This presentation discusses green software and energy efficiency at the application level. It provides background on the Software Improvement Group, which analyzes over 90 systems annually and provides management advisory services and software quality certification. The presentation introduces a taxonomy of green aspects of software, including computational efficiency, algorithmic efficiency, data structures, and functional necessity. It discusses approaches to optimizing some of these aspects, like energy-aware coding of algorithms and data structures. The presentation also notes challenges like the currently energy-oblivious nature of most software development.

1. Green Software – A Framework
Optimisation of IT Energy-Efficiency at the Application Level
Joost Visser
12 April 2011 T +31 20 314 0950
info@sig.eu
www.sig.eu

2. This presentation
2 I 16
Software Improvement Group
• Background, activities
Greenness and Software
• Does software consume energy?
• Green aspects of software – a taxonomy
• Approaches to some aspects
• Challenges
Outlook
© 2011 Software Improvement Group

3. Software Improvement Group
Background 3 I 16
• Spin-off from CWI in 2000, self-owned, independent
• Strong academic background, innovative, award-winning, profitable
• Member of the consortium Green IT Amsterdam region
Activity
• Management advisory, fact-based
• Accredited software analysis lab employs analysis tools and models
• Experienced staff transforms analysis data into advice
Track record
• Finance, government, logistics, telecom, manufacturing, energy, …
• We analyze over 90 systems annually
© 2011 Software Improvement Group

4. Who is using our services?
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Financials & insurance companies Public Retail/Logistics Technology Utilities/Telco
© 2010 Software Improvement Group

5. Selected services
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Software Risk Assessment
• In-depth investigation of software quality and risks
• Answers specific research questions
Software Monitoring
• Continuous measurement, feedback, and decision support
• Guard quality from start to finish
Software Product Certification
• Five levels of technical quality
• Evaluation by SIG, certification by TÜV Informationstechnik
Sustainability Scans
• Energy-efficiency at the application level
• Identify opportunities for optimisation
© 2011 Software Improvement Group

6. 6 I 16
The most strategic aspect of energy
efficient computing will be the evolution
of application software to facilitate
system-wide energy efficiency.
Communications of the ACM , March 2010, vol. 53, No. 3
Towards Energy-Efficient Computing
!
by David J. Brown (Sun Microsystems) and Charles Reams (Cambridge University)
© 2011 Software Improvement Group

7. Power Loss Chain
Extended version …
7 I 16
Image source:
Performing the right work?
British Computer Society
Data Centre Specialist Group
Performing the work right?
Algorithmic inefficiency
Computational 25% 75% Optimal cycles and storage
efficiency
Functional Frivolous features
65% 35% Useful work
necessity
Percentages are indicative only
© 2011 Software Improvement Group

8. Application-level energy-efficiency
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Why?
• On the level of hardware, network, and data centre progress has been made.
• Window for optimisation is shrinking.
• Focussed on reducing energy loss in the power supply chain.
• HW, NW, DC consume energy on behalf of application software.
• Software design and construction are currently mostly energy-oblivious.
• Focus on reducing energy demand at the source.
© 2011 Software Improvement Group

9. Taxonomy
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Data retention
Greening by IT Responsiveness
Graphical presentation
Green Grid
Green Data Center Algorithmic
Green IT Green Hardware Data structures
Protocols
Functional necessity
Greening of IT
Computational efficiency
Green Software
Environment
Green Software
Rework
Development
Maintainability
Testability
© 2011 Software Improvement Group

10. Software Development
1964 – resource aware
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© 2011 Software Improvement Group

11. Software development
Now – resource agnostic
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• Large scale. Global distribution. Failure rates estimated at 30%.
• Graphical development environments perform continuous compilation.
• Nightly regression testing. Test environments duplicate production.
© 2011 Software Improvement Group

12. Application-level energy-efficiency
Estimate energy 12 I 16
Energy-ware coding
How? consequences of of algorithms, data
requirements structures,
Eliminate frivolous communication,
requirements concurrency.
require design build test operate
Estimate energy
Monitor energy
consequences of
consumption
design decisions
High-quality coding
Provide feedback to
Consider less to minimize build,
development
wasteful alternatives test, re-work, and
maintenance effort
© 2011 Software Improvement Group

13. ISO/IEC 9126, Part 1
Software product quality characteristics
13 I 16
ISO/IEC 9126
Software Product Quality
functionality portability
reliability efficiency
usability maintainability
Adaptability
Time Installability
Analysability behaviour Co-existence
Changeability Resource Replaceability
Stability utilisation
!
Testability !
!
Greenness
! Sustainability!
© 2011 Software Improvement Group

14. Trade-offs
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Energy efficiency versus functionality
• Non-essential features may lead to energy waste
• E.g.: continuous client-side reporting of server status
• E.g.: check spelling as you type, wizards (remember Clippy?)
Energy efficiency versus performance
• Optimising for performance is not necessarily energy-efficient
• E.g.: guaranteed response times may require over-dimensioned hardware
Energy efficiency versus reuse and adaptability
• E.g.: Packaged solution may not allow application-specific optimisation
• E.g.: Loose coupling via web services may increase communication overhead
© 2011 Software Improvement Group

15. Challenges
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Maturity of software production processes
• Need for awareness, commitment, communication, organisation
• Additional control variable in an already complex process
“You can’t control what you can’t measure”
Tom DeMarco
Attribution of energy consumption to applications
• Hardware consumes energy to run applications
• Multiple applications run on multiple machines in parallel and/or interleaved
==> Attribution is hard and necessarily imprecise
Comparability between applications
• Energy consumption must be seen in relation to delivered functionality
• Comparability only between functionally equivalent applications
==> Common standard is hard to define
© 2011 Software Improvement Group

16. Going forward …
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…
… …
… …
Framework
Network
From: ideas
To: actions
© 2010 Software Improvement Group

17. 17 I 16
Dr. ir. Joost Visser
j.visser@sig.eu
http://twitter.com/jstvssr
www.sig.eu
+31 20 314 0950
© 2011 Software Improvement Group

18. 18 I 16
© 2010 Software Improvement Group