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Lecture 5 Estimation-revised Estimate size, then Estimate effort, schedule and cost from size

CS 551. Lecture 5 Estimation-revised Estimate size, then Estimate effort, schedule and cost from size. Project Metrics. Cost and schedule estimation Measure progress Calibrate models for future estimating Metric/Scope Manager Product Number of projects x number of metrics = 15-20.

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Lecture 5 Estimation-revised Estimate size, then Estimate effort, schedule and cost from size

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  1. CS 551 Lecture 5 Estimation-revised Estimate size, then Estimate effort, schedule and cost from size

  2. Project Metrics • Cost and schedule estimation • Measure progress • Calibrate models for future estimating • Metric/Scope Manager Product Number of projects x number of metrics = 15-20

  3. Approaches to Cost Estimtation • By expert • By analogies • Decomposition • Parkinson’s Law; work expands to fill time available • Pricing to win: price is set at customer willingness to pay • Lines of Code • Function Points • Mathematical Models: Function Points & COCOMO

  4. Boehm: “A project can not be done in less than 75% of theoretical time” Time Ttheoretical 75% * Ttheoretical Linear increase Staff-month Impossible design But, how can I estimate staff months? Ttheoretical = 2.5 * 3√staff-months

  5. Sizing Software Projects • Effort = (productivity)-1 (size)c productivity ≡ staff-months/kloc size ≡ kloc Staff months 500 Lines of Code or Function Points

  6. Understanding the equations Consider a transaction project of 38,000 lines of code, what is the shortest time it will take to develop? Module development is about 400 SLOC/staff month Effort = (productivity)-1 (size)c = (1/.400 KSLOC/SM) (38 KSLOC)1.02 = 2.5 (38)1.02 ≈ 100 SM Min time = .75 T= (.75)(2.5)(SM)1/3 ≈ 1.875(100)1/3 ≈ 1.875 x 4.63 ≈ 9 months

  7. How many software engineers? • 1 full time staff week = 40 hours, 1 student week = 20 hours. • Therefore, our estimation of 100 staff months is actually 200 student months. • The period of coding is December 2004 through April 2005, which is a period of 5 months. • 200 staff months/5 months = 40 student software engineers, therefore simplification is mandatory As of 8Nov07

  8. Productivity= f (size) Bell Laboratories data Capers Jones data Productivity (Function points / staff month) Function Points

  9. Average Change Processing Time: for two Systems of Systems Average workdays to process changes Thanks to Barry Boehm

  10. SW SW Effect of ignoring software structure • Software risks discovered too late • Slow, buggy change management (WBS-based) Software SW Thanks to Barry Boehm

  11. Software Development Schedule TrendsNumber of Years ≈ 0.04 * cube root (NCKSLOC) SW Years to Develop Software,Hardware HW Thousands of source lines of code (KSLOC)

  12. The Cone of Uncertainty: Usual result of total commitment Better to buy information to reduce risk ^ Inadequate PDR Thanks to Barry Boehm 05/22/2007 (c) USC-CSSE 12

  13. There is Another Cone of Uncertainty:Shorter increments are better Uncertainties in competition, technology, organizations, mission priorities 05/22/2007 (c) USC-CSSE 13

  14. The Incremental Commitment Life Cycle Process: Overview Stage I: Definition Stage II: Development and Operations Anchor Point Milestones Concurrently engr. Incr.N (ops), N+1 (devel), N+2 (arch) Concurrently engr. OpCon, rqts, arch, plans, prototypes

  15. ICM Stage II: Increment View

  16. Increment View Thanks to Barry Boehm

  17. RUP/ICM Anchor Points Enable Concurrent Engineering C V A D I O C C C C O C D R R R C R Thanks to Barry Boehm

  18. Lines of Code • LOC ≡ Line of Code • KLOC ≡ Thousands of LOC • KSLOC ≡ Thousands of Source LOC • NCKSLOC ≡ New or Changed KSLOC

  19. Bernstein’s rule of thumb Productivity per staff-month: • 50 NCSLOC for OS code (or real-time system) • 250-500 NCSLOC for intermediary applications (high risk, on-line) • 500-1000 NCSLOC for normal applications (low risk, on-line) • 10,000 – 20,000 NCSLOC for reused code Reuse note: Sometimes, reusing code that does not provide the exact functionality needed can be achieved by reformatting input/output. This decreases performance but dramatically shortens development time.

  20. Productivity: Measured in 2000

  21. QSE Lambda Protocol • Prospectus • Measurable Operational Value • Prototyping or Modeling • sQFD • Schedule, Staffing, Quality Estimates • ICED-T • Trade-off Analysis

  22. Heuristics for requirements engineering • Move some of the desired functionality into version 2 • Deliver product in stages 0.2, 0.4… • Eliminate features • Simplify Features • Reduce Gold Plating • Relax the specific feature specificaitons

  23. Function Point (FP) Analysis • Useful during requirement phase • Substantial data supports the methodology • Software skills and project characteristics are accounted for in the Adjusted Function Points • FP is technology and project process dependent so that technology changes require recalibration of project models. • Converting Unadjusted FPs (UFP) to LOC for a specific language (technology) and then use a model such as COCOMO.

  24. Function Point Calculations • Unadjusted Function Points UFP= 4I + 5O + 4E + 10L + 7F, Where I ≡ Count of input types that are user inputs and change data structures. O ≡ Count of output types E ≡ Count of inquiry types or inputs controlling execution. • [think menu selections] L ≡ Count of logical internal files, internal data used by system • [think index files; they are group of logically related data entirely within the applications boundary and maintained by external inputs. ] F ≡ Count of interfaces data output or shared with another application Note that the constants in the nominal equation can be calibrated to a specific software product line.

  25. Complexity Table

  26. Complexity Factors 1. Problem Domain ___ 2. Architecture Complexity ___ 3. Logic Design -Data ___ 4. Logic Design- Code ___ Total ___ Complexity = Total/4 = _________

  27. Problem DomainMeasure of Complexity (1 is simple and 5 is complex) • All algorithms and calculations are simple. • Most algorithms and calculations are simple. • Most algorithms and calculations are moderately complex. • Some algorithms and calculations are difficult. • Many algorithms and calculations are difficult. Score ____

  28. Architecture ComplexityMeasure of Complexity (1 is simple and 5 is complex) 1. Code ported from one known environment to another. Application does not change more than 5%. 2. Architecture follows an existing pattern. Process design is straightforward. No complex hardware/software interfaces. 3. Architecture created from scratch. Process design is straightforward. No complex hardware/software interfaces. 4. Architecture created from scratch. Process design is complex. Complex hardware/software interfaces exist but they are well defined and unchanging. 5. Architecture created from scratch. Process design is complex. Complex hardware/software interfaces are ill defined and changing. Score ____

  29. Logic Design -Data Score ____

  30. Logic Design- Code Score __

  31. Complexity Factors 1. Problem Domain ___ 2. Architecture Complexity ___ 3. Logic Design -Data ___ 4. Logic Design- Code ___ Total ___ Complexity = Total/4 = _________

  32. Computing Function Points See http://www.engin.umd.umich.edu/CIS/course.des/cis525/js/f00/artan/functionpoints.htm

  33. Function Points Qualifiers • Based on counting data structures • Focus is on-line data base systems • Less accurate for WEB applications • Even less accurate for Games, finite state machine and algorithm software • Not useful for extended machine software and compliers An alternative to NCKSLOC because estimates can be based on requirements and design data.

  34. Initial Conversion http://www.qsm.com/FPGearing.html

  35. Pros: Language independent Understandable by client Simple modeling Hard to fudge Visible feature creep Cons: Labor intensive Extensive training Inexperience results in inconsistent results Weighted to file manipulation and transactions Systematic error introduced by single person, multiple raters advised Function Point pros and cons

  36. Heuristics to do Better Estimates • Decompose Work Breakdown Structure to lowest possible level and type of software. • Review assumptions with all stakeholders • Do your homework - past organizational experience • Retain contact with developers • Update estimates and track new projections (and warn) • Use multiple methods • Reuse makes it easier (and more difficult) • Use ‘current estimate’ scheme

  37. Specification for Development Plan • Project • Feature List • Development Process • Size Estimates • Staff Estimates • Schedule Estimates • Organization • Gantt Chart

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