Contents

require 'thread' unless defined?(Mutex)

# Global variable for the default thread pool size.
$pmap_default_thread_count ||= 64

module PMap
  def self.included(base)
    base.class_eval do
      # Parallel "map" for any Enumerable.
      # Requires a block of code to run for each Enumerable item.
      # [thread_count] is number of threads to create. Optional.
      def pmap(thread_count=nil, &proc)
        raise ArgumentError, "thread_count must be at least one." unless
          thread_count.nil? or (thread_count.respond_to?(:>=) and thread_count >= 1)
        # This seems overly fussy... (code smell)
        in_array = self.to_a        # I'm not sure how expensive this is...
        size = in_array.size
        thread_count = [thread_count||$pmap_default_thread_count, size].min
        out_array = Array.new(size)
        semaphore = Mutex.new
        index = -1                  # Our use of index is protected by semaphore
        threads = (0...thread_count).map {
          Thread.new {
            i = nil
            while (semaphore.synchronize {i = (index += 1)}; i < size)
              out_array[i] = yield(in_array[i])
            end
          }
        }
        threads.each {|t| t.join}
        out_array
      end

      # Parallel "each" for any Enumerable.
      # Requires a block of code to run for each Enumerable item.
      # [thread_count] is number of threads to create. Optional.
      def peach(thread_count=nil, &proc)
        # This is doing some extra work: building a return array that is
        # thrown away. How can I share the core code of "pmap" here and omit
        # the output array creation?
        pmap(thread_count, &proc)
        self
      end
    end
  end
end

module Enumerable
  include PMap
end

Version data entries

1 entries across 1 versions & 1 rubygems

Version	Path
pmap-0.1.0	lib/pmap.rb