddle();
} elseif ($a2 == $b2) { 4
fiddle();
} else {
fiddle();
}
} elseif ($e == $f) { 5
for ($n = 0; $n < $h; $n++) { 6
fiddle();
}
} else {
fiddle();
}
}
}
Cycloma&c
complexity
-­‐
example

phploc 1.6.1 by Sebastian Bergmann.
Directories: 6
Files: 20
Lines of Code (LOC): 5478
Cyclomatic Complexity / Lines of Code: 0.13
Comment Lines of Code (CLOC): 2143
Non-Comment Lines of Code (NCLOC): 3335
Namespaces: 0
Interfaces: 1
Classes: 18
Abstract: 2 (11.11%)
Concrete: 16 (88.89%)
Average Class Length (NCLOC): 191
Methods: 151
Scope:
Non-Static: 143 (94.70%)
Static: 8 (5.30%)
Visibility:
Public: 116 (76.82%)
Non-Public: 35 (23.18%)
Average Method Length (NCLOC): 22
Cyclomatic Complexity / Number of Methods: 3.72
Anonymous Functions: 0
Functions: 2
Constants: 4
Global constants: 3
Class constants: 1
phploc

Low
Avg
High
V.High
Complexity
1-­‐4
5-­‐7
8-­‐10
>
11
Cycloma&c
complexity
-­‐
thresholds

Metric
Low
Avg
High
V.High
CYCLO/Line
of
code
0.16
0.20
0.24
0.36
LOC/Method
7
10
13
19.5
NOM/Class
4
7
10
15
Source:
Object-­‐Oriented
Metrics
in
Prac5ce
(based
on
45
Java
projects)
JAVA

Metric
Low
Avg
High
V.High
CYCLO/Line
of
code
0.20
0.25
0.30
0.45
LOC/Method
5
10
16
24
NOM/Class
4
9
15
22.5
Source:
Object-­‐Oriented
Metrics
in
Prac5ce
(based
on
37
C++
projects)
C++

Weighted
Method
Count
–
total
complexity
of
a
class
Average
Method
Weight
–
average
complexity
of
a
method
WMC
and
AMW

Metric
Low
Avg
High
V.High
WMC
5
14
31
47
AMW
1.1
2.0
3.1
4.7
LOC/Class
28
70
130
195
Source:
Object-­‐Oriented
Metrics
in
Prac5ce
(based
on
45
Java
projects)
JAVA

Metric
Low
Avg
High
V.High
WMC
4
23
72
108
AMW
1.0
2.5
4.8
7.0
LOC/Class
20
90
240
360
Source:
Object-­‐Oriented
Metrics
in
Prac5ce
(based
on
37
C++
projects)
C++

Coverage
report

Coverage
report

C.R.A.P

Change
Risk
Analysis
and
Predic&ons
C.R.A.P

Code
coverage
=
100%
Code
coverage
=
0%
C.R.A.P
formula

C.R.A.P
thresholds

“NPATH is an objective measure of
software complexity related to
the ease with which software
can be comprehensively tested”
Edgar H. Sibley
NPATH
–
acyclic
execu&on
path
complexity

expressions Number of && and || operators in expression
if NP(<if-range>)+NP(<expr>)+1
if-else NP(<if-range>)+NP(<else-range>)+NP(<expr>)
while NP(<while-range>)+NP(<expr>)+1
for NP(<for-range>)+NP(<expr1>)+NP(<expr2>)+
NP(<expr3>)+1
break 1
continue 1
return 1
sequential 1
function call 1
NPATH
–
acyclic
execu&on
path
complexity

class Foo {
public function example() {
if ($a == $b) {
if ($a1 == $b1) {
fiddle();
} else {
fiddle();
}
}
if ($e == $f && $g == $z) {
for ($n = 0; $n < $h; $n++) {
fiddle();
}
}
return true;
}
}
NPATH
–
example

class Foo {
public function example() {
if ($a == $b) {
if ($a1 == $b1) {
fiddle();
} else { 3
fiddle();
}
}
if ($e == $f && $g == $z) {
for ($n = 0; $n < $h; $n++) {
fiddle(); 4
}
}
return true; 1
}
}
NPATH
–
example

PHP_Depend 0.10.6 by Manuel Pichler
Parsing source files:
.................... 20
Executing CyclomaticComplexity-Analyzer:
............. 261
Executing ClassLevel-Analyzer:
............ 247
Executing CodeRank-Analyzer:
. 28
Executing Coupling-Analyzer:
............. 267
Executing Hierarchy-Analyzer:
............ 246
Executing Inheritance-Analyzer:
. 30
Executing NPathComplexity-Analyzer:
.............. 283
Executing NodeCount-Analyzer:
........ 174
Executing NodeLoc-Analyzer:
.......... 205
Generating pdepend log files, this may take a moment.
Time: 00:05; Memory: 25.50Mb
PHP
Depend

PHP
Mess
Detector

Overview
pyramid

Size
and
complexity
–
direct
metrics

Size
and
complexity
–
computed
propor&ons

System
coupling
–
direct
metrics

System
coupling
–
computed
propor&ons

System
inheritance

Complete
Overview
Pyramid

Metric
Low
Avg
High
CYCLO/LOC
0.16
0.20
0.24
LOC/NOM
7
10
13
NOM/NOC
4
7
10
NOC/NOP
6
17
26
CALLS/NOM
2.01
2.62
3.2
FANOUT/CALLS
0.56
0.62
0.68
ANDC
0.25
0.41
0.57
AHH
0.09
0.21
0.32
hBp://pdepend.org/
PHP

Metrics
visualisa&on
with
Sonar

Metrics
visualisa&on
with
Sonar

Viola&ons
repor&ng

-­‐-­‐
Very
bad
-­‐
Bad
0
Average
+
Good
++
Very
good
SIG
Maintainability
Model

Technical
Debt

“We
believe
that
soIware
metrics,
in
general,
are
just
tools.
No
single
metric
can
tell
the
whole
story;
it’s
just
one
more
data
point.
“
“Metrics
are
meant
to
be
used
by
developers,
not
the
other
way
around
–
the
metric
should
work
for
you,
you
should
not
have
to
work
for
the
metric.
“
“Metrics
should
never
be
an
end
unto
themselves.
Metrics
are
meant
to
help
you
think,
not
to
do
the
thinking
for
you.”
• Alberto
Savoia
Summary

• PHP
Depend
-­‐
hmp://pdepend.org/
• PHP
Mess
Detector
-­‐
hmp://phpmd.org/
• Manuel’s
home
page
-­‐
hmp://manuel-­‐pichler.de/
• PHPUnit
-­‐
hmp://www.phpunit.de/
• phploc
-­‐
hmp://sebas&anbergmann.github.com/phploc/
• Sonar
-­‐
hmp://www.sonarsource.org/
Resources

“Object-­‐Oriented
Metrics
in
Prac&ce”
by
Michele
Lanza
and
Radu
Marinescu
(ISBN
978-­‐3540244295)
Object-­‐Oriented
Metrics
in
Prac&ce

• hmp://www.flickr.com/photos/romainguy/102073478/
• hmp://www.flickr.com/photos/shanafin/615680234/
• hmp://www.flickr.com/photos/pahudson/3080270873/
• hmp://www.flickr.com/photos/smohundro/2243554264/
• hmp://www.flickr.com/photos/m_a_melendez/5956157581/
• hmp://www.flickr.com/photos/elkit/7182541802/
• hmp://www.flickr.com/photos/rickyromero/4209571303/
Thanks
to…

Ques&ons?
hmps://joind.in/6445
Ques&ons?