1 复习. 2 Main Three Elements Plan Period plan product plan Project Plan Measure Size...

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Main Three ElementsMain Three Elements Plan

Period plan product plan Project Plan

Measure Size measurement defect measurement quality measurement.

Manage Time, commitments, schedules and quality.

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MesureMesure Size measurement

Classification of codes Defect measurement

Defect injection; Defect removal;

Quality measurement Product quality---yield; Process quality---A/FR.

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PlanPlan The forms of period plan, product plan, and pr

oject plan; How to make above plans?

Estimate based on the historical data. period plan, based on ? product plan, based on ? Project plan, based on ?

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period planperiod plan Table 4.1 Weekly activity summary (Page

34). Understand where you spend time Judge that a large task will likely take nearly

the maximum time and a simple task close to the minimum.

Plan the subsequent work

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product plan A properly produced product plan include

s three things: The size and important features of the produ

ct to be produced; An estimate of the time required to do the wo

rk; A projection of the schedule.

Planning for large and small tasks Three basic plan elements:

size estimates, projected hours, and the schedule.( 规模估计、项目时间、项目时间 )

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Some definitions Product: is something you produce for a

co-worker, an employer or a customer. Project: typically produce a product. Task: is a defined element of work. Process: describe the way do the project. Plans: describe the way a specific project

is to be done. How, when and at what cost Job: is something you do, either a product

or a task.

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Balanced estimate (均衡估计 )

A balanced set of estimates has about as many overestimates as underestimate.

The advantage of having balance estimates is that on average your jobs will take about as long as you estimated.

The key to good estimating, however, is to learn to make balanced estimates.

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Program Size measurement

Program Size measurement

LOC (Lines of code) JCL—Job Control Language ( 可交付的作业控制语言 )

Include: Statements, data define, data declaration, input/output formats define etc.

Exclude: Comments, empty lines. The following C program has 3 LOC.

if （ a>b ） max=a; else max=b; printf(“The max number is%d\n”,max);

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The gantt chartThe gantt chart

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checkpointscheckpoints What is checkpoint?

Break the work into several parts. When each part is completed,you have made a defi

ned level of progress. Measurable schedule points like this are called chec

kpoints or milestones. Each checkpoint is a identifiable point, with a p

lanned completion date. you can readily see if you are on schedule or falling

behind.

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Making a project schedule

Making a project schedule

Step1:analyzing the job in enough detail to identify its several component tasks.

Step2:estimate the size for each of these smaller tasks and determine the amount of work.

Step3:list each task on a Gannt chart with a schedule bar to show when it will start and end.

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Tracking earned value(积分 )

Tracking earned value(积分 )

To see table9.1 (page 106), table9.2 (page 108) Calculating each task’s percentage of the total project.

If some task completed, you will earn some values,which named earned value.

If reach an earned value of100%, means you complete all the works.

By using earned value,could do the work in different order than originally planned and still track progress against the plan.

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Summarizing weekly times


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Calculating period times and rates

Calculating period times and rates

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PSP Process FlowPSP Process Flow

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Defects & Software quality

Defects & Software quality

Defects are the primary measure of quality in PSP.

Finding and fixing defects will do great help to improving software quality.

Finding and fixing defects is necessary but not sufficient to assure software quality.

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Date Number Type Inject Remove Fix Time Fix Defect—— —— ——— ——— ———— ———— ————— Description—————————————————————————

—————————————————————————

—————————————————————————

Help to gather defect data. Describe each defect in enough detail

so you can later understand it. Analyze the data to see where you

injected and removed defect,and which types caused the most trouble.

Defect Recording Log

Defect Recording Log

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Reviewing before compiling

Reviewing before compiling

Reasons: 1.it take same time to do a review

whether before or after compiling. 2.reviewing first will save a lot of

compile time. 3.once have compiled,reviews are

not as thorough. 4.compiling is equally effective

before or after review. 5.the more the defects in

compiling, the more in test.

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Why do checklists help?Why do checklists help? Checklist

A series of procedural steps that you want to follow precisely.

Generally used in various situations Before you do shopping---shopping list Before the flight takes off---checklist Countdown of shuttle---the checklist having h

undreds of steps But still exploded twice!

Can also be a source of ideas! (when write paper)

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Building a personal checklist (1/2)


Make a list by type of the numbers of defects found in each phase

Rank the defect types in descending order of the number of defects found in compile and test (Missed in code review).

For those few defect types with most defects, examine the Defect Recording Logs to see what specific problems caused the most trouble.

For defects resulting from the most important problems, determine the steps to take in the code view to find them.

Make entries in the Code Review Checklist to ensure that you take these steps.

After using the new checklist, examine the defects again in the same way.

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If the checklist was effective at finding these most important defects, add another type and use it again.

If the checklist was not effective at finding some defect types, try to find a better solution and try it again.

In developing or updating the checklist, group similar checks together and do not duplicate them.

Apply code review by the new checklist to each of your new developed program to verify its effectiveness.

After defects analysis, it is also a good idea to consider what steps might prevent these defects in the future. Such as updating the coding standard or adding a step to the design process.

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Improving the checklistImproving the checklist Make a habit of regularly reviewing your defect data an

d reexamining the check list. Make the checklist becoming an encapsulation of your

personal experience. Steps:

Collect the defect data by recording to date and to date % items in your checklist.

During the postmortem phase for each program, analysis the defect data and your checklist, to update or drop items. For dropping items, you must use the most five to ten pro

grams’ defect data. For updating items, you’d better to do that after finding

several same defects missed in your review phase. Periodically prune( 剪除 ) your checklist to keep your fo

cus attention.

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Coding standardsCoding standards While the principal code review standard is the

programming language syntax specification, a coding standard specifies coding styles or formats.

A standard is an officially accepted basis for comparison. A coding standard thus define an accepted set of coding practices which can serve as a model for your work.

Coding standards is an effective means of preventing defects in coding phase.

See table 14.9 for a coding standard

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Defect densityDefect density Defect density(Dd): the defects per t

housand lines of code, measured by defects/KLOC. Add up the total numbers of defects fo

und. Count the number of new and change

d LOC Calculate the defects per KLOC

Be sure not include library routine and copy part in counting LOC.

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Defect estimationDefect estimation Using data of previously developed progr

ams to calculate the Dplan

Ddplan = 1000*(D1+D2+…+Di)/(N1+N2+…+Ni

) Dplan = Nplan*Ddplan/1000 ， or Dplan = Nplan*Dto date/Nto date.

The calculation of expected number of defects to be injected and removed in each phase. Dphase = Dplanned total*Dto date %/100.

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Measurement of defect-removalMeasurement of defect-removal

Measure defect-removal effectiveness Defect-Removal Rate: number of defect

s removed in one hour. Defect-Removal Yield( 效益 ): Percentag

e of the defects found by a removal method.

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Yield of defect removing

Yield of defect removing

Def. Removed/Hour: Defects found rate in one phase

Also we would like to know how many defects were found and how many were missed in one defects removing phase---Yield

Moreover, Process Yield = the percentage of the defects fo

und before the first compile and test. That is the percentage of the defects found in review

phases (code review and design review), the percentage of the defects found initiatively （主动地） , not passively （被动地） .

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Yield CalculationYield Calculation Yield plan Yield actual Yield To Date Yield = 100*(Defects removed before

compile)/(Defects injected before compile).

See example of calculation in table 16.2

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Two meanings of the Design Defect

Two meanings of the Design Defect

Define all those defects injected in the design phase to be design defects

Define those defect types that involve issues of programming function, logic, performance, and timing to be design defects

In this class, we follow the second definition

Thus generally we say that types 10 to 40 in table 12.1 are coding defects and types 50 to 100 are design defects.

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Ease of finding defects in design and code review

Ease of finding defects in design and code review

You review a smaller modules of your own codes;

You know the logic of your codes and you know what it should do;

You understand the unusual cases and odd conditions;

So you’re the only person who can ensure the products are essentially defect-free. If you do not produce a defect-free program, no one else can do it for you!

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Calculating the Yield Values(1/2)


Applying Yield method to any defect-removal step Phase yield = 100*(defects removed during

phase/defects in product at phase entry) The calculation of Yield Values for each ph

ase is shown in Figure 18.4 on page 245. When subsequently find defects, the yield

of all the phases that missed those defects declines

17/ （ 17+2 ）与 17/ （ 17+15 ）的区别。

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Process Yield = 100*(defects removed before compile)/ (defects injected before compile)

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Estimating the ultimate YieldEstimating the ultimate Yield

The key problem is that we don’t know how many defects remained in the product after we do the last testing

Two ways of estimatingCount the defects during the rest useful life of our software product;Just assume that the remaining defects in a product equal the number found in the last removal phase. That is the same as assuming that the yield of the last test phase was 50%

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Estimating the ultimate YieldEstimating the ultimate Yield

Modification of the Yield Values of each phase 17/(17+15+8) = 42.5% changed to

17/(17+15+8+8) = 35.4% With historical data on the actual

yield for each defect-removal phase, you could make more accurate ultimate yields estimates.

With enough yield data, you could even calculate statistical ranges for the number of defects remaining.

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The steps of approaching the final goal

The steps of approaching the final goal

Making your process Yield = 100% First you need to have the goal; It takes time to practise and practise again a

nd again; Do your work professionally, like learning to

play a musical instrument. That is, doing your work with disciplined quality methods: Gathering Data, analysis your data and modify yo

ur defect removal methods Do you work from simple to complicated, fr

om a small program to a large program.

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Process measureProcess measure

Quality of program Quality of process The way you work

Better program Change the way you work

取决于取决于

Know your process

Measure the quality of process

need

need

need

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Simplifying the calculation of COQ

Simplifying the calculation of COQ

PSP counts all compile time as failure costs. Even include some defect-free compile time.

PSP counts all test time as failure costs. PSP counts all review time as appraisal costs. Appraisal COQ: sum of all review time as a per

centage of total development time; Failure COQ: sum of all compile and test time

as a percentage of total development time; See the example of table 19.1

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A/FR-Appraisal/Failure RatioA/FR-Appraisal/Failure Ratio Simpler calculate: code review

time/(compile time+test time); It measures the relative amount

of time spent finding defects before the first compile.

You should attempt to achieve A/FR of 2 or more.

Why? See figure 19.1-19.6 Improving the product quality; Saving test time.

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How to achieve A/FRs above 2.0 ?

How to achieve A/FRs above 2.0 ?

Putting more time on code reviewing; This will not improve program quality!!! It is important to productively use

review time in finding defects. Code review with high quality.

For frequently missed defects. Insert appropriate steps in checklist. Take more time,find more

defects,increase A/FR

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Calculating the true COQ

Calculating the true COQ

Break the review, compile, and test times to their respective appraisal and failure time. C=CF+CA; R=RF+RA; T=TF+TA.

Appraisal COQ=100*(RA +CA +TA)/totaltime Failure COQ=100*(RF +CF +TF)/totaltime. See example in table 19.1 and table 19.3. To use this method,you need a stopwatch

!

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Making a commitment to quality

Making a commitment to quality

To decided that quality is important

To establish the goal of producing defect-free program

To manage our fallibility( 失误 ). Care enough to continue doing.

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Challenge yourself to do superior work and you will be surprised at what you can accomplish.

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project plan summary


PSP Project Plan Summary

Student Student x Date 03/23/04

Program Program # 12

Instructor Mr.liu Language Ada

Summary Plan Actual To Date

Minutes/LOC 6.30 4.93 5.92

LOC/Hour 9.52 12.17 10.14

Defects/KLOC 94.79

Yield

A/FR

Program Size (LOC): Plan Actual To Date

Total new and changed 51 58 211

Maximum Size 65

Minimum Size 37

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

Planning 16 18 66 5.3

Design 27 44 127 10.2

Code 146 104 544 43.5

Code review 12 38 74 5.9

Compile 26 11 88 7

Test 68 29 232 18.6

Postmortem 26 42 119 9.5

Total 321 286 1250 100

Maximum Time 410

Minimum Time 233

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Defects Injected Plan Actual To Date To Date % Def/Hour

Planning

Design 1 4 20.0

Code 5 16 80.0

Code review

Compile

Test

Total 6 20 100.0

Defects Removed Plan Actual To Date To Date % Def/Hour

Planning

Design

Code

Code review 2 5 25.0

Compile 2 10 50.0

Test 2 5 25.0

Total 6 20 100.0

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Student Student x Date 03/30/04 Program Program # 13 Instructor Mr.liu Language Ada

Summary Plan Actual To Date Minutes/LOC 5.92 4.87 5.73 LOC/Hour 10.14 12.32 10.47 Defects/KLOC 94.79 106.4 96.9 Yield A/FR Program Size (LOC): Plan Actual To Date Total new and changed 58 47 258 Maximum Size 72

Minimum Size 41

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Time in Phase (min.) Plan Actual To Date To Date % Planning 18 22 88 6.0 Design 35 24 151 10.2 Code 149 93 637 43.1 Code review 20 37 111 7.5 Compile 24 4 92 6.2 Test 64 8 240 16.2 Postmortem 33 41 160 10.8 Total 343 229 1479 100 Maximum Time 426 Minimum Time 243

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Defects Injected Plan Actual To Date To Date % Def/Hour Planning Design 1 4 16.0 Code 5 5 21 84.0 Code review Compile Test Total 6 5 25 100.0 Defects Removed Plan Actual To Date To Date % Def/Hour Planning Design Code Code review 2 3 8 32.0 Compile 3 2 12 48.0 Test 1 0 5 20.0 Total 6 5 25 100.0

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Student Student x Date 03/30/04 Program Program # 15 Instructor Mr.liu Language Ada

Summary Plan Actual To Date Minutes/LOC 5.48 4.60 5.35 LOC/Hour 10.95 13.04 11.21 Defects/KLOC 92.53 52.6 86.7 Yield 40.0 100.0% 45.5 A/FR 0.375 1.93 0.44 Program Size (LOC): Plan Actual To Date Total new and changed 49 57 392 Maximum Size 62

Minimum Size 36 Time in Phase (min.) Plan Actual To Date To Date % Planning 17 20 140 6.7 Design 29 38 233 11.1 Code 116 119 911 43.4 Code review 21 29 174 8.3 Compile 15 5 105 5.0 Test 41 10 289 13.8

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