Removed debug code.
[rubyvote] / lib / rubyvote / condorcet.rb
index 68b3c70..d0210ef 100644 (file)
@@ -32,7 +32,7 @@
 ## the CloneproofSSDVote classes but should not be used directly.
 
 class CondorcetVote < ElectionVote
-
+  
   def initialize(votes=nil)
     unless defined?(@candidates)
       @candidates = Array.new
@@ -48,68 +48,58 @@ class CondorcetVote < ElectionVote
 
   def tally_vote(vote=nil)
 
-    vote.each_with_index do |winner, index|
+    vote.each_with_index do |winners, index|
       if vote.flatten.length < @candidates.length
-        implied_losers = @candidates.select { |c| not vote.include?(c) }
+        implied_losers = @candidates.select { |c| not vote.flatten.include?(c) }
         vote.push(implied_losers)
       end
       if vote.length - 1 == index
         losers = []
       else
-        losers = vote.last( vote.flatten.length - index )
+        losers = vote.flatten.last( vote.flatten.length - index - 1)
       end
 
       losers.each do |place|
         place = [place] unless place.class == Array
         place.each do |loser|
           
-          next if winner == loser
-
-          @votes[winner] = Hash.new unless @votes.has_key?(winner)
-          @votes[loser] = Hash.new unless @votes.has_key?(loser)
+          winners = [winners] unless winners.class == Array
+          next if winners.include?(loser)
+          winners.each do |winner|
+            @votes[winner] = Hash.new unless @votes.has_key?(winner)
+            @votes[loser] = Hash.new unless @votes.has_key?(loser)
+
+            if @votes[winner].has_key?(loser)
+              @votes[winner][loser] += 1
+            else
+              @votes[winner][loser] = 1
+            end
 
-          if @votes[winner].has_key?(loser)
-            @votes[winner][loser] += 1
-          else
-            @votes[winner][loser] = 1
+            # make sure we have a comparable object
+            @votes[loser][winner] = 0 unless @votes[loser].has_key?( winner )
           end
-
-          # make sure we have a comparable object
-          @votes[loser][winner] = 0 unless @votes[loser].has_key?( winner )
-
-          @candidates << loser unless @candidates.include?( loser )
         end
       end
     end
   end
 
-  def result
-    top_result = resultFactory( self )
-    until @candidates.empty?
-      aResult = resultFactory( self )
-      top_result.full_results << aResult
-      filter_out(aResult)
-    end
-    top_result
-  end
-
   protected
+
   def verify_vote(vote=nil)
     vote.instance_of?( Array ) and
       vote == vote.uniq
   end
-
 end
 
 class PureCondorcetVote < CondorcetVote
-  def resultFactory(init)
-    PureCondorcetResult.new(init)
+  def result
+    PureCondorcetResult.new(self)
   end
 end
 
 class CloneproofSSDVote < CondorcetVote
-  def resultFactory(init)
-    CloneproofSSDResult.new(init)
+  def result
+    CloneproofSSDResult.new(self)
   end
 end
 
@@ -122,17 +112,60 @@ end
 ## directly.
 
 class CondorcetResult < ElectionResult
+  attr_reader :matrix
+  
   def initialize(voteobj=nil)
     unless voteobj and voteobj.kind_of?( CondorcetVote )
       raise ArgumentError, "You must pass a CondorcetVote array.", caller
     end
     super(voteobj)
+    @matrix = voteobj.votes
+  end
+  
+  def victories_and_ties
+    victors = Array.new
+    ties = Array.new
+    victories = Hash.new
+    candidates = @matrix.keys.sort
+    
+    candidates.each do |candidate|
+      candidates.each do |challenger|
+        next if candidate == challenger
+        diff = @matrix[candidate][challenger] - @matrix[challenger][candidate]
+        if diff > 0 
+          victors << [candidate, challenger, diff]
+        elsif diff == 0 && ties.include?([challenger, candidate]) == false
+          ties << [candidate, challenger] 
+        end
+      end
+    end  
+    
+    victors.each do |list|
+      if victories.has_key?(list[0])
+        victories[list[0]][list[1]] = list[2]       
+      else
+        victories[list[0]] = Hash.new
+        victories[list[0]][list[1]] = list[2]
+      end
+    end
+    
+    return victories, ties    
   end
 
+  def ranked_candidates
+    if not defined?(@ranked_candidates)
+      @ranked_candidates = build_ranked_candidates()
+    end
+
+    @ranked_candidates
+  end
+        
   protected
   def defeats(candidates=nil, votes=nil)
-    candidates = @election.candidates unless candidates
-    votes = @election.votes unless votes
+    candidates ||= @election.candidates || []
+    # we're assumign that if there are candidates, there must be at
+    # least one vote for them
+    votes ||= @election.votes 
 
     defeats = Array.new
     candidates.each do |candidate|
@@ -146,6 +179,27 @@ class CondorcetResult < ElectionResult
 
     defeats
   end
+  
+  def build_ranked_candidates
+    # build a lis of ranked candidates by dropping the winner and
+    # cursing
+
+    ranked_candidates = []
+
+    resultobj = self.dup
+    candidates = self.election.candidates
+
+    until candidates.empty? 
+      ranked_candidates << resultobj.winners
+      
+      new_voteobj = resultobj.election.dup
+      candidates = new_voteobj.candidates
+      new_voteobj.candidates.delete_if {|x| resultobj.winners.include?(x)}
+      resultobj = new_voteobj.result
+    end
+
+    ranked_candidates
+  end
 
 end
 
@@ -156,10 +210,15 @@ class PureCondorcetResult < CondorcetResult
   end
 
   protected
+  
   def condorcet
     votes = @election.votes
     candidates = @election.candidates
 
+    unless votes.length > 0 and candidates.length > 0
+      return @winners=[]
+    end
+
     victors = Hash.new
     candidates.each do |candidate|
       victors[candidate] = Array.new
@@ -170,11 +229,18 @@ class PureCondorcetResult < CondorcetResult
       victors[winner] << loser
     end
 
-    winners = @election.candidates.find_all do |candidate|
-        victors[candidate].length == @election.candidates.length - 1
+    victory_margin = 1
+    while true
+      winners = @election.candidates.find_all do |candidate|
+        victors[candidate].length == @election.candidates.length - victory_margin
+      end
+      if winners.length > 0
+        @winners = winners
+        return @winners
+      else
+        victory_margin += 1
+      end
     end
-
-    @winners << winners if winners.length == 1
   end
 end
 
@@ -185,9 +251,10 @@ class CloneproofSSDResult < CondorcetResult
   end
 
   protected
+
   def cpssd
     votes = @election.votes
-    candidates = *@election.candidates
+    candidates = @election.candidates.dup
 
     def in_schwartz_set?(candidate, candidates, transitive_defeats)
       candidates.each do |challenger|
@@ -205,15 +272,22 @@ class CloneproofSSDResult < CondorcetResult
 
       # see the array with the standard defeats
       transitive_defeats = self.defeats(candidates, votes)
+      defeats_hash = Hash.new
+      transitive_defeats.each { |td| defeats_hash[td] = 1 }
 
+      candidates = [candidates] unless candidates.class == Array
       candidates.each do |cand1|
         candidates.each do |cand2|
-          candidates.each do |cand3|
-            if transitive_defeats.include?( [ cand2, cand1 ] ) and
-                transitive_defeats.include?( [ cand1, cand3 ] ) and
-                not transitive_defeats.include?( [ cand2, cand3 ] ) and
-                not cand2 == cand3
-              transitive_defeats << [ cand2, cand3 ]
+          unless cand1 == cand2
+            candidates.each do |cand3|
+              if not cand2 == cand3 and 
+                  not cand1 == cand3 and 
+                  defeats_hash[[cand2, cand1]] and
+                  defeats_hash[[cand1, cand3]] and
+                  not defeats_hash[[cand2, cand3]] 
+                transitive_defeats << [cand2, cand3]
+                defeats_hash[[cand2, cand3]] = 1
+              end
             end
           end
         end

Benjamin Mako Hill || Want to submit a patch?