sample/philos.rb

   1 #
   2 # The Dining Philosophers - thread example
   3 #
   4 require "thread"
   5
   6 srand
   7 #srand
   8 N=9                             # number of philosophers
   9 $forks = []
  10 for i in 0..N-1
  11   $forks[i] = Mutex.new
  12 end
  13 $state = "-o"*N
  14
  15 def wait
  16   sleep rand(20)/10.0
  17 end
  18
  19 def think(n)
  20   wait
  21 end
  22
  23 def eat(n)
  24   wait
  25 end
  26
  27 def philosopher(n)
  28   while true
  29     think n
  30     $forks[n].lock
  31     if not $forks[(n+1)%N].try_lock
  32       $forks[n].unlock          # avoid deadlock
  33       next
  34     end
  35     $state[n*2] = ?|;
  36     $state[(n+1)%N*2] = ?|;
  37     $state[n*2+1] = ?*;
  38     print $state, "\n"
  39     eat(n)
  40     $state[n*2] = ?-;
  41     $state[(n+1)%N*2] = ?-;
  42     $state[n*2+1] = ?o;
  43     print $state, "\n"
  44     $forks[n].unlock
  45     $forks[(n+1)%N].unlock
  46   end
  47 end
  48
  49 for n in 0..N-1
  50   Thread.start(n){|i| philosopher(i)}
  51   sleep 0.1
  52 end
  53
  54 sleep