From: Jeffrey Flint <jeffrey.flint@...>
Date: 2008-01-09T12:33:21+09:00
Subject: thread scheduling question

This code sends a message around a ring of queues.  When each queue
pops, it prints out its message.

The code seems to work, but it seems to hang on the io, which I don't
understand.  I would expect the messages to print very quickly.  The
messages only print inside of irb when I depress the carriage return
repeatedly.

Thank you!

Jeff


=================================
require 'thread'

class Ring
  attr_writer :size, :mbox, :agents
  attr_reader :size, :mbox, :agents

  def initialize (size)
    @size   = size
    @mbox   = []
    @agents = []
    (1..size).each do
      @mbox << Queue.new
    end

    (0..size-1).each do |index|
      @agents << Thread.new(index) do |i|
        loop do
          msg = @mbox[i].pop
          case msg
              when "start"
                @mbox[(i+1)%size] << 1 if i == 0

              when "halt"
                  break

              else
                  print("#{i}: #{msg}: #{Thread.current} #{Time.now}\n")
              STDOUT.flush
              (@mbox[(i+1)%size] << msg + 1) if i!=0
              Thread.pass
          end
        end
      end
    end
  end

  def rpc(i, msg)
    @mbox[i] << msg
  end

  def start ()
    rpc(0,"start")
  end

  def halt ()
    @mbox.each { |m| m << "halt" }
    @agents.each {|thr| thr.join }
  end

end

R = Ring.new(10)
R.start

Attachments:
http://www.ruby-forum.com/attachment/1266/ring.rb

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