Algorithmic software cost modeling uses mathematical functions to estimate project costs based on inputs like project characteristics, development processes, and product attributes. COCOMO is a widely used algorithmic cost modeling method that estimates effort in person-months and development time based on source lines of code and cost adjustment factors. It has basic, intermediate, and detailed models and accounts for factors like application domain experience, process quality, and technology changes.

1. Algorithmic Software Cost
Modeling
Kasun Ranga Wijeweera
(krw19870829@gmail.com)

2. Algorithmic Cost Modeling
• A mathematical function is used to estimate
the cost
– Inputs: Project, Process, Product
– Decided by project managers
• Historical data are studied to derive the
function
• Commonly used product attribute is LOC
(code size)

3. Software Productivity
• The rate at which individual software
engineers involve in development process is
known as software productivity
• Although quality assurance is a factor in
productivity assessment, the productivity is not
quality oriented
• The useful functionality produced per time unit
should be measured

4. Productivity Measures
• Size related measures:
– Lines of delivered source code
– Object code instructions
– Etc
• Function related measures:
– Functionality of the delivered software
– E.g. Function points

5. Lines of Code
• What programs should be considered as part of
the system?
• Assumption of the model:
– The relationship between system size and volume
of documentation is linear
• Key thing to remember:
– Uncertainty is more important than the initial line
– Seek justifiable bounds

6. Productivity Comparison
• Low level language verses high level language
• Verbose code verses compact code

7. Function Points
• Program characteristics are considered
– External inputs and outputs
– User interactions
– External interfaces
– Files used by the system
• Corresponding weights are assigned to each
characteristic

8. FPs and LOC
• FPs can be used to estimate LOC
– LOC = AVC * (Number of FPs)
– AVC is a factor which depends on the
programming language
• Assembly language: AVC = 200 to 300
• 4 GL language: AVC = 2 to 40
• FPs are subjective and dependent on the
estimator
– FP automation is impossible

9. Productivity Estimates
• Real time embedded systems
– 40 to 60 LOC per month
• Systems programs
– 150 to 400 LOC per month
• Commercial applications
– 200 to 900 LOC per month

10. Productivity Factors
• Application domain experience
• Process quality
• Product size
• Technology support
• Working environment

11. Changing Technologies
• Previous estimating experience does not carry
over to new systems due to changes in
technology
– Use of web services
– Use of CASE tools and program generators
– Development for and with reuse
– Using scripting languages

12. COCOMO
• Constructive Cost Model (COCOMO)
• Estimates are derived as functions of variables
• Data of past projects must be available
• First published by Dr. Barry Boehm in 1981
• Derived through statistical regression of data
from 63 past projects

13. Example
Size 2000
SLOC
8000
SLOC
32000
SLOC
128000
SLOC
MM 5 21 91 392
Schedule
Months
5 8 14 24
Staff 1.1 2.7 6.5 16
SLOC/
MM
400 376 352 327

14. Basic Effort Equation
• (Effort) = A * (Size) ^ (Exponent)
• (Effort) = (EAF) * A * (Size) ^ (Exponent)
• Estimates the man-months (MM) of effort for
software development project
– 1 MM = 152 hours of development
• Size is the source lines of code (SLOC)

15. Modes and Models of COCOMO
• Three modes
– Organic mode
– Semidetached mode
– Embedded mode
• Three models
– Basic model
– Intermediate model
– Detailed model

16. Modes of COCOMO
• Organic mode
– Similar to an earlier project
– Familiar and stable environment
– E.g. Accounting system
• Semidetached mode
– Between Organic and Embedded modes
• Embedded mode
– New project involving new inventions
– E.g. Real-time systems

17. Models of COCOMO
• Basic model
– Roughly estimates project cost, performance and
schedule
• Intermediate model
– EAF (Effort Adjustment Factor) is used from 15
cost drivers
• Detailed model
– Different Effort Multipliers are used for each phase
of project

18. Effort Equation : Basic
• (Effort) = A * (Size) ^ (Exponent)
• A is a constant which depends on the mode of
development
– Organic: 2.4, Semidetached: 3.0, Embedded: 3.6
• (Exponent) is also a constant which depends
on the mode of development
– Organic: 1.05, Semidetached: 1.12, Embedded:
1.20
• Size should be in KSLOC (1000 SLOC)

19. Schedule Equation : Basic
• Minimum time to develop (MTDEV)
• (MTDEV) = 2.5 * (Effort) ^ (Exponent)
• Exponent is a constant which depends on the
mode
– Organic: 0.38, Semidetached: 0.35, Embedded:
0.32
• 2.5 is constant for all modes
• MTDEV is independent from the number of
people assigned

20. Effort Equation : Intermediate
• (Effort) = (EAF) * A * (Size) ^ (Exponent)
• A is a constant which depends on the mode of
development
– Organic: 3.2, Semidetached: 3.0, Embedded: 2.8
• (Exponent) is also a constant which depends
on the mode of development
– Organic: 1.05, Semidetached: 1.12, Embedded:
1.20
• Size should be in KSLOC (1000 SLOC)

21. EAF (Effort Adjustment Factor)
• EAF = Product of effort multipliers

22. Schedule Equation : Intermediate
• Minimum time to develop (MTDEV)
• (MTDEV) = 2.5 * (Effort) ^ (Exponent)
• Exponent is a constant which depends on the
mode
– Organic: 0.38, Semidetached: 0.35, Embedded:
0.32
• 2.5 is constant for all modes
• MTDEV is independent from the number of
people assigned

23. Tool Demonstration
http://sunset.usc.edu/research/COCOMOII/expert_co
como/expert_cocomo2000.html

24. Thank you!