Cocomo

Cocomo

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  SEG3300 R.L. Probert1 COCOMO ModelsCOCOMO Models
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  SEG3300 R.L. Probert2 Project Management and Mr.Project Management and Mr. MurphyMurphy 1. Logic is a systematic method of coming to the wrong conclusion with confidence. 2. Technology is dominated by those who manage what they do not understand. 3. Nothing ever gets built on schedule or within budget. 4. If mathematically you end up with the incorrect answer, try multiplying by the page number.
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  SEG3300 R.L. Probert3
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  SEG3300 R.L. Probert4 MotivationMotivation The software cost estimation provides: • the vital link between the general concepts and techniques of economic analysis and the particular world of software engineering. • Software cost estimation techniques also provides an essential part of the foundation for good software management.
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  SEG3300 R.L. Probert5 Cost of a projectCost of a project • The cost in a project is due to: – due the requirements for software, hardware and human resources – the cost of software development is due to the human resources needed – most cost estimates are measured in person-months (PM)
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  SEG3300 R.L. Probert6 Cost of a project (.)Cost of a project (.) • the cost of the project depends on the nature and characteristics of the project, at any point, the accuracy of the estimate will depend on the amount of reliable information we have about the final product.
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  SEG3300 R.L. Probert7 Software Cost EstimationSoftware Cost Estimation
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  SEG3300 R.L. Probert8 Introduction to COCOMOIntroduction to COCOMO modelsmodels • The COstructive COst Model (COCOMO) is the most widely used software estimation model in the world. It • The COCOMO model predicts the effort and duration of a project based on inputs relating to the size of the resulting systems and a number of "cost drives" that affect productivity.
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  SEG3300 R.L. Probert9 EffortEffort • Effort Equation – PM = C * (KDSI)n (person-months) • where PM = number of person-month (=152 working hours), • C = a constant, • KDSI = thousands of "delivered source instructions" (DSI) and • n = a constant.
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  SEG3300 R.L. Probert10 ProductivityProductivity • Productivity equation – (DSI) / (PM) • where PM = number of person-month (=152 working hours), • DSI = "delivered source instructions"
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  SEG3300 R.L. Probert11 ScheduleSchedule • Schedule equation – TDEV = C * (PM)n (months) • where TDEV = number of months estimated for software development.
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  SEG3300 R.L. Probert12 Average StaffingAverage Staffing • Average Staffing Equation – (PM) / (TDEV) (FSP) • where FSP means Full-time-equivalent Software Personnel.
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  SEG3300 R.L. Probert13 COCOMO ModelsCOCOMO Models • COCOMO is defined in terms of three different models: – the Basic model, – the Intermediate model, and – the Detailed model. • The more complex models account for more factors that influence software projects, and make more accurate estimates.
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  SEG3300 R.L. Probert14 The Development modeThe Development mode • the most important factors contributing to a project's duration and cost is the Development Mode • Organic Mode: The project is developed in a familiar, stable environment, and the product is similar to previously developed products. The product is relatively small, and requires little innovation. • Semidetached Mode: The project's characteristics are intermediate between Organic and Embedded.
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  SEG3300 R.L. Probert15 The Development modeThe Development mode • the most important factors contributing to a project's duration and cost is the Development Mode: • Embedded Mode: The project is characterized by tight, inflexible constraints and interface requirements. An embedded mode project will require a great deal of innovation.
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  SEG3300 R.L. Probert16 ModesModes Feature Organic Semidetached Embedded Organizational understanding of product and objectives Thorough Considerable General Experience in working with related software systems Extensive Considerable Moderate Need for software conformance with pre-established requirements Basic Considerable Full Need for software conformance with external interface specifications Basic Considerable Full
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  SEG3300 R.L. Probert17 Modes (.)Modes (.) Feature Organic Semidetached Embedded Concurrent development of associated new hardware and operational procedures Some Moderate Extensive Need for innovative data processing architectures, algorithms Minimal Some Considerable Premium on early completion Low Medium High Product size range <50 KDSI <300KDSI All
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  SEG3300 R.L. Probert18 Cost Estimation ProcessCost Estimation Process Cost=SizeOfTheProject x Productivity
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  SEG3300 R.L. Probert19 Cost Estimation ProcessCost Estimation Process Errors Effort Development Time Size Table Lines of Code Number of Use Case Function Point Estimation Process Number of Personnel
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  SEG3300 R.L. Probert20 Project Size - MetricsProject Size - Metrics 1. Number of functional requirements 2. Cumulative number of functional and non-functional requirements 3. Number of Customer Test Cases 4. Number of ‘typical sized’ use cases 5. Number of inquiries 6. Number of files accessed (external, internal, master) 7. Total number of components (subsystems, modules, procedures, routines, classes, methods) 8. Total number of interfaces 9. Number of System Integration Test Cases 10. Number of input and output parameters (summed over each interface) 11. Number of Designer Unit Test Cases 12. Number of decisions (if, case statements) summed over each routine or method 13. Lines of Code, summed over each routine or method
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  SEG3300 R.L. Probert21 Project Size – Metrics(.)Project Size – Metrics(.) Availability of Size Estimation Metrics: Development Phase Available Metrics a Requirements Gathering 1, 2, 3 b Requirements Analysis 4, 5 d High Level Design 6, 7, 8, 9 e Detailed Design 10, 11, 12 f Implementation 12, 13
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  SEG3300 R.L. Probert22 Function PointsFunction Points • STEP 1: measure size in terms of the amount of functionality in a system. Function points are computed by first calculating an unadjusted function point count (UFC). Counts are made for the following categories •External inputs – those items provided by the user that describe distinct application-oriented data (such as file names and menu selections) •External outputs – those items provided to the user that generate distinct application-oriented data (such as reports and messages, rather than the individual components of these)
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  SEG3300 R.L. Probert23 Function Points(.)Function Points(.) • External inquiries – interactive inputs requiring a response • External files – machine-readable interfaces to other systems • Internal files – logical master files in the system
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  SEG3300 R.L. Probert24 Function Points(..)Function Points(..) • STEP 2: Multiply each number by a weight factor, according to complexity (simple, average or complex) of the parameter, associated with that number. The value is given by a table:
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  SEG3300 R.L. Probert25 Function Points(...)Function Points(...) • STEP 3: Calculate the total UFP (Unadjusted Function Points) • STEP 4: Calculate the total TCF (Technical Complexity Factor) by giving a value between 0 and 5 according to the importance of the following points:
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  SEG3300 R.L. Probert26 Function Points(....)Function Points(....) • Technical Complexity Factors: – 1. Data Communication – 2. Distributed Data Processing – 3. Performance Criteria – 4. Heavily Utilized Hardware – 5. High Transaction Rates – 6. Online Data Entry – 7. Online Updating – 8. End-user Efficiency – 9. Complex Computations – 10. Reusability – 11. Ease of Installation – 12. Ease of Operation – 13. Portability – 14. Maintainability
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  SEG3300 R.L. Probert27 Function Points(.....)Function Points(.....) • STEP 5: Sum the resulting numbers too obtain DI (degree of influence) • STEP 6: TCF (Technical Complexity Factor) by given by the formula – TCF=0.65+0.01*DI • STEP 6: Function Points are by given by the formula – FP=UFP*TCF
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  SEG3300 R.L. Probert28 ExampleExample
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  SEG3300 R.L. Probert29 Example (.)Example (.)
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  SEG3300 R.L. Probert30 Example (..)Example (..) • Technical Complexity Factors: – 1. Data Communication 3 – 2. Distributed Data Processing 0 – 3. Performance Criteria 4 – 4. Heavily Utilized Hardware 0 – 5. High Transaction Rates 3 – 6. Online Data Entry 3 – 7. Online Updating 3 – 8. End-user Efficiency 3 – 9. Complex Computations 0 – 10. Reusability 3 – 11. Ease of Installation 3 – 12. Ease of Operation 5 – 13. Portability 3 – 14. Maintainability 3 » DI =30(Degree of Influence)
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  SEG3300 R.L. Probert31 Example (…)Example (…) • Function Points – FP=UFP*(0.65+0.01*DI)= 55*(0.65+0.01*30)=52.25 – That means the is FP=52.25
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  SEG3300 R.L. Probert32 Relation between LOC and FPRelation between LOC and FP • Relationship: – LOC = Language Factor * FP – where • LOC (Lines of Code) • FP (Function Points)
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  SEG3300 R.L. Probert33 Relation between LOC andRelation between LOC and FP(.)FP(.) Assuming LOC’s per FP for: Java = 53, C++ = 64 aKLOC = FP * LOC_per_FP / 1000 It means for the SpellChekcer Example: (Java) LOC=52.25*53=2769.25 LOC or 2.76 KLOC
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  SEG3300 R.L. Probert34 Effort ComputationEffort Computation • The Basic COCOMO model computes effort as a function of program size. The Basic COCOMO equation is: – E = aKLOC^b • Effort for three modes of Basic COCOMO. Mode a b Organic 2.4 1.05 Semi- detached 3.0 1.12 Embedded 3.6 1.20
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  SEG3300 R.L. Probert35 ExampleExample
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  SEG3300 R.L. Probert36 Effort ComputationEffort Computation • The intermediate COCOMO model computes effort as a function of program size and a set of cost drivers. The Intermediate COCOMO equation is: – E = aKLOC^b*EAF • Effort for three modes of intermediate COCOMO. Mode a b Organic 3.2 1.05 Semi- detached 3.0 1.12 Embedded 2.8 1.20
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  SEG3300 R.L. Probert37 Effort computation(.)Effort computation(.)• Effort Adjustment Factor Cost Driver Very Low Low Nominal High Very High Extra High Required Reliability .75 .88 1.00 1.15 1.40 1.40 Database Size .94 .94 1.00 1.08 1.16 1.16 Product Complexity .70 .85 1.00 1.15 1.30 1.65 Execution Time Constraint 1.00 1.00 1.00 1.11 1.30 1.66 Main Storage Constraint 1.00 1.00 1.00 1.06 1.21 1.56 Virtual Machine Volatility .87 .87 1.00 1.15 1.30 1.30 Comp Turn Around Time .87 .87 1.00 1.07 1.15 1.15 Analyst Capability 1.46 1.19 1.00 .86 .71 .71 Application Experience 1.29 1.13 1.00 .91 .82 .82 Programmers Capability 1.42 1.17 1.00 .86 .70 .70 Virtual machine Experience 1.21 1.10 1.00 .90 .90 .90 Language Experience 1.14 1.07 1.00 .95 .95 .95 Modern Prog Practices 1.24 1.10 1.00 .91 .82 .82 SW Tools 1.24 1.10 1.00 .91 .83 .83 Required Dev Schedule 1.23 1.08 1.00 1.04 1.10 1,10
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  SEG3300 R.L. Probert38 Effort Computation (..)Effort Computation (..) Total EAF = Product of the selected factors Adjusted value of Effort: Adjusted Person Months: APM = (Total EAF) * PM
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  SEG3300 R.L. Probert39 ExampleExample
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  SEG3300 R.L. Probert40 Software Development TimeSoftware Development Time • Development Time Equation Parameter Table: Development Time, TDEV = C * (APM **D) Number of Personnel, NP = APM / TDEV Parameter Organic Semi- detached Embedded C 2.5 2.5 2.5 D 0.38 0.35 0.32
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  SEG3300 R.L. Probert41 Distribution of EffortDistribution of Effort • A development process typically consists of the following stages: • - Requirements Analysis • - Design (High Level + Detailed) • - Implementation & Coding • - Testing (Unit + Integration)
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  SEG3300 R.L. Probert42 Distribution of Effort (.)Distribution of Effort (.) The following table gives the recommended percentage distribution of Effort (APM) and TDEV for these stages: Percentage Distribution of Effort and Time Table: Req Analysis Design, HLD + DD Implementation Testing Effort 23% 29% 22% 21% 100% TDEV 39% 25% 15% 21% 100%
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  SEG3300 R.L. Probert43 Error EstimationError Estimation • Calculate the estimated number of errors in your design, i.e.total errors found in requirements, specifications, code, user manuals, and bad fixes: – Adjust the Function Point calculated in step1 AFP = FP ** 1.25 – Use the following table for calculating error estimates Error Type Error / AFP Requirements 1 Design 1.25 Implementation 1.75 Documentation 0.6 Due to Bug Fixes 0.4
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  SEG3300 R.L. Probert44 All TogetherAll Together Design Unadjusted Function Point (UFP table) Modify FP=UFP*TCF Classes*(2Function Points) TCF KLOC=Max[aKLOC, bKLOC] LOC=13.20*Num of Method LOC=18.25*Num of Method AFP=FP*1.25 Compute Errors = AFP*Y Compute Effort: Person Month, PM=A*(KLOC**B) bKLOC=∑ (LOCs for all Classes)/1000 Adjusted PM: APM=(total EAF)*PM Development Time: TDEV=C*(APM**D)Factor:1-15 Number of personnel: NP=APM/TDEV DI=∑ratings of selected factors 14 TCF=0.65+0.01*∑(DI)j 1 Min[TCF]=0.65; Max[TCF]=1.35 aKLOC=FP*LOC_per_FP/1000 Java=53; C++=64 EAF=Product of selected factor NP Effort time Req APM TDEV Result