Cost Estimation

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Cost Estimation
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Overview

• To frame our discussion, consider
• How do we measure development activity?
• How can we predict the time, effort and cost of a
  development project?
• What factors influence time, effort and cost of a
  development activity?
• How should we characterize these influences?

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Outline

• Introduction
• Cocomo
• Function Points
• LOC

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Strategies

• Mathematical Modeling
• Empiricism
• Practice

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Cocomo

• Effort as a function of lines-of-code where b
  and c are constants dependent on the project type.

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Cocomo Project Types

• Organic
• A relatively small team develops software in a
  known environment. Those involved generally have
  significant experience with projects of this
  type. These tend to be small projects. (b2.4,
  c1.05)
• Embedded
• These projects involve the development where the
  intended environment poses significant
  constraints. The product is "embedded" in an
  environment which is inflexible. (b3.0, c1.12 )
• Semidetached
• The team may show a mixture of experience and
  inexperienced people. The project may be larger
  than that in the organic type. (b3.6, c1.20)

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Cocomo Cost Drivers
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Function/Feature Points

• Function points are a measure of the size of
  computer applications and the projects that build
  them. The size is measured from a functional, or
  user, point of view. It is independent of the
  computer language, development methodology,
  technology or capability of the project team used
  to develop the application.
• Function points tend to be useful in data
  oriented applications.

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Function/Feature Points (1)
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Function/Feature Points (2)
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Function/Feature Points (3)

• DI is the sum of 14 characteristics on a six
  point scale (0 - no influence to 5 - strong
  influence).
• Characteristics
• Data Communications
• Distributed Function
• Performance
• Heavily Used Configuration
• Transaction Rate
• On-line Data Entry
• End-user Efficiency
• On-line Update
• Complex Processing
• Re-usability
• Installation Ease
• Operational Ease
• Multiple Sites
• Facilitate Change

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FP - Example
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FP - Example (2)
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FP and Size Estimates

• Language Source Statements
• Assembler 320
• C 150
• COBOL 106
• FORTRAN 106
• Pascal 91
• RPG 80
• Prolog 64
• LISP 64
• SmallTalk 21
• Query
• Languages 16

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Coding Metrics

• Lines of Code
• Cyclomatic Complexity

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Lines of Code

• Lines of code (LOC or KLOC) is typically
  correlated with effort. Boehm, Walston-Felix, and
  Halstead all indicate Effort as a function of
  lines of code.

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LOC - Support

• Easy to Determine
• Easy to Automate
• Easy to Enforce

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LOC - Objections

• Some programmers write more verbose programs than
  others.
• Difficult to compare programs written in
  different languages.
• Some lines are more complex than others.

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LOC - Data
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Whats a Line?

• define LOWER 0 / lower limit of table /
• define UPPER 300 / upper limit of table /
• define STEP 20 / step size /
• main()
• int fahr
• for (fahrLOWER fahrUPPERfahrfahrSTEP)
• printf("4d 6.1f\n", fahr, (5.0/9.0)(fahr-32))

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LOC - Definition
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Cyclomatic Complexity

• is based on determining how complicated the
  control flow a program (procedure or function)
  is. The control flow is represented as directed
  graph.

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Cyclomatic Complexity (2)

• Nodes (n)
• Conditional
• Edges (e)
• Predicate Node
• Ve-np
• p is the number of components. Typically with a
  single program p1.

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Cyclomatic Complexity (3)
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Example
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