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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2013-05-03 19:03:42 +02:00
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#include <algorithm> // For std::min
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2011-11-12 20:44:06 +01:00
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#include <cassert>
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#include <cstring>
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#include "material.h"
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using namespace std;
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namespace {
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// Polynomial material balance parameters
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2013-05-03 19:03:42 +02:00
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// pair pawn knight bishop rook queen
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2014-05-31 14:23:03 +02:00
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const int LinearCoefficients[6] = { 1852, -162, -1122, -183, 249, -154 };
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2013-05-03 19:03:42 +02:00
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2014-05-31 14:23:03 +02:00
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const int QuadraticCoefficientsSameSide[][PIECE_TYPE_NB] = {
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// OUR PIECES
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// pair pawn knight bishop rook queen
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2013-11-30 20:12:34 +01:00
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{ 0 }, // Bishop pair
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2013-05-03 19:03:42 +02:00
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{ 39, 2 }, // Pawn
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{ 35, 271, -4 }, // knight OUR PIECES
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2013-11-30 20:12:34 +01:00
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{ 0, 105, 4, 0 }, // Bishop
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{ -27, -2, 46, 100, -141 }, // Rook
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{-177, 25, 129, 142, -137, 0 } // Queen
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};
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2014-05-31 14:23:03 +02:00
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const int QuadraticCoefficientsOppositeSide[][PIECE_TYPE_NB] = {
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// THEIR PIECES
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// pair pawn knight bishop rook queen
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2013-11-30 20:12:34 +01:00
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{ 0 }, // Bishop pair
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{ 37, 0 }, // Pawn
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{ 10, 62, 0 }, // Knight OUR PIECES
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{ 57, 64, 39, 0 }, // Bishop
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{ 50, 40, 23, -22, 0 }, // Rook
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{ 98, 105, -39, 141, 274, 0 } // Queen
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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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// Endgame evaluation and scaling functions are accessed directly and not through
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// the function maps because they correspond to more than one material hash key.
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2012-01-01 01:52:19 +01:00
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Endgame<KXK> EvaluateKXK[] = { Endgame<KXK>(WHITE), Endgame<KXK>(BLACK) };
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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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Endgame<KBPsK> ScaleKBPsK[] = { Endgame<KBPsK>(WHITE), Endgame<KBPsK>(BLACK) };
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Endgame<KQKRPs> ScaleKQKRPs[] = { Endgame<KQKRPs>(WHITE), Endgame<KQKRPs>(BLACK) };
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Endgame<KPsK> ScaleKPsK[] = { Endgame<KPsK>(WHITE), Endgame<KPsK>(BLACK) };
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Endgame<KPKP> ScaleKPKP[] = { Endgame<KPKP>(WHITE), Endgame<KPKP>(BLACK) };
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2011-11-12 20:44:06 +01:00
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// Helper templates used to detect a given material distribution
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template<Color Us> bool is_KXK(const Position& pos) {
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const Color Them = (Us == WHITE ? BLACK : WHITE);
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2013-08-20 20:02:33 +02:00
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return !pos.count<PAWN>(Them)
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&& pos.non_pawn_material(Them) == VALUE_ZERO
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&& pos.non_pawn_material(Us) >= RookValueMg;
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2011-11-12 20:44:06 +01:00
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}
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template<Color Us> bool is_KBPsKs(const Position& pos) {
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return pos.non_pawn_material(Us) == BishopValueMg
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&& pos.count<BISHOP>(Us) == 1
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&& pos.count<PAWN >(Us) >= 1;
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2011-11-12 20:44:06 +01:00
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}
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template<Color Us> bool is_KQKRPs(const Position& pos) {
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const Color Them = (Us == WHITE ? BLACK : WHITE);
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2013-08-20 20:02:33 +02:00
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return !pos.count<PAWN>(Us)
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&& pos.non_pawn_material(Us) == QueenValueMg
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&& pos.count<QUEEN>(Us) == 1
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&& pos.count<ROOK>(Them) == 1
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&& pos.count<PAWN>(Them) >= 1;
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2011-11-12 20:44:06 +01:00
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}
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2014-05-31 14:23:03 +02:00
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/// imbalance() calculates the imbalance by comparing the piece count of each
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2013-05-03 19:03:42 +02:00
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/// piece type for both colors.
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template<Color Us>
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int imbalance(const int pieceCount[][PIECE_TYPE_NB]) {
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const Color Them = (Us == WHITE ? BLACK : WHITE);
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int pt1, pt2, pc, v;
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int value = 0;
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// Second-degree polynomial material imbalance by Tord Romstad
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2013-11-30 20:12:34 +01:00
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for (pt1 = NO_PIECE_TYPE; pt1 <= QUEEN; ++pt1)
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2013-05-03 19:03:42 +02:00
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{
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pc = pieceCount[Us][pt1];
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if (!pc)
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continue;
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v = LinearCoefficients[pt1];
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2013-11-30 20:12:34 +01:00
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for (pt2 = NO_PIECE_TYPE; pt2 <= pt1; ++pt2)
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2014-05-31 14:23:03 +02:00
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v += QuadraticCoefficientsSameSide[pt1][pt2] * pieceCount[Us][pt2]
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+ QuadraticCoefficientsOppositeSide[pt1][pt2] * pieceCount[Them][pt2];
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2013-05-03 19:03:42 +02:00
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value += pc * v;
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}
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2014-05-31 14:23:03 +02:00
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2013-05-03 19:03:42 +02:00
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return value;
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}
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2011-11-12 20:44:06 +01:00
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} // namespace
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2013-05-03 19:03:42 +02:00
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namespace Material {
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2011-11-12 20:44:06 +01:00
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2013-05-03 19:03:42 +02:00
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/// Material::probe() takes a position object as input, looks up a MaterialEntry
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2012-06-04 18:25:51 +02:00
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/// object, and returns a pointer to it. If the material configuration is not
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/// already present in the table, it is computed and stored there, so we don't
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/// have to recompute everything when the same material configuration occurs again.
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2011-11-12 20:44:06 +01:00
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2013-05-03 19:03:42 +02:00
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Entry* probe(const Position& pos, Table& entries, Endgames& endgames) {
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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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Key key = pos.material_key();
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Entry* e = entries[key];
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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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// If e->key matches the position's material hash key, it means that we
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2011-11-12 20:44:06 +01:00
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// have analysed this material configuration before, and we can simply
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// return the information we found the last time instead of recomputing it.
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2012-06-04 18:25:51 +02:00
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if (e->key == key)
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return e;
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2011-11-12 20:44:06 +01:00
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2013-08-20 20:02:33 +02:00
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std::memset(e, 0, sizeof(Entry));
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2012-06-04 18:25:51 +02:00
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e->key = key;
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e->factor[WHITE] = e->factor[BLACK] = (uint8_t)SCALE_FACTOR_NORMAL;
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2013-05-03 19:03:42 +02:00
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e->gamePhase = game_phase(pos);
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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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// Let's look if we have a specialized evaluation function for this particular
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// material configuration. Firstly we look for a fixed configuration one, then
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// for a generic one if the previous search failed.
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2012-06-04 18:25:51 +02:00
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if (endgames.probe(key, e->evaluationFunction))
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return e;
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2011-11-12 20:44:06 +01:00
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if (is_KXK<WHITE>(pos))
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{
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2012-06-04 18:25:51 +02:00
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e->evaluationFunction = &EvaluateKXK[WHITE];
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return e;
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2011-11-12 20:44:06 +01:00
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}
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if (is_KXK<BLACK>(pos))
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{
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2012-06-04 18:25:51 +02:00
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e->evaluationFunction = &EvaluateKXK[BLACK];
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return e;
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2011-11-12 20:44:06 +01:00
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}
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// OK, we didn't find any special evaluation function for the current
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// material configuration. Is there a suitable scaling function?
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//
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// We face problems when there are several conflicting applicable
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// scaling functions and we need to decide which one to use.
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EndgameBase<ScaleFactor>* sf;
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2012-06-04 18:25:51 +02:00
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if (endgames.probe(key, sf))
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2011-11-12 20:44:06 +01:00
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{
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2012-06-04 18:25:51 +02:00
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e->scalingFunction[sf->color()] = sf;
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return e;
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2011-11-12 20:44:06 +01:00
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}
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2014-05-31 14:23:03 +02:00
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// Generic scaling functions that refer to more than one material
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// distribution. They should be probed after the specialized ones.
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2011-11-12 20:44:06 +01:00
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// Note that these ones don't return after setting the function.
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if (is_KBPsKs<WHITE>(pos))
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2012-06-04 18:25:51 +02:00
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e->scalingFunction[WHITE] = &ScaleKBPsK[WHITE];
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2011-11-12 20:44:06 +01:00
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if (is_KBPsKs<BLACK>(pos))
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2012-06-04 18:25:51 +02:00
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e->scalingFunction[BLACK] = &ScaleKBPsK[BLACK];
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2011-11-12 20:44:06 +01:00
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if (is_KQKRPs<WHITE>(pos))
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2012-06-04 18:25:51 +02:00
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e->scalingFunction[WHITE] = &ScaleKQKRPs[WHITE];
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2011-11-12 20:44:06 +01:00
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else if (is_KQKRPs<BLACK>(pos))
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2012-06-04 18:25:51 +02:00
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e->scalingFunction[BLACK] = &ScaleKQKRPs[BLACK];
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2011-11-12 20:44:06 +01:00
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Value npm_w = pos.non_pawn_material(WHITE);
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Value npm_b = pos.non_pawn_material(BLACK);
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2014-05-31 14:23:03 +02:00
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if (npm_w + npm_b == VALUE_ZERO && pos.pieces(PAWN))
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2011-11-12 20:44:06 +01:00
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{
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2013-08-20 20:02:33 +02:00
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if (!pos.count<PAWN>(BLACK))
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2011-11-12 20:44:06 +01:00
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{
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2013-08-20 20:02:33 +02:00
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assert(pos.count<PAWN>(WHITE) >= 2);
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2012-06-04 18:25:51 +02:00
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e->scalingFunction[WHITE] = &ScaleKPsK[WHITE];
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2011-11-12 20:44:06 +01:00
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}
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2013-08-20 20:02:33 +02:00
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else if (!pos.count<PAWN>(WHITE))
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2011-11-12 20:44:06 +01:00
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{
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2013-08-20 20:02:33 +02:00
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assert(pos.count<PAWN>(BLACK) >= 2);
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2012-06-04 18:25:51 +02:00
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e->scalingFunction[BLACK] = &ScaleKPsK[BLACK];
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2011-11-12 20:44:06 +01:00
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}
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2013-08-20 20:02:33 +02:00
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else if (pos.count<PAWN>(WHITE) == 1 && pos.count<PAWN>(BLACK) == 1)
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2011-11-12 20:44:06 +01:00
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{
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// This is a special case because we set scaling functions
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// for both colors instead of only one.
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2012-06-04 18:25:51 +02:00
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e->scalingFunction[WHITE] = &ScaleKPKP[WHITE];
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e->scalingFunction[BLACK] = &ScaleKPKP[BLACK];
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2011-11-12 20:44:06 +01:00
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}
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}
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2013-11-30 20:12:34 +01:00
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// No pawns makes it difficult to win, even with a material advantage. This
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2014-05-31 14:23:03 +02:00
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// catches some trivial draws like KK, KBK and KNK and gives a very drawish
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// scale factor for cases such as KRKBP and KmmKm (except for KBBKN).
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2013-08-20 20:02:33 +02:00
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if (!pos.count<PAWN>(WHITE) && npm_w - npm_b <= BishopValueMg)
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2014-05-31 14:23:03 +02:00
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e->factor[WHITE] = uint8_t(npm_w < RookValueMg ? SCALE_FACTOR_DRAW : npm_b <= BishopValueMg ? 4 : 12);
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2011-11-12 20:44:06 +01:00
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2013-08-20 20:02:33 +02:00
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if (!pos.count<PAWN>(BLACK) && npm_b - npm_w <= BishopValueMg)
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2014-05-31 14:23:03 +02:00
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e->factor[BLACK] = uint8_t(npm_b < RookValueMg ? SCALE_FACTOR_DRAW : npm_w <= BishopValueMg ? 4 : 12);
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if (pos.count<PAWN>(WHITE) == 1 && npm_w - npm_b <= BishopValueMg)
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e->factor[WHITE] = (uint8_t) SCALE_FACTOR_ONEPAWN;
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if (pos.count<PAWN>(BLACK) == 1 && npm_b - npm_w <= BishopValueMg)
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e->factor[BLACK] = (uint8_t) SCALE_FACTOR_ONEPAWN;
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2011-11-12 20:44:06 +01:00
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// Compute the space weight
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2012-09-16 17:16:15 +02:00
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if (npm_w + npm_b >= 2 * QueenValueMg + 4 * RookValueMg + 2 * KnightValueMg)
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2011-11-12 20:44:06 +01:00
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{
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2013-08-20 20:02:33 +02:00
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int minorPieceCount = pos.count<KNIGHT>(WHITE) + pos.count<BISHOP>(WHITE)
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+ pos.count<KNIGHT>(BLACK) + pos.count<BISHOP>(BLACK);
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2011-11-12 20:44:06 +01:00
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2013-08-20 20:02:33 +02:00
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e->spaceWeight = make_score(minorPieceCount * minorPieceCount, 0);
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2011-11-12 20:44:06 +01:00
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}
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// Evaluate the material imbalance. We use PIECE_TYPE_NONE as a place holder
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2014-05-31 14:23:03 +02:00
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// for the bishop pair "extended piece", which allows us to be more flexible
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2011-11-12 20:44:06 +01:00
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// in defining bishop pair bonuses.
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2013-05-03 19:03:42 +02:00
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const int pieceCount[COLOR_NB][PIECE_TYPE_NB] = {
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2013-08-20 20:02:33 +02:00
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{ pos.count<BISHOP>(WHITE) > 1, pos.count<PAWN>(WHITE), pos.count<KNIGHT>(WHITE),
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pos.count<BISHOP>(WHITE) , pos.count<ROOK>(WHITE), pos.count<QUEEN >(WHITE) },
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{ pos.count<BISHOP>(BLACK) > 1, pos.count<PAWN>(BLACK), pos.count<KNIGHT>(BLACK),
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pos.count<BISHOP>(BLACK) , pos.count<ROOK>(BLACK), pos.count<QUEEN >(BLACK) } };
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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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e->value = (int16_t)((imbalance<WHITE>(pieceCount) - imbalance<BLACK>(pieceCount)) / 16);
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return e;
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2011-11-12 20:44:06 +01:00
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}
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2013-05-03 19:03:42 +02:00
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/// Material::game_phase() calculates the phase given the current
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2011-11-12 20:44:06 +01:00
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/// position. Because the phase is strictly a function of the material, it
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2012-06-04 18:25:51 +02:00
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/// is stored in MaterialEntry.
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2011-11-12 20:44:06 +01:00
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2013-05-03 19:03:42 +02:00
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Phase game_phase(const Position& pos) {
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2011-11-12 20:44:06 +01:00
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Value npm = pos.non_pawn_material(WHITE) + pos.non_pawn_material(BLACK);
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return npm >= MidgameLimit ? PHASE_MIDGAME
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: npm <= EndgameLimit ? PHASE_ENDGAME
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: Phase(((npm - EndgameLimit) * 128) / (MidgameLimit - EndgameLimit));
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}
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2013-05-03 19:03:42 +02:00
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} // namespace Material
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