The Dining Philosophers problem is a classic multi-process synchronization problem. The
problem consists of five philosophers sitting at a table who do nothing but think and eat.
Between each philosopher, there is a single stick. In order to eat, a philosopher must
have both sticks. A problem can arise if each philosopher grabs the stick on the right,
then waits for the stick on the left. In this case a deadlock has occurred, and all
philosophers will starve. Also, the philosophers should be fair. Each philosopher should
be able to eat as much as the rest.
. . . click on the blue bullets to change program parameters. The first four control
the sound track(the last one makes them shut up). The three slide bars control the speed,
thinking time, and eating time.
The algorithm . . .
Initially, all philosophers are thinking. As they think, their eyes randomly(direction
probability determined by the slider) move around. If a philosopher's eyes do a complete
counter-clock wise circle, it will become hungry and its eyebrows will bow in. The
philosopher will then wait for one stick, then the other. To prevent deadlocks, one of the
sticks is marked. If a philosopher picks up the marked stick, it must put it back down and
try the other stick. When this happens, the philosopher will raise its right eyebrow. Once
the philosopher has both sticks, it will begin eating. After each bite, there is a chance
(controlled by the slider) that the philosopher will start thinking again. The philosopher
will then swap the sticks in its hands and return them. This is done so that the marked
stick will not remain in the same place.
The secrets of the implementation . . . Each philosopher is its own thread. There is an
additonal thread that is used to control the repainting. Each stick is represented by an
instance of a class. When a philosopher wishes to pick up or drop a stick, it will make a
call to the appropriate stick. To ensure that two philosophers do not simultaneously grab
the same stick, a synchronized method is used. The images were ray-traced using The source of it all . . .
