git.oblomov.eu Git - milivella/blob - vella_pop.rb

   1 #!/usr/bin/ruby
   2
   3 =begin
   4 What drives popularity? Are Pareto popularity distributions possible? likely?
   5 guaranteed?
   6 =end
   7
   8 class Array
   9         def pick_one
  10                 return nil if empty?
  11                 self[rand(self.length)]
  12         end
  13 end
  14
  15 class Popularity
  16         # A Character has a name and nothing more
  17         class Character
  18                 attr :name
  19                 def initialize(name)
  20                         @name = name.intern
  21                 end
  22         end
  23
  24         # A Star is just a Character, no special abilities
  25         class Star < Character ; end
  26
  27         # A Commoner is a Character with one or more voting strategies
  28         class Commoner < Character
  29                 # The simplest voting strategy: pick a random one
  30                 def random_vote(popularity, total)
  31                         popularity.keys.pick_one
  32                 end
  33
  34                 # A voting strategy that picks a random star, weighting
  35                 # more popular ones more
  36                 def popular_vote(popularity, total)
  37                         # if nobody voted yet, pick a random one
  38                         return random_vote(popularity, total) if total == 0
  39                         pick = rand(total)
  40                         popularity.each do |star, pop|
  41                                 return star if pick < pop
  42                                 pick -= pop
  43                         end
  44                 end
  45
  46         end
  47
  48         # Add a new Star
  49         def add_star(n)
  50                 case n
  51                 when String
  52                         name = n
  53                 when Integer
  54                         name = "Star #%u" % n
  55                 else
  56                         raise ArgumentError, "#{n} is neither a String nor an Integer"
  57                 end
  58
  59                 @stars[name.intern] = Star.new(name)
  60         end
  61
  62         # Add a new Commoner
  63         def add_commoner(n)
  64                 case n
  65                 when String
  66                         name = n
  67                 when Integer
  68                         name = "Commoner #%u" % n
  69                 else
  70                         raise ArgumentError, "#{n} is neither a String nor an Integer"
  71                 end
  72
  73                 @commoners[name.intern] = Commoner.new(name)
  74         end
  75
  76         # Today
  77         def today ; @day ; end
  78         # Yesterday
  79         def yesterday
  80                 raise if @day == 0
  81                 @day-1
  82         end
  83
  84         # Initialize a new popularity day
  85         def push_popularity
  86                 @popularity << Hash.new do |h, k|
  87                         raise ArgumentError, "no such Star '#{k}'" unless @stars.key? k
  88                         h[k] = []
  89                 end
  90         end
  91
  92         def new_day
  93                 @day += 1
  94                 push_popularity
  95         end
  96
  97         def initialize
  98                 @stars = {}
  99                 @commoners = {}
 100                 @popularity = []
 101                 reset
 102         end
 103
 104         def reset
 105                 @day = 0
 106                 @popularity.clear
 107                 push_popularity
 108         end
 109
 110         def stars ; @stars.keys ; end
 111         def commoners ; @commoners.keys ; end
 112
 113         # Get :day's [default: today] popularity for :stars [default: all stars].
 114         # Returns:
 115         #   a hash star => number of commoners that voted for it that day
 116         def popularity(o={})
 117                 pop = @popularity[o[:day] || today]
 118                 sel = {}
 119                 [o[:stars] || stars].flatten.each do |s|
 120                         sel[s] = pop[s].length
 121                 end
 122                 return sel
 123         end
 124
 125         # an Array of [star, popularity] ordered by popularity
 126         def grade(o={})
 127                 popularity(o).to_a.sort { |s1, s2| s2.last <=> s1.last }
 128         end
 129
 130         def vote(o = {})
 131                 pop_org = popularity(:day => yesterday)
 132                 # to allow giving stars with no popularity a chance,
 133                 # we allow a :mul and :add option to the voting session.
 134                 mul = o[:mul] || 1
 135                 add = o[:add] || 0
 136                 tot = 0
 137                 pop = {}
 138                 pop_org.each do |star, p|
 139                         pop[star] = p*mul + add
 140                         tot += pop[star]
 141                 end
 142                 @commoners.each do |name, commoner|
 143                         star = commoner.popular_vote(pop, tot)
 144                         @popularity[today][star] << name
 145                 end
 146         end
 147
 148 end
 149
 150 pop = Popularity.new
 151
 152 5.times do |i| pop.add_star(i) end
 153 100.times do |i| pop.add_commoner(i) end
 154
 155 puts pop.grade.map { |s, p| "#{s} (#{p})" }.join(', ')
 156
 157 puts
 158 1000.times do
 159         pop.new_day
 160         pop.vote
 161         puts pop.grade.map { |s, p| "#{s} (#{p})" }.join(', ')
 162 end
 163
 164 puts
 165 pop.reset
 166 1000.times do
 167         pop.new_day
 168         pop.vote(:add => 1)
 169         puts pop.grade.map { |s, p| "#{s} (#{p})" }.join(', ')
 170 end
 171
 172 puts
 173 pop.reset
 174 1000.times do
 175         pop.new_day
 176         pop.vote(:mul => 10, :add => 1)
 177         puts pop.grade.map { |s, p| "#{s} (#{p})" }.join(', ')
 178 end
 179