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

Sebas&an  Marek,  So.ware  Architect  

Magic  behind  the  numbers    

So.ware  metrics  in  prac&ce  

@proofek  

•  a  Pole  living  in  Sheffield  •  over  12  years  in  

development  •  Pascal,  C++,  PHP,  perl,  

python,  Java  •  co-­‐author  of  2  PHP  books    •  big  fan  of  process  

automa&on  •  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  

Most  effec&ve  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

So.ware  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  documenta&on  

•  Convoluted  design  

•  Intensive  patch  mechanism  (hacking)  

•  Large  size  

•  Severe  duplica&on  

•  Obsolete  parts  (dead  code)  

•  Long  build  &mes  

•  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  

Cycloma&c  Complexity  (CYCLO)  

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

Cycloma&c  Complexity  Number  (CCN)  

Condi3onal  statements:    •  ?  •  case  •  elseif  •  for  •  foreach  •  if  •  while  

CCN2  

Condi3onal  statements:    •  ?  •  case  •  elseif  •  for  •  foreach  •  if  •  while  

•  &&  •  ||  •  or  •  and  •  xor  

Cycloma&c  Complexity  

Condi3onal  statements:    •  ?  •  case  •  elseif  •  for  •  foreach  •  if  •  while  

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

Cycloma&c  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(); } } }

Cycloma&c  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(); } } }

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  

Cycloma&c  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  Prac5ce  (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  Prac5ce  (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  

Source:  Object-­‐Oriented  Metrics  in  Prac5ce  (based  on  45  Java  projects)  

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  

C++  

Source:  Object-­‐Oriented  Metrics  in  Prac5ce  (based  on  37  C++  projects)  

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  

Coverage  report  

Coverage  report  

C.R.A.P  

C.R.A.P  

Change  Risk  Analysis  and    Predic&ons  

C.R.A.P  formula  

Code  coverage  =  100%  

Code  coverage  =  0%  

C.R.A.P  thresholds  

NPATH  –  acyclic  execu&on  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  execu&on  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(); } else { 3 fiddle(); } }

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

return true; 1 } }

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  propor&ons  

System  coupling  –  direct  metrics  

System  coupling  –  computed  propor&ons  

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  

hBp://pdepend.org/  

Metrics  visualisa&on  with  Sonar  

Metrics  visualisa&on  with  Sonar  

Viola&ons  repor&ng  

SIG  Maintainability  Model  

-­‐-­‐  -­‐  0  +  ++    

Very  bad  Bad  Average  Good  Very  good  

Technical  Debt  

Summary  

“We  believe  that  soIware  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  -­‐  hmp://pdepend.org/  •  PHP  Mess  Detector  -­‐  hmp://phpmd.org/  •  Manuel’s  home  page  -­‐  hmp://manuel-­‐pichler.de/  •  PHPUnit  -­‐  hmp://www.phpunit.de/  •  phploc  -­‐  hmp://sebas&anbergmann.github.com/phploc/  •  Sonar  -­‐  hmp://www.sonarsource.org/  

Object-­‐Oriented  Metrics  in  Prac&ce  

“Object-­‐Oriented  Metrics  in  Prac&ce”  by  Michele  Lanza  and  Radu  Marinescu  (ISBN  978-­‐3540244295)  

Thanks  to…  

•  hmp://www.flickr.com/photos/romainguy/102073478/  •  hmp://www.flickr.com/photos/shanafin/615680234/  •  hmp://www.flickr.com/photos/pahudson/3080270873/  •  hmp://www.flickr.com/photos/smohundro/2243554264/  •  hmp://www.flickr.com/photos/m_a_melendez/5956157581/  •  hmp://www.flickr.com/photos/elkit/7182541802/  •  hmp://www.flickr.com/photos/rickyromero/4209571303/    

Ques&ons?  

Ques&ons?  

hmps://joind.in/6445