ruby pmap

pmap.rb

# Ruby pmap, like Scala's pmap method.
# ------------------------------------
#   modified from t-a-w.blogspot.com

require 'thread'

module Enumerable
  def pmap(n)
    todo = Queue.new
    
    each {|x| todo << [x] }
    n.times { todo << nil }
    
    threads = (1..n).map do
      Thread.new do
        while x = todo.pop
         yield(x[0])
        end
      end
    end
    
    threads.each {|t| t.join }
  end
end

# -- Examples
# -- Notice that if you increase the concurrency in pmap(3)
# -- the total time to run this program decreases.
# 
# class Person
#   attr_accessor :name
# end
# peeps = [
#   Person.new.tap {|p| p.name = "Joe" },
#   Person.new.tap {|p| p.name = "Jane" },
#   Person.new.tap {|p| p.name = "David" }
# ]
#
# peeps.pmap(3) do |person|
#   puts "found david" if person.name == "David"
#   sleep 1
# end
#