From: James Edward Gray II <james@...>
Date: 2007-08-20T09:33:04+09:00
Subject: Re: [QUIZ] Process Rings (#135)

On Aug 19, 2007, at 6:49 PM, Tom Danielsen wrote:

>
> Ok.... this is my first attempt at using callcc in ruby.

Neat idea.

Here's my own version using fork():

#!/usr/bin/env ruby -wKU

unless ARGV.size == 2
   abort "Usage:  #{File.basename($PROGRAM_NAME)} PROCESSES CYCLES"
end
processes, cycles = ARGV.map { |n| n.to_i }

parent, child                = true, false
parent_reader, parent_writer = IO.pipe
reader,        writer        = IO.pipe
my_reader                    = parent_reader

puts "Creating #{processes} processes..."
processes.times do |process|
   if fork
     break
   else
     parent_reader.close unless parent_reader.closed?
     writer.close

     parent         = false
     my_reader      = reader
     reader, writer = IO.pipe
   end
   child = true if process == processes - 1
end
if child
   puts "Done."
   my_writer = parent_writer
else
   parent_writer.close
   my_writer = writer
end

if parent
   puts "Timer started."
   start_time = Time.now
   puts "Sending a message around the ring #{cycles} times..."
   cycles.times do
     my_writer.puts "0 Ring message"
     my_writer.flush
     raise "Failure" unless my_reader.gets =~ /\A#{processes} Ring  
message\Z/
   end
   puts "Done:  success."
   puts "Time in seconds:  #{(Time.now - start_time).to_i}"
else
   my_reader.each do |message|
     if message =~ /\A(\d+)\s+(.+)/
       my_writer.puts "#{$1.to_i + 1} #{$2}"
       my_writer.flush
     end
   end
end

__END__

And here's a threaded attempt:

#!/usr/bin/env ruby -wKU

begin
   require "fastthread"
   puts "Using the fastthread library."
rescue LoadError
   require "thread"
   puts "Using the standard Ruby thread library."
end

module MRing
   class Forward
     def initialize(count, parent)
       @child = count.zero? ? parent : Forward.new(count - 1, parent)
       @queue = Queue.new

       run
     end

     def send_message(message)
       @queue.enq message
     end

     private

     def run
       Thread.new do
         loop do
           message = @queue.deq
           if message =~ /\A(\d+)\s+(.+)/
             @child.send_message "#{$1.to_i + 1} #{$2}"
           end
         end
       end
     end
   end

   class Parent < Forward
     def initialize(processes, cycles)
       @processes = processes
       @cycles    = cycles

       puts "Creating #{processes} processes..."
       super(processes, self)
     end

     private

     def run
       puts "Timer started."
       start_time = Time.now
       puts "Sending a message around the ring #{@cycles} times..."
       @cycles.times do
         @child.send_message "0 Ring message"
         raise "Failure" unless @queue.deq =~ /\A#{@processes} Ring  
message\Z/
       end
       puts "Done:  success."
       puts "Time in seconds:  #{(Time.now - start_time).to_i}"
     end
   end
end

if __FILE__ == $PROGRAM_NAME
   unless ARGV.size == 2
     abort "Usage:  #{File.basename($PROGRAM_NAME)} PROCESSES CYCLES"
   end
   processes, cycles = ARGV.map { |n| n.to_i }

   MRing::Parent.new(processes, cycles)
end

__END__

James Edward Gray II