L1 Introduction to the PSP

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PSP Fundamentals: L1 Introduction to the PSP September 2007

Sponsored by the U.S. Department of Defense

2007 by Carnegie Mellon University

This material is approved for public release. Distribution is limited by the Software Engineering Institute to attendees.

PSP Fundamentals

Introduction to the PSP


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2007 Carnegie Mellon University

PSP Fundamentals: L1 Introduction to the PSP

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Lecture Topics

What is a Process

What is a Personal Process

What is the Personal Software Process

Introducing the PSP

PSP Results


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Question

What do you know about your performance today?


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What do you know about your performance?

Did I meet the commitments for:

Content

Schedule

Quality

Did the stakeholders like

the product?

the way in which I managedand communicated?

Requirements Product

Most developers understand their performance from outside the box.


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What do you know about your performance?

How do I spend my time?

Which activities take the most time,which ones the least?

How do I make and track my plans?

When will I be done?

How many defects will be in the final

product?How consistent am I?

When are defects injected and removed?

Am I getting better?

Requirements Product

But, most developers have less insight into how they do the work.


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What is a Personal Process?

When you use a process for your personal work, it is called a personal

process.

It is usually developed from your personal experience.

You may start with a proven process that was developed by

someone else.

You modify and improve the process to suit your needs.


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Why Define and Use a Personal Process?

Consistency

results are more likely to be similar.

work becomes more predictable.

Efficiency

structures and guides your work (orders the steps, avoids rework)

keeps you focused on what needs to be done now

Basis for improvement

gathering data on your work helps determine which steps

take the most time

cause you the most trouble

are least effective

this information helps identify improvement opportunities


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What is the Personal Software Process?

PSP is a personal process for writing software.

The PSP was developed by Watts Humphrey and is a application of

successful industrial-strength practices distilled to a personal level.

It is not the only process for writing software. It may not even be the

best process for you. But we ask that you follow this process for the

next five days.After youve completed the course you should

examine your PSP data from the class

review your experiences and Process Improvement Proposals

tailor the PSP to meet your needs, or define a PSP from scratch

to meet your needs


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PSP Principles

Every developer is different; to be most effective, developers must plan

their work and they must base their plans on personal data.

To consistently improve their performance, developers must measuretheir work and use their results to improve.

To produce quality products, developers must feel personally

responsible for the quality of their products. Superior products are notproduced by accident; developers must strive to do quality work.

It costs less to find and fix defects earlier in a process than later.

It is more efficient to prevent defects than to find and fix them.The right way is always the fastest and cheapest way to do a job.


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PSP Process Elements

Document the process entry criteria, phases/steps, and exit criteria. The purpose is toprovide expert-level guidance as you use the

process.

P hase P urpose To guide you in deve loping m odule -level programs

Inputs Required Problem descriptionPSP project plan summary form

Time and defect recording logsDefect type standardStop watch (optional)

1 P la nn in g - P ro du ce or ob ta in a req ui rem en ts st at eme nt .- E stimate the required development time.

- Enter the plan data in the project plan summary form.- Comple te the time log.

2 Develo pment - D es ign th e prog ram.- Implement the design.- Compile the program and fix and log all defects found.

- Test the program and fix and log all defects found.- Comple te the time recording log.

3 P ostmortem C omple te the projec t p lan sum mary form with actua ltime, defect, and size data.

Exit C ri ter ia - A thoroughly te s ted program- Comple ted project plan summary with estimated and

actual data- Comple ted defect and time logs

Scripts

Measures Measure the process and the product. Theyprovide insight into how the process isworking and the status of the work.

Student Date

Program Program #Instructor Language

Summary Plan Actual To Date

LOC/Hour

ActualTime

Planned Time

CPI(Cost-Performance Index)(Actual/Planned)

%Reuse

%NewReuse

Test Defects/KLOC

TotalDefects/KLOC

Yield%

%Appraisal COQ

%Failure COQ

COQA/F Ratio

Program Size (LOC): Plan Actual To DateBase(B)

(Measured) (Measur ed)

Deleted (D)(Estimated) (Counted)

Modified (M)(Estimated) (Counted)

Added (A)(N-M) (T-B+D-R)

Reused (R)(Estimated) (Counted)

TotalNew & Changed (N)(Estimated) (A+M)

TotalLOC(T)(N+ B- M- D+ R) ( Mea sur ed)

TotalNew Reused(Estimated) (Counted)

TotalObjectLOC(E)(Estimated) (Counted)

Upper Prediction Interval (70%)

Lower PredictionInterval(70%)

Time in Phase (min.) Plan Actual To Date To Date %

Planning

Design

Design review

Code

Code review

Compile

Test

Postmortem

Total

TotalTime UPI(70%)

Total Time LPI (70%)

Forms Provide a convenient and consistentframework for gathering and retainingdata

Standards Provide consistent definitions thatguide the work and gathering of data.


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Scripts

Scripts provide expert-level guidance for doing the work.

PSP0 Process Script

Purpose To guide the development of module-level programs

Entry Criteria - Problem description- PSP0 Project Plan Summary form - Time and Defect Recording logs- Defect Type standard- Stopwatch (optional)

Step Activities Description

1 Planning - Produce or obtain a requirements statement.- Estimate the required development time.- Enter the plan data in the Project Plan Summary form.- Complete the Time Recording log.

2 Development - Design the program.- Implement the design.- Compile the program, and fix and log all defects found.

- Test the program, and fix and log all defects found.- Complete the Time Recording log.

3 Postmortem Complete the Project Plan Summary form with actual time, defect, and size

data.

Exit Criteria - A thoroughly tested program- Completed Project Plan Summary form with estimated and actual data

- Completed Time and Defect Recording logs


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Basic Process Measures -1

Measures help you quantify the process and the product.

The reason to measure a process is to understand it.

how much time is spent in various activities

what is produced at various times

how many defects are injected and removed, and whenWith these data, developers can better

plan and estimate the work to be done

evaluate the results

improve the process for the next project


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Basic Process Measures -2

To measure the process, the work is divided into a defined set of tasks

or activities called phases.

The measures for each phase are

time spent in that phase

defects injected in that phase

defects removed in that phase

The product size is also measured, but only when the work package is

complete.

These measures provide the foundation for all TSPI measurements,

analyses, and planning.


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Forms

Forms provide a convenient and consistent framework for gathering

and retaining data.

Example forms in the PSP are the Time Log and the Defect Log.

The Time Log is used to record time on task data.

The Defect Log is used to record defect information.

Data entry on forms is almost always automated via a tool that supports

the overall process.


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PSP F d t l L1 I t d ti t th PSP


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Putting the Elements Together

Requirements

Project

plansummary

Working Program Project and processdata summary forms

Timeand

defectlogs

guideProcessscripts

andstandards

PSP0Planning

Implementation

Design

Code

Compile

Unit Test

Postmortem

PSP F d t l L1 I t d ti t th PSP


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Characteristics of a Good Process

A good process has some of the following characteristics

Early defect removal.

Easy to highlight cost of rework.

Support for the plan, do, check, improve paradigm.

A good process should provide expert guidance in a simple, easy to followmanner. It should not be voluminous and contain tutorial information.

A guideline Watts Humphrey used when defining the PSP and TSP was that aprocess script should seldom be more than a page in length.



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Learning the PSP -1

The PSP is introduced in discrete, upward-compatible steps.

You write one or more module-sized programs at each step.

You gather and analyze data on your work.

You use the results to improve your personal performance.



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Learning the PSP -2

PSP will be introduced in threesteps:

PSP0: You establish ameasured performancebaseline.

PSP1: You practice size

and effort estimation. PSP2: You practice defect

and yield management.

This week, you will write programsusing PSP0, PSP1, and PSP2.

PSP1Planning and Tracking

PSP2Quality Management

TSPTeam development

PSP0Defining and Using

Processes



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Course Results

We now have data on over 30,000 programs written using the PSP.

The following charts show how others have improved during the PSP

course.

size and effort estimating

compile and test time


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2007 Carnegie Mellon University 24

Compile and Test Time 810 Engineers

0

5

10

15

2025

30

35

4045

50

1 2 3 4 5 6 7 8 9 10

Program Number

Com

pileandTestTimeas%

of

DevelopmentTime

Upper

Average

Lower



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Messages to Remember

A personal process is a set of steps that individuals use to guide their

work.

Defining and using a personal process helps individuals to plan, do,

track, and improve their work.

Scripts, measures, forms, and standards are elements of a good

process definition.



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L1 Introduction to the PSP

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