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

Magic behind the numbers Software metrics in practiceSebastian 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

AgendaWhat I will be talking about•  Code metrics•  Design metricsWhat 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 particularcharacteristic of a measured entity to a numerical value” Source: Object-Oriented Metrics in Practice

Software design “Good design quality metrics are notnecessarily 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 theamount of decision logic in a single software module.

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

CCN2Conditional statements:•  ? •  &&•  case •  ||•  elseif •  or•  for •  and•  foreach •  xor•  if•  while

Cyclomatic complexityConditional statements:•  ? •  &&•  case •  ||•  elseif •  or•  for •  and•  foreach •  xor•  if •  catch•  while

Cyclomatic complexity - exampleclass 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 - exampleclass 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 - exampleclass 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 - exampleclass 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 - exampleclass 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 - exampleclass 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 - exampleclass 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 - exampleclass 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(); } }}

phplocphploc 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.HighComplexity 1-4 5-7 8-10 > 11

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

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

WMC and AMWWeighted Method Count – total complexity of a classAverage Method Weight – average complexity of a method

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

C++Metric Low Avg High V.HighWMC 4 23 72 108AMW 1.0 2.5 4.8 7.0LOC/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.PChangeRiskAnalysis and Change Risk Analysis and PredictionsPredictions

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

NPATH – acyclic execution path complexityNPATH 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 complexityexpressions 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 – exampleclass 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 – exampleclass 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 – exampleclass 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 – exampleclass 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 – exampleclass 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; }}

NPATH – exampleclass 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; }}

NPATH – exampleclass 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; }}

NPATH – exampleclass 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; }}

NPATH – exampleclass 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; }}

NPATH – exampleclass 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; }}

NPATH – exampleclass 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; }}

NPATH – exampleclass 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; }}

NPATH – exampleclass 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; }}

NPATH – exampleclass 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 – exampleclass 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; }}

PHP DependPHP_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 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

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

Metrics visualisation with Sonar

Violations reporting

SIG Maintainability Model-- Very bad- Bad0 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)

QuestionsQuestions?https://joind.in/4758

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

by Sebastian Marek on Jan 28, 2012

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