dining_philosophers.py

dining_philosophers.py

import sys
import random
import time
from threading import *

class Philosopher(Thread):
	def __init__(self, waiter, lfork, rfork):
		Thread.__init__(self)
		self.waiter = waiter
		self.lfork = lfork
		self.rfork = rfork

	def acquire_forks(self):
		self.waiter.acquire()
		self.lfork.acquire()
		self.rfork.acquire()

	def release_forks(self):
		self.lfork.release()
		self.rfork.release()
		self.waiter.release()

	def think(self):
		time.sleep(random.uniform(0, 3))

	def eat(self):
		print "{}: i am eating".format(self.name)
		time.sleep(random.uniform(0, 3))

	def run(self):
		#while 1:
		for i in range(50):
			self.think()
			self.acquire_forks()
			self.eat()
			self.release_forks()

if __name__ == "__main__":

	if len(sys.argv) != 2:
		sys.exit(0)

	count = int(sys.argv[1])
	philosophers = []

	forks = [Semaphore(1) for i in xrange(count)]
	waiter = Semaphore(count - 1)

	for i in range(count):
		philosophers.append(Philosopher(waiter, forks[i], forks[(i + 1) % count]))	

	for p in philosophers:
		p.start()

	for p in philosophers:
		p.join()