PHP Benelux 2012: Magic behind the numbers. Software metrics in practice

Magic behind the
numbers

Software metrics in
practice

Sebastian Marek, Software Architect

@proofek

•  a Pole living in Sheffield
•  over 10 years PHP
experience
•  co-author of 2 PHP books
•  big fan of process
automation
•  TDD and CI
•  occasionally contributes
to open source projects
•  wants to be a knight

Agenda

What I will be talking about
•  Code metrics
•  Design metrics

What I will not be talking about
•  Project metrics

https://joind.in/4758

Most effective code quality measure

What is a metric?

“It is the mapping of a particular
characteristic of a measured entity to
a numerical value”

Source: Object-Oriented Metrics in Practice

Software design

“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

System maintenance

•  Obsolete documentation
•  Convoluted design
•  Intensive patch mechanism (hacking)
•  Large size
•  Severe duplication
•  Obsolete parts (dead code)
•  Long build times
•  Loss of original developers

Simple metrics

•  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

Cyclomatic Complexity (CYCLO)

Cyclomatic complexity measures the
amount of decision logic in a single software
module.

Cyclomatic Complexity Number (CCN)

Conditional statements:
•  ?
•  case
•  elseif
•  for
•  foreach
•  if
•  while

CCN2

•  ? •  &&
•  case •  ||
•  elseif •  or
•  for •  and
•  foreach •  xor
•  if
•  while

Cyclomatic complexity

•  ? •  &&
•  case •  ||
•  elseif •  or
•  for •  and
•  foreach •  xor
•  if •  catch
•  while

Cyclomatic complexity - example
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();
}
}
}

class Foo {
public function example() { 1
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();
}
}
}

class Foo {
if ($a == $b) { 2
if ($a1 == $b1) {
fiddle();
} elseif ($a2 == $b2) {
fiddle();
} else {
fiddle();
}
} elseif ($e == $f) {
for ($n = 0; $n < $h; $n++) {
fiddle();
}
} else {
fiddle();
}
}
}

class Foo {
if ($a == $b) { 2
if ($a1 == $b1) { 3
fiddle();
} elseif ($a2 == $b2) {
fiddle();
} else {
fiddle();
}
} elseif ($e == $f) {
for ($n = 0; $n < $h; $n++) {
fiddle();
}
} else {
fiddle();
}
}
}

class Foo {
if ($a == $b) { 2
if ($a1 == $b1) { 3
fiddle();
} elseif ($a2 == $b2) { 4
fiddle();
} else {
fiddle();
}
} elseif ($e == $f) {
for ($n = 0; $n < $h; $n++) {
fiddle();
}
} else {
fiddle();
}
}
}

class Foo {
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++) {
fiddle();
}
} else {
fiddle();
}
}
}

class Foo {
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();
}
}
}

class Foo {
if ($a == $b) {
if ($a1 == $b1) {
fiddle();
} elseif ($a2 == $b2) {
fiddle();
} else {
fiddle();
} 6
} elseif ($e == $f) {
for ($n = 0; $n < $h; $n++) {
fiddle();
}
} else {
fiddle();
}
}
}

phploc
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

Cyclomatic complexity - thresholds

Low Avg High V.High
Complexity 1-4 5-7 8-10 > 11

JAVA

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 Practice (based on 45 Java projects)

C++

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 Practice (based on 37 C++ projects)

WMC and AMW

Weighted Method Count – total complexity of a class

Average Method Weight – average complexity of a method

JAVA

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 Practice (based on 45 Java projects)

C++

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 Practice (based on 37 C++ projects)

C.R.A.P

Change
Risk
Analysis and
Change Risk Analysis and Predictions

Predictions

C.R.A.P formula

Code coverage = 100%

Code coverage = 0%

NPATH – acyclic execution path complexity

NPATH is an objective measure of software
complexity related to the ease with which
software can be comprehensively tested
Edgar H. Sibley

NPATH – acyclic execution 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 – example
class Foo {

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 {

if ($a == $b) {
if ($a1 == $b1) {
fiddle(); 1
} else {
fiddle();
}
}

if ($e == $f && $g == $z) {
for ($n = 0; $n < $h; $n++) {
fiddle();
}
}

return true;
}
}

NPATH – example
class Foo {

if ($a == $b) {
if ($a1 == $b1) {
fiddle(); 1
} else {
fiddle(); 2
}
}

if ($e == $f && $g == $z) {
for ($n = 0; $n < $h; $n++) {
fiddle();
}
}

return true;
}
}

NPATH – example
class Foo {

if ($a == $b) {
if ($a1 == $b1) { 2
fiddle(); 1
} else {
fiddle(); 2
}
}

if ($e == $f && $g == $z) {
for ($n = 0; $n < $h; $n++) {
fiddle();
}
}

return true;
}
}

NPATH – example
class Foo {

if ($a == $b) {
if ($a1 == $b1) {
fiddle();
} else { 2
fiddle();
}
}

if ($e == $f && $g == $z) {
for ($n = 0; $n < $h; $n++) {
fiddle();
}
}

return true;
}
}

NPATH – example
class Foo {

if ($a == $b) { 2
if ($a1 == $b1) {
fiddle();
} else { 2
fiddle();
}
}

if ($e == $f && $g == $z) {
for ($n = 0; $n < $h; $n++) {
fiddle();
}
}

return true;
}
}

NPATH – example
class Foo {

if ($a == $b) { 2
if ($a1 == $b1) {
fiddle();
} else { 2
fiddle();
}
} 3

if ($e == $f && $g == $z) {
for ($n = 0; $n < $h; $n++) {
fiddle();
}
}

return true;
}
}

NPATH – example
class Foo {

if ($a == $b) {
if ($a1 == $b1) {
fiddle();
} else { 3
fiddle();
}
}

if ($e == $f && $g == $z) {
for ($n = 0; $n < $h; $n++) {
fiddle();
}
}

return true;
}
}

NPATH – example
class Foo {

if ($a == $b) {
if ($a1 == $b1) {
fiddle();
} else { 3
fiddle();
}
}

if ($e == $f && $g == $z) {
for ($n = 0; $n < $h; $n++) {
fiddle(); 1
}
}

return true;
}
}

NPATH – example
class Foo {

if ($a == $b) {
if ($a1 == $b1) {
fiddle();
} else { 3
fiddle();
}
}

if ($e == $f && $g == $z) {
for ($n = 0; $n < $h; $n++) { 1
fiddle(); 1
}
}

return true;
}
}

NPATH – example
class Foo {

if ($a == $b) {
if ($a1 == $b1) {
fiddle();
} else { 3
fiddle();
}
}

if ($e == $f && $g == $z) {
for ($n = 0; $n < $h; $n++) { 1
fiddle(); 1
} 2
}

return true;
}
}

NPATH – example
class Foo {

if ($a == $b) {
if ($a1 == $b1) {
fiddle();
} else { 3
fiddle();
}
}

if ($e == $f && $g == $z) {
for ($n = 0; $n < $h; $n++) {
fiddle(); 2
}
}

return true;
}
}

NPATH – example
class Foo {

if ($a == $b) {
if ($a1 == $b1) {
fiddle();
} else { 3
fiddle();
}
}

if ($e == $f && $g == $z) { 3
for ($n = 0; $n < $h; $n++) {
fiddle(); 2
}
}

return true;
}
}

NPATH – example
class Foo {

if ($a == $b) {
if ($a1 == $b1) {
fiddle();
} else { 3
fiddle();
}
}

if ($e == $f && $g == $z) { 3
for ($n = 0; $n < $h; $n++) {
fiddle(); 2
}
} 4

return true;
}
}

NPATH – example
class Foo {

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;
}
}

NPATH – example
class Foo {

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
class Foo {

if ($a == $b) {
if ($a1 == $b1) {
fiddle();
} else {
fiddle();
}
}
12
if ($e == $f && $g == $z) {
for ($n = 0; $n < $h; $n++) {
fiddle();
}
}

return true;
}
}

PHP Depend
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

Size and complexity – direct metrics

Size and complexity – computed proportions

System coupling – direct metrics

System coupling – computed proportions

PHP

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

http://pdepend.org/

Metrics visualisation with Sonar

SIG Maintainability Model

-- Very bad
- Bad
0 Average
+ Good
++ Very good

Summary

“We believe that software 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

Resources

•  PHP Depend - http://pdepend.org/
•  PHP Mess Detector - http://phpmd.org/
•  Manuel’s home page - http://manuel-pichler.de/
•  PHPUnit - http://www.phpunit.de/
•  phploc - http://sebastianbergmann.github.com/phploc/
•  Sonar - http://www.sonarsource.org/
•  “Object-Oriented Metrics in Practice” by Michele Lanza
and Radu Marinescu (ISBN 978-3540244295)

Questions

Questions?

https://joind.in/4758

PHP Benelux 2012: Magic behind the numbers. Software metrics in practice

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PHP Benelux 2012: Magic behind the numbers. Software metrics in practice