Simulating Vehicle traffic for Bruce Wayner <winshocker@gmail.com>

README.md

run with:

ruby simulating_vehicles.rb

or to see each vehicle:

ruby -v simulating_vehicles.rb

You'll have to tally the results yourself across many runs, but this is way more than you deserve. (And you really need to understand it before you turn it in.)

Sample-Output.txt

$ time ruby -v simulating_vehicles.rb
ruby 1.9.2p0 (2010-08-18 revision 29036) [i386-darwin9.8.0]
leaves at    0 w/40 arriving   55 [40] [40 @ 55]
leaves at   12 w/2  arriving   79 [42] [42 @ 79]
leaves at   24 w/40 arriving   86 [82] [82 @ 86]
leaves at   44 w/40 arriving  108 [122] [122 @ 108]
leaves at   59 w/1  arriving  127 [123] [123 @ 127]
leaves at   90 w/4  arriving  149 [127] [127 @ 149]
leaves at  111 w/2  arriving  166 [129] [129 @ 166]
leaves at  139 w/1  arriving  197 [130] [130 @ 197]
leaves at  154 w/2  arriving  224 [132] [132 @ 224]
leaves at  177 w/40 arriving  231 [172] [172 @ 231]
leaves at  206 w/40 arriving  260 [212] [212 @ 260]
leaves at  227 w/40 arriving  296 [252] [252 @ 296]
leaves at  259 w/2  arriving  311 [254] [254 @ 311]
leaves at  265 w/1  arriving  321 [255] [255 @ 321]
leaves at  276 w/2  arriving  342 [257] [257 @ 342]
leaves at  293 w/1  arriving  344 [258] [258 @ 344]
leaves at  319 w/2  arriving  372 [260] [260 @ 372]
leaves at  324 w/40 arriving  394 [300] [300 @ 394]
leaves at  352 w/40 arriving  420 [340] [340 @ 420]
leaves at  376 w/1  arriving  433 [341] [341 @ 433]
leaves at  392 w/40 arriving  452 [381] [381 @ 452]
leaves at  412 w/40 arriving  464 [421] [421 @ 464]
leaves at  441 w/1  arriving  504 [422] [422 @ 504]
leaves at  473 w/3  arriving  523 [425] [425 @ 523]
leaves at  507 w/3  arriving  571 [428] [428 @ 571]
leaves at  537 w/2  arriving  606 [430] [430 @ 606]
leaves at  571 w/1  arriving  623 [431] [431 @ 623]
leaves at  589 w/40 arriving  639 [471] [471 @ 639]
leaves at  605 w/2  arriving  671 [473] [473 @ 671]
leaves at  640 w/1  arriving  695 [474] [474 @ 695]
leaves at  646 w/40 arriving  702 [514] [514 @ 702]
leaves at  660 w/3  arriving  717 [517] [514 @ 702]
leaves at  669 w/4  arriving  722 [521] [514 @ 702]
leaves at  691 w/1  arriving  751 [522] [514 @ 702]
=> 514 @ 702

real	0m0.026s
user	0m0.016s
sys	0m0.008s

simulating_vehicles.rb

module Simulation
  class Config
    class << self
      # 50..70 (seconds)
      attr_accessor :travel_time_range
      # 5..35 (seconds)
      attr_accessor :departure_rate_range
      # key=passengers, value=percentage
      # { 1 => 20, 2 => 30, ... }
      attr_accessor :passengers_probability

      def passengers
        raise "No passenger capacities configured" if self.passengers_probability.empty?

        sample = rand(100)
        self.passengers_probability.sort.each do |passengers,probability|
          sample -= probability
          return passengers if sample <= 0
        end
        return 0
      end

      def departure_delay
        low = self.departure_rate_range.begin
        high = self.departure_rate_range.end
        span = high - low + (self.departure_rate_range.exclude_end? ? 0 : 1)
        return low + rand(span)
      end
      def travel_time
        low = self.travel_time_range.begin
        high = self.travel_time_range.end
        span = high - low + (self.travel_time_range.exclude_end? ? 0 : 1)
        return low + rand(span)
      end
    end
  end

  class Vehicle
    attr_reader   :departure_time, :travel_time, :arrival_time
    attr_accessor :passengers
    def initialize(departs_at)
      @departure_time = departs_at
      @passengers = Config.passengers
      @travel_time = Config.travel_time
      @arrival_time = @departure_time + @travel_time
    end

    def to_s
      "leaves at %4d w/%-2d arriving %4d"%[self.departure_time,
                                           self.passengers,
                                           self.arrival_time]
    end
  end
end

Simulation::Config.departure_rate_range = 5..35 # (seconds)
Simulation::Config.travel_time_range = 50..70   # (seconds)
Simulation::Config.passengers_probability = { 1 => 20, 2 => 30, 3 => 10, 4 => 10, 40 => 30 }

next_departure = 0
vehicles = []
simple_sum = 0
final_count, final_time = 0, 0
loop do
  vehicle = Simulation::Vehicle.new(next_departure)
  vehicles << vehicle
  simple_sum += vehicle.passengers
  final_count, final_time = vehicles.sort_by {|v| v.arrival_time }.inject([0,0]) do |(count,time),v|
    if count >= 500
      [count,time]
    else
      [count+v.passengers, v.arrival_time]
    end
  end
  puts "#{vehicle} [#{simple_sum}] [#{final_count} @ #{final_time}]" if $VERBOSE
  next_departure += Simulation::Config.departure_delay
  break if final_count >= 500 && next_departure > final_time
end
puts "=> #{final_count} @ #{final_time}"