monitor.rb

require 'thread'
# jruby 9.1.7.0 (2.3.1)
# 1. ------inherit Mutex-------
# class Counter < Mutex
#   attr_reader :number
#   def initialize
#     @number = 0
#     super
#   end

#   def plus
#     synchronize do
#       @number += 1
#     end
#   end
# end
# 2. ------include Monitor------
# class Counter
#   include MonitorMixin
#   attr_reader :number
#   def initialize
#     @number = 0
#     super
#   end

#   def plus
#     synchronize do
#       @number += 1
#     end
#   end
# end
# 3. ------error example------
# class Counter
#   attr_reader :number
#   def initialize
#     @number = 0
#   end

#   def plus
#     @number += 1
#   end
# end
# 4. ------use Mutex------
# class Counter
#   attr_reader :number
#   def initialize
#     @number = 0
#     @mutex = Mutex.new
#   end

#   def plus
#     @mutex.synchronize do
#       @number += 1
#     end
#   end
# end
# 5. -------------------
# maybe has some problems
# class Counter
#   attr_reader :number, :q
#   def initialize
#     @number = 0
#     @q = Queue.new
#   end

#   def start
#     (1..20_000).each do
#       @q.push(1)
#     end
#   end

#   def plus
#     while line = q.pop
#       @number += 1
#       p @number
#     end
#   end
# end


# c = Counter.new
# t1 = Thread.new { 10_000.times { c.plus } }
# t2 = Thread.new { 10_000.times { c.plus } }
# t1.join
# t2.join
# c = Counter.new
# c.start
# t1 = Thread.new { 10_000.times { c.plus } }
# t2 = Thread.new { 10_000.times { c.plus } }
# t1.join
# t2.join
# puts c.number

# q = Queue.new

# (1..10).each do
#   Thread.new {
#     while line = q.pop
#       print "#{Thread.current} #{line}"
#     end
#   }
# end

# while (u = gets)
#   q.push(u)
# end

# def counters_with_mutex
#   mutex = Mutex.new
#   counters = [0, 0, 0, 0, 0, 0, 0, 0, 0, 0]

#   5.times.map do
#     Thread.new do
#       100000.times do
#         mutex.synchronize do
#           counters.map! { |counter| counter + 1 }
#         end
#       end
#     end
#   end.each(&:join)

#   counters.inspect
# end

# def counters_without_mutex
#   counters = [0, 0, 0, 0, 0, 0, 0, 0, 0, 0]

#   5.times.map do
#     Thread.new do
#       100000.times do
#         counters.map! { |counter| counter + 1 }
#       end
#     end
#   end.each(&:join)

#   counters.inspect
# end

# puts counters_with_mutex
# # => [500000, 500000, 500000, 500000, 500000, 500000, 500000, 500000, 500000, 500000]

# puts counters_without_mutex
# # => [500000, 447205, 500000, 500000, 500000, 500000, 203656, 500000, 500000, 500000]

mutex = Mutex.new
flags = [false, false, false, false, false, false, false, false, false, false]

threads = 50.times.map do
  Thread.new do
    100000.times do
      puts flags.to_s
      mutex.synchronize do
        flags.map! { |f| !f }
      end
    end
  end
end
threads.each(&:join)