Software in Pictures 2008-03-12

Software in pictures Tudor Gîrba www.tudorgirba.com

Software is complex. 29% Succeeded 18% Failed 53% Challenged The Standish Group, 2004

How large is your project?

How large is your project? 1’000’000 lines of code

How large is your project? 1’000’000 lines of code * 2 = 2’000’000 seconds

How large is your project? 1’000’000 lines of code * 2 = 2’000’000 seconds / 3600 = 560 hours

How large is your project? 1’000’000 lines of code * 2 = 2’000’000 seconds / 3600 = 560 hours / 8 = 70 days

How large is your project? 1’000’000 lines of code * 2 = 2’000’000 seconds / 3600 = 560 hours / 8 = 70 days / 20 = 3 months

fo rw ar d en gin ee rin g { { { { { { } { { } } actual development } } } { } } }

fo rw g rin ar ee d gin en gin en ee se rin erv g re { { { { { { } { { } } actual development } } } { } } }

McCabe = 21 NOM 0 = 102 3 ,00 75 = C LO Metrics Queries Visualizations ... { { { { } } } } { }

What are software metrics?

Youcannot control what you cannot measure. Tom de Marco

Software metrics are measurements which relate to software systems, processes or related documents

Metrics compress the system into numbers.

Examples of size metrics NOM - number of methods NOA - number of attributes LOC - number of lines of code NOS - number of statements NOC - number of children Lorentz, Kidd, 1994 Chidamber, 1994

McCabe cyclomatic complexity counts the number of possible paths through the code of a function. McCabe, 1977

Queries reduce the analysis space.

Detection Strategies are metric-based queries to detect design ﬂaws. Lanza, Marinescu 2006 Rule 1 METRIC 1 > Threshold 1 AND Quality problem Rule 2 METRIC 2 < Threshold 2

Example: a God Class centralizes too much intelligence in the system. Lanza, Marinescu 2006 Class uses directly more than a few attributes of other classes ATFD > FEW Functional complexity of the class is very high AND GodClass WMC ! VERY HIGH Class cohesion is low TCC < ONE THIRD

Software in pictures Tudor Gîrba www.tudorgirba.com

1956 2006

1956 2006 ?

Visualization compresses the system into pictures.

1854, London, cholera epidemic

A picture is worth a thousand words.

UML took it literally :)

We are visual beings.

How many groups do you see?

Gestalt principles proximity similarity enclosure connectivity

More Gestalt principles closure continuity

We are visual beings.

A picture is worth a thousand words.

UML took it literally :)

Example: what is ?

Polymetric views show up to 5 metrics. Lanza, 2003 Width metric Height metric Position metrics Color metric

System Complexity shows class hierarchies. Lanza, Ducasse, 2003 attributes methods lines

Class Blueprint shows class internals. Lanza, Ducasse, 2005 Initialize Interface Internal Accessor Attribute invocation and access direction

Class Blueprint has a rich vocabulary. internal access Access external Attribute access Invocation Regular Constant invocations Overriding Delegating lines Method Extending Setter Abstract Getter

Class Blueprint shows class internals.

Distribution Map shows properties over structure. Ducasse etal, 2006 31 parts, 394 elements and 9 properties

Code City shows where your code lives. Wettel, Lanza, 2007 classes are buildings grouped in quarters of packages

Object Flow shows how objects move. Lienhard etal, 2007 objects ﬂowing through other objects

fo rw g rin ar ee d gin en gin en ee se rin erv g re { { { { { { } { { } } actual development } } } { } } }

{ { } } } { { { } } re v er se en gin ee rin g reverse engineering fo rw ar actual development d en gin ee rin g { { } } { { } }

Spectographs show change activity. Wu etal, 2004 commit time

Evolution Matrix shows changes in classes. Lanza, Ducasse, 2002 Idle class Pulsar class Supernova class White dwarf class

Evolution Matrix shows changes in classes

What happens with inheritance? A A A A A B C B C B C B B D D D E ver .1 ver. 2 ver. 3 ver. 4 ver. 5

History contains too much data. A A A A A A A A A A A A A A A A A A A A B C B C B C B B B C B C B C B B B C B C B C B B B C B C B C B B D D D E D D D E D D D E D D D E ver .1 ver. 2 ver. 3 ver. 4 ver. 5 ver .1 ver. 2 ver. 3 ver. 4 ver. 5 ver .1 ver. 2 ver. 3 ver. 4 ver. 5 ver .1 ver. 2 ver. 3 ver. 4 ver. 5 A A A A A A A A A A A A A A A A A A A A B C B C B C B B B C B C B C B B B C B C B C B B B C B C B C B B D D D E D D D E D D D E D D D E ver .1 ver. 2 ver. 3 ver. 4 ver. 5 ver .1 ver. 2 ver. 3 ver. 4 ver. 5 ver .1 ver. 2 ver. 3 ver. 4 ver. 5 ver .1 ver. 2 ver. 3 ver. 4 ver. 5 A A A A A A A A A A A A A A A A A A A A B C B C B C B B B C B C B C B B B C B C B C B B B C B C B C B B D D D E D D D E D D D E D D D E ver .1 ver. 2 ver. 3 ver. 4 ver. 5 ver .1 ver. 2 ver. 3 ver. 4 ver. 5 ver .1 ver. 2 ver. 3 ver. 4 ver. 5 ver .1 ver. 2 ver. 3 ver. 4 ver. 5 A A A A A A A A A A A A A A A A A A A A B C B C B C B B B C B C B C B B B C B C B C B B B C B C B C B B D D D E D D D E D D D E D D D E ver .1 ver. 2 ver. 3 ver. 4 ver. 5 ver .1 ver. 2 ver. 3 ver. 4 ver. 5 ver .1 ver. 2 ver. 3 ver. 4 ver. 5 ver .1 ver. 2 ver. 3 ver. 4 ver. 5

A A A A A B C B C B C B B D D D E ver .1 ver. 2 ver. 3 ver. 4 ver. 5 A is persistent, B is stable, C was removed, E is newborn ...

Hierarchy Evolution encapsulates time. Girba etal, 2005 A changed methods changed age lines C B Removed Removed D E A is persistent, B is stable, C was removed, E is newborn ...

Hierarchy Evolution reveals patterns. Girba etal, 2005

Evolution Radar shows co-change relationships. D’Ambros, Lanza 2006 one package and its co-change relationships

moose.unibe.ch

But, what actually happens behind the scene?

System Complexity 1 node type 1 edge type 3 metrics Class Blueprint 3 node types 2 edge types 3 metrics 8 properties

A small experiment

1, 13, 27, 4, 96

What were the numbers?

What was the last advertisement you saw?

Not so easy!

Each visualization provides a language that needs to be learnt.

So, what does happen behind the scene?

Principle: Minimize chart junk Tufte, 1990

Excel default

Excel default Excel default + 6 actions

Distribution Map shows properties. Ducasse etal, 2006

Principle: Maximize data ink Tufte, 1990 Tufte, 1990

InfoBug is cute and condensed. Chuah, Eick, 2006

So, what does happen behind the scene?

Example 1: CVS shows activity.

Who did this?

Alphabetical order is no order.

Ownership Map orders histories to reveal patterns. Girba etal, 2006

Example 2: Who copied from whom? (john 23.06.03) public boolean stillValid (ToDoItem I, Designer dsgr) { (bill 09.01.05) if (!isActive()) { (bill 09.01.05) return false (bill 09.01.05) } (steve 16.02.05) List offs = i.getOffenders(); (john 23.06.03) Object dm = offs.firstElement(); (steve 16.02.05) ListSet newOffs = computeOffenders(dm); (john 23.06.03) boolean res = offs.equals(newOffs); (john 23.06.03) return res; (george 13.02.05) public boolean stillValid (ToDoItem I, Designer dsgr) { (bill 11.13.05) if (!isActive()) { (bill 11.13.05) return false (bill 11.13.05) } (steve 16.02.05) List offs = i.getOffenders(); (george 13.02.05) Object dm = offs.firstElement(); (steve 16.02.05) ListSet newOffs = computeOffenders(dm); (george 13.02.05) boolean res = offs.equals(newOffs); (george 13.02.05) return res;

What is useless? (john 23.06.03) public boolean stillValid (ToDoItem I, Designer dsgr) { (bill 09.01.05) if (!isActive()) { (bill 09.01.05) return false (bill 09.01.05) } (steve 16.02.05) List offs = i.getOffenders(); (john 23.06.03) Object dm = offs.firstElement(); (steve 16.02.05) ListSet newOffs = computeOffenders(dm); (john 23.06.03) boolean res = offs.equals(newOffs); (john 23.06.03) return res; (george 13.02.05) public boolean stillValid (ToDoItem I, Designer dsgr) { (bill 11.13.05) if (!isActive()) { (bill 11.13.05) return false (bill 11.13.05) } (steve 16.02.05) List offs = i.getOffenders(); (george 13.02.05) Object dm = offs.firstElement(); (steve 16.02.05) ListSet newOffs = computeOffenders(dm); (george 13.02.05) boolean res = offs.equals(newOffs); (george 13.02.05) return res;

When did changes happen? 23.06.03 public boolean stillValid (ToDoItem I, Designer dsgr) { 09.01.05 if (!isActive()) { 09.01.05 return false 09.01.05 } 16.02.05 List offs = i.getOffenders(); 23.06.03 Object dm = offs.firstElement(); 16.02.05 ListSet newOffs = computeOffenders(dm); 23.06.03 boolean res = offs.equals(newOffs); 23.06.03 return res; 13.02.05 public boolean stillValid (ToDoItem I, Designer dsgr) { 11.13.05 if (!isActive()) { 11.13.05 return false 11.13.05 } 16.02.05 List offs = i.getOffenders(); 13.02.05 Object dm = offs.firstElement(); 16.02.05 ListSet newOffs = computeOffenders(dm); 13.02.05 boolean res = offs.equals(newOffs); 13.02.05 return res;

Clone Evolution shows how developers copy. Balint etal, 2006

Not every picture is worth a thousand words.

One more thing ...

Visualization is art, too.

Tudor Gîrba www.tudorgirba.com creativecommons.org/licenses/by/3.0/

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Software in Pictures 2008-03-12

by Tudor Girba on Mar 16, 2008

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