80 lines
2.9 KiB
C++
80 lines
2.9 KiB
C++
/***************************************************************************
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* Copyright (C) 2009 by Stefan Bühler *
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* stbuehler@web.de *
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* *
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* This program is free software; you can redistribute it and/or modify *
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* it under the terms of the GNU General Public License as published by *
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* the Free Software Foundation; either version 2 of the License, or *
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* (at your option) any later version. *
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* *
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* This program is distributed in the hope that it will be useful, *
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* but WITHOUT ANY WARRANTY; without even the implied warranty of *
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the *
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* GNU General Public License for more details. *
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* *
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* You should have received a copy of the GNU General Public License *
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* along with this program; if not, write to the *
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* Free Software Foundation, Inc., *
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* 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA. *
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***************************************************************************/
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#include "ai.h"
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namespace toruschess {
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// NOPIECE = 0, PAWN = 1, KNIGHT = 2, BISHOP = 3, ROOK = 4, QUEEN = 5, KING = 6
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static int piece_value[] = {
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0, 1, 3, 3, 5, 9, 10
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};
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static const int MAXVAL = 10000;
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static const int NOMOVE = -MAXVAL - 1;
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static const int DRAWVAL = -7;
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/* standard minimax search; saves the best move in *move if move != NULL;
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* balance is the current "heuristic value" of a state (mult with curp to get the
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* rating for a specifig player)
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*/
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static int minimax(Field &field, int bal, Player curp, unsigned int depth, Move *move) {
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if (depth == 0) return curp * bal;
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int mx = NOMOVE;
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for (int x = 0; x < 8; x++)
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for (int y = 0; y < 8; y++) {
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Pos p(x, y);
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if (field.player(p) != curp) continue;
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int cbal = bal;
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QList<Move> moves = field.validMoves(p);
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foreach(Move m, moves) {
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field.move_unchecked(m);
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cbal -= m.prevTo();
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int val = -minimax(field, cbal, Player(-curp), depth-1, NULL);
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if (val > mx) {
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mx = val;
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if (move) *move = m;
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}
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field.undo_unchecked(m);
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if (mx == MAXVAL) return mx;
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}
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}
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if (mx == NOMOVE) {
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if (field.inCheck(curp)) return -MAXVAL;
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return curp * DRAWVAL;
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}
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return mx;
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}
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Move ai::getMove(Field &field, Player curp, int depth) {
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int balance = 0;
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for (int x = 0; x < 8; x++)
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for (int y = 0; y < 8; y++) {
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Pos p(x,y);
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balance += field.player(p) * piece_value[field.piece(p)];
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}
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Move move;
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minimax(field, balance, curp, depth, &move);
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return move;
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}
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}
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