Software Visualization

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Software Visualization

• CS 7450 - Information Visualization
• November 14, 2000

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Software Visualization

• Definition

The use of the crafts of typography, graphic
design, animation, and cinematography with modern
human- computer interaction and computer graphics
technology to facilitate both the human
understanding and effective use of computer
software.Price, Baecker and Small, 98
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Challenge

• Software clearly is abstract data
• Unlike much information visualization, however,
  software is often dynamic, thus requiring our
  visualizations reflect the time dimension
• History views
• Animation
• ...

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Subdomains

• Two main subareas of software visualization
• Program visualization - Use of visualization to
  help programmers, coders, developers. Software
  engineering focus
• Algorithm visualization - Use of visualization to
  help teach algorithms and data structures.
  Pedagogy focus

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Subareas

• Program Visualization
• Software engineering
• Debugging
• Program analysis
• Systems

• Algorithm Visualization
• Pedagogy
• Systems
• Use in classroom
• Empirical study

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Todays Talk

• This is a very big area, so talk will just give a
  flavor of the kinds of techniques and systems
  that have been created
• Lots of figures
• Some demos and videos

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Program Visualization

• Can be as simple as enhanced views of program
  source
• Can be as complex as views of the execution of a
  highly parallel program, its data structures,
  run-time heap, etc.

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Enhanced Code Views
Primarily used as a documentation aid
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SeeSoft System

• Pulled-back, far away view of source code
• Map one line of source to one line of pixels
• Can indicate line indentation, etc.
• Like taping your source code to the wall, walking
  far away, then looking back at it

Eick, Steffen and Sumner 92
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System View
15,000 lines of code in 52 files
Video
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Use

• Tracking (typically means mapping this data
  attribute to color)
• Code modification (when, by whom)
• Bug fixes
• Code coverage or hotspots in tests
• Interactive, can change color mappings, can brush
  views, and so on

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Tarantula

• New system that were working on here
• Utilizes SeeSoft code view methodology
• Shows results of tests in a suite
• Helps viewer track down location of faults

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TarantulaView
Demo
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Step Up

• Next step in program visualization is to help
  debugging and performance optimization by
  visualizing program executions
• Data, data structures, run-time heap, memory,
  control flow, data flow, hot spots, ...

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Graph Visualization

• Area that weve already studied which is very
  important to SV
• Graphs pop up everywhere in software
• Common use Visualize a call graph, visualize a
  flow chart, ...

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Sample CallGraph View
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FIELD

• Program development and analysis environment with
  a wide assortment of different program views
• Integrated a variety of UNIX tools
• Utilized central message server architecture in
  which tools communicated through message passing

Reiss 90
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FIELD Interface
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Dynamic Call Graph View
On call stack
Currently active
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Class Browser
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Heap View
Color could be When allocated Block size Where
allocated
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3D Call Graph
Selected file
Groups of calls
Collapsed file
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PV System

• Used for understanding application and system
  behavior for purposes of debugging and tuning
• Users look for trends, anomalies, and
  correlations
• Ran on RISC/6000 workstations using AIX
• Trace-driven, can be viewed on-line or off

Kimelman, Rosenburg and Roth 94
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Different Views

• Hardware-level performance info
• Instruction execution rates, cache utilization,
  processor utilization
• Operating system level activity
• Context switches, system calls, address space
  activity
• Communication library level activity
• Message passing, interprocessor communication
• Language run-time activity
• Dynamic memory allocation, parallel loop
  scheduling
• Application-level activity
• Data structure accesses, algorithm phase
  transitions

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Accumulated process times
Call tree
Process run history
Kernel performance stats
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Memory view
Code views
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Utility

• Papers about PV provide a number of specific
  examples of how tool was used to help find and
  diagnose performance problems
• Authors say that one negative is just limitations
  of workstation display---need to open and align
  lots of windows and that becomes difficult

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Commercial Systems

• A number of commercial program development
  environments have begun to incorporate program
  visualization tools such as these
• Majority are PC-based
• Has not become as wide-spread as I would have
  anticipated

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Other Languages

• Can use program visualization techniques to
  depict software in other languages
• Functional Lisp
• Logical Prolog
• Object-oriented C

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Concurrent Programs

• Understanding parallel programs is even more
  difficult than serial
• Visualization and animation seem naturals for
  illustrating concurrency
• Temporal mapping of program execution to
  animation becomes critical

Kraemer Stasko 93
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Performance Visualization

• One big aspect in concurrent programs is to
  understand how the computation is performing
• Where can be speeded up
• Processor utilization
• Message traffic
• ...

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PerformanceViews
Kiviat Diagram
Message traffic
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POLKA

• We developed a system, POLKA, that was designed
  to help people build visualizations of concurrent
  programs
• Used for both program and algorithm visualization
• Used for different programming models message
  passing, shared memory threads, ...

Stasko Kraemer 93
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Message Passing Systems
PVM/Conch
Topol, Stasko, Sunderam 98

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Shared Memory Threads
Pthreads
Zhao Stasko 95
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PVaniM

• Visualizing PVM programs on-line
• Must use sampling, not tracing due to sheer
  number of events
• Shows machine loads, host utilization, memory
  used, messages sent, communication patterns, etc.

Topol, Stasko Sunderam 98
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PVaniM
Basic system UI
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Algorithm Visualization

• Learning about algorithms is one of the most
  difficult things for computer science students
• Very abstract, complex, difficult to grasp
• Idea Can we make the data and operations of
  algorithms more concrete to help people
  understand them?

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Algorithm Animation

• Common name for area
• Dynamic visualizations of the operations and data
  of computer algorithm as it executes
• Abstraction is key concept

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Sorting Out Sorting

• Seminal work in area
• 30 minute video produced by Ron Baecker at
  Toronto in 1981
• Illustrates and compares nine sorting algorithms
  as they run on different data sets

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SoS Views
Video
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Balsa

• First main system in area
• Used in electronic classroom at Brown
• Introduced use of multiple views and interesting
  event model

Brown 88
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Example Animation
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Tango

• Added smooth animation to algorithm animation
• Simplification of the design/programming process
  (easier programming model and framework)
• Formal model of the animation, the
  Path-Transition Paradigm

Stasko 90
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Tango
Multiple frames from bubblesort
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Tango Model

• Image, Location, Path, Transition

Location fromloc, toloc Image
ball Path path1, path2 Transition
mover ball AssocRetrieve("ID",
paramvalue) fromloc ImageLoc(ball,
Center) toloc LocCreate(0.4, 0.7) path1
PathMakeType(Clockwise) path2
PathExample(fromloc, toloc, path1) mover
TransCreate(Move, ball, path2) TransPerform(mover
)
Samplecode
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POLKA

• Improved animation design model
• Object-oriented paradigm
• Multiple animation windows
• Much richer visualization/animation capabilities

Stasko Kraemer 93
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POLKA
Demo
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POLKA Model

• Location, AnimObject, Action
• Introduce explicit animation time (frame)

0 1 2 3 4 5 6 7 8 9
t
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POLKA Programming Model
Circle circ Loc loc, center
Action act int len circ new
Circle(this,1, 0.2,0.3, 0.1,"red", 1.0)
circ-Originate(time) center
circ-Where(PART_C) loc new Loc(0.6,
0.5) act new Action("MOVE", center, loc,
20) len circ-Program(time, act) time
Animate(time, len)
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Semantic Zooming
Sorting 5000 elements
View all data
Zoom to first 10
Zoom further
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Polka-3D

• 3-D and VR version of Polka
• Same animation model
• Use third dimension to
• Enhance visual aesthetics
• Portray 3-D data
• Encode more program attributes
• Not sure appropriate for algorithm animation

Stasko Wehrli 93
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POLKA-3D
Quicksort side view Blue dots are as in 2-d
view Colored planes represent exhanges
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Zeus

• Successor to Balsa
• Utilized sound and provided 3D version
• Provided visualizations of many computational
  geometry algorithms

Brown 91
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Zeus Animations
Video
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Evaluating Effectiveness

• Do algorithm animations actually help students
  learn?
• Thats the claim, but unproven
• Conducted a number of empirical studies to answer
  question
• Compare learning with animation to learning
  without
• Measuring understanding is difficult

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Results

• Somewhat mixed, but some studies do show benefits
• - Potential for pedagogical aid is there, but
  just cant throw animation at algorithm and
  expect it to help
• Interaction is a key
• Blindly watching algorithm animation not really
  helpful
• Student must interact with animation and be
  engaged
• Animations help motivation, can make algorithm
  less intimidating

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Current State of SV

• Research continues
• Some use of algorithm animations as pedagogical
  aids
• Program visualization trickling into commercial
  tools

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Whats Needed? (PV)

• Better analysis of what software developers want
  and need
• Flexible displays providing overview and detail
• Improved tracing/monitoring/analysis capabilities

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Whats Needed? (AA)

• Focus on interactive tools
• Simpler animation construction
• Empirical validation of value

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References

• All referred to papers
• Software Visualization, MIT Press, 1998