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Lucian Voinea
Visualizing the Evolution of CodeThe Visual Code Navigator (VCN)
Nunspeet, 24.11.2008
The software maintenance challenge
Software maintenance costs
80% of TCO( total cost of ownership)=
Mostly spent on understanding software
Often caused by uninformed decisions
• What is software visualization?
• Code Evolution Visualization in VCNo Line of code levelo File level
• Conclusions
Outline
What is software visualization?
Scientific Visualization: “The use of computers or techniques for comprehending data or to extract knowledge from the results of simulations, computations, or measurements”[McCormick et al, 1987]
Information Visualization: “Visualization applied to abstract quantities and relations in order to get insight in the data” [Chi, 2000][Diehl, 2006][…]
Software Visualization: “Information visualization applied to software artefacts e.g. source code, design documents, profiling logs, and dynamic data structures in order to better write, understand and maintain, software”
Software visualization vs visual programming
visual programmingtool
software visualizationtool
SW engineer
the visual artifact space
the software
visualprogramming
programvisualization
is readby
creates
generates
is analyzed by
creates
is examined by
Software visualization pipeline
softwaredata
dataacquisition
internaldata
dataprocessing
datamapping
enricheddata
visualrepresentations
graphicsrendering
imagehumaninterpretation
software analysis
data visualization
Software visualization classifications
Matrix of techniques [Myers, 1990]
type of data
time aspect
Dynamic(behavior)
Static(structure)
Code Data Algorithm
VCN
few many
evolution
Visual Code Navigator (VCN)
a toolset that provides different, but strongly interconnected views on software source codeVCN
VCNdatabase
CVS
SVN
Data processing enginesSCM
Code evolution visualization
Goal: Understand when, why, and how software changed to cope with future activities (e.g. refactoring, release scheduling, test planning etc.)
Dev
elo
per
sM
anag
emen
t
Use cases:- identify the system parts that could be affected by a change or migration- identify the system areas that are subject to debugging in the near future- get context dependent code editing suggestions - discover the developer network
Benefits:- assess impact more accurately- better plan maintenance activities- reduce software understanding time- minimize error injection probability
Code evolution visualization in VCN
Line of code level File level
CVSscan CVSgrab
Evolution visualization at line level
Goal: Understand how did a file evolve.- What were the major refactorings, contributions- Who is in charge of a given piece of code
CVSscan
if self.bShowClusterColor:glBlendFunc(GL_ONE_MINUS_...glEnable(GL_BLEND)yPos = 0 bSwitch = Truefor i in lCushionMap:if bSwitch:
cushions.drawColorCl..else:cushions.drawColorClus…bSwitch = not bSwitchyPos = yPos + i
glDisable(GL_BLEND) #cushion clustersglBlendFunc(GL_ZERO,GL_... glEnable(GL_BLEND)yPos = 0 bSwitch = True
Timev1 v2 v3 v4 v5
Color - encodes a line metric
Deleted lines Lines to be
inserted
Constant line New lines Legend
Normal Layout
Discrete time (versions) Discrete time (versions)
Horizontal Layout
Color encodes authors Color encodes line contents
Time (version)
File line
Time (version)
File line
Evolution visualization at line level
CVSscan
Version 2Version 1 Version 3
File 2 Version 1 Version 2
File 3 Version 1 Version 2
File 1
Time
Project
Evolution visualization at file level
CVSgrab
Goal: Understand how did a project evolve.
Version 2Version 1 Version 3
File 2 Version 1 Version 2
File 3 Version 1 Version 2
File 1
Time
Project
Release IDSizeComplexitySearched word…
Release IDSizeComplexitySearched word…
Evolution visualization at file level
CVSgrab
Goal: Understand how did a project evolve.
Sorting and clustering operations
Conclusion:
1. Software is not in a mature state (development is not stabilized).2. It is difficult to maintain (high activity in large files).3. Highly complex (≈ 30% have McCabe’s metric ≥ 7 per 30 lines of code)
Case: Shall we buy this software stack ?
Evolution visualization at file level
CVSgrab
Case: What is the risk of releasing the software now?
Conclusion:
1. There are currently no large scale debugging activities performed2. The largest recent debugging activity was localized to one folder3. Changes in the identified folder do not propagate outside
Evolution visualization at file level
CVSgrab
Conclusion:
Well distributed knowledge
Risky distribution of knowledge
Case: What is the risk of one person leaving the team ?
Evolution visualization at file level
CVSgrab
Conclusions
Software Visualization• is a new but quickly growing field; many tools are emerging at a high pace
• promising but validation is still a problem; integration is a must!
Visual Code Navigator• contains two tools for analyzing source code evolution (CVSscan, CVSgrab)
• offers a set of visual techniques that can supports a large variety of analysis scenarios
• tries to bridge the gap between research and industry by tight integration with common software configuration management (SCM) systems (e.g., CVS, Subversion)
Thank you for your attention !
http://www.win.tue.nl/~lvoinea/VCN.htmlhttp://www.win.tue.nl/vis/
