draw.cpp

   1 /***************************************************************************
   2                       draw.cpp  -  Draw recognition
   3                              -------------------
   4     begin                : Sun Nov 28 2007
   5     copyright            : (C) 2007 by Maurizio Monge
   6     email                : monge@linuz.sns.it
   7  ***************************************************************************/
   8
   9 /***************************************************************************
  10  *                                                                         *
  11  *   This program is free software; you can redistribute it and/or modify  *
  12  *   it under the terms of the GNU General Public License as published by  *
  13  *   the Free Software Foundation; either version 2 of the License, or     *
  14  *   (at your option) any later version.                                   *
  15  *                                                                         *
  16  ***************************************************************************/
  17
  18 #include "engine.h"
  19
  20 /* check if the position can be considered draw for 50mvs rule or repetition */
  21 bool Engine::check_draw()
  22 {
  23     if(board.fifty >= 50) /* 50mvs rule, at the moment */
  24         return true;
  25
  26     /* for the latest reversible moves check if the hash value
  27         (for this player) is the same         */
  28     int first_candidate = MAX(board.num_old_hashes-(board.fifty/2)*2, 0);
  29
  30     /* -4 because it is impossible that the previous position is
  31        equal to the  current one :) */
  32     for(int i=board.num_old_hashes-4;i>=first_candidate;i-=2)
  33     {
  34         if(board.hash == board.old_hashes[i])
  35             return true;
  36     }
  37
  38     return insufficient_material();
  39 }
  40
  41 bool Engine::insufficient_material()
  42 {
  43     for(int i=0;i<2;i++)
  44     {
  45         int mt = (i ? 5 : -1);
  46
  47         if(board.mat_tracking[PAWN+mt].count > 0
  48           || board.mat_tracking[QUEEN+mt].count > 0
  49           || board.mat_tracking[ROOK+mt].count > 0)
  50           return false;
  51
  52         /* ok, unless the 2 bishop are on squares of the same color :) */
  53         if(board.mat_tracking[BISHOP+mt].count >= 2)
  54           return false;
  55
  56         if(board.mat_tracking[KNIGHT+mt].count >= 1 &&
  57             board.mat_tracking[BISHOP+mt].count >= 1)
  58           return false;
  59
  60         /* let's not consider insufficient material in 3-knights engames! */
  61         if(board.mat_tracking[KNIGHT+mt].count >= 3)
  62           return false;
  63     }
  64     return true;
  65 }