src/game.cpp

   1 /* Copyright (C) 2007-2012 Vincent Ollivier
   2  *
   3  * Purple Haze is free software: you can redistribute it and/or modify
   4  * it under the terms of the GNU General Public License as published by
   5  * the Free Software Foundation, either version 3 of the License, or
   6  * (at your option) any later version.
   7  *
   8  * Purple Haze is distributed in the hope that it will be useful,
   9  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  10  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
  11  * GNU General Public License for more details.
  12  *
  13  * You should have received a copy of the GNU General Public License
  14  * along with this program. If not, see <http://www.gnu.org/licenses/>.
  15  */
  16
  17 #include <cassert>
  18 #include <iostream>
  19
  20 #include "game.h"
  21
  22 void Game::clear_killers()
  23 {
  24     for (int i = 0; i < MAX_PLY; ++i) {
  25         for (int j = 0; j < MAX_KILLERS; ++j) {
  26             killer_moves[i][j] = Move();
  27         }
  28     }
  29 }
  30
  31 void Game::add_piece(Color c, PieceType t, Square s)
  32 {
  33     const int i = pieces.count(c, t);
  34     pieces.set_position(c, t, i, s);
  35     board[s] = Piece(c, t, i);
  36     pieces.inc_nb_pieces(c, t);
  37
  38     // Update Zobrist hash
  39     Position& pos = current_position();
  40     zobrist.update_piece(pos.hash(), c, t, s);
  41
  42     // Hack: for the material hash, the position is irrelevant but each piece
  43     // needs a unique hash so we are using Square(i) in place of the position.
  44     // Remove the previous total
  45     zobrist.update_piece(pos.material_hash(), c, t, Square(i));
  46     // Add the new total
  47     zobrist.update_piece(pos.material_hash(), c, t, Square(i + 1));
  48 }
  49
  50 void Game::del_piece(Color c, PieceType t, int i)
  51 {
  52     // Remove the piece, and put in its place the higher index piece of the
  53     // same color and type in order to avoid holes (idea from Mediocre Chess)
  54     const Square emptied = pieces.position(c, t, i); // Get piece's position
  55     board[emptied] = Piece();                        // Remove it from board
  56     pieces.dec_nb_pieces(c, t);                      // and from pieces list
  57     const int j = pieces.count(c, t);                // Last piece's index
  58     if (i != j && pieces.count(c, t) > 0) {
  59         // Swap i and j and update board
  60         Square s = pieces.position(c, t, j);         // Last piece's position
  61         pieces.set_position(c, t, i, s);             // Fill the hole left
  62         board[s] = Piece(c, t, i);                   // Update board
  63     }
  64     // Update Zobrist hash
  65     Position& pos = current_position();
  66     zobrist.update_piece(pos.hash(), c, t, emptied);
  67
  68     // Same hack here for the material hash than in add_piece()
  69     zobrist.update_piece(pos.material_hash(), c, t, Square(j + 1));
  70     zobrist.update_piece(pos.material_hash(), c, t, Square(j));
  71 }
  72
  73 void Game::new_position()
  74 {
  75     // Save the state of the current position
  76     tree.push();
  77
  78     // Remove the previous en passant square from the Zobrist hash
  79     Position& pos = current_position();
  80     zobrist.update_en_passant(pos.hash(), pos.en_passant());
  81
  82     // Prepare the position for a new move
  83     pos.change_side();
  84     zobrist.change_side(pos.hash());
  85 }
  86
  87 void Game::del_position()
  88 {
  89     // Revert back to previous position
  90     tree.pop();
  91 }
  92
  93 /*
  94  * Killer move setter for the Killer Heuristic in move ordering.
  95  */
  96 void Game::set_killer(const Move move, const int depth)
  97 {
  98     if (move != killer_moves[depth][0]) {
  99         killer_moves[depth][1] = killer_moves[depth][0];
 100         killer_moves[depth][0] = move;
 101     }
 102 }