lib/.svn/text-base/libpplayer.rb.netbeans-base

   1 # == Synopsis
   2 #
   3 # Library to support a Trap the Cap player that uses potentials to select the
   4 # best move
   5 #
   6 # == Author
   7 # Neil Smith
   8 #
   9 # == Change history
  10 # Version 1.1::  23 April 2008
  11
  12 require 'lib/libttc'
  13 require 'lib/libgenetics'
  14
  15
  16 # Play Trap the Cap by using potential fields.  For each possible move,
  17 # calculate the field strength and pick the move with the lowest potential
  18 class Potential_player
  19
  20   attr_reader :friend_pull, :enemy_pull, :base_pull,
  21     :safe_bonus, :capture_bonus
  22
  23   def initialize(args, verbose = false)
  24     @friend_pull   = args[:friend_pull]   || 1
  25     @enemy_pull    = args[:enemy_pull]    || 0.5
  26     @base_pull     = args[:base_pull]     || 2
  27     @safe_bonus    = args[:safe_bonus]    || 8
  28     @capture_bonus = args[:capture_bonus] || 10
  29
  30     @verbose = verbose
  31   end
  32
  33   # Find the best move of the possible ones
  34   def best_move(game, die_result)
  35     me = game.current_player
  36     possible_moves = game.possible_moves(die_result, me)
  37     scored_moves = possible_moves.collect do |m|
  38       begin
  39         game.apply_move! m
  40         score = score_position(game, me)
  41 #        game.undo_move!
  42       rescue GameWonNotice
  43         score = 10000
  44       ensure
  45         game.undo_move!
  46       end
  47       puts "#{m} scores #{score}" if @verbose
  48       [m, score]
  49     end
  50     best_move = (scored_moves.max {|a, b| a[1] <=> b[1]})[0]
  51   end
  52
  53   # Calculate the potential score of a position for a given player
  54   def score_position(game, player)
  55     score = 0
  56     game.pieces.each_value do |piece|
  57       here = piece.position
  58       if piece.colour == player
  59         game.pieces.each_value do |other_piece|
  60           if other_piece.colour == player
  61             score += game.board.distance_between[here.place][other_piece.position.place] * @friend_pull
  62           else
  63             score += game.board.distance_between[here.place][other_piece.position.place] * @enemy_pull
  64           end
  65         end
  66         score += piece.contains.length * @capture_bonus
  67         score += game.board.distance_between[here.place][game.board.positions[player].place] *
  68         piece.contains.length * @base_pull
  69       elsif here == game.board.positions[player]
  70         score += @safe_bonus
  71       end
  72     end
  73     score
  74   end
  75
  76
  77   # Convert a player to a bitstring
  78   def to_bitstring
  79     (@friend_pull * 4).to_i.to_bitstring(4).gray_encode +
  80       (@enemy_pull * 4).to_i.to_bitstring(4).gray_encode +
  81       (@base_pull * 4).to_i.to_bitstring(4).gray_encode +
  82       @safe_bonus.to_bitstring(4).gray_encode +
  83       @capture_bonus.to_bitstring(4).gray_encode
  84   end
  85
  86   # Convert a player to a genome
  87   def to_genome
  88     Genome.new(self.to_bitstring)
  89   end
  90 end
  91
  92
  93 class Genome
  94
  95   # Create a potential player from a genome
  96   def to_potential_player
  97     friend_pull   = @genome[0,  4].gray_decode.to_decimal.to_f / 4
  98     enemy_pull    = @genome[4,  4].gray_decode.to_decimal.to_f / 4
  99     base_pull     = @genome[8,  4].gray_decode.to_decimal.to_f / 4
 100     safe_bonus    = @genome[12, 4].gray_decode.to_decimal
 101     capture_bonus = @genome[16, 4].gray_decode.to_decimal
 102     Potential_player.new({:friend_pull => friend_pull,
 103         :enemy_pull => enemy_pull, :base_pull => base_pull,
 104         :safe_bonus => safe_bonus, :capture_bonus => capture_bonus})
 105   end
 106 end