From: Giuseppe Bilotta <giuseppe.bilotta@gmail.com>
Date: Sat, 25 Apr 2009 15:41:37 +0000 (+0200)
Subject: Add popularity script
X-Git-Url: http://git.oblomov.eu/milivella/commitdiff_plain

Add popularity script
---

diff --git a/vella_pop.rb b/vella_pop.rb
new file mode 100755
index 0000000..43fe69f
--- /dev/null
+++ b/vella_pop.rb
@@ -0,0 +1,179 @@
+#!/usr/bin/ruby
+
+=begin
+What drives popularity? Are Pareto popularity distributions possible? likely?
+guaranteed?
+=end
+
+class Array
+	def pick_one
+		return nil if empty?
+		self[rand(self.length)]
+	end
+end
+
+class Popularity
+	# A Character has a name and nothing more
+	class Character
+		attr :name
+		def initialize(name)
+			@name = name.intern
+		end
+	end
+
+	# A Star is just a Character, no special abilities
+	class Star < Character ; end
+
+	# A Commoner is a Character with one or more voting strategies
+	class Commoner < Character
+		# The simplest voting strategy: pick a random one
+		def random_vote(popularity, total)
+			popularity.keys.pick_one
+		end
+
+		# A voting strategy that picks a random star, weighting
+		# more popular ones more
+		def popular_vote(popularity, total)
+			# if nobody voted yet, pick a random one
+			return random_vote(popularity, total) if total == 0
+			pick = rand(total)
+			popularity.each do |star, pop|
+				return star if pick < pop
+				pick -= pop
+			end
+		end
+
+	end
+
+	# Add a new Star
+	def add_star(n)
+		case n
+		when String
+			name = n
+		when Integer
+			name = "Star #%u" % n
+		else
+			raise ArgumentError, "#{n} is neither a String nor an Integer"
+		end
+
+		@stars[name.intern] = Star.new(name)
+	end
+
+	# Add a new Commoner
+	def add_commoner(n)
+		case n
+		when String
+			name = n
+		when Integer
+			name = "Commoner #%u" % n
+		else
+			raise ArgumentError, "#{n} is neither a String nor an Integer"
+		end
+
+		@commoners[name.intern] = Commoner.new(name)
+	end
+
+	# Today
+	def today ; @day ; end
+	# Yesterday
+	def yesterday
+		raise if @day == 0
+		@day-1
+	end
+
+	# Initialize a new popularity day
+	def push_popularity
+		@popularity << Hash.new do |h, k|
+			raise ArgumentError, "no such Star '#{k}'" unless @stars.key? k
+			h[k] = []
+		end
+	end
+
+	def new_day
+		@day += 1
+		push_popularity
+	end
+
+	def initialize
+		@stars = {}
+		@commoners = {}
+		@popularity = []
+		reset
+	end
+
+	def reset
+		@day = 0
+		@popularity.clear
+		push_popularity
+	end
+
+	def stars ; @stars.keys ; end
+	def commoners ; @commoners.keys ; end
+
+	# Get :day's [default: today] popularity for :stars [default: all stars].
+	# Returns:
+       	#   a hash star => number of commoners that voted for it that day
+	def popularity(o={})
+		pop = @popularity[o[:day] || today]
+		sel = {}
+		[o[:stars] || stars].flatten.each do |s|
+			sel[s] = pop[s].length
+		end
+		return sel
+	end
+
+	# an Array of [star, popularity] ordered by popularity
+	def grade(o={})
+		popularity(o).to_a.sort { |s1, s2| s2.last <=> s1.last }
+	end
+
+	def vote(o = {})
+		pop_org = popularity(:day => yesterday)
+		# to allow giving stars with no popularity a chance,
+		# we allow a :mul and :add option to the voting session.
+		mul = o[:mul] || 1
+		add = o[:add] || 0
+		tot = 0
+		pop = {}
+		pop_org.each do |star, p|
+			pop[star] = p*mul + add
+			tot += pop[star]
+		end
+		@commoners.each do |name, commoner|
+			star = commoner.popular_vote(pop, tot)
+			@popularity[today][star] << name
+		end
+	end
+
+end
+
+pop = Popularity.new
+
+5.times do |i| pop.add_star(i) end
+100.times do |i| pop.add_commoner(i) end
+
+puts pop.grade.map { |s, p| "#{s} (#{p})" }.join(', ')
+
+puts
+1000.times do
+	pop.new_day
+	pop.vote
+	puts pop.grade.map { |s, p| "#{s} (#{p})" }.join(', ')
+end
+
+puts
+pop.reset
+1000.times do
+	pop.new_day
+	pop.vote(:add => 1)
+	puts pop.grade.map { |s, p| "#{s} (#{p})" }.join(', ')
+end
+
+puts
+pop.reset
+1000.times do
+	pop.new_day
+	pop.vote(:mul => 10, :add => 1)
+	puts pop.grade.map { |s, p| "#{s} (#{p})" }.join(', ')
+end
+