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PHP Benelux 2012: Magic behind the numbers. Software metrics in practice
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.
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PHP Benelux 2012: Magic behind the numbers. Software metrics in practice
- 1. Magic behind the numbers Software metrics in practice Sebastian Marek, Software Architect
- 2. @proofek • a Poleliving 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 willbe talking about • Code metrics • Design metrics What I will not be talking about • Project metrics https://joind.in/4758
- 4. Most effective codequality measure
- 6. What is ametric? “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 “Gooddesign 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 bySebastian 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 WeightedMethod 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.
- 31.
- 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 – acyclicexecution 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 – acyclicexecution 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 classFoo { public function example() { if ($a == $b) { if ($a1 == $b1) { fiddle(); } else { fiddle(); } } if ($e == $f && $g == $z) { for ($n = 0; $n < $h; $n++) { fiddle(); } } return true; } }
- 38. NPATH – example classFoo { public function example() { if ($a == $b) { if ($a1 == $b1) { fiddle(); 1 } else { fiddle(); } } if ($e == $f && $g == $z) { for ($n = 0; $n < $h; $n++) { fiddle(); } } return true; } }
- 39. NPATH – example classFoo { public function example() { if ($a == $b) { if ($a1 == $b1) { fiddle(); 1 } else { fiddle(); 2 } } if ($e == $f && $g == $z) { for ($n = 0; $n < $h; $n++) { fiddle(); } } return true; } }
- 40. NPATH – example classFoo { public function example() { if ($a == $b) { if ($a1 == $b1) { 2 fiddle(); 1 } else { fiddle(); 2 } } if ($e == $f && $g == $z) { for ($n = 0; $n < $h; $n++) { fiddle(); } } return true; } }
- 41. NPATH – example classFoo { public function example() { if ($a == $b) { if ($a1 == $b1) { fiddle(); } else { 2 fiddle(); } } if ($e == $f && $g == $z) { for ($n = 0; $n < $h; $n++) { fiddle(); } } return true; } }
- 42. NPATH – example classFoo { public function example() { if ($a == $b) { if ($a1 == $b1) { fiddle(); } else { 2 fiddle(); } } if ($e == $f && $g == $z) { for ($n = 0; $n < $h; $n++) { fiddle(); } } return true; } }
- 43. NPATH – example classFoo { public function example() { if ($a == $b) { 2 if ($a1 == $b1) { fiddle(); } else { 2 fiddle(); } } if ($e == $f && $g == $z) { for ($n = 0; $n < $h; $n++) { fiddle(); } } return true; } }
- 44. NPATH – example classFoo { public function example() { if ($a == $b) { 2 if ($a1 == $b1) { fiddle(); } else { 2 fiddle(); } } 3 if ($e == $f && $g == $z) { for ($n = 0; $n < $h; $n++) { fiddle(); } } return true; } }
- 45. NPATH – example classFoo { public function example() { if ($a == $b) { if ($a1 == $b1) { fiddle(); } else { 3 fiddle(); } } if ($e == $f && $g == $z) { for ($n = 0; $n < $h; $n++) { fiddle(); } } return true; } }
- 46. NPATH – example classFoo { public function example() { if ($a == $b) { if ($a1 == $b1) { fiddle(); } else { 3 fiddle(); } } if ($e == $f && $g == $z) { for ($n = 0; $n < $h; $n++) { fiddle(); 1 } } return true; } }
- 47. NPATH – example classFoo { public function example() { if ($a == $b) { if ($a1 == $b1) { fiddle(); } else { 3 fiddle(); } } if ($e == $f && $g == $z) { for ($n = 0; $n < $h; $n++) { 1 fiddle(); 1 } } return true; } }
- 48. NPATH – example classFoo { public function example() { if ($a == $b) { if ($a1 == $b1) { fiddle(); } else { 3 fiddle(); } } if ($e == $f && $g == $z) { for ($n = 0; $n < $h; $n++) { 1 fiddle(); 1 } 2 } return true; } }
- 49. NPATH – example classFoo { public function example() { if ($a == $b) { if ($a1 == $b1) { fiddle(); } else { 3 fiddle(); } } if ($e == $f && $g == $z) { for ($n = 0; $n < $h; $n++) { fiddle(); 2 } } return true; } }
- 50. NPATH – example classFoo { public function example() { if ($a == $b) { if ($a1 == $b1) { fiddle(); } else { 3 fiddle(); } } if ($e == $f && $g == $z) { for ($n = 0; $n < $h; $n++) { fiddle(); 2 } } return true; } }
- 51. NPATH – example classFoo { public function example() { if ($a == $b) { if ($a1 == $b1) { fiddle(); } else { 3 fiddle(); } } if ($e == $f && $g == $z) { 3 for ($n = 0; $n < $h; $n++) { fiddle(); 2 } } return true; } }
- 52. NPATH – example classFoo { public function example() { if ($a == $b) { if ($a1 == $b1) { fiddle(); } else { 3 fiddle(); } } if ($e == $f && $g == $z) { 3 for ($n = 0; $n < $h; $n++) { fiddle(); 2 } } 4 return true; } }
- 53. NPATH – example classFoo { public function example() { if ($a == $b) { if ($a1 == $b1) { fiddle(); } else { 3 fiddle(); } } if ($e == $f && $g == $z) { for ($n = 0; $n < $h; $n++) { fiddle(); 4 } } return true; } }
- 54. NPATH – example classFoo { public function example() { if ($a == $b) { if ($a1 == $b1) { fiddle(); } else { 3 fiddle(); } } if ($e == $f && $g == $z) { for ($n = 0; $n < $h; $n++) { fiddle(); 4 } } return true; 1 } }
- 55. NPATH – example classFoo { public function example() { if ($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 0.10.6by 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.
- 58.
- 59. Size and complexity– direct metrics
- 60. Size and complexity– computed proportions
- 61. System coupling –direct metrics
- 62. System coupling –computed proportions
- 63.
- 64.
- 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.
- 67.
- 68.
- 69. SIG Maintainability Model -- Very bad - Bad 0 Average + Good ++ Very good
- 70.
- 71. Summary “We believe thatsoftware 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.