2011-11-12 20:44:06 +01:00
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/*
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Stockfish, a UCI chess playing engine derived from Glaurung 2.1
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Copyright (C) 2004-2008 Tord Romstad (Glaurung author)
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2014-05-31 14:23:03 +02:00
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Copyright (C) 2008-2014 Marco Costalba, Joona Kiiski, Tord Romstad
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2011-11-12 20:44:06 +01:00
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Stockfish 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 3 of the License, or
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(at your option) any later version.
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Stockfish 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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You should have received a copy of the GNU General Public License
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along with this program. If not, see <http://www.gnu.org/licenses/>.
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*/
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2012-01-01 01:52:19 +01:00
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#include <algorithm>
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2011-11-12 20:44:06 +01:00
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#include <cassert>
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2012-09-16 17:16:15 +02:00
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#include "bitboard.h"
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2011-11-12 20:44:06 +01:00
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#include "bitcount.h"
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#include "endgame.h"
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2012-06-04 18:25:51 +02:00
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#include "movegen.h"
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2011-11-12 20:44:06 +01:00
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using std::string;
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namespace {
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2013-11-30 20:12:34 +01:00
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// Table used to drive the king towards the edge of the board
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2011-11-12 20:44:06 +01:00
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// in KX vs K and KQ vs KR endgames.
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2013-11-30 20:12:34 +01:00
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const int PushToEdges[SQUARE_NB] = {
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2011-11-12 20:44:06 +01:00
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100, 90, 80, 70, 70, 80, 90, 100,
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90, 70, 60, 50, 50, 60, 70, 90,
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80, 60, 40, 30, 30, 40, 60, 80,
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70, 50, 30, 20, 20, 30, 50, 70,
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70, 50, 30, 20, 20, 30, 50, 70,
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80, 60, 40, 30, 30, 40, 60, 80,
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90, 70, 60, 50, 50, 60, 70, 90,
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100, 90, 80, 70, 70, 80, 90, 100,
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};
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2013-11-30 20:12:34 +01:00
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// Table used to drive the king towards a corner square of the
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2011-11-12 20:44:06 +01:00
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// right color in KBN vs K endgames.
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2013-11-30 20:12:34 +01:00
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const int PushToCorners[SQUARE_NB] = {
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2011-11-12 20:44:06 +01:00
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200, 190, 180, 170, 160, 150, 140, 130,
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190, 180, 170, 160, 150, 140, 130, 140,
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180, 170, 155, 140, 140, 125, 140, 150,
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170, 160, 140, 120, 110, 140, 150, 160,
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160, 150, 140, 110, 120, 140, 160, 170,
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150, 140, 125, 140, 140, 155, 170, 180,
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140, 130, 140, 150, 160, 170, 180, 190,
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130, 140, 150, 160, 170, 180, 190, 200
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};
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2013-11-30 20:12:34 +01:00
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// Tables used to drive a piece towards or away from another piece
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const int PushClose[8] = { 0, 0, 100, 80, 60, 40, 20, 10 };
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const int PushAway [8] = { 0, 5, 20, 40, 60, 80, 90, 100 };
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#ifndef NDEBUG
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bool verify_material(const Position& pos, Color c, Value npm, int num_pawns) {
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return pos.non_pawn_material(c) == npm && pos.count<PAWN>(c) == num_pawns;
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}
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#endif
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// Map the square as if strongSide is white and strongSide's only pawn
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// is on the left half of the board.
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Square normalize(const Position& pos, Color strongSide, Square sq) {
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assert(pos.count<PAWN>(strongSide) == 1);
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if (file_of(pos.list<PAWN>(strongSide)[0]) >= FILE_E)
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sq = Square(sq ^ 7); // Mirror SQ_H1 -> SQ_A1
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if (strongSide == BLACK)
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sq = ~sq;
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return sq;
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}
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2011-11-12 20:44:06 +01:00
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2014-05-31 14:23:03 +02:00
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// Get the material key of Position out of the given endgame key code
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// like "KBPKN". The trick here is to first forge an ad-hoc FEN string
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// and then let a Position object do the work for us.
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2012-01-01 01:52:19 +01:00
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Key key(const string& code, Color c) {
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2011-11-12 20:44:06 +01:00
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2012-01-01 01:52:19 +01:00
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assert(code.length() > 0 && code.length() < 8);
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assert(code[0] == 'K');
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2011-11-12 20:44:06 +01:00
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2013-11-30 20:12:34 +01:00
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string sides[] = { code.substr(code.find('K', 1)), // Weak
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code.substr(0, code.find('K', 1)) }; // Strong
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2011-11-12 20:44:06 +01:00
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2012-06-04 18:25:51 +02:00
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std::transform(sides[c].begin(), sides[c].end(), sides[c].begin(), tolower);
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2011-11-12 20:44:06 +01:00
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2014-05-31 14:23:03 +02:00
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string fen = sides[0] + char(8 - sides[0].length() + '0') + "/8/8/8/8/8/8/"
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+ sides[1] + char(8 - sides[1].length() + '0') + " w - - 0 10";
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2011-11-12 20:44:06 +01:00
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2012-06-04 18:25:51 +02:00
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return Position(fen, false, NULL).material_key();
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2011-11-12 20:44:06 +01:00
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}
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2012-01-01 01:52:19 +01:00
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template<typename M>
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void delete_endgame(const typename M::value_type& p) { delete p.second; }
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2011-11-12 20:44:06 +01:00
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} // namespace
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2012-01-01 01:52:19 +01:00
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/// Endgames members definitions
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2011-11-12 20:44:06 +01:00
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Endgames::Endgames() {
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2012-01-01 01:52:19 +01:00
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add<KPK>("KPK");
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add<KNNK>("KNNK");
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add<KBNK>("KBNK");
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add<KRKP>("KRKP");
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add<KRKB>("KRKB");
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add<KRKN>("KRKN");
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2013-05-03 19:03:42 +02:00
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add<KQKP>("KQKP");
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2012-01-01 01:52:19 +01:00
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add<KQKR>("KQKR");
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add<KNPK>("KNPK");
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2013-05-03 19:03:42 +02:00
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add<KNPKB>("KNPKB");
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2012-01-01 01:52:19 +01:00
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add<KRPKR>("KRPKR");
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2013-11-30 20:12:34 +01:00
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add<KRPKB>("KRPKB");
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2012-01-01 01:52:19 +01:00
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add<KBPKB>("KBPKB");
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add<KBPKN>("KBPKN");
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add<KBPPKB>("KBPPKB");
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add<KRPPKRP>("KRPPKRP");
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2011-11-12 20:44:06 +01:00
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}
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Endgames::~Endgames() {
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2012-01-01 01:52:19 +01:00
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for_each(m1.begin(), m1.end(), delete_endgame<M1>);
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for_each(m2.begin(), m2.end(), delete_endgame<M2>);
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2011-11-12 20:44:06 +01:00
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}
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2012-01-01 01:52:19 +01:00
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template<EndgameType E>
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void Endgames::add(const string& code) {
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2011-11-12 20:44:06 +01:00
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2012-06-04 18:25:51 +02:00
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map((Endgame<E>*)0)[key(code, WHITE)] = new Endgame<E>(WHITE);
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map((Endgame<E>*)0)[key(code, BLACK)] = new Endgame<E>(BLACK);
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2011-11-12 20:44:06 +01:00
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}
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/// Mate with KX vs K. This function is used to evaluate positions with
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2014-05-31 14:23:03 +02:00
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/// king and plenty of material vs a lone king. It simply gives the
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2011-11-12 20:44:06 +01:00
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/// attacking side a bonus for driving the defending king towards the edge
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/// of the board, and for keeping the distance between the two kings small.
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template<>
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2012-01-01 01:52:19 +01:00
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Value Endgame<KXK>::operator()(const Position& pos) const {
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2011-11-12 20:44:06 +01:00
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2013-11-30 20:12:34 +01:00
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assert(verify_material(pos, weakSide, VALUE_ZERO, 0));
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2013-08-20 20:02:33 +02:00
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assert(!pos.checkers()); // Eval is never called when in check
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2011-11-12 20:44:06 +01:00
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2012-06-04 18:25:51 +02:00
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// Stalemate detection with lone king
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2013-11-30 20:12:34 +01:00
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if (pos.side_to_move() == weakSide && !MoveList<LEGAL>(pos).size())
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2013-08-20 20:02:33 +02:00
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return VALUE_DRAW;
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2012-06-04 18:25:51 +02:00
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2013-11-30 20:12:34 +01:00
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Square winnerKSq = pos.king_square(strongSide);
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Square loserKSq = pos.king_square(weakSide);
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2011-11-12 20:44:06 +01:00
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2013-11-30 20:12:34 +01:00
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Value result = pos.non_pawn_material(strongSide)
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+ pos.count<PAWN>(strongSide) * PawnValueEg
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+ PushToEdges[loserKSq]
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+ PushClose[square_distance(winnerKSq, loserKSq)];
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2011-11-12 20:44:06 +01:00
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2013-11-30 20:12:34 +01:00
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if ( pos.count<QUEEN>(strongSide)
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|| pos.count<ROOK>(strongSide)
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2014-05-31 14:23:03 +02:00
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||(pos.count<BISHOP>(strongSide) && pos.count<KNIGHT>(strongSide))
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2013-11-30 20:12:34 +01:00
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|| pos.bishop_pair(strongSide))
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2013-08-20 20:02:33 +02:00
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result += VALUE_KNOWN_WIN;
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2011-11-12 20:44:06 +01:00
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2013-11-30 20:12:34 +01:00
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return strongSide == pos.side_to_move() ? result : -result;
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2011-11-12 20:44:06 +01:00
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}
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/// Mate with KBN vs K. This is similar to KX vs K, but we have to drive the
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/// defending king towards a corner square of the right color.
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template<>
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2012-01-01 01:52:19 +01:00
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Value Endgame<KBNK>::operator()(const Position& pos) const {
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2011-11-12 20:44:06 +01:00
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2013-11-30 20:12:34 +01:00
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assert(verify_material(pos, strongSide, KnightValueMg + BishopValueMg, 0));
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assert(verify_material(pos, weakSide, VALUE_ZERO, 0));
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2011-11-12 20:44:06 +01:00
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2013-11-30 20:12:34 +01:00
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Square winnerKSq = pos.king_square(strongSide);
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Square loserKSq = pos.king_square(weakSide);
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Square bishopSq = pos.list<BISHOP>(strongSide)[0];
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2011-11-12 20:44:06 +01:00
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2014-05-31 14:23:03 +02:00
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// kbnk_mate_table() tries to drive toward corners A1 or H8. If we have a
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// bishop that cannot reach the above squares, we flip the kings in order
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// to drive the enemy toward corners A8 or H1.
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2013-05-03 19:03:42 +02:00
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if (opposite_colors(bishopSq, SQ_A1))
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2011-11-12 20:44:06 +01:00
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{
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2013-11-30 20:12:34 +01:00
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winnerKSq = ~winnerKSq;
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loserKSq = ~loserKSq;
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2011-11-12 20:44:06 +01:00
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}
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Value result = VALUE_KNOWN_WIN
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2013-11-30 20:12:34 +01:00
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+ PushClose[square_distance(winnerKSq, loserKSq)]
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+ PushToCorners[loserKSq];
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2011-11-12 20:44:06 +01:00
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2013-11-30 20:12:34 +01:00
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return strongSide == pos.side_to_move() ? result : -result;
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2011-11-12 20:44:06 +01:00
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}
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/// KP vs K. This endgame is evaluated with the help of a bitbase.
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template<>
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2012-01-01 01:52:19 +01:00
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Value Endgame<KPK>::operator()(const Position& pos) const {
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2011-11-12 20:44:06 +01:00
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2013-11-30 20:12:34 +01:00
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assert(verify_material(pos, strongSide, VALUE_ZERO, 1));
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assert(verify_material(pos, weakSide, VALUE_ZERO, 0));
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2011-11-12 20:44:06 +01:00
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2013-11-30 20:12:34 +01:00
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// Assume strongSide is white and the pawn is on files A-D
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Square wksq = normalize(pos, strongSide, pos.king_square(strongSide));
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Square bksq = normalize(pos, strongSide, pos.king_square(weakSide));
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Square psq = normalize(pos, strongSide, pos.list<PAWN>(strongSide)[0]);
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2011-11-12 20:44:06 +01:00
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2013-11-30 20:12:34 +01:00
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Color us = strongSide == pos.side_to_move() ? WHITE : BLACK;
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2011-11-12 20:44:06 +01:00
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2013-11-30 20:12:34 +01:00
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if (!Bitbases::probe_kpk(wksq, psq, bksq, us))
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2011-11-12 20:44:06 +01:00
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return VALUE_DRAW;
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2013-11-30 20:12:34 +01:00
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Value result = VALUE_KNOWN_WIN + PawnValueEg + Value(rank_of(psq));
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2011-11-12 20:44:06 +01:00
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2013-11-30 20:12:34 +01:00
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return strongSide == pos.side_to_move() ? result : -result;
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2011-11-12 20:44:06 +01:00
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}
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/// KR vs KP. This is a somewhat tricky endgame to evaluate precisely without
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/// a bitbase. The function below returns drawish scores when the pawn is
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/// far advanced with support of the king, while the attacking king is far
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/// away.
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template<>
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2012-01-01 01:52:19 +01:00
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Value Endgame<KRKP>::operator()(const Position& pos) const {
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2011-11-12 20:44:06 +01:00
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2013-11-30 20:12:34 +01:00
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assert(verify_material(pos, strongSide, RookValueMg, 0));
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assert(verify_material(pos, weakSide, VALUE_ZERO, 1));
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2011-11-12 20:44:06 +01:00
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2013-11-30 20:12:34 +01:00
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Square wksq = relative_square(strongSide, pos.king_square(strongSide));
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Square bksq = relative_square(strongSide, pos.king_square(weakSide));
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Square rsq = relative_square(strongSide, pos.list<ROOK>(strongSide)[0]);
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Square psq = relative_square(strongSide, pos.list<PAWN>(weakSide)[0]);
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2011-11-12 20:44:06 +01:00
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2014-05-31 14:23:03 +02:00
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Square queeningSq = make_square(file_of(psq), RANK_1);
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2011-11-12 20:44:06 +01:00
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Value result;
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// If the stronger side's king is in front of the pawn, it's a win
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2013-11-30 20:12:34 +01:00
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if (wksq < psq && file_of(wksq) == file_of(psq))
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2014-05-31 14:23:03 +02:00
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result = RookValueEg - square_distance(wksq, psq);
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2011-11-12 20:44:06 +01:00
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// If the weaker side's king is too far from the pawn and the rook,
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2013-11-30 20:12:34 +01:00
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// it's a win.
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else if ( square_distance(bksq, psq) >= 3 + (pos.side_to_move() == weakSide)
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&& square_distance(bksq, rsq) >= 3)
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2014-05-31 14:23:03 +02:00
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result = RookValueEg - square_distance(wksq, psq);
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2011-11-12 20:44:06 +01:00
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// If the pawn is far advanced and supported by the defending king,
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// the position is drawish
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2012-01-01 01:52:19 +01:00
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else if ( rank_of(bksq) <= RANK_3
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2013-11-30 20:12:34 +01:00
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&& square_distance(bksq, psq) == 1
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2012-01-01 01:52:19 +01:00
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&& rank_of(wksq) >= RANK_4
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2013-11-30 20:12:34 +01:00
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&& square_distance(wksq, psq) > 2 + (pos.side_to_move() == strongSide))
|
2014-05-31 14:23:03 +02:00
|
|
|
result = Value(80) - 8 * square_distance(wksq, psq);
|
2011-11-12 20:44:06 +01:00
|
|
|
|
|
|
|
else
|
2014-05-31 14:23:03 +02:00
|
|
|
result = Value(200) - 8 * ( square_distance(wksq, psq + DELTA_S)
|
|
|
|
- square_distance(bksq, psq + DELTA_S)
|
|
|
|
- square_distance(psq, queeningSq));
|
2011-11-12 20:44:06 +01:00
|
|
|
|
2013-11-30 20:12:34 +01:00
|
|
|
return strongSide == pos.side_to_move() ? result : -result;
|
2011-11-12 20:44:06 +01:00
|
|
|
}
|
|
|
|
|
|
|
|
|
|
|
|
/// KR vs KB. This is very simple, and always returns drawish scores. The
|
|
|
|
/// score is slightly bigger when the defending king is close to the edge.
|
|
|
|
template<>
|
2012-01-01 01:52:19 +01:00
|
|
|
Value Endgame<KRKB>::operator()(const Position& pos) const {
|
2011-11-12 20:44:06 +01:00
|
|
|
|
2013-11-30 20:12:34 +01:00
|
|
|
assert(verify_material(pos, strongSide, RookValueMg, 0));
|
|
|
|
assert(verify_material(pos, weakSide, BishopValueMg, 0));
|
2011-11-12 20:44:06 +01:00
|
|
|
|
2013-11-30 20:12:34 +01:00
|
|
|
Value result = Value(PushToEdges[pos.king_square(weakSide)]);
|
|
|
|
return strongSide == pos.side_to_move() ? result : -result;
|
2011-11-12 20:44:06 +01:00
|
|
|
}
|
|
|
|
|
|
|
|
|
2014-05-31 14:23:03 +02:00
|
|
|
/// KR vs KN. The attacking side has slightly better winning chances than
|
2011-11-12 20:44:06 +01:00
|
|
|
/// in KR vs KB, particularly if the king and the knight are far apart.
|
|
|
|
template<>
|
2012-01-01 01:52:19 +01:00
|
|
|
Value Endgame<KRKN>::operator()(const Position& pos) const {
|
2011-11-12 20:44:06 +01:00
|
|
|
|
2013-11-30 20:12:34 +01:00
|
|
|
assert(verify_material(pos, strongSide, RookValueMg, 0));
|
|
|
|
assert(verify_material(pos, weakSide, KnightValueMg, 0));
|
2011-11-12 20:44:06 +01:00
|
|
|
|
2013-11-30 20:12:34 +01:00
|
|
|
Square bksq = pos.king_square(weakSide);
|
|
|
|
Square bnsq = pos.list<KNIGHT>(weakSide)[0];
|
|
|
|
Value result = Value(PushToEdges[bksq] + PushAway[square_distance(bksq, bnsq)]);
|
|
|
|
return strongSide == pos.side_to_move() ? result : -result;
|
2011-11-12 20:44:06 +01:00
|
|
|
}
|
|
|
|
|
|
|
|
|
2014-05-31 14:23:03 +02:00
|
|
|
/// KQ vs KP. In general, this is a win for the stronger side, but there are a
|
|
|
|
/// few important exceptions. A pawn on 7th rank and on the A,C,F or H files
|
|
|
|
/// with a king positioned next to it can be a draw, so in that case, we only
|
|
|
|
/// use the distance between the kings.
|
2013-05-03 19:03:42 +02:00
|
|
|
template<>
|
|
|
|
Value Endgame<KQKP>::operator()(const Position& pos) const {
|
|
|
|
|
2013-11-30 20:12:34 +01:00
|
|
|
assert(verify_material(pos, strongSide, QueenValueMg, 0));
|
|
|
|
assert(verify_material(pos, weakSide, VALUE_ZERO, 1));
|
2013-05-03 19:03:42 +02:00
|
|
|
|
2013-11-30 20:12:34 +01:00
|
|
|
Square winnerKSq = pos.king_square(strongSide);
|
|
|
|
Square loserKSq = pos.king_square(weakSide);
|
|
|
|
Square pawnSq = pos.list<PAWN>(weakSide)[0];
|
2013-05-03 19:03:42 +02:00
|
|
|
|
2013-11-30 20:12:34 +01:00
|
|
|
Value result = Value(PushClose[square_distance(winnerKSq, loserKSq)]);
|
2013-05-03 19:03:42 +02:00
|
|
|
|
2013-11-30 20:12:34 +01:00
|
|
|
if ( relative_rank(weakSide, pawnSq) != RANK_7
|
|
|
|
|| square_distance(loserKSq, pawnSq) != 1
|
|
|
|
|| !((FileABB | FileCBB | FileFBB | FileHBB) & pawnSq))
|
|
|
|
result += QueenValueEg - PawnValueEg;
|
2013-05-03 19:03:42 +02:00
|
|
|
|
2013-11-30 20:12:34 +01:00
|
|
|
return strongSide == pos.side_to_move() ? result : -result;
|
2013-05-03 19:03:42 +02:00
|
|
|
}
|
|
|
|
|
|
|
|
|
2011-11-12 20:44:06 +01:00
|
|
|
/// KQ vs KR. This is almost identical to KX vs K: We give the attacking
|
|
|
|
/// king a bonus for having the kings close together, and for forcing the
|
2014-05-31 14:23:03 +02:00
|
|
|
/// defending king towards the edge. If we also take care to avoid null move for
|
|
|
|
/// the defending side in the search, this is usually sufficient to win KQ vs KR.
|
2011-11-12 20:44:06 +01:00
|
|
|
template<>
|
2012-01-01 01:52:19 +01:00
|
|
|
Value Endgame<KQKR>::operator()(const Position& pos) const {
|
2011-11-12 20:44:06 +01:00
|
|
|
|
2013-11-30 20:12:34 +01:00
|
|
|
assert(verify_material(pos, strongSide, QueenValueMg, 0));
|
|
|
|
assert(verify_material(pos, weakSide, RookValueMg, 0));
|
2011-11-12 20:44:06 +01:00
|
|
|
|
2013-11-30 20:12:34 +01:00
|
|
|
Square winnerKSq = pos.king_square(strongSide);
|
|
|
|
Square loserKSq = pos.king_square(weakSide);
|
2011-11-12 20:44:06 +01:00
|
|
|
|
2012-09-16 17:16:15 +02:00
|
|
|
Value result = QueenValueEg
|
|
|
|
- RookValueEg
|
2013-11-30 20:12:34 +01:00
|
|
|
+ PushToEdges[loserKSq]
|
|
|
|
+ PushClose[square_distance(winnerKSq, loserKSq)];
|
2011-11-12 20:44:06 +01:00
|
|
|
|
2013-11-30 20:12:34 +01:00
|
|
|
return strongSide == pos.side_to_move() ? result : -result;
|
2011-11-12 20:44:06 +01:00
|
|
|
}
|
|
|
|
|
|
|
|
|
2013-08-20 20:02:33 +02:00
|
|
|
/// Some cases of trivial draws
|
|
|
|
template<> Value Endgame<KNNK>::operator()(const Position&) const { return VALUE_DRAW; }
|
2011-11-12 20:44:06 +01:00
|
|
|
|
|
|
|
|
2014-05-31 14:23:03 +02:00
|
|
|
/// KB and one or more pawns vs K. It checks for draws with rook pawns and
|
2012-01-01 01:52:19 +01:00
|
|
|
/// a bishop of the wrong color. If such a draw is detected, SCALE_FACTOR_DRAW
|
|
|
|
/// is returned. If not, the return value is SCALE_FACTOR_NONE, i.e. no scaling
|
2011-11-12 20:44:06 +01:00
|
|
|
/// will be used.
|
|
|
|
template<>
|
2012-01-01 01:52:19 +01:00
|
|
|
ScaleFactor Endgame<KBPsK>::operator()(const Position& pos) const {
|
2011-11-12 20:44:06 +01:00
|
|
|
|
2013-11-30 20:12:34 +01:00
|
|
|
assert(pos.non_pawn_material(strongSide) == BishopValueMg);
|
|
|
|
assert(pos.count<PAWN>(strongSide) >= 1);
|
2011-11-12 20:44:06 +01:00
|
|
|
|
2013-11-30 20:12:34 +01:00
|
|
|
// No assertions about the material of weakSide, because we want draws to
|
2011-11-12 20:44:06 +01:00
|
|
|
// be detected even when the weaker side has some pawns.
|
|
|
|
|
2013-11-30 20:12:34 +01:00
|
|
|
Bitboard pawns = pos.pieces(strongSide, PAWN);
|
|
|
|
File pawnFile = file_of(pos.list<PAWN>(strongSide)[0]);
|
2011-11-12 20:44:06 +01:00
|
|
|
|
|
|
|
// All pawns are on a single rook file ?
|
2012-06-04 18:25:51 +02:00
|
|
|
if ( (pawnFile == FILE_A || pawnFile == FILE_H)
|
2012-01-01 01:52:19 +01:00
|
|
|
&& !(pawns & ~file_bb(pawnFile)))
|
2011-11-12 20:44:06 +01:00
|
|
|
{
|
2013-11-30 20:12:34 +01:00
|
|
|
Square bishopSq = pos.list<BISHOP>(strongSide)[0];
|
2014-05-31 14:23:03 +02:00
|
|
|
Square queeningSq = relative_square(strongSide, make_square(pawnFile, RANK_8));
|
2013-11-30 20:12:34 +01:00
|
|
|
Square kingSq = pos.king_square(weakSide);
|
2011-11-12 20:44:06 +01:00
|
|
|
|
2012-01-01 01:52:19 +01:00
|
|
|
if ( opposite_colors(queeningSq, bishopSq)
|
2013-11-30 20:12:34 +01:00
|
|
|
&& square_distance(queeningSq, kingSq) <= 1)
|
|
|
|
return SCALE_FACTOR_DRAW;
|
2011-11-12 20:44:06 +01:00
|
|
|
}
|
2013-05-03 19:03:42 +02:00
|
|
|
|
2014-05-31 14:23:03 +02:00
|
|
|
// If all the pawns are on the same B or G file, then it's potentially a draw
|
2013-05-03 19:03:42 +02:00
|
|
|
if ( (pawnFile == FILE_B || pawnFile == FILE_G)
|
|
|
|
&& !(pos.pieces(PAWN) & ~file_bb(pawnFile))
|
2013-11-30 20:12:34 +01:00
|
|
|
&& pos.non_pawn_material(weakSide) == 0
|
|
|
|
&& pos.count<PAWN>(weakSide) >= 1)
|
2013-05-03 19:03:42 +02:00
|
|
|
{
|
2014-05-31 14:23:03 +02:00
|
|
|
// Get weakSide pawn that is closest to the home rank
|
2013-11-30 20:12:34 +01:00
|
|
|
Square weakPawnSq = backmost_sq(weakSide, pos.pieces(weakSide, PAWN));
|
|
|
|
|
|
|
|
Square strongKingSq = pos.king_square(strongSide);
|
|
|
|
Square weakKingSq = pos.king_square(weakSide);
|
|
|
|
Square bishopSq = pos.list<BISHOP>(strongSide)[0];
|
|
|
|
|
2014-05-31 14:23:03 +02:00
|
|
|
// There's potential for a draw if our pawn is blocked on the 7th rank,
|
2013-11-30 20:12:34 +01:00
|
|
|
// the bishop cannot attack it or they only have one pawn left
|
|
|
|
if ( relative_rank(strongSide, weakPawnSq) == RANK_7
|
|
|
|
&& (pos.pieces(strongSide, PAWN) & (weakPawnSq + pawn_push(weakSide)))
|
|
|
|
&& (opposite_colors(bishopSq, weakPawnSq) || pos.count<PAWN>(strongSide) == 1))
|
|
|
|
{
|
|
|
|
int strongKingDist = square_distance(weakPawnSq, strongKingSq);
|
|
|
|
int weakKingDist = square_distance(weakPawnSq, weakKingSq);
|
|
|
|
|
2014-05-31 14:23:03 +02:00
|
|
|
// It's a draw if the weak king is on its back two ranks, within 2
|
2013-11-30 20:12:34 +01:00
|
|
|
// squares of the blocking pawn and the strong king is not
|
|
|
|
// closer. (I think this rule only fails in practically
|
|
|
|
// unreachable positions such as 5k1K/6p1/6P1/8/8/3B4/8/8 w
|
|
|
|
// and positions where qsearch will immediately correct the
|
|
|
|
// problem such as 8/4k1p1/6P1/1K6/3B4/8/8/8 w)
|
|
|
|
if ( relative_rank(strongSide, weakKingSq) >= RANK_7
|
|
|
|
&& weakKingDist <= 2
|
|
|
|
&& weakKingDist <= strongKingDist)
|
|
|
|
return SCALE_FACTOR_DRAW;
|
|
|
|
}
|
2013-05-03 19:03:42 +02:00
|
|
|
}
|
|
|
|
|
2011-11-12 20:44:06 +01:00
|
|
|
return SCALE_FACTOR_NONE;
|
|
|
|
}
|
|
|
|
|
|
|
|
|
2014-05-31 14:23:03 +02:00
|
|
|
/// KQ vs KR and one or more pawns. It tests for fortress draws with a rook on
|
|
|
|
/// the third rank defended by a pawn.
|
2011-11-12 20:44:06 +01:00
|
|
|
template<>
|
2012-01-01 01:52:19 +01:00
|
|
|
ScaleFactor Endgame<KQKRPs>::operator()(const Position& pos) const {
|
2011-11-12 20:44:06 +01:00
|
|
|
|
2013-11-30 20:12:34 +01:00
|
|
|
assert(verify_material(pos, strongSide, QueenValueMg, 0));
|
|
|
|
assert(pos.count<ROOK>(weakSide) == 1);
|
|
|
|
assert(pos.count<PAWN>(weakSide) >= 1);
|
|
|
|
|
|
|
|
Square kingSq = pos.king_square(weakSide);
|
|
|
|
Square rsq = pos.list<ROOK>(weakSide)[0];
|
|
|
|
|
|
|
|
if ( relative_rank(weakSide, kingSq) <= RANK_2
|
|
|
|
&& relative_rank(weakSide, pos.king_square(strongSide)) >= RANK_4
|
|
|
|
&& relative_rank(weakSide, rsq) == RANK_3
|
|
|
|
&& ( pos.pieces(weakSide, PAWN)
|
|
|
|
& pos.attacks_from<KING>(kingSq)
|
|
|
|
& pos.attacks_from<PAWN>(rsq, strongSide)))
|
2012-01-01 01:52:19 +01:00
|
|
|
return SCALE_FACTOR_DRAW;
|
2013-11-30 20:12:34 +01:00
|
|
|
|
2011-11-12 20:44:06 +01:00
|
|
|
return SCALE_FACTOR_NONE;
|
|
|
|
}
|
|
|
|
|
|
|
|
|
2014-05-31 14:23:03 +02:00
|
|
|
/// KRP vs KR. This function knows a handful of the most important classes of
|
|
|
|
/// drawn positions, but is far from perfect. It would probably be a good idea
|
|
|
|
/// to add more knowledge in the future.
|
2011-11-12 20:44:06 +01:00
|
|
|
///
|
|
|
|
/// It would also be nice to rewrite the actual code for this function,
|
2014-05-31 14:23:03 +02:00
|
|
|
/// which is mostly copied from Glaurung 1.x, and isn't very pretty.
|
2011-11-12 20:44:06 +01:00
|
|
|
template<>
|
2012-01-01 01:52:19 +01:00
|
|
|
ScaleFactor Endgame<KRPKR>::operator()(const Position& pos) const {
|
2011-11-12 20:44:06 +01:00
|
|
|
|
2013-11-30 20:12:34 +01:00
|
|
|
assert(verify_material(pos, strongSide, RookValueMg, 1));
|
|
|
|
assert(verify_material(pos, weakSide, RookValueMg, 0));
|
2011-11-12 20:44:06 +01:00
|
|
|
|
2013-11-30 20:12:34 +01:00
|
|
|
// Assume strongSide is white and the pawn is on files A-D
|
|
|
|
Square wksq = normalize(pos, strongSide, pos.king_square(strongSide));
|
|
|
|
Square bksq = normalize(pos, strongSide, pos.king_square(weakSide));
|
|
|
|
Square wrsq = normalize(pos, strongSide, pos.list<ROOK>(strongSide)[0]);
|
|
|
|
Square wpsq = normalize(pos, strongSide, pos.list<PAWN>(strongSide)[0]);
|
|
|
|
Square brsq = normalize(pos, strongSide, pos.list<ROOK>(weakSide)[0]);
|
2011-11-12 20:44:06 +01:00
|
|
|
|
2012-01-01 01:52:19 +01:00
|
|
|
File f = file_of(wpsq);
|
|
|
|
Rank r = rank_of(wpsq);
|
2014-05-31 14:23:03 +02:00
|
|
|
Square queeningSq = make_square(f, RANK_8);
|
2013-11-30 20:12:34 +01:00
|
|
|
int tempo = (pos.side_to_move() == strongSide);
|
2011-11-12 20:44:06 +01:00
|
|
|
|
|
|
|
// If the pawn is not too far advanced and the defending king defends the
|
|
|
|
// queening square, use the third-rank defence.
|
|
|
|
if ( r <= RANK_5
|
|
|
|
&& square_distance(bksq, queeningSq) <= 1
|
|
|
|
&& wksq <= SQ_H5
|
2012-01-01 01:52:19 +01:00
|
|
|
&& (rank_of(brsq) == RANK_6 || (r <= RANK_3 && rank_of(wrsq) != RANK_6)))
|
|
|
|
return SCALE_FACTOR_DRAW;
|
2011-11-12 20:44:06 +01:00
|
|
|
|
|
|
|
// The defending side saves a draw by checking from behind in case the pawn
|
|
|
|
// has advanced to the 6th rank with the king behind.
|
|
|
|
if ( r == RANK_6
|
|
|
|
&& square_distance(bksq, queeningSq) <= 1
|
2012-01-01 01:52:19 +01:00
|
|
|
&& rank_of(wksq) + tempo <= RANK_6
|
|
|
|
&& (rank_of(brsq) == RANK_1 || (!tempo && abs(file_of(brsq) - f) >= 3)))
|
|
|
|
return SCALE_FACTOR_DRAW;
|
2011-11-12 20:44:06 +01:00
|
|
|
|
|
|
|
if ( r >= RANK_6
|
|
|
|
&& bksq == queeningSq
|
2012-01-01 01:52:19 +01:00
|
|
|
&& rank_of(brsq) == RANK_1
|
2011-11-12 20:44:06 +01:00
|
|
|
&& (!tempo || square_distance(wksq, wpsq) >= 2))
|
2012-01-01 01:52:19 +01:00
|
|
|
return SCALE_FACTOR_DRAW;
|
2011-11-12 20:44:06 +01:00
|
|
|
|
|
|
|
// White pawn on a7 and rook on a8 is a draw if black's king is on g7 or h7
|
|
|
|
// and the black rook is behind the pawn.
|
|
|
|
if ( wpsq == SQ_A7
|
|
|
|
&& wrsq == SQ_A8
|
|
|
|
&& (bksq == SQ_H7 || bksq == SQ_G7)
|
2012-01-01 01:52:19 +01:00
|
|
|
&& file_of(brsq) == FILE_A
|
|
|
|
&& (rank_of(brsq) <= RANK_3 || file_of(wksq) >= FILE_D || rank_of(wksq) <= RANK_5))
|
|
|
|
return SCALE_FACTOR_DRAW;
|
2011-11-12 20:44:06 +01:00
|
|
|
|
|
|
|
// If the defending king blocks the pawn and the attacking king is too far
|
|
|
|
// away, it's a draw.
|
|
|
|
if ( r <= RANK_5
|
|
|
|
&& bksq == wpsq + DELTA_N
|
|
|
|
&& square_distance(wksq, wpsq) - tempo >= 2
|
|
|
|
&& square_distance(wksq, brsq) - tempo >= 2)
|
2012-01-01 01:52:19 +01:00
|
|
|
return SCALE_FACTOR_DRAW;
|
2011-11-12 20:44:06 +01:00
|
|
|
|
|
|
|
// Pawn on the 7th rank supported by the rook from behind usually wins if the
|
|
|
|
// attacking king is closer to the queening square than the defending king,
|
|
|
|
// and the defending king cannot gain tempi by threatening the attacking rook.
|
|
|
|
if ( r == RANK_7
|
|
|
|
&& f != FILE_A
|
2012-01-01 01:52:19 +01:00
|
|
|
&& file_of(wrsq) == f
|
2011-11-12 20:44:06 +01:00
|
|
|
&& wrsq != queeningSq
|
|
|
|
&& (square_distance(wksq, queeningSq) < square_distance(bksq, queeningSq) - 2 + tempo)
|
|
|
|
&& (square_distance(wksq, queeningSq) < square_distance(bksq, wrsq) + tempo))
|
|
|
|
return ScaleFactor(SCALE_FACTOR_MAX - 2 * square_distance(wksq, queeningSq));
|
|
|
|
|
|
|
|
// Similar to the above, but with the pawn further back
|
|
|
|
if ( f != FILE_A
|
2012-01-01 01:52:19 +01:00
|
|
|
&& file_of(wrsq) == f
|
2011-11-12 20:44:06 +01:00
|
|
|
&& wrsq < wpsq
|
|
|
|
&& (square_distance(wksq, queeningSq) < square_distance(bksq, queeningSq) - 2 + tempo)
|
|
|
|
&& (square_distance(wksq, wpsq + DELTA_N) < square_distance(bksq, wpsq + DELTA_N) - 2 + tempo)
|
|
|
|
&& ( square_distance(bksq, wrsq) + tempo >= 3
|
|
|
|
|| ( square_distance(wksq, queeningSq) < square_distance(bksq, wrsq) + tempo
|
|
|
|
&& (square_distance(wksq, wpsq + DELTA_N) < square_distance(bksq, wrsq) + tempo))))
|
|
|
|
return ScaleFactor( SCALE_FACTOR_MAX
|
|
|
|
- 8 * square_distance(wpsq, queeningSq)
|
|
|
|
- 2 * square_distance(wksq, queeningSq));
|
|
|
|
|
2014-05-31 14:23:03 +02:00
|
|
|
// If the pawn is not far advanced and the defending king is somewhere in
|
2011-11-12 20:44:06 +01:00
|
|
|
// the pawn's path, it's probably a draw.
|
|
|
|
if (r <= RANK_4 && bksq > wpsq)
|
|
|
|
{
|
2012-01-01 01:52:19 +01:00
|
|
|
if (file_of(bksq) == file_of(wpsq))
|
2011-11-12 20:44:06 +01:00
|
|
|
return ScaleFactor(10);
|
2012-01-01 01:52:19 +01:00
|
|
|
if ( abs(file_of(bksq) - file_of(wpsq)) == 1
|
2011-11-12 20:44:06 +01:00
|
|
|
&& square_distance(wksq, bksq) > 2)
|
|
|
|
return ScaleFactor(24 - 2 * square_distance(wksq, bksq));
|
|
|
|
}
|
|
|
|
return SCALE_FACTOR_NONE;
|
|
|
|
}
|
|
|
|
|
2013-11-30 20:12:34 +01:00
|
|
|
template<>
|
|
|
|
ScaleFactor Endgame<KRPKB>::operator()(const Position& pos) const {
|
|
|
|
|
|
|
|
assert(verify_material(pos, strongSide, RookValueMg, 1));
|
|
|
|
assert(verify_material(pos, weakSide, BishopValueMg, 0));
|
|
|
|
|
|
|
|
// Test for a rook pawn
|
|
|
|
if (pos.pieces(PAWN) & (FileABB | FileHBB))
|
|
|
|
{
|
|
|
|
Square ksq = pos.king_square(weakSide);
|
|
|
|
Square bsq = pos.list<BISHOP>(weakSide)[0];
|
|
|
|
Square psq = pos.list<PAWN>(strongSide)[0];
|
|
|
|
Rank rk = relative_rank(strongSide, psq);
|
|
|
|
Square push = pawn_push(strongSide);
|
|
|
|
|
|
|
|
// If the pawn is on the 5th rank and the pawn (currently) is on
|
|
|
|
// the same color square as the bishop then there is a chance of
|
|
|
|
// a fortress. Depending on the king position give a moderate
|
|
|
|
// reduction or a stronger one if the defending king is near the
|
|
|
|
// corner but not trapped there.
|
|
|
|
if (rk == RANK_5 && !opposite_colors(bsq, psq))
|
|
|
|
{
|
|
|
|
int d = square_distance(psq + 3 * push, ksq);
|
|
|
|
|
|
|
|
if (d <= 2 && !(d == 0 && ksq == pos.king_square(strongSide) + 2 * push))
|
|
|
|
return ScaleFactor(24);
|
|
|
|
else
|
|
|
|
return ScaleFactor(48);
|
|
|
|
}
|
|
|
|
|
|
|
|
// When the pawn has moved to the 6th rank we can be fairly sure
|
|
|
|
// it's drawn if the bishop attacks the square in front of the
|
|
|
|
// pawn from a reasonable distance and the defending king is near
|
|
|
|
// the corner
|
|
|
|
if ( rk == RANK_6
|
|
|
|
&& square_distance(psq + 2 * push, ksq) <= 1
|
|
|
|
&& (PseudoAttacks[BISHOP][bsq] & (psq + push))
|
|
|
|
&& file_distance(bsq, psq) >= 2)
|
|
|
|
return ScaleFactor(8);
|
|
|
|
}
|
|
|
|
|
|
|
|
return SCALE_FACTOR_NONE;
|
|
|
|
}
|
2011-11-12 20:44:06 +01:00
|
|
|
|
2014-05-31 14:23:03 +02:00
|
|
|
/// KRPP vs KRP. There is just a single rule: if the stronger side has no passed
|
|
|
|
/// pawns and the defending king is actively placed, the position is drawish.
|
2011-11-12 20:44:06 +01:00
|
|
|
template<>
|
2012-01-01 01:52:19 +01:00
|
|
|
ScaleFactor Endgame<KRPPKRP>::operator()(const Position& pos) const {
|
2011-11-12 20:44:06 +01:00
|
|
|
|
2013-11-30 20:12:34 +01:00
|
|
|
assert(verify_material(pos, strongSide, RookValueMg, 2));
|
|
|
|
assert(verify_material(pos, weakSide, RookValueMg, 1));
|
2011-11-12 20:44:06 +01:00
|
|
|
|
2013-11-30 20:12:34 +01:00
|
|
|
Square wpsq1 = pos.list<PAWN>(strongSide)[0];
|
|
|
|
Square wpsq2 = pos.list<PAWN>(strongSide)[1];
|
|
|
|
Square bksq = pos.king_square(weakSide);
|
2011-11-12 20:44:06 +01:00
|
|
|
|
|
|
|
// Does the stronger side have a passed pawn?
|
2013-11-30 20:12:34 +01:00
|
|
|
if (pos.pawn_passed(strongSide, wpsq1) || pos.pawn_passed(strongSide, wpsq2))
|
2011-11-12 20:44:06 +01:00
|
|
|
return SCALE_FACTOR_NONE;
|
|
|
|
|
2013-11-30 20:12:34 +01:00
|
|
|
Rank r = std::max(relative_rank(strongSide, wpsq1), relative_rank(strongSide, wpsq2));
|
2011-11-12 20:44:06 +01:00
|
|
|
|
|
|
|
if ( file_distance(bksq, wpsq1) <= 1
|
|
|
|
&& file_distance(bksq, wpsq2) <= 1
|
2013-11-30 20:12:34 +01:00
|
|
|
&& relative_rank(strongSide, bksq) > r)
|
2011-11-12 20:44:06 +01:00
|
|
|
{
|
|
|
|
switch (r) {
|
|
|
|
case RANK_2: return ScaleFactor(10);
|
|
|
|
case RANK_3: return ScaleFactor(10);
|
|
|
|
case RANK_4: return ScaleFactor(15);
|
|
|
|
case RANK_5: return ScaleFactor(20);
|
|
|
|
case RANK_6: return ScaleFactor(40);
|
|
|
|
default: assert(false);
|
|
|
|
}
|
|
|
|
}
|
|
|
|
return SCALE_FACTOR_NONE;
|
|
|
|
}
|
|
|
|
|
|
|
|
|
2012-01-01 01:52:19 +01:00
|
|
|
/// K and two or more pawns vs K. There is just a single rule here: If all pawns
|
|
|
|
/// are on the same rook file and are blocked by the defending king, it's a draw.
|
2011-11-12 20:44:06 +01:00
|
|
|
template<>
|
2012-01-01 01:52:19 +01:00
|
|
|
ScaleFactor Endgame<KPsK>::operator()(const Position& pos) const {
|
2011-11-12 20:44:06 +01:00
|
|
|
|
2013-11-30 20:12:34 +01:00
|
|
|
assert(pos.non_pawn_material(strongSide) == VALUE_ZERO);
|
|
|
|
assert(pos.count<PAWN>(strongSide) >= 2);
|
|
|
|
assert(verify_material(pos, weakSide, VALUE_ZERO, 0));
|
2011-11-12 20:44:06 +01:00
|
|
|
|
2013-11-30 20:12:34 +01:00
|
|
|
Square ksq = pos.king_square(weakSide);
|
|
|
|
Bitboard pawns = pos.pieces(strongSide, PAWN);
|
|
|
|
Square psq = pos.list<PAWN>(strongSide)[0];
|
|
|
|
|
2014-05-31 14:23:03 +02:00
|
|
|
// If all pawns are ahead of the king, on a single rook file and
|
|
|
|
// the king is within one file of the pawns, it's a draw.
|
2013-11-30 20:12:34 +01:00
|
|
|
if ( !(pawns & ~in_front_bb(weakSide, rank_of(ksq)))
|
|
|
|
&& !((pawns & ~FileABB) && (pawns & ~FileHBB))
|
|
|
|
&& file_distance(ksq, psq) <= 1)
|
|
|
|
return SCALE_FACTOR_DRAW;
|
2011-11-12 20:44:06 +01:00
|
|
|
|
|
|
|
return SCALE_FACTOR_NONE;
|
|
|
|
}
|
|
|
|
|
|
|
|
|
2014-05-31 14:23:03 +02:00
|
|
|
/// KBP vs KB. There are two rules: if the defending king is somewhere along the
|
|
|
|
/// path of the pawn, and the square of the king is not of the same color as the
|
|
|
|
/// stronger side's bishop, it's a draw. If the two bishops have opposite color,
|
|
|
|
/// it's almost always a draw.
|
2011-11-12 20:44:06 +01:00
|
|
|
template<>
|
2012-01-01 01:52:19 +01:00
|
|
|
ScaleFactor Endgame<KBPKB>::operator()(const Position& pos) const {
|
2011-11-12 20:44:06 +01:00
|
|
|
|
2013-11-30 20:12:34 +01:00
|
|
|
assert(verify_material(pos, strongSide, BishopValueMg, 1));
|
|
|
|
assert(verify_material(pos, weakSide, BishopValueMg, 0));
|
2013-08-20 20:02:33 +02:00
|
|
|
|
2013-11-30 20:12:34 +01:00
|
|
|
Square pawnSq = pos.list<PAWN>(strongSide)[0];
|
|
|
|
Square strongBishopSq = pos.list<BISHOP>(strongSide)[0];
|
|
|
|
Square weakBishopSq = pos.list<BISHOP>(weakSide)[0];
|
|
|
|
Square weakKingSq = pos.king_square(weakSide);
|
2011-11-12 20:44:06 +01:00
|
|
|
|
|
|
|
// Case 1: Defending king blocks the pawn, and cannot be driven away
|
2013-11-30 20:12:34 +01:00
|
|
|
if ( file_of(weakKingSq) == file_of(pawnSq)
|
|
|
|
&& relative_rank(strongSide, pawnSq) < relative_rank(strongSide, weakKingSq)
|
|
|
|
&& ( opposite_colors(weakKingSq, strongBishopSq)
|
|
|
|
|| relative_rank(strongSide, weakKingSq) <= RANK_6))
|
2012-01-01 01:52:19 +01:00
|
|
|
return SCALE_FACTOR_DRAW;
|
2011-11-12 20:44:06 +01:00
|
|
|
|
|
|
|
// Case 2: Opposite colored bishops
|
2013-11-30 20:12:34 +01:00
|
|
|
if (opposite_colors(strongBishopSq, weakBishopSq))
|
2011-11-12 20:44:06 +01:00
|
|
|
{
|
|
|
|
// We assume that the position is drawn in the following three situations:
|
|
|
|
//
|
|
|
|
// a. The pawn is on rank 5 or further back.
|
|
|
|
// b. The defending king is somewhere in the pawn's path.
|
|
|
|
// c. The defending bishop attacks some square along the pawn's path,
|
|
|
|
// and is at least three squares away from the pawn.
|
|
|
|
//
|
|
|
|
// These rules are probably not perfect, but in practice they work
|
|
|
|
// reasonably well.
|
|
|
|
|
2013-11-30 20:12:34 +01:00
|
|
|
if (relative_rank(strongSide, pawnSq) <= RANK_5)
|
2012-01-01 01:52:19 +01:00
|
|
|
return SCALE_FACTOR_DRAW;
|
2011-11-12 20:44:06 +01:00
|
|
|
else
|
|
|
|
{
|
2013-11-30 20:12:34 +01:00
|
|
|
Bitboard path = forward_bb(strongSide, pawnSq);
|
2011-11-12 20:44:06 +01:00
|
|
|
|
2013-11-30 20:12:34 +01:00
|
|
|
if (path & pos.pieces(weakSide, KING))
|
2012-01-01 01:52:19 +01:00
|
|
|
return SCALE_FACTOR_DRAW;
|
2011-11-12 20:44:06 +01:00
|
|
|
|
2013-11-30 20:12:34 +01:00
|
|
|
if ( (pos.attacks_from<BISHOP>(weakBishopSq) & path)
|
|
|
|
&& square_distance(weakBishopSq, pawnSq) >= 3)
|
2012-01-01 01:52:19 +01:00
|
|
|
return SCALE_FACTOR_DRAW;
|
2011-11-12 20:44:06 +01:00
|
|
|
}
|
|
|
|
}
|
|
|
|
return SCALE_FACTOR_NONE;
|
|
|
|
}
|
|
|
|
|
|
|
|
|
2014-05-31 14:23:03 +02:00
|
|
|
/// KBPP vs KB. It detects a few basic draws with opposite-colored bishops
|
2011-11-12 20:44:06 +01:00
|
|
|
template<>
|
2012-01-01 01:52:19 +01:00
|
|
|
ScaleFactor Endgame<KBPPKB>::operator()(const Position& pos) const {
|
2011-11-12 20:44:06 +01:00
|
|
|
|
2013-11-30 20:12:34 +01:00
|
|
|
assert(verify_material(pos, strongSide, BishopValueMg, 2));
|
|
|
|
assert(verify_material(pos, weakSide, BishopValueMg, 0));
|
2011-11-12 20:44:06 +01:00
|
|
|
|
2013-11-30 20:12:34 +01:00
|
|
|
Square wbsq = pos.list<BISHOP>(strongSide)[0];
|
|
|
|
Square bbsq = pos.list<BISHOP>(weakSide)[0];
|
2011-11-12 20:44:06 +01:00
|
|
|
|
2012-01-01 01:52:19 +01:00
|
|
|
if (!opposite_colors(wbsq, bbsq))
|
2011-11-12 20:44:06 +01:00
|
|
|
return SCALE_FACTOR_NONE;
|
|
|
|
|
2013-11-30 20:12:34 +01:00
|
|
|
Square ksq = pos.king_square(weakSide);
|
|
|
|
Square psq1 = pos.list<PAWN>(strongSide)[0];
|
|
|
|
Square psq2 = pos.list<PAWN>(strongSide)[1];
|
2012-01-01 01:52:19 +01:00
|
|
|
Rank r1 = rank_of(psq1);
|
|
|
|
Rank r2 = rank_of(psq2);
|
2011-11-12 20:44:06 +01:00
|
|
|
Square blockSq1, blockSq2;
|
|
|
|
|
2013-11-30 20:12:34 +01:00
|
|
|
if (relative_rank(strongSide, psq1) > relative_rank(strongSide, psq2))
|
2011-11-12 20:44:06 +01:00
|
|
|
{
|
2013-11-30 20:12:34 +01:00
|
|
|
blockSq1 = psq1 + pawn_push(strongSide);
|
2014-05-31 14:23:03 +02:00
|
|
|
blockSq2 = make_square(file_of(psq2), rank_of(psq1));
|
2011-11-12 20:44:06 +01:00
|
|
|
}
|
|
|
|
else
|
|
|
|
{
|
2013-11-30 20:12:34 +01:00
|
|
|
blockSq1 = psq2 + pawn_push(strongSide);
|
2014-05-31 14:23:03 +02:00
|
|
|
blockSq2 = make_square(file_of(psq1), rank_of(psq2));
|
2011-11-12 20:44:06 +01:00
|
|
|
}
|
|
|
|
|
|
|
|
switch (file_distance(psq1, psq2))
|
|
|
|
{
|
|
|
|
case 0:
|
2014-05-31 14:23:03 +02:00
|
|
|
// Both pawns are on the same file. It's an easy draw if the defender firmly
|
|
|
|
// controls some square in the frontmost pawn's path.
|
2012-01-01 01:52:19 +01:00
|
|
|
if ( file_of(ksq) == file_of(blockSq1)
|
2013-11-30 20:12:34 +01:00
|
|
|
&& relative_rank(strongSide, ksq) >= relative_rank(strongSide, blockSq1)
|
2012-01-01 01:52:19 +01:00
|
|
|
&& opposite_colors(ksq, wbsq))
|
|
|
|
return SCALE_FACTOR_DRAW;
|
2011-11-12 20:44:06 +01:00
|
|
|
else
|
|
|
|
return SCALE_FACTOR_NONE;
|
|
|
|
|
|
|
|
case 1:
|
2014-05-31 14:23:03 +02:00
|
|
|
// Pawns on adjacent files. It's a draw if the defender firmly controls the
|
|
|
|
// square in front of the frontmost pawn's path, and the square diagonally
|
|
|
|
// behind this square on the file of the other pawn.
|
2011-11-12 20:44:06 +01:00
|
|
|
if ( ksq == blockSq1
|
2012-01-01 01:52:19 +01:00
|
|
|
&& opposite_colors(ksq, wbsq)
|
2011-11-12 20:44:06 +01:00
|
|
|
&& ( bbsq == blockSq2
|
2013-11-30 20:12:34 +01:00
|
|
|
|| (pos.attacks_from<BISHOP>(blockSq2) & pos.pieces(weakSide, BISHOP))
|
2011-11-12 20:44:06 +01:00
|
|
|
|| abs(r1 - r2) >= 2))
|
2012-01-01 01:52:19 +01:00
|
|
|
return SCALE_FACTOR_DRAW;
|
2011-11-12 20:44:06 +01:00
|
|
|
|
|
|
|
else if ( ksq == blockSq2
|
2012-01-01 01:52:19 +01:00
|
|
|
&& opposite_colors(ksq, wbsq)
|
2011-11-12 20:44:06 +01:00
|
|
|
&& ( bbsq == blockSq1
|
2013-11-30 20:12:34 +01:00
|
|
|
|| (pos.attacks_from<BISHOP>(blockSq1) & pos.pieces(weakSide, BISHOP))))
|
2012-01-01 01:52:19 +01:00
|
|
|
return SCALE_FACTOR_DRAW;
|
2011-11-12 20:44:06 +01:00
|
|
|
else
|
|
|
|
return SCALE_FACTOR_NONE;
|
|
|
|
|
|
|
|
default:
|
|
|
|
// The pawns are not on the same file or adjacent files. No scaling.
|
|
|
|
return SCALE_FACTOR_NONE;
|
|
|
|
}
|
|
|
|
}
|
|
|
|
|
|
|
|
|
2014-05-31 14:23:03 +02:00
|
|
|
/// KBP vs KN. There is a single rule: If the defending king is somewhere along
|
|
|
|
/// the path of the pawn, and the square of the king is not of the same color as
|
|
|
|
/// the stronger side's bishop, it's a draw.
|
2011-11-12 20:44:06 +01:00
|
|
|
template<>
|
2012-01-01 01:52:19 +01:00
|
|
|
ScaleFactor Endgame<KBPKN>::operator()(const Position& pos) const {
|
2011-11-12 20:44:06 +01:00
|
|
|
|
2013-11-30 20:12:34 +01:00
|
|
|
assert(verify_material(pos, strongSide, BishopValueMg, 1));
|
|
|
|
assert(verify_material(pos, weakSide, KnightValueMg, 0));
|
|
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Square pawnSq = pos.list<PAWN>(strongSide)[0];
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Square strongBishopSq = pos.list<BISHOP>(strongSide)[0];
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Square weakKingSq = pos.king_square(weakSide);
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if ( file_of(weakKingSq) == file_of(pawnSq)
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&& relative_rank(strongSide, pawnSq) < relative_rank(strongSide, weakKingSq)
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&& ( opposite_colors(weakKingSq, strongBishopSq)
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|| relative_rank(strongSide, weakKingSq) <= RANK_6))
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2012-01-01 01:52:19 +01:00
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return SCALE_FACTOR_DRAW;
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2011-11-12 20:44:06 +01:00
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return SCALE_FACTOR_NONE;
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}
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2014-05-31 14:23:03 +02:00
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/// KNP vs K. There is a single rule: if the pawn is a rook pawn on the 7th rank
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/// and the defending king prevents the pawn from advancing, the position is drawn.
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2011-11-12 20:44:06 +01:00
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template<>
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2012-01-01 01:52:19 +01:00
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ScaleFactor Endgame<KNPK>::operator()(const Position& pos) const {
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2011-11-12 20:44:06 +01:00
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2013-11-30 20:12:34 +01:00
|
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assert(verify_material(pos, strongSide, KnightValueMg, 1));
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assert(verify_material(pos, weakSide, VALUE_ZERO, 0));
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2011-11-12 20:44:06 +01:00
|
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|
2013-11-30 20:12:34 +01:00
|
|
|
// Assume strongSide is white and the pawn is on files A-D
|
|
|
|
Square pawnSq = normalize(pos, strongSide, pos.list<PAWN>(strongSide)[0]);
|
|
|
|
Square weakKingSq = normalize(pos, strongSide, pos.king_square(weakSide));
|
2011-11-12 20:44:06 +01:00
|
|
|
|
2013-11-30 20:12:34 +01:00
|
|
|
if (pawnSq == SQ_A7 && square_distance(SQ_A8, weakKingSq) <= 1)
|
2012-01-01 01:52:19 +01:00
|
|
|
return SCALE_FACTOR_DRAW;
|
2011-11-12 20:44:06 +01:00
|
|
|
|
|
|
|
return SCALE_FACTOR_NONE;
|
|
|
|
}
|
|
|
|
|
|
|
|
|
2014-05-31 14:23:03 +02:00
|
|
|
/// KNP vs KB. If knight can block bishop from taking pawn, it's a win.
|
|
|
|
/// Otherwise the position is drawn.
|
2013-05-03 19:03:42 +02:00
|
|
|
template<>
|
|
|
|
ScaleFactor Endgame<KNPKB>::operator()(const Position& pos) const {
|
|
|
|
|
2013-11-30 20:12:34 +01:00
|
|
|
Square pawnSq = pos.list<PAWN>(strongSide)[0];
|
|
|
|
Square bishopSq = pos.list<BISHOP>(weakSide)[0];
|
|
|
|
Square weakKingSq = pos.king_square(weakSide);
|
2013-05-03 19:03:42 +02:00
|
|
|
|
|
|
|
// King needs to get close to promoting pawn to prevent knight from blocking.
|
|
|
|
// Rules for this are very tricky, so just approximate.
|
2013-11-30 20:12:34 +01:00
|
|
|
if (forward_bb(strongSide, pawnSq) & pos.attacks_from<BISHOP>(bishopSq))
|
|
|
|
return ScaleFactor(square_distance(weakKingSq, pawnSq));
|
2013-05-03 19:03:42 +02:00
|
|
|
|
|
|
|
return SCALE_FACTOR_NONE;
|
|
|
|
}
|
|
|
|
|
|
|
|
|
2014-05-31 14:23:03 +02:00
|
|
|
/// KP vs KP. This is done by removing the weakest side's pawn and probing the
|
|
|
|
/// KP vs K bitbase: If the weakest side has a draw without the pawn, it probably
|
|
|
|
/// has at least a draw with the pawn as well. The exception is when the stronger
|
|
|
|
/// side's pawn is far advanced and not on a rook file; in this case it is often
|
|
|
|
/// possible to win (e.g. 8/4k3/3p4/3P4/6K1/8/8/8 w - - 0 1).
|
2011-11-12 20:44:06 +01:00
|
|
|
template<>
|
2012-01-01 01:52:19 +01:00
|
|
|
ScaleFactor Endgame<KPKP>::operator()(const Position& pos) const {
|
2011-11-12 20:44:06 +01:00
|
|
|
|
2013-11-30 20:12:34 +01:00
|
|
|
assert(verify_material(pos, strongSide, VALUE_ZERO, 1));
|
|
|
|
assert(verify_material(pos, weakSide, VALUE_ZERO, 1));
|
2011-11-12 20:44:06 +01:00
|
|
|
|
2013-11-30 20:12:34 +01:00
|
|
|
// Assume strongSide is white and the pawn is on files A-D
|
|
|
|
Square wksq = normalize(pos, strongSide, pos.king_square(strongSide));
|
|
|
|
Square bksq = normalize(pos, strongSide, pos.king_square(weakSide));
|
|
|
|
Square psq = normalize(pos, strongSide, pos.list<PAWN>(strongSide)[0]);
|
2011-11-12 20:44:06 +01:00
|
|
|
|
2013-11-30 20:12:34 +01:00
|
|
|
Color us = strongSide == pos.side_to_move() ? WHITE : BLACK;
|
2011-11-12 20:44:06 +01:00
|
|
|
|
|
|
|
// If the pawn has advanced to the fifth rank or further, and is not a
|
|
|
|
// rook pawn, it's too dangerous to assume that it's at least a draw.
|
2013-11-30 20:12:34 +01:00
|
|
|
if (rank_of(psq) >= RANK_5 && file_of(psq) != FILE_A)
|
2011-11-12 20:44:06 +01:00
|
|
|
return SCALE_FACTOR_NONE;
|
|
|
|
|
2012-01-01 01:52:19 +01:00
|
|
|
// Probe the KPK bitbase with the weakest side's pawn removed. If it's a draw,
|
|
|
|
// it's probably at least a draw even with the pawn.
|
2013-11-30 20:12:34 +01:00
|
|
|
return Bitbases::probe_kpk(wksq, psq, bksq, us) ? SCALE_FACTOR_NONE : SCALE_FACTOR_DRAW;
|
2011-11-12 20:44:06 +01:00
|
|
|
}
|