Dining philosophers in Ruby with Celluloid. Modified from https://gist.github.com/bugant/4984042

dining.rb

require 'rubygems'
require 'celluloid'

class Waiter
  include Celluloid
  FORK_FREE = 0
  FORK_USED = 1
  attr_reader :philosophers
  attr_reader :forks
  attr_reader :eating

  def initialize(forks)
    @philosophers = []
    @eating = []
    @forks = Array.new(forks, FORK_FREE)
  end

  def welcome(philosopher)
    @philosophers << philosopher
    philosopher.async.think
  end

  def hungry(philosopher)
    pos = @philosophers.index(philosopher)

    left_pos = pos
    right_pos = (pos + 1) % @forks.size
    if @forks[left_pos] == FORK_FREE && @forks[right_pos] == FORK_FREE
      @forks[left_pos] = FORK_USED
      @forks[right_pos] = FORK_USED
      @eating << philosopher
      philosopher.async.eat
    else
      # it's not your turn, keep thinking
      philosopher.async.think
    end
  end

  def drop_forks(philosopher)
    pos = @philosophers.index(philosopher)
    left_pos = pos
    right_pos = (pos + 1) % @forks.size
    @forks[left_pos] = FORK_FREE
    @forks[right_pos] = FORK_FREE
    @eating -= [philosopher]
    philosopher.async.think
  end
end

class Philosopher
  include Celluloid
  attr_reader :name
  attr_reader :waiter

  def initialize(name, waiter)
    @name = name
    @waiter = waiter
    waiter.async.welcome(Actor.current)
  end

  def think
    puts "#{name} is thinking"
    sleep(rand)
    puts "#{name} gets hungry"
    waiter.async.hungry(Actor.current)
  end

  def eat
    puts "#{name} is eating"
    sleep(rand)
    puts "#{name} burps"
    waiter.async.drop_forks(Actor.current)
  end
end

names = %w{Heraclitus Aristotle Epictetus Schopenhauer Popper}
waiter = Waiter.new(names.size)
philosophers = names.map {|name| Philosopher.new(name, waiter)}

# The main thread is done! Sleep forever
sleep