1. cost22 1 Question of the day u If you were the boss, what would you do for cost estimation?

2. cost22 2 Cost Estimation Estimates based on LOC

3. cost22 3 Prediction Formulas E=  X   >1  <1  =1 TTYP1 – which one did Henry Ford experience? Size cost

4. cost22 4 Cost Estimation Models u LOC models – Boehm's COCOMO – Putnam's Model (SLIM) u non-LOC models – Function Points u combination – COCOMO2

5. cost22 5 Boehm's COCOMO u Software Engineering Economics u Prentice-Hall c1981 u type COCOMO in a search engine - many www sites

6. cost22 6 COnstructive COst MOdel u Basic – macro - overview of whole project with one metric of KSLOC u Intermediate – multiplicative adjustment factors u Detailed – applying model to each phase

7. cost22 7 Modes of Software Development u Organic – detached, often batch u Semidetached – e.g. transaction processing u Embedded – e.g. os kernel

8. cost22 8 Programmer Effort u Application Programs – PM = 2.4 * (KDSI) 1.05 u Utility Programs – PM = 3.0 * (KDSI) 1.12 u Systems Programs – PM = 3.6 * (KDSI) 1.20

9. cost22 9 Example for effort u Size Appl Util Sys u 5K 13.0 18.2 24.8 u 10K 26.9 39.5 57.1 u 15K 41.2 62.2 92.8 u 20K 55.8 86.0 131.1 u 25K 70.5 110.4 171.3 u 30K 85.3 135.3 213.2 u 35K 100.3 160.8 256.6 u 40K 115.4 186.8 301.1 u 45K 130.6 213.2 346.9 u 50K 145.9 239.9 393.6

10. cost22 10 Development Time (Months) u Application Programs – TDEV = 2.5 * (PM) 0.38 u Utility Programs – TDEV = 2.5 * (PM) 0.35 u Systems Programs – TDEV = 2.5 * (PM) 0.32

11. cost22 11 Example for development time u size appl util sys u 5K 6.63 6.90 6.99 u 10K 8.74 9.06 9.12 u 15K 10.27 10.62 10.66 u 20K 11.52 11.88 11.90 u 25K 12.60 12.97 12.96 u 30K 13.55 13.93 13.91 u 35K 14.40 14.80 14.75 u 40K 15.19 15.59 15.53 u 45K 15.92 16.33 16.25 u 50K 16.61 17.02 16.92

12. cost22 12 Average Staffing Levels u Calculate by dividing PM by TDEV

13. cost22 13 Example for staffing levels u size appl util sys u 5K 1.96 2.63 3.55 u 10K 3.08 4.37 6.26 u 15K 4.01 5.87 8.71 u 20K 4.84 7.23 11.02 u 25K 5.60 8.51 13.21 u 30K 6.30 9.72 15.33 u 35K 6.97 10.87 17.39 u 40K 7.60 11.98 19.39 u 45K 8.20 13.05 21.35 u 50K 8.79 14.09 23.27

14. cost22 14 Productivity u The productivity is defined as LOC per time unit. u The usual units are LOC/Programmer-Day u Divide final size of project by total programmer-days of effort for the whole software development

15. cost22 15 TTYP2 u What is the effort, productivity, staffing and delivery time for an application project that takes 82K loc? u What is the effort, productivity, staffing and delivery time for a system project that take 200K loc?

16. cost22 16 COCOMO Effort Multipliers u product attributes – required reliability 0.75 - 1.40 – data-base size 0.94 - 1.16 – product complexity 0.70 - 1.65 u 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

17. cost22 17 Putnam's Cost Estimation Model u macro-estimation model that uses LOC u relationship between cost and the amount of time available for the development effort. u The model supports the 'mythical man- month' idea

18. cost22 18 Putnam's Model u Uses the Rayleigh Curve – Shows Instantaneous Programmer-power vs Time – Empirically verified on other projects

19. cost22 19 Rayleigh Curve u The rayleigh curve is a product of at times e raised to the -bt squared u The at dominates at first giving a steep rise and then the negative power of e lowers the value slowly

20. cost22 20 Rayleigh Curve u y : instantaneous programmer-power u K : total lifecycle cost ( in programmer-years) u t : time from beginning of project u td: delivery time u e= 2.71828...

21. cost22 21 Software Equation u There must be a relationship between the lifecycle development effort, the development time and the size of the project. u This relationship is given in the Software Equation

22. cost22 22 Software Equation u S s = C*K 1/3 t d 4/3 – where: – S s is the estimated size of the software system – K is the total lifecycle effort in programmer- years – C is the technology constant – t d is the development time (in years)

23. cost22 23 Putnam by spread- sheet

24. cost22 24 Summary u What could you do as a manager to improve cost estimation?