Philosophers! Homework #4 solved




This is based on Exercise 4.17 from the text.
Solve the dining philosophers problem by focusing on the state of the philosophers
rather than the forks. In particular, let eating[n] be a boolean array; eating[i] is
true if Philosopher[i] is eating and is false otherwise.
(a) Specify a global invariant, then develop a coarse-grained solution, and finally develop
a fine-grained solution that uses semaphores for synchronization. Your solution should
be deadlock-free, but an individual philosopher might starve. Use the technique of
passing the baton. Describe how your fine-grained solution matches the semantics of
the coarse-grained solution.
Implement your fine-grained solution in either Racket, Python or Pthreads. Be
sure to use only semaphores for synchronization and mutual exclusion. Name the
semaphores well. Insert your invariant at relevant places as an assertion, i.e., the
evaluation of a boolean expression or expressions which, if false, halts the program
with an error message.
(b) Modify your answer to (a) to avoid starvation. In particular, if a philosopher wants
to eat, eventually he or she gets to eat. Describe your strategy in clear language. If it
lends itself to an invariant (not all strategies do), state that clearly.
Develop both coarse-grained and fine-grained solutions, and implement the finegrained solution in your chosen language.
Writeup: There should be three files submitted:
• The writeup, which includes both parts, justifications, etc. It should look something like the examples in the textbooks. You can use Andrews-like pseudocode
• A runnable (or compilable on unix) solution to part (a).
• A runnable (or compilable on unix) solution to part (b).
Due date: Wednesday, February 25, midnight.