Sebastian Marek, Software Architect

Magic behind the numbers

Software metrics in

practice

@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

“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

Software design

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

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

•  && •  || •  or •  and •  xor

Cyclomatic complexity

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

•  && •  || •  or •  and •  xor •  catch

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(); } } }

Cyclomatic complexity - example

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(); } } }

Cyclomatic complexity - example

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

Cyclomatic complexity - example

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

Cyclomatic 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 == $f) { for ($n = 0; $n < $h; $n++) { fiddle(); } } else { fiddle(); } } }

Cyclomatic 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++) { fiddle(); } } else { fiddle(); } } }

Cyclomatic 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(); } } }

Cyclomatic complexity - example

class Foo { public function example() {

6

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(); } } }

phploc phploc 1.6.1 by Sebastian Bergmann.Directories: 6Files: 20Lines of Code (LOC): 5478 Cyclomatic Complexity / Lines of Code: 0.13Comment Lines of Code (CLOC): 2143Non-Comment Lines of Code (NCLOC): 3335Namespaces: 0Interfaces: 1Classes: 18 Abstract: 2 (11.11%) Concrete: 16 (88.89%) Average Class Length (NCLOC): 191Methods: 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: 3.72Anonymous Functions: 0Functions: 2Constants: 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++

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 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

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 Practice (based on 45 Java projects)

C++

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 Practice (based on 37 C++ projects)

Coverage report

C.R.A.P

C.R.A.P

Change Risk Analysis and Predictions

Change Risk Analysis and 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 { 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(); 1 } 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(); 1 } else { fiddle(); 2 } }

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) { 2 fiddle(); 1 } else { fiddle(); 2 } }

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) {

2 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) {

2 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 == $b) { 2 if ($a1 == $b1) {

2 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 == $b) { 2 if ($a1 == $b1) {

2 fiddle(); } else { fiddle(); } } 3

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

NPATH – example class Foo { public function example() {

if ($a == $b) {

3

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) {

3

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

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

NPATH – example class Foo { public function example() {

if ($a == $b) {

3

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

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

NPATH – example class Foo { public function example() {

if ($a == $b) {

3

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

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

NPATH – example class Foo { public function example() {

if ($a == $b) {

3

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

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

2 fiddle(); } } return true; } }

NPATH – example class Foo { public function example() {

if ($a == $b) {

3

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

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

2 fiddle(); } } return true; } }

NPATH – example class Foo { public function example() {

if ($a == $b) {

3

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

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

2 fiddle(); } } return true; } }

NPATH – example class Foo { public function example() {

if ($a == $b) {

3

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

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

2 fiddle(); } } 4 return true; } }

NPATH – example class Foo { public function example() {

if ($a == $b) {

3

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

if ($e == $f && $g == $z) {

4 for ($n = 0; $n < $h; $n++) { fiddle(); } } return true; } }

NPATH – example class Foo { public function example() {

if ($a == $b) {

3

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

if ($e == $f && $g == $z) {

4 for ($n = 0; $n < $h; $n++) { fiddle(); } } return true; 1 } }

NPATH – example class Foo { public function example() {

12

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

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

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

PHP Mess Detector

Overview pyramid

Size and complexity – direct metrics

Size and complexity – computed proportions

System coupling – direct metrics

System coupling – computed proportions

System inheritance

Complete Overview Pyramid

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

Metrics visualisation with Sonar

Violations reporting

SIG Maintainability Model

-- - 0 + ++

Very bad Bad Average Good Very good

Technical Debt

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