Sprint Length, Integration Frequency, and Other Matters of...
Transcript of Sprint Length, Integration Frequency, and Other Matters of...
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THE USE OF CADENCE IN AGILE AND TRADITIONAL PROJECTS
Sprint Length, Integration Frequency, and Other Matters of Rhythm
Kathy Iberle
March 14, 2013
Rose City SPIN
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AGILE TODAY
• “The team works for a fixed period of time
called a sprint.” Ken Schwaber; 2002
• “A regular iteration rhythm acts like a
heartbeat for the project.” Mike Cohn; 2006
Fixed-length iterations are
an example of cadence
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CADENCE
• Cadence: a regular, predictable rhythm
within a process.
• Cadence increases efficiency by cutting
out duplicated or avoidable work.
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CADENCE IN SCRUM
© 2013, Iberle Consulting Group, Inc.
Graphic courtesy of Mountain Goat Software
STANDUP MEETING [DAILY]
SPRINT REVIEW [1X/ SPRINT]
SPRINT PLANNING MEETING
[1X / SPRINT]
RETROSPECTIVE [1X/ SPRINT]
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WHAT IS A GOOD CADENCE?
• Not too frequent, not too infrequent
• That’s nice – can we be any more exact?
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A SCIENTIFIC WAY TO LOOK AT CADENCE
1. Identify the benefits of the cadence
2. Identify the cost of the cadence
3. Apply mathematics to find optimal point
Fortunately, once you’ve seen the math, you
rarely need to do actual calculations
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A BRIEF HISTORY
Queueing Theory Erlang’s Theorems 1909
Little’s Law 1961
Waterfall Royce (1970) Mil-Std 671 (1979)
Evo: Gilb 1980s
Stagewise model Bennington 1956
NASA, IBM 1960s
Scrum: Schwaber, Beedle 1997 XP:
Beck 1999
Anderson Kanban 2007
Kanban: Ohno 1950s
The Machine That Changed the World Womack 1980s
Henry Ford 1912
Toyota Production System: Toyoda, Ohno 1940s
Packet Switching Kleinrock 1960s
JIT manufacturing 1980s
Managing the Design Factory Reinertsen 1997
Agile Software Methods
Lean Methods
Alan Ward 1999-2004
Leffingwell Shalloway 2009-present
Matrix Analytic Method, etc.
Agile Manifesto 2001 Poppendieck
2003
Plan-Driven Software Methods
2nd-Generation Lean
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SPRINTS SPLIT THE WORK INTO BATCHES
• Waterfall: no stopping points
• Agile: stopping point after each sprint
What do we lose if there are no stopping points?
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THE COST OF LONGER SPRINTS
Holding Cost includes the cost of:
• Rework due to not getting earlier feedback from customer on whether features are satisfactory
• Extra effort to fix bugs because they weren’t found earlier
• Lost sales due to not having the chance to change or add a feature based on new information
• Lost profit because we didn’t ship, sell, or otherwise use any features before the end of the project
More Sprints => Lower Holding Cost
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HOLDING COST ACCUMULATES
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Holding cost for first month’s work is paid 11 times
If we continue for a year without stopping:
Cost of holding one month’s work for one month =
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HOLDING COST ACCUMULATES
© 2013 Iberle Consulting Group, Inc.
Holding cost for first month’s work is paid 11 times
If we continue for a year without stopping:
Holding cost for second month’s work is paid 10 times
Cost of holding one month’s work for one month =
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HOLDING COST ACCUMULATES
© 2013 Iberle Consulting Group, Inc.
Holding cost for first month’s work is paid 11 times
If we continue for a year without stopping:
Holding cost for second month’s work is paid 10 times
Holding cost for third month’s work is paid 9 times
Cost of holding one month’s work for one month =
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HOLDING COST ACCUMULATES
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Total cost of holding the work for an entire year: = H * = H * 66 Where H = cost of holding one month’s work for one month
𝑖
11
𝑖=1
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THE BENEFIT OF SPRINTS
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Total holding cost for six month sprints = H * 2 * = H * 30 𝑖
5
𝑖=1
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THE BENEFIT OF SPRINTS
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Total holding cost for three month sprints = H * 4 * = H * 12 𝑖
2
𝑖=1
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0
20
40
60
80
100
120
140
0 4 8 12 16 20 24 28 32 36 40 44 48 52
# sprints per year
Total holding cost per year
TOTAL HOLDING COST
1 week sprint
3 week sprint
52 week sprint
3 month sprint
4 week sprint 2 week
sprint
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THE COST OF SHORT SPRINTS
What does it cost each time we start or end
a sprint?
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TRANSACTION COST – SHORT SPRINTS
What does it cost each time we start or end
a sprint?
• Running system integration and test
• Holding sprint review and sprint planning meetings
• Final defect review & decision-making
• This is called the transaction cost
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TRANSACTION COST FOR SHORTER SPRINTS
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Total transaction cost for six month sprints:
Total transaction cost for three month sprints:
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TOTAL TRANSACTION COST
0
2
4
6
8
10
12
0 4 8 12 16 20 24 28 32 36 40 44 48 52
# sprints per year
Total transaction cost per year
3 week sprint
4 week sprint
2 week sprint
1 week sprint
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0
20
40
60
80
100
120
140
160
0 4 8 12 16 20 24 28 32 36 40 44 48 52# Sprints Per Year
Total Cost
Total transaction cost per year
Total holding cost per year
“SWEET SPOT”
TOTAL COST = HOLDING COST PLUS TRANSACTION COST
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CHANGING THE TRANSACTION COST
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T = 2 Sweet spot = 6 week sprints
Reduce transaction cost by 90% T = 0.2 Sweet spot = 2 week sprints
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WHAT THIS MEANS TO US • Big gains when moving from 1 sprint/year to 6 sprints per year
• After that, exact sprint length doesn’t make nearly as much difference ….
• Unless the transaction cost is dramatically reduced
0
20
40
60
80
100
120
140
160
0 4 8 12 16 20 24 28 32 36 40 44 48 52# Sprints Per Year
Total Cost
Total transaction cost peryearTotal holding cost per year
“SWEET SPOT”
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MIKE COHN ON SPRINT LENGTH
• How long priorities can
remain unchanged
• Willingness to go without
outside feedback
• The amount of uncertainty
• Overhead of iterating
• Ease of getting feedback
From Mike Cohn’s book Agile Estimating and Planning
Holding Cost
Transaction Cost
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2ND-GENERATION LEAN VIEW
• Rework due to not getting earlier feedback from customer on whether features are satisfactory
• Extra effort to fix bugs because they weren’t found earlier
• Lost sales due to not having the chance to change or add a feature
• Cost of system integration and test
• Cost of holding sprint review meetings
• Final defect review & decision-making
From Mike Cohn’s book Agile Estimating and Planning
Holding Cost
Transaction Cost
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CONTINUOUS INTEGRATION
• Not immune to the cost trade-off!
• What are the holding costs of integration?
• What are the transaction costs?
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CONTINUOUS INTEGRATION
• There is a sweet spot for integration
• Consider these transaction costs:
• Check-in, including required pre-check-in tests
• Running the integration tests
• Diagnosing defects or errors reported by tests – including false positives!
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REVISIT SCRUM
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Graphic courtesy of Mountain Goat Software
STANDUP MEETING [DAILY]
SPRINT REVIEW [1X/ SPRINT]
SPRINT PLANNING MEETING
[1X / SPRINT]
RETROSPECTIVE [1X/ SPRINT]
INTEGRATION & TEST [??]
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ALIGN YOUR CADENCES
Week 0 Week 4 Week 8 Week 12 Week 16 Week 20 Week 24 Week 28
• Cadences for the same project should
be multiples of each other
• For instance, retrospective every other sprint
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THE IMPORTANCE OF PREDICTABILITY
• The predictability of cadence is critical
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OTHER APPLICATIONS OF CADENCE
• Product introduction
• Use of Part-Time Resources
• Testing
• Status meetings
• Other ideas?
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THE BOTTOM LINE
• The best cadence is the one which
minimizes the total cost
• Total cost is driven by both holding cost and
transaction cost
• The “sweet spot” for total cost is usually broad
and flat
• Moving the “sweet spot” may require an
order-of-magnitude reduction in transaction cost
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REFERENCES ON CADENCE Everything you ever wanted to know about cadence: The Principles of Product Development Flow: Second Generation Lean Product Development by Don Reinertsen
Cadence to coordinate large projects Agile Software Requirements : Lean Requirements Practices for Teams, Programs, and the Enterprise by Dean Leffingwell
Decoupling the Scrum cadences Kanban: Successful Evolutionary Change for Your Technology Business by David J. Anderson
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Thank You! This slide set is available at www.kiberle.com/articles Learn more about cadence at www.kiberle.com/links PNSQC 2013 Invited Speaker: Lean in the Test Lab: The Potential for Big Improvements Workshop on Wednesday, October 16 – Lean in the Test Lab – Work Smarter, Not Harder