Software metrics can provide useful insights into code quality and complexity. Code metrics like lines of code, cyclomatic complexity, and weighted method count measure characteristics like code size, logic complexity, and class complexity. Design metrics evaluate qualities like coupling and cohesion. Metrics are most effective when used to identify improvement opportunities rather than to judge the overall quality of code or designs. Calculating and tracking metrics over time can help optimize code and catch regressions during development.

1. Magic behind the
numbers
Software metrics in
practice
Sebastian Marek, Software Architect

2. @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

3. Agenda
What I will be talking about
• Code metrics
• Design metrics
What I will not be talking about
• Project metrics
https://joind.in/4758

4. Most effective code quality measure

6. 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

7. 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

8. 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

9. 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

10. Cyclomatic Complexity (CYCLO)
Cyclomatic complexity measures the
amount of decision logic in a single software
module.

11. Cyclomatic Complexity Number (CCN)
Conditional statements:
• ?
• case
• elseif
• for
• foreach
• if
• while

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

13. Cyclomatic complexity
Conditional statements:
• ? • &&
• case • ||
• elseif • or
• for • and
• foreach • xor
• if • catch
• while

14. 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();
}
}
}

15. 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();
}
}
}

16. 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();
}
}
}

17. 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();
}
}
}

18. 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();
}
}
}

19. 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();
}
}
}

20. 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();
}
}
}

21. Cyclomatic complexity - example
class Foo {
public function example() {
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();
}
}
}

22. 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

23. Cyclomatic complexity - thresholds
Low Avg High V.High
Complexity 1-4 5-7 8-10 > 11

24. 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)

25. 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)

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

27. 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)

28. 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)

29. Coverage report

31. C.R.A.P

32. C.R.A.P
Change
Risk
Analysis and
Change Risk Analysis and Predictions
Predictions

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

35. 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

36. 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

37. 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;
}
}

38. 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;
}
}

39. 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;
}
}

40. 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;
}
}

41. NPATH – example
class Foo {
public function example() {
if ($a == $b) {
if ($a1 == $b1) {
fiddle();
} else { 2
fiddle();
}
}
if ($e == $f && $g == $z) {
for ($n = 0; $n < $h; $n++) {
fiddle();
}
}
return true;
}
}

42. NPATH – example
class Foo {
public function example() {
if ($a == $b) {
if ($a1 == $b1) {
fiddle();
} else { 2
fiddle();
}
}
if ($e == $f && $g == $z) {
for ($n = 0; $n < $h; $n++) {
fiddle();
}
}
return true;
}
}

43. NPATH – example
class Foo {
public function example() {
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;
}
}

44. NPATH – example
class Foo {
public function example() {
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;
}
}

45. 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();
}
}
return true;
}
}

46. 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(); 1
}
}
return true;
}
}

47. 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++) { 1
fiddle(); 1
}
}
return true;
}
}

48. 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++) { 1
fiddle(); 1
} 2
}
return true;
}
}

49. 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(); 2
}
}
return true;
}
}

50. 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(); 2
}
}
return true;
}
}

51. NPATH – example
class Foo {
public function example() {
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;
}
}

52. NPATH – example
class Foo {
public function example() {
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;
}
}

53. 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;
}
}

54. 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
}
}

55. NPATH – example
class Foo {
public function example() {
if ($a == $b) {
if ($a1 == $b1) {
fiddle();
} else {
fiddle();
}
}
12
if ($e == $f && $g == $z) {
for ($n = 0; $n < $h; $n++) {
fiddle();
}
}
return true;
}
}

56. 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

57. PHP Mess Detector

58. Overview pyramid

59. Size and complexity – direct metrics

60. Size and complexity – computed proportions

61. System coupling – direct metrics

62. System coupling – computed proportions

63. System inheritance

64. Complete Overview Pyramid

65. 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/

66. Metrics visualisation with Sonar

67. Metrics visualisation with Sonar

68. Violations reporting

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

70. Technical Debt

71. 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

72. 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)

73. Questions
Questions?
https://joind.in/4758