From: Robert Klemme <bob.news@...>
Date: 2004-05-04T01:59:00+09:00
Subject: Re: model for my problem (network simulator)

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"Gergely Kontra" <kgergely@mcl.hu> schrieb im Newsbeitrag
news:20040503161710.GA16300@mlabdial.hit.bme.hu...
> Hello!
>
> I'd like to ask for help for my problem. Maybe the Q isn't
> ruby-specific, but I WILL implement it in ruby, and I want to make a
> rubyish program. I hope I can learn from the problem.
>
> So: I had to write a network simulator. It consists of nodes, link
> between nodes. The delay of the link should be user-programmable (maybe
> proc is the right way, but it must be evaluated in the object's scope,
> because delay is not independent of the link's state...
>
> And finally the simulator has agents. Agents are programs, which can
> migrate. Migration is requested by agent. (Request goes to the node, and
> the node does the actual migration...)
> Agent must know about their own location, it can ask the node about
> outgoing links (so nodes must know about links ending at the node, of
> course).
>
> Shall I submit my code? Or did anybody has a model for it already?

What was your question exactly?  You seem to have implemented the simulator
already...

As a general OO rule of thumb, take all the interesting nouns and make them
classes.  This seems to be pretty much straightforward in your case.

The thing I find more interesting is the scheduling.  This could be done
like this (attached).

Regards

    robert

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#!/usr/bin/ruby

# not really needed, just for completeness
class Event
  def execute(simulator)
    # whatever
  end
end


class Simulator
  attr :now

  def initialize
    # quick and dirty: hash; other data structure is more efficient
    @schedule = Hash.new {|h,k| h[k] = []}
    @now = nil
  end

  def go
    until @schedule.empty?
      @now = @schedule.keys.sort[0]
      puts "Time = #{@now}"
      @schedule[@now].each {|event| event.execute(self) }
      @schedule.delete @now
    end

    @now = nil
  end

  def schedule(time, event)
    raise "Can't travel back in time" if @now && @now >= time
    @schedule[time] << event
  end
end


class SampleEvent < Event
  def initialize(count, interval)
    @count, @interval = count, interval
  end

  def execute(s)
    puts "  Executing #{inspect}"
    @count -= 1
    s.schedule( s.now + @interval, self ) if @count > 0
  end
end


e1 = SampleEvent.new 10, 2
e2 = SampleEvent.new 7, 3

sim = Simulator.new

sim.schedule( 0, e1 )
sim.schedule( 0, e2 )

sim.go


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