forky.rb

require 'drb'

# Forky(enum) {|e| something(e) }
#   almost same as
#     enum.each {|e| something(e) }
#   but each block runs on other processes without using thread.
#
# 1. Forky makes flags
# 2. Forky starts DRb server which only has flags
# 3. Forky runs each process asynchronously which process make the flag true after the process finished
# 4. When all flags became true, this method finishs.
#
# ISSUES:
#
# * `sleep 0.2 # dirty` is obviously dirty and dangerous
# * port should not be fixed in 1234
def Forky(enum)
  flags = Array.new(enum.to_a.size, :forky_empty)
  def flags.finish?
    return false unless all? {|i| i != :forky_empty }
    DRb.stop_service
    true
  end

  r, w = IO.pipe
  fork do
    DRb.start_service 'druby://localhost:1234', flags
    w.puts "ready"
    w.close
    r.close
    DRb.thread.join
  end
  r.gets
  w.close

  client = DRbObject.new nil, 'druby://localhost:1234'
  enum.each_with_index do |e, i|
    fork do
      client[i] = yield e
    end
  end

  loop do
    tmp = client[0..-1]
    if client.finish?
      return tmp
    end
    sleep 0.01
  end
end

if __FILE__ == $0
  t = Time.now

  results = Forky(0...10) do |i|
    sleep(tmp = rand)
    p i
    tmp
  end

  puts "It took #{Time.now - t}sec."
  p results
end