1. Using COCOMO for Software Decisions - from COCOMO II Book, Section 2
LiGuo Huang
Computer Science and Engineering
Southern Methodist University

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 drivers 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 = $3.728*1.18 = $4.4M
Annual Maintenance Cost
Annual Software Change = 100*(0.20) = 20KSLOC
Cost = 2.94*(20)^1.10*$8K=$635K

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 = ($80)*(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 = 3.8
Well worth the investment

6. Setting Project Budget and Schedules
TDEV=3.67*(PM)^[ *(E-0.91)] = 3.67*(466)^0.318 = 26 months
Constructive phase effort and schedule (Table A.5)
Effort=0.76*(466)=354 PM; Schedule=0.625*26=16.25 Months;
Staff Level = 354/16.25=21.8 people
Staff needed for construction activities (Table A. 11)
Requirements = 21.8*0.08=1.7 people
Product Design =21.8*0.16=3.5 people

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)
3,608
4,048
4,400
4,840
5,544
Maint. Effort Mult.
1.35
1.15
0.98
Maint. Cost (*2 for Nominal)
11,880
10,120
8,800
8,624
9,680
Life-cycle Cost
15,488
14,168
13,200
13,464
15,224

8. Value-Based Tradeoff Analysis Cost of Downtime = $38*(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)
Availability
=MTBF/(MTBF+MTTR)
.50
.90
.997
0.9999
Downtime
.10
.003
0.0001
Cost=$38*Downtime
$1500M
$300M
$10M
$0.3M
$0.01M
SW Life-cycle Cost
$15.5M
$14.2M
$13.2M
$13.5M
$15.2M
Ownership Cost
$1515M
$314M
$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 personal
Average applications, platform experience ½-level lower
Resulting cost = $4400k*(1.05)*(1.045)=$4828k
Risk reserve = $428k

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
Adaptation of assessment 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

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
SU = 25: better structured, documented
UNFM = 0.4: reduced degree of unfamilarity
20KSLOC * [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. Conclusions COCOMO II is useful in many decision situations
Support objective discussion and negotiation
Most analysis can be done with hard calculator
Simpler, easier to explain
Usage builds shared understanding and trust