/Shared/cs322/submit/proj3

• your names at the top,
• the command to run your code,
• known issues
• a general description of the synchronization solution for each version
  (What are the shared data? What is the purpose of each semaphore or each condition variable? How are starvation and deadlock prevented?) and
• some console result (sample input/output that your program read and created).

You may work in groups of two. Collaboration within a group is, of course, unrestricted. You may discuss the program with members of other groups, but what you turn in must be your own group's work.

It is a violation to the Honor Code not to acknowledge others' work fully and openly.
You should cite any online resources you consulted to help you solve this project.
You may NOT directly copy any code or any text from anywhere.

Managing a Hair Salon

• a waiting room with a receptionist and n comfy chairs for waiting clients, and
• a hair cutting room with one chair and a stylist.

Life in the salon is all walk-ins. There are no appointments and clients are accepted as they arrive.

The salon operates as follows.

• If there are no clients to be served, the stylist chats with the receptionist.
• When a client arrives the stylist reluctantly stops chatting and takes the client.
• But if the stylist has a client already the new client takes a chair in the waiting room.
• If all chairs are full the receptionist rudely tells the new client to come back later.
• When the stylist finishes washing and cutting a client's hair she takes the client who has been waiting the longest.
• If no client is waiting she goes back to chatting with the receptionist.

Implementation

• One version uses semaphores.
• The other uses a different locking method such as monitors or other sophisticated mechanisms from java.concurrent package.

	java HairSalon 5 > output

The user manually enters on the terminal as the program executes

1. the name of the arriving client and
2. an integer that is the time needed for the client's cut
   (to simulate the hair cut we may call Thread.sleep(num*1000)).

The application runs until the user enters Ctrl+c on the console.

The application provides informative messages about the simulation, i.e. threads write output as they transit from one state to another.

An example of the console input is

beth 7
sammy 3
felix 4
lise 5
joe 4
aicha 4
mike 3 
alma 5

beth enters the salon.
beth sits down in the waiting room (chair 1).
The stylist reluctantly finishes chatting with the receptionist.
The stylist takes beth inside and starts the hair washing.
sammy enters the salon.
sammy sits down in the waiting room (chair 2).
felix enters the salon.
felix sits down in the waiting room (chair 3).
The stylist finishes cutting beth's hair and blowing it dry (took 7).
beth admires the new hair-style and leaves with a smile.
The stylist takes sammy inside and starts the hair washing.
The stylist finishes cutting sammy's hair and blowing it dry (took 3).
sammy admires the new hair-style and leaves with a smile.
The stylist takes felix inside and starts the hair washing.
lise enters the salon.
lise sits down in the waiting room (chair 2).
joe enters the salon.
joe sits down in the waiting room (chair 3).
The stylist finishes cutting felix's hair and blowing it dry (took 4).
felix admires the new hair-style and leaves with a smile.
The stylist takes lise inside and starts the hair washing.
aicha enters the salon.
aicha sits down in the waiting room (chair 3).
mike enters the salon.
The receptionist tells mike to come back later, and he leaves, grumbling about the wait.
The stylist finishes cutting lise's hair and blowing it dry (took 5).
lise admires the new hair-style and leaves with a smile.
The stylist takes joe inside and starts the hair washing.
The stylist finishes cutting joe's hair and blowing it dry (took 4).
joe admires the new hair-style and leaves with a smile.
The stylist takes aicha inside and starts the hair washing.
alma enters the salon.
alma sits down in the waiting room (chair 2).
The stylist finishes cutting aicha's hair and blowing it dry (took 4).
aicha admires the new hair-style and leaves with a smile.
The stylist takes alma inside and starts the hair washing.
The stylist finishes cutting alma's hair and blowing it dry (took 5).
alma admires the new hair-style and leaves with a smile.
With no waiting clients the stylist resumes gossiping with the receptionist.

Note

• Amazon & Google use discrete event simulations to measure the efficiency of the hardware and software that balances the load on their many servers.
• Economists use discrete event simulations to model heterogeneous agents interacting in an economic system.
• Designers of computer hardware use discrete event simulations to model the flow of information in partially-designed hypothetical CPUs.

Resources

1. Java Concurrency Tutorial (Oracle)
2. Concurrency Programming (Microsoft): Key Rules, slide 22
3. Java Thread
4. Java Synchronization
5. Synchronization Lecture

Grading

This project is graded out of 20 points.