1. Activities During SPP Size Estimation
Critical & Difficult area of the project planning
Conventional Methods (LOC/FP Approach)
compute LOC/FP using estimates of information
domain values
use historical effort for the project

2. LOC Example

3. LOC cont.. Include all lines When comments and blank lines are ignored
Executable statements
13 (5-17)

4. Effort Effort=LOC/ Productivity =18/50 =0.36pm
Suppose productivity of your Organization is 50 LOC/pm
Labor rate is 8000Rs/pm
Calculate Effort and Total cost of this increment
Effort=LOC/ Productivity
=18/50
=0.36pm
Total cost=Rate * pm(Effort)
=8000*0.36
=2880Rs.
Cost per LOC=Total cost/LOC
2880/18=160Rs.

5. COCOMO Model Basic

6. The Constructive Cost Model (COCOMO)
COCOMO is one of the most widely used software estimation models in the world
It was developed by Barry Boehm in 1981
COCOMO predicts the effort and schedule for a software product development based on inputs relating to the size of the software and a number of cost drivers that affect productivity

7. COCOMO Models
COCOMO has three different models that reflect the complexity:
the Basic Model
the Intermediate Model
and the Detailed Model

8. Basic Model Applicable to small to medium sized software projects
Use for a quick and rough estimates
Three modes of software development are considered
Organic
Semi-detached
Embedded

9. Organic Mode
A small team of experienced programmers develop software in a very familiar environment
Require little Innovation
Size range ( 0-50 KLOC)

10. Semi-detached mode
An intermediate mode between the organic mode and embedded mode
Depending on the problem at hand, the team include the mixture of experienced and less experienced people
Require medium Innovation
Development environment is medium
Size range ( KLOC)

11. Embedded mode Project has tight constraints
Hard to find experienced persons
Require significant Innovation
Development environment is complex
Size range ( over 300 KLOC)

12. COCOMO: Some Assumptions
Primary cost driver is the number of Delivered Source Instructions (DSI) / Delivered Line Of Code developed by the project
COCOMO estimates assume that the project will enjoy good management by both the developer and the customer

13. Basic COCOMO Model: Formula
The basic COCOMO equation
E= ab (KLOC or KDSI) bb
D= cb (E) db
P=E/D where
E is the effort applied in person-months,
D is the development time in months,
KLOC / KDSI is the estimated number of delivered lines of code for the project (expressed in thousands)
P is the number of people required and
ab, bb, cb and db are coefficients given in next slide.

14. Contd… Software project ab bb cb db Organic 2.4 1.05 2.5 0.38
Semi-detached
Embedded

15. Basic COCOMO Model: Equation

16. Basic COCOMO Model: Example
E.g. 2: We have determined our project fits the characteristics of Semi-Detached mode
We estimate our project will have 32,000 Delivered Source Instructions. Using the formulas, we can estimate:
Effort = 3.0*(32) = 146 man-months
Schedule = 2.5*(146) = 14 months
Productivity = 32,000 DSI / 146 MM = 219 DSI/MM
Average Staffing = 146 MM /14 months = 10 FSP

17. Basic COCOMO Model: Example
E.g.1: Suppose that a project was estimated to be 400 KLOC. Calculate the effort and development time for each of the three modes I.e., organic, semidetached and embedded
The basic COCOMO equation take the form:
E = ab(KLOC) bb
D = cb(E) db

18. FP based Estimation For above mentioned system
Student can be registered
Courses can be added/updated.
Student can view courses
Student can inquire his/her registration status

19. FP based Estimation Count Simple Average Complex
External Inp 3 * = 9
External Out 4 * =16
External Inq 1 * = 3
Internal Files 4 * =28
External Files 0 * = 0
Count Total= =56

20. Calculation of sum(Fi)
Total of 0-5 rating of following 14 questions:
Does the system require reliable back-up/recovery? 3
Are specialized data communications required?
Are there distributed processing functions?
Is performance critical?
Will run in heavily utilized operating environment?
On-line data entry required?
For on-line data entry, will it require multiple screens?
Are ILF’s updated on-line?
Are input, output, files, or inquiries complex?
Is the internal processing complex?
Is the code designed to be reusable?
Are conversion and installation included?
Is the system designed for installation in different organizations? 0
Is the application designed to facilitate change and ease of use? 1 20

21. The estimated number of FP is derived:
FPestimated = count-total X [ X Sum (Fi)]
FPestimated = 56 * ( *29)
=52.64 or 53
If organizational average productivity = 5 FP/pm.
Effort=FP/Productivity
=53/5=10.6 person-months
labor rate = 8000Rs. per month,
Total Cost = labor rate * Person Month(Effort)
=8000*10.6=84800Rs.
Cost per FP=Total Cost/FP
=84800/53=1600Rs.

22. Reference
Pressman 15, 22,23
Section: ,15.3, 22.2,23.6