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Text File  |  1998-01-16  |  760b  |  55 lines
  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 i in 0..N-1
  50.   Thread.start{philosopher(i)}
  51.   sleep 0.1
  52. end
  53.  
  54. sleep
  55.