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

LOC Example

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

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.

COCOMO Model Basic

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

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

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

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

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 ( 50 - 300 KLOC)

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

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

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.

Contd… Software project ab bb cb db Organic 2.4 1.05 2.5 0.38 Semi-detached 3.0 1.12 2.5 0.35 Embedded 3.6 1.20 2.5 0.32

Basic COCOMO Model: Equation

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) 1.12 = 146 man-months Schedule = 2.5*(146) 0.35 = 14 months Productivity = 32,000 DSI / 146 MM = 219 DSI/MM Average Staffing = 146 MM /14 months = 10 FSP

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

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

FP based Estimation Count Simple Average Complex External Inp 3 * 3 4 6 = 9 External Out 4 * 4 5 7 =16 External Inq 1 * 3 4 6 = 3 Internal Files 4 * 7 10 15 =28 External Files 0 * 5 7 10 = 0 Count Total= =56

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? 2 Are there distributed processing functions? 0 Is performance critical? 2 Will run in heavily utilized operating environment? 1 On-line data entry required? 4 For on-line data entry, will it require multiple screens? 5 Are ILF’s updated on-line? 5 Are input, output, files, or inquiries complex? 2 Is the internal processing complex? 3 Is the code designed to be reusable? 0 Are conversion and installation included? 1 Is the system designed for installation in different organizations? 0 Is the application designed to facilitate change and ease of use? 1 20

The estimated number of FP is derived: FPestimated = count-total X [0.65 + 0.01 X Sum (Fi)] FPestimated = 56 * (0.65+.01*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.

Reference Pressman 15, 22,23 Section: 15.2.1,15.3, 22.2,23.6