Ruby script for comparing multithreaded operation in Ruby implementations (eg. Ruby vs. JRuby).

thread_example.rb

# Simple Ruby/JRuby program to illustrate that MRI Ruby uses only one CPU,
# while JRuby will use all available CPU's. (Inspection tool not included;
# you can use Activity Monitor on a Mac, or htop on many Unix distros.
#
# Keith R. Bennett, @keithrbennett


NUM_THREADS = 5
SLEEP_DURATION_IN_SEC = 2


# If running in JRuby, formats a number string with the default locale's
# thousands separator.
def format_integer(number)
  if RUBY_PLATFORM == 'java'
    # java.util.Locale.default = java.util.Locale::FRANCE
    # java.util.Locale.default = java.util.Locale::GERMANY
    java.text.NumberFormat.instance.java_send('format', [Java::long], number)
    else
      number.to_s
    end
end
    

# Function that will be run in each new thread.    
def thread_func(thread_num)
  iterations = 0
  random_generator = Random.new
  loop do
    iterations += 1
    if random_generator.rand(10_000_000) == 0
      puts "Hit on thread #{thread_num}, " +
          "iteration #{format_integer(iterations)}, " +
          "going to sleep for #{SLEEP_DURATION_IN_SEC} seconds(s)."
      sleep SLEEP_DURATION_IN_SEC
    end
  end
end


def main
  
  threads = []

  NUM_THREADS.times do |thread_num|
    thread = Thread.new("Thread #{thread_num}") { thread_func(thread_num) }
    puts "Started thread_func for thread #{thread_num}, #{thread.inspect}"
    threads << thread
  end
  threads.each { |thread| thread.join }
end


main