Simple, plain Ruby implementation of parallel map/each

pmap.rb

#!/usr/bin/env ruby
require 'thread'

Thread.abort_on_exception = true

module Enumerable
  def peach n=nil, &block
    pmap n, &block
    self
  end

  def pmap n=nil
    n = size if n.nil? || n > size
    q = Queue.new
    each { |i| q.push i }

    rs = []
    ws = Array.new(n).map do
      Thread.new do
        loop do
          begin
            i = q.pop true
          rescue ThreadError
            break
          end

          rs << yield(i)
        end
      end
    end

    ws.map(&:join)
    rs
  end
end

r = (1..5).peach do |i|
  sleep i
  puts i
end

puts r.inspect