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Cost Estimation

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data-base size 0.94 - 1.16. product complexity 0.70 - 1.65. computer attributes ... Ss is the estimated size of the software system ... – PowerPoint PPT presentation

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Title: Cost Estimation


1
Cost Estimation
  • Estimates based on LOC

2
Boehm's COCOMO
  • Software Engineering Economics
  • Prentice-Hall c1981
  • type COCOMO in a search engine - many www sites

3
COnstructive COst MOdel
  • Basic
  • macro - overview of whole project with one metric
    of KSLOC
  • Intermediate
  • multiplicative adjustment factors
  • Detailed
  • applying model to each phase

4
Modes of Software Development
  • Organic
  • detached, often batch
  • Semidetached
  • e.g. transaction processing
  • Embedded
  • e.g. os kernel

5
Programmer Effort
  • Application Programs
  • PM 2.4 (KDSI)1.05
  • Utility Programs
  • PM 3.0 (KDSI)1.12
  • Systems Programs
  • PM 3.6 (KDSI)1.20

6
Example for effort
  • Size Appl Util Sys
  • 5K 13.0 18.2 24.8
  • 10K 26.9 39.5 57.1
  • 15K 41.2 62.2 92.8
  • 20K 55.8 86.0 131.1
  • 25K 70.5 110.4 171.3
  • 30K 85.3 135.3 213.2
  • 35K 100.3 160.8 256.6
  • 40K 115.4 186.8 301.1
  • 45K 130.6 213.2 346.9
  • 50K 145.9 239.9 393.6

7
Development Time (Months)
  • Application Programs
  • TDEV 2.5 (PM) 0.38
  • Utility Programs
  • TDEV 2.5 (PM) 0.35
  • Systems Programs
  • TDEV 2.5 (PM) 0.32

8
Example for development time
  • size appl util sys
  • 5K 6.63 6.90 6.99
  • 10K 8.74 9.06 9.12
  • 15K 10.27 10.62 10.66
  • 20K 11.52 11.88 11.90
  • 25K 12.60 12.97 12.96
  • 30K 13.55 13.93 13.91
  • 35K 14.40 14.80 14.75
  • 40K 15.19 15.59 15.53
  • 45K 15.92 16.33 16.25
  • 50K 16.61 17.02 16.92

9
Average Staffing Levels
  • Calculate by dividing PM by TDEV

10
Example for staffing levels
  • size appl util sys
  • 5K 1.96 2.63 3.55
  • 10K 3.08 4.37 6.26
  • 15K 4.01 5.87 8.71
  • 20K 4.84 7.23 11.02
  • 25K 5.60 8.51 13.21
  • 30K 6.30 9.72 15.33
  • 35K 6.97 10.87 17.39
  • 40K 7.60 11.98 19.39
  • 45K 8.20 13.05 21.35
  • 50K 8.79 14.09 23.27

11
Productivity
  • The productivity is defined as LOC per time unit.
  • The usual units are LOC/Programmer-Day
  • Divide final size of project by total
    programmer-days of effort for the whole software
    development

12
TTYP1
  • What is the effort, productivity, staffing and
    delivery time for an application project that
    takes 175K loc?
  • What is the effort, productivity, staffing and
    delivery time for a system project that take 400K
    loc?

13
COCOMO Effort Multipliers
  • product attributes
  • required reliability 0.75 - 1.40
  • data-base size 0.94 -
    1.16
  • product complexity 0.70 - 1.65
  • computer attributes
  • execution time constraint 1.00 - 1.66
  • main storage constraint 1.00 - 1.56
  • virtual machine volatility 0.87 - 1.30
  • computer turnaround time 0.87 - 1.15

14
Putnam's Cost Estimation Model
  • macro-estimation model that uses LOC
  • relationship between cost and the amount of time
    available for the development effort.
  • The model supports the 'mythical man-month' idea

15
Putnam's Model
  • Uses the Rayleigh Curve
  • Shows Instantaneous Programmer-power vs Time
  • Empirically verified on other projects

16
Rayleigh Curve
  • The rayleigh curve is a product of at times e
    raised to the -bt squared
  • The at dominates at first giving a steep rise and
    then the negative power of e lowers the value
    slowly

17
Rayleigh Curve
  • y instantaneous programmer-power
  • K total lifecycle cost ( in programmer-years)
  • t time from beginning of project
  • td delivery time
  • e 2.71828...

18
Software Equation
  • There must be a relationship between the
    lifecycle development effort, the development
    time and the size of the project.
  • This relationship is given in the Software
    Equation

19
Software Equation
  • Ss CK1/3 td4/3
  • where
  • Ss is the estimated size of the software system
  • K is the total lifecycle effort in
    programmer-years
  • C is the technology constant
  • td is the development time (in years)

B is special skills factor P is productivity
parameter
20
Putnam by spread-sheet
21
Thursday, Oct 19
  • Function Point Estimation
  • Read Pressman pp 440-444 and 653-654
  • Read SOS sec 4.4.4
  • PLQ Wednesday
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