1. Using COCOMO for Software Decisions - from COCOMO II Book, Section 2.6
Barry Boehm
CS 510, Fall 2016
Edited & presented by Jim Alstad

2. Outline COCOMO II Objective: Decision Support
Example Company: UST, Inc. Auto Parts
Frequent Software Decisions
Investment; Business Case Analysis
Setting Project Budgets and Schedules
Performing Tradeoff Analysis
Cost Risk Management
Development vs. Reuse
Legacy Software Phaseout
Software Process Improvement
Software Organizational Decisions
Conclusions

3. UST, Inc. Auto Parts Company
Large manufacturing company
200-person software organization
Considering development of manufacturing control system (MCS)
100 KSLOC; nominal driver ratings; $8K/PM
Scaling exponent
E= ( )=1.10
Estimated effort and cost
Effort=2.94*100^1.10 = 466 PM
Cost = 466 PM * $8K/PM = $3.728M

4. UST, Inc. Auto Parts Company (Cont.)
Plus Inception (6%) and Transition (12%) costs
Acquisition Cost = $3.728M*1.18 = $4.4M
Annual Maintenance Cost
Annual Software Change = 100*(0.20) = 20 KSLOC
Cost = 2.94*(20)^1.10*$8K=$635K
Jim: Added “$3.728M”.

5. MCS Business Case Analysis
MCS estimate to reduce manufacturing inventory 20%
Enables more just-in-time arrival of suppliers components
Current Manufacturing inventory valued at $80M
Inventory carrying costs average around 25%
Inventory control, property taxes, capital costs, etc.
MCS savings in reduced inventory carrying costs = ($80M)*(0.25)*(0.2)=$4M/Year
MCS savings subtracts software maintenance cost =$4M-0.635M=$3.365M
5-year-ROI = (5 * $3.365M - $4.4M) / $4.4M = 2.8
Well worth the investment
Jim: Added “$80M”.

6. Setting Project Budgets and Schedules
TDEV=3.67*(PM)^[ *(E-0.91)] = 3.67*(466)^0.318 = 26 month
Construction phase schedule and effort
Effort=0.76*(466 PM)=354 PM; Schedule=0.625*26=16.25 Month;
Staff Level = 354/16.25=28.8 people
Jim: Added “466 PM”.
Jim: Replaced “Development” with “Construction”.

7. Performing Tradeoff Analysis MCS Life-cycle Costs vs. Reliability Level
RELY Rating
Very Low
Low
Nominal
High
Very High
Dev. Effort Mult.
0.82
0.92
1.0
1.10
1.26
Dev. Cost ($K)
3608
4048
4400
4940
5544
Maint. Effort Mult.
1.35
1.15
0.98
Maint. Cost (*2 for Nominal:
20%/year * 10 years)
11,880
10,120
8,800
8,624
9,680
Life-cycle Cost
15,488
14,168
13,200
13,464
15,224
Jim: Explain “Maint. Effort Mult.” as combined cost of 1) developing at the required RELY level, and 2) dealing with extra debugging and bug fixing for lower-RELY software.

8. Value-Based Tradeoff Analysis Cost of Downtime = $38K*(Downtime)
RELY Rating
Very Low
Low
Nominal
High
Very High
Mean Time to Failure (hr) 1 10
300
10,000
300,000
Mean Time to Repair (hr)
Avail=
MTBF/(MTBF+MTTR)
.50
.90
.997
0.9999
Downtime
.10
.003
0.0001
Cost=$38K*Downtime
$1660M
$330M
$10M
$0.33M
$0.01M
SW Life-cycle Cost
$15.5M
$14.2M
$13.2M
$13.5M
$15.2M
Ownership Cost
$1675.5M
$344.2M
$23.2M
$13.8M

9. Outline COCOMO II Objective: Decision Support
Example Company: UST, Inc. Auto Parts
Frequent Software Decisions
Investment; Business Case Analysis
Setting Project Budgets and Schedules
Performing Tradeoff Analysis
Cost Risk Management
Development vs. Reuse
Legacy Software Phaseout
Software Process Improvement
Software Organizational Decisions
Conclusions

10. Cost Risk Management Risk reserve for requirement volatility
Estimate as high as 15%
Resulting cost = 2.94*(100+15)^1.10*($8K)=$5130K
Risk reserve = $5130K – 4400K = $730K
Risk reserve for less experienced personnel
Average applications, platform experience ½-level lower
Resulting cost = $4400K*(1.05)*(1.045)=$4828K
Risk reserve = $428K
Jim: “k” -> “K” throughout. “Platform” -> “platform”.

11. Development vs. Reuse Possibility of reusing a 40 KSLOC component
Reuse parameters not a strong match
% design modified DM=40
% code modified CM=50
% integration redone IM=100
Understanding penalty SU=50
SW unfamiliarity UMFM=1.0
Assessment and assimilation AA =5%
Equivalent new lines of code =
40k*[(0.4*40+0.3*50+0.3*100)/100+(5+50*1.0)/100]
= 40k * ( ) = 46.4KSLOC
Not a good decision to reuse
Jim: “Adaptation of assessment” -> “Assessment and assimilation”

12. Legacy Software Phaseout
Candidate: Corporate property accounting system
50K COBOL program; 20% annual change (10K)
SU = 50: poorly structured, documented
UNFM = 0.7: few people familiar with code
Equivalent annual maintenance size =
10KSLOC * [1 + (50*0.7)/100] = 13.5 KSLOC/year
3 years: 40.5K SLOC
Replacement could use MCS GUI, DBMS
Only 20 KSLOC of new software needed; 20% annual change (4KSLOC)
SU = 25: better structured, documented
UNFM = 0.4: New developers familiar with the code
4KSLOC * [1+ (25*0.4)/100] = 4.4 KSLOC/year
3 years + development = 3* = 33.2 KSLOC
Better to phase out and replace legacy SW

13. Software Process Improvement
UST currently at Process maturity Level 2
Planning & control, config. Management, quality assurance
Cost to achieve level 3 (process group, training, product engr.)
Process group: (2yr)*(4 persons)*($96K/yr) = $768K
Training: (200 persons)*(3weeks)*($96K/yr) = $1108K
Contingency = $124K; Total = = $2000K
Benefit: scale exponent reduced by =.0156, to 1.10 – =
From 100^1.10 = to 100^ = 147.5, or 7% less effort
Annual savings = (200 persons)*(96K/yr)(.07)=$1344K
5 year ROI = [5*$1344K-$2000K]/$2000K = 2.36
Again, well worth the investment

14. Outline COCOMO II Objective: Decision Support
Example Company: UST, Inc. Auto Parts
Frequent Software Decisions
Investment; Business Case Analysis
Setting Project Budgets and Schedules
Performing Tradeoff Analysis
Cost Risk Management
Development vs. Reuse
Legacy Software Phaseout
Software Process Improvement
Software Organizational Decisions
Conclusions

15. COCOMO II Experience Factory: I
Rescope
System objectives: fcn’y, perf., quality No
Cost,
Sched,
Risks
COCOMO 2.0
Ok?
Yes
Corporate parameters: tools, processes, reuse

16. COCOMO II Experience Factory: II
Rescope
Execute project to next Milestone
System objectives: fcn’y, perf., quality No
Cost,
Sched,
Risks
Revise Milestones, Plans, Resources
COCOMO 2.0
Ok?
Yes
Corporate parameters: tools, processes, reuse
M/S Results
Milestone plans,
resources No
Ok?
Milestone expectations
Revised Expectations
Yes
Done? No
Yes
End

17. COCOMO II Experience Factory: III
Rescope
Execute project to next Milestone
System objectives: fcn’y, perf., quality No
Cost,
Sched,
Risks
Revise Milestones, Plans, Resources
COCOMO 2.0
Ok?
Yes
Corporate parameters: tools, processes, reuse
M/S Results
Milestone plans,
resources No
Ok?
Milestone expectations
Revised Expectations
Yes
Accumulate COCOMO 2.0 calibration
data
Done?
Recalibrate COCOMO 2.0 No
Yes
End

18. COCOMO II Experience Factory: IV
Rescope
Execute project to next Milestone
System objectives: fcn’y, perf., quality No
Cost,
Sched,
Risks
Revise Milestones, Plans, Resources
COCOMO 2.0
Ok?
Yes
Corporate parameters: tools, processes, reuse
M/S Results
Milestone plans,
resources No
Ok?
Improved Corporate Parameters
Cost, Sched,
Quality drivers
Milestone expectations
Revised Expectations
Yes
Evaluate Corporate SW Improvement Strategies
Accumulate COCOMO 2.0 calibration
data
Done?
Recalibrate COCOMO 2.0 No
Yes
End

19. Conclusions COCOMO II is useful in many decision situations
Supports objective discussion and negotiation
Most analyses can be done with hand calculator
Simpler, easier to explain
Usage builds shared understanding and trust
Jim: 3 following slides, on homework assignment, deleted.