#!/usr/bin/ruby
# thread_exclusion_1.rb

require 'thread'

mutex = Mutex.new
x = y = 0
diff = 0
Thread.new {
  loop do
    mutex.synchronize do
      x+=1
      y+=1
    end
  end
}
Thread.new {
  loop do
    mutex.synchronize do
      diff += (x-y).abs
    end
  end
}
sleep(1) # Here main thread is put to sleep
puts "difference = #{diff}"