Question

I’m trying to come up with some programming puzzles focused on multi-threading. Most of the problems I’ve been able to come up with, so far, have been pretty domain specific. Does anybody have any decent programming puzzles for developers attempting to learn the core concepts of multi-threading applications?

Answer 1

There are a number of topics covered at this link.

Multithreaded Programming with ThreadMentor : A Tutorial

Edit:

Here are some direct links to the problems listed at that link, along with their initial descriptions.

ThreadMentor : The Dining Philosopher’s Problem
ThreadMentor : The Dining Philosopher’s Problem: The Lefty-Righty Version

The dining philosophers problem is invented by E. W. Dijkstra. Imagine that five philosophers who spend their lives just thinking and easting. In the middle of the dining room is a circular table with five chairs. The table has a big plate of spaghetti. However, there are only five chopsticks available, as shown in the following figure. Each philosopher thinks. When he gets hungry, he sits down and picks up the two chopsticks that are closest to him. If a philosopher can pick up both chopsticks, he eats for a while. After a philosopher finishes eating, he puts down the chopsticks and starts to think.

ThreadMentor : The Cigarette Smoker’s Problem

This problem is due to S. S. Patil in 1971. Suppose a cigarette requires three ingredients, tobacco, paper and match. There are three chain smokers. Each of them has only one ingredient with infinite supply. There is an agent who has infinite supply of all three ingredients. To make a cigarette, the smoker has tobacco (resp., paper and match) must have the other two ingredients paper and match (resp., tobacco and match, and tobacco and paper). The agent and smokers share a table. The agent randomly generates two ingredients and notifies the smoker who needs these two ingredients. Once the ingredients are taken from the table, the agent supplies another two. On the other hand, each smoker waits for the agent’s notification. Once it is notified, the smoker picks up the ingredients, makes a cigarette, smokes for a while, and goes back to the table waiting for his next ingredients.

ThreadMentor : The Producer/Consumer (or Bounded-Buffer) Problem

Suppose we have a circular buffer with two pointers in and out to indicate the next available position for depositing data and the position that contains the next data to be retrieved. See the diagram below. There are two groups of threads, producers and consumers. Each producer deposits a data items into the in position and advances the pointer in, and each consumer retrieves the data item in position out and advances the pointer out.

ThreadMentor : The Roller Coaster Problem

Suppose there are n passengers and one roller coaster car. The passengers repeatedly wait to ride in the car, which can hold maximum C passengers, where C < n. However, the car can go around the track only when it is full. After finishes a ride, each passenger wanders around the amusement park before returning to the roller coaster for another ride. Due to safety reasons, the car only rides T times and then shot-off.

This one has additional constraints:

1. The car always rides with exactly C passengers;
2. No passengers will jump off the car while the car is running;
3. No passengers will jump on the car while the car is running;
4. No passengers will request another ride before they can get off the car.

ThreadMentor : The Bridge Problem

The description for this one relies on images. Here is a modified quote with image references removed.

Consider a narrow bridge that can only allow three vehicles in the same direction to cross at the same time. If there are three vehicles on the bridge, any incoming vehicle must wait until the bridge is clear.

When a vehicle exits the bridge, we have two cases to consider. Case 1, there are other vehicles on the bridge; and Case 2 the exiting vehicle is the last one on bridge. In the first case, one new vehicle in the same direction should be allowed to proceed.

Case 2 is more complicated and has two subcases. In this case, the exiting vehicle is the last vehicle on the bridge. If there are vehicles waiting in the opposite direction, one of them should be allowed to proceed. Or, if there is no vehicle waiting in the opposite direction, then let the waiting vehicle in the same direction to proceed.