CSE-332 Software Design Methods The Mythical Man-Month 박성우 POSTECH October 20, 2015

The Mythical Man-Month Book on software engineering and project management Book on the human elements of software engineering “The Bible of Software Engineering” Everybody quotes it. Some people read it. A few people go by it.

Mythical Man-Month All programmers are optimist. “all will go well” For a large programming effort, the probability becomes vanishingly small. The man-month as a unit for measuring the size of a job? a dangerous and deceptive myth valid only when there is no communication among workers communication = training + intercommunication

Brooks’s Law “Adding manpower to a late software project makes it later.” The number of months of a project depends on its sequential constraint. We can derive schedules using fewer men and more months. We cannot derive schedules using more men and fewer months. Most software projects have gone awry for lack of calendar time.

Productivity Variations Measured performance of a group of experienced programmers Ratios between best and worst performances: 10:1 on productivity measurements 5:1 on program speed and space measurements A $20,000/year programmer may well be 10 times as productive as a $10,000/year programmer.

As Few Minds As Possible One wants a system to be built by as few minds as possible. If a 200-man project has 25 managers who are the most competent, then fire the 175 troops and put the managers back to programming! The Ideal of the small sharp team, which by common consensus shouldn’t exceed 10 people. But we want to use considerable manpower. Goal: Few minds are involved in design and construction, yet many hands are brought to bear.

Surgical Team Surgeon: chief programmer defines specifications needs great talent, ten years of experience, considerable knowledge unilaterally settles all differences of judgments Copilot: alter ego of the surgeon, but less experienced knows all the code intimately researches alternative design strategies insurance against disaster to the surgeon Toolsmith: see to the tools needed or wanted by his surgeon Tester: devises test cases and test data Administrator, Editor, Secretaries, Program clerks, Language lawyer

10-man Programming Team Surgeon Copilot Toolsmith Tester Administrator Editor