International Journal of Scientific & Engineering Research Volume 2, Issue 6, June-2011 1
ISSN 2229-5518
Analysis of Software Cost Estimation using
COCOMO II
T.N.Sharma
approaches. COCOMO II includes two underlying information models. The first is a framework for describing a software project, including models for process, culture, stakeholders, methods, tools and the size/complexity of the software product. The second is an experience base that can be used to estimate the likely includes significant updates to COCOMO to improve its applicability to modern processes, methods, tools and technologies. It also includes a much larger, more pertinent database of modern precedents and improves the adaptability of the model so it can be optimized across a broad spectrum of domains and project circumstances. This paper presents cost estimation of various projects using COCOMO II. This article also presents statistical analysis for relevance of base COCOMO II model for effort estimation in present scenario.
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Software cost estimation is a prediction of the cost of the resources that will be required to complete all of the
work of the software project.
Software has a bad reputation about cost estimation. Large software projects have tended to have a very high frequency of schedule overruns, cost overruns, quality problems, and outright cancellations. Instead of it bad reputation, it is important to note that some large soft- ware projects are finished on time, stay within their budgets, and operate successfully when deployed. Currently a new generation of software processes and products is changing the way organizations develop software. The new approaches – evolutionary, risk driven and collaborative software processes; fourth generation languages and application generators; commercial off the
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T.N.Sharma is undergoing his research work from Department of Statis- tics, University of Rajashthan, Jaipur (India).Mob.:9414248794. Email: tnsharma@rediffmail.com
shelf (COTS) and reuse driven software approaches; fast track software development approaches; software process maturity initiatives – lead to significant benefit in terms of improved software quality and reduced software cost, risk and cycle time.
COCOMO II model tailored to these new forms of soft- ware development, including rationales for the model decisions. The major new modeling capabilities of CO- COMO II are a tailorable family of software sizing mod- els, involving Object Points, Function Points, and Source Lines of Code; nonlinear models for software reuse and reengineering; an exponent-driver approach for modeling relative software diseconomies of scale; and several addi- tions, deletions, and updates to previous COCOMO ef- fort-multiplier cost drivers. This model is serving as a framework for an extensive current data collection and analysis effort to further refine and calibrate the model’s estimation capabilities.
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In COCOMO II, the amount of effort in person-months, PM, is estimated by the formula:
The amount of calendar time, TDEV, it will take to devel- op the product is estimated by
TDEVNS = C x (PMNS)F
5 where F = D + 0.2 x 0.01 x I SFj
j=1
nomies of scale that are encountered for software projects of dissimilar magnitude.
• Precedentedness(PREC)
• Development Flexibility (FLEX)
• Architecture / Risk Resolution (RESL)
• Team Cohesion (TEAM)
• Process Maturity (PMAT)
= D + 0.2 x (E – B)
In COCOMO-II effort is expressed as person month(PM). COCOMO II treats the number of person-hours per month, PH/PM, as an adjustable factor with a nominal value of 152 hours/PM.
• The value of n is 16 for the Post-Architecture model effort multipliers, Emi, and 6 for the Early Design model, the number of SFi stands for ex- ponential scale factors.
• The values of A, B, C, D, SF1 …, and SF5 for the Early Design model are the same as those for the Post-Architecture model.
Baseline Effort Constants:
A = 2.94; B = 0.91
n
PM = A x SizeE x IT EM
i=1
5
where E = B + 0.01 x i, SFj
j = 1
Baseline Schedule Constants:
C = 3.67; D = 0.28
The application size is exponent is aggregated of five scale factors that describe relative economies or diseco-
Cost drivers are characteristics of software development that influence effort in carrying out a certain project. Un- like the scale factors cost drivers are selected based on the rationale that they have a linear affect on effort. There are
17 effort multipliers that are utilized in the COCOMO II
model to regulate the development effort.
• Required Software Reliability (RELY)
• Data Base Size (DATA)
• Developed for Reusability (RUSE)
• Documentation Match to Life-Cycle Needs (DO- CU)
• Execution Time Constraint (TIME)
• Main Storage Constraint (STOR)
• Platform Volatility (PVOL)
• Analyst Capability (ACAP)
• Programmer Capability (PCAP)
• Personnel Continuity (PCON)
• Applications Experience (APEX)
• Platform Experience (PLEX)
• Language and Tool Experience (LTEX)
• Use of Software Tools (TOOL)
• Multisite Development (SITE)
• Required Development Schedule (SCED)
As first case study we have taken a project in considera- tion which was developed for an very famous advocate
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International Journal of Scientific & Engineering Research Volume 2, Issue 6, June-2011 3
ISSN 2229-5518
firm. The project takes care billing and case information of the firm.
After completion of project we calculated the efforts (Person-Month) using COCOMO II and got the actual time taken to develop the project. Total line of code of C# is 7187 i.e. 7.1 KLOC.
Here
5
I SFj =18.97
j=1
5
E = B + 0.01 x I SFj = 1.097
j = 1
Baseline Effort Constants: A = 2.94; B = 0.91 Baseline Schedule Constants: C = 3.67; D = 0.28 | ||||||||
Driver | Symbol | VL | L | N | H | VH | XH | Our Value |
RELY | EM1 | 0.82 | 0.92 | 1.00 | 1.10 | 1.26 | .82 | |
DATA | EM2 | 0.90 | 1.00 | 1.14 | 1.28 | 0.9 | ||
CPLX | EM3 | 0.73 | 0.87 | 1.00 | 1.17 | 1.34 | 1.74 | .87 |
RUSE | EM4 | 0.95 | 1.00 | 1.07 | 1.15 | 1.24 | 1.0 | |
DOCU | EM5 | 0.81 | 0.91 | 1.00 | 1.11 | 1.23 | 1.0 | |
TIME | EM6 | 1.00 | 1.11 | 1.29 | 1.63 | 1.0 | ||
STOR | EM7 | 1.00 | 1.05 | 1.17 | 1.46 | 1.0 | ||
PVOL | EM8 | 0.87 | 1.00 | 1.15 | 1.30 | 0.87 | ||
ACAP | EM9 | 1.42 | 1.19 | 1.00 | 0.85 | 0.71 | 0.85 | |
PCAP | EM10 | 1.34 | 1.15 | 1.00 | 0.88 | 0.76 | 0.88 | |
PCON | EM11 | 1.29 | 1.12 | 1.00 | 0.90 | 0.81 | 0.90 | |
APEX | EM12 | 1.22 | 1.10 | 1.00 | 0.88 | 0.81 | 0.88 | |
PLEX | EM13 | 1.19 | 1.09 | 1.00 | 0.91 | 0.85 | 0.85 | |
LTEX | EM14 | 1.20 | 1.09 | 1.00 | 0.91 | 0.84 | 0.91 | |
TOOL | EM15 | 1.17 | 1.09 | 1.00 | 0.90 | 0.78 | 0.90 | |
SITE | EM16 | 1.22 | 1.09 | 1.00 | 0.93 | 0.86 | 0.80 | 0.80 |
SCED | EM17 | 1.43 | 1.14 | 1.00 | 1.00 | 1.00 | 1.0 |
n
l1 EM = 0.184295
i=1
n
PM = A x SizeE x l1 EM
i=1
5 where E = B + 0.01 x I SFj
j = 1
Applying the values on formula : Here we have
A = 2.94
Size = 7.1
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E = 1.097
B = .91
l1 EM = 0.184295
PM = 4.67724
Actual time taken for this project is 4 Months.
We have applied above COCOMO II formula on 4 soft-
ware projects which produces us the results as per follow-
ing table. Also we have taken the actual person month in
the table.
S.N. | Name of Project | Technology | KLOC | n IT EM i=1 | 5 i, SFj j=1 | Estimated PM using COCOMO II | Actual PM |
1 | Advocate’s Desktop | C#.Net | 7.1 | 0.184 | 18.97 | 4.6 | 4 |
2 | Online TrueLogic | DotNet | 15.01 | 0.204 | 18.97 | 11.83 | 9.5 |
3 | Online Project Management | Java | 7.8 | .204 | 18.97 | 5.76 | 4 |
4 | Unit Converter | Android | 1.6 | .1546 | 18.97 | .76 (22 Days) | .53 (16 Days) |
This brief article shows how to make cost estimates using COCOMO II for a sample project, and outlines basic steps, terms, and tools used. Obviously, ad hoc estimates are prone to error. COCOMO II make it easy for you to
clarify not only an expected project cost and duration, but also prompt you to verify all basic sides of a software project by providing clear, compact, and concise terms, methodology, which are tested on a wide range of real- life projects and thus reduce essentially project risks and provide reasonable grounds for communication with a project stockholder. Paper presents difference in between estimation by COCOMO II and actual time taken by the project.
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