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When will my Feature

be Ready?

A Practical ProbabilisticApproach to Development

Estimation

Leandro Caniglia

Caesar Systems

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Awareness

Knownknowns

Unknownknowns

Knownunknowns

Unknownunknowns

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0 200

50

100

150

Cumulative number of

tasks

days

tasks

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0 200

50

100

150

days

closed

tasks

Cumulative number of

tasks

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0 200

50

100

150

Knownknown

Unknownunknown

Knownunknown

days

closed

tasks

Cumulative number of

tasks

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0 200

50

100

150

Awareness = Learning

Knownknown

Unknownunknown

Knownunknown

days

closed

tasks

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0 200

50

100

150

Generalization

Knownknown

Unknownunknown

Knownunknown

days

closed

tasks

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0 200

50

100

150

Expected Learning Pace

days

closed

tasks

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Bad and GoodQuestions When will the feature be ready?

What's the probability to have the

feature ready in 1 month?

How long would it take to have

the feature ready with 80% of

certainty?

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Measuring

1 PushSelf2 LoadAssoc13 SendSelector1 #on:

4 StoreTemporary15 LoadTemporary16 SendSelector2#messageCount7 Return

CompiledMethod >>#messageCount 1

| reader | 2

reader := ByteCodeReaderon: self. 3

^readermessageCount 4loc

4bytecodes7messageCo

unt

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Complexity Metrics

Lines of Code (LOC)

Metho

ds

Classes

# of bytecodes# of sends incursion# of arguments (arity) numberOfSubWords (4 in this case)

# of ivars (slots)# of methods

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ProbabilityDistributions

etrics are not number

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Demo

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Feature Estimation

ProblemHow can we calculate the probability

distribution associated to a feature?

SolutionCreate a probabilistic model of the problem

and run a Monte Carlo simulation on it.

Remember!

Metrics are not numbers but distributions.

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Development Metrics

Code

# of methods /class

# of methods

Change set

Dev Team speed additivity

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Dev Team Metrics

Speed

# of change sets integrated / dayIntegrated

change sechangeset

holidays

vacations

interruptionsdistractions

illness

hw failures

Delays included

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Dev Team Metrics

% of method survival by change set

Additivity

mth1mth2mth3

mthmthmth

original

changeset

currentstatein

memo

ry

refactoring renaming formatting

Actions included

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Feature Size

NewClass

New

NewExisting

ExistingClass

1. Sketch a preliminary design of the feature

2. Count classesclasses = C

w(C)

w(C)

1 ; if C isnew0.5 ;otherwise

4.0

3.5

12

30.5 ;otherwise

2

5

7

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Dev Team Focus

Focus

% of resources assigned to thefeature

focus % of people * % of time

Other

tasks% of resources assigned to everythingelse other 100% - focus

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changeset

changeset

A Stochastic Model

DevTeam

focus =

p

p

1 p

feature related

other tasks

additivity

focused

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Monte Carlo Simulation

1 2 3 4 5 6

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Demo

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Good Questions &AnswersWhen will the feature be ready?What's the probability of having

the feature ready in 1 month?

How long would it take to havethe feature ready with 80% or

certainty?