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Moved DroidFish project to trunk/
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Peter Osterlund
285
DroidFish/jni/stockfish/material.cpp
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285
DroidFish/jni/stockfish/material.cpp
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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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Copyright (C) 2008-2010 Marco Costalba, Joona Kiiski, Tord Romstad
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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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#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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// Values modified by Joona Kiiski
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const Value MidgameLimit = Value(15581);
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const Value EndgameLimit = Value(3998);
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// Scale factors used when one side has no more pawns
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const int NoPawnsSF[4] = { 6, 12, 32 };
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// Polynomial material balance parameters
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const Value RedundantQueenPenalty = Value(320);
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const Value RedundantRookPenalty = Value(554);
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const int LinearCoefficients[6] = { 1617, -162, -1172, -190, 105, 26 };
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const int QuadraticCoefficientsSameColor[][8] = {
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{ 7, 7, 7, 7, 7, 7 }, { 39, 2, 7, 7, 7, 7 }, { 35, 271, -4, 7, 7, 7 },
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{ 7, 25, 4, 7, 7, 7 }, { -27, -2, 46, 100, 56, 7 }, { 58, 29, 83, 148, -3, -25 } };
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const int QuadraticCoefficientsOppositeColor[][8] = {
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{ 41, 41, 41, 41, 41, 41 }, { 37, 41, 41, 41, 41, 41 }, { 10, 62, 41, 41, 41, 41 },
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{ 57, 64, 39, 41, 41, 41 }, { 50, 40, 23, -22, 41, 41 }, { 106, 101, 3, 151, 171, 41 } };
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// Endgame evaluation and scaling functions accessed direcly and not through
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// the function maps because correspond to more then one material hash key.
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Endgame<Value, KmmKm> EvaluateKmmKm[] = { Endgame<Value, KmmKm>(WHITE), Endgame<Value, KmmKm>(BLACK) };
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Endgame<Value, KXK> EvaluateKXK[] = { Endgame<Value, KXK>(WHITE), Endgame<Value, KXK>(BLACK) };
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Endgame<ScaleFactor, KBPsK> ScaleKBPsK[] = { Endgame<ScaleFactor, KBPsK>(WHITE), Endgame<ScaleFactor, KBPsK>(BLACK) };
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Endgame<ScaleFactor, KQKRPs> ScaleKQKRPs[] = { Endgame<ScaleFactor, KQKRPs>(WHITE), Endgame<ScaleFactor, KQKRPs>(BLACK) };
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Endgame<ScaleFactor, KPsK> ScaleKPsK[] = { Endgame<ScaleFactor, KPsK>(WHITE), Endgame<ScaleFactor, KPsK>(BLACK) };
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Endgame<ScaleFactor, KPKP> ScaleKPKP[] = { Endgame<ScaleFactor, KPKP>(WHITE), Endgame<ScaleFactor, KPKP>(BLACK) };
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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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return pos.non_pawn_material(Them) == VALUE_ZERO
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&& pos.piece_count(Them, PAWN) == 0
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&& pos.non_pawn_material(Us) >= RookValueMidgame;
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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) == BishopValueMidgame
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&& pos.piece_count(Us, BISHOP) == 1
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&& pos.piece_count(Us, PAWN) >= 1;
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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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return pos.piece_count(Us, PAWN) == 0
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&& pos.non_pawn_material(Us) == QueenValueMidgame
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&& pos.piece_count(Us, QUEEN) == 1
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&& pos.piece_count(Them, ROOK) == 1
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&& pos.piece_count(Them, PAWN) >= 1;
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}
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} // namespace
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/// MaterialInfoTable c'tor and d'tor allocate and free the space for Endgames
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void MaterialInfoTable::init() { Base::init(); if (!funcs) funcs = new Endgames(); }
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MaterialInfoTable::~MaterialInfoTable() { delete funcs; }
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/// MaterialInfoTable::get_material_info() takes a position object as input,
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/// computes or looks up a MaterialInfo object, and returns a pointer to it.
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/// If the material configuration is not already present in the table, it
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/// is stored there, so we don't have to recompute everything when the
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/// same material configuration occurs again.
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MaterialInfo* MaterialInfoTable::get_material_info(const Position& pos) const {
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Key key = pos.get_material_key();
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MaterialInfo* mi = probe(key);
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// If mi->key matches the position's material hash key, it means that we
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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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if (mi->key == key)
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return mi;
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// Initialize MaterialInfo entry
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memset(mi, 0, sizeof(MaterialInfo));
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mi->key = key;
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mi->factor[WHITE] = mi->factor[BLACK] = (uint8_t)SCALE_FACTOR_NORMAL;
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// Store game phase
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mi->gamePhase = MaterialInfoTable::game_phase(pos);
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// Let's look if we have a specialized evaluation function for this
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// particular material configuration. First we look for a fixed
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// configuration one, then a generic one if previous search failed.
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if ((mi->evaluationFunction = funcs->get<EndgameBase<Value> >(key)) != NULL)
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return mi;
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if (is_KXK<WHITE>(pos))
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{
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mi->evaluationFunction = &EvaluateKXK[WHITE];
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return mi;
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}
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if (is_KXK<BLACK>(pos))
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{
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mi->evaluationFunction = &EvaluateKXK[BLACK];
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return mi;
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}
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if (!pos.pieces(PAWN) && !pos.pieces(ROOK) && !pos.pieces(QUEEN))
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{
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// Minor piece endgame with at least one minor piece per side and
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// no pawns. Note that the case KmmK is already handled by KXK.
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assert((pos.pieces(KNIGHT, WHITE) | pos.pieces(BISHOP, WHITE)));
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assert((pos.pieces(KNIGHT, BLACK) | pos.pieces(BISHOP, BLACK)));
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if ( pos.piece_count(WHITE, BISHOP) + pos.piece_count(WHITE, KNIGHT) <= 2
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&& pos.piece_count(BLACK, BISHOP) + pos.piece_count(BLACK, KNIGHT) <= 2)
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{
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mi->evaluationFunction = &EvaluateKmmKm[WHITE];
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return mi;
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}
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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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if ((sf = funcs->get<EndgameBase<ScaleFactor> >(key)) != NULL)
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{
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mi->scalingFunction[sf->color()] = sf;
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return mi;
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}
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// Generic scaling functions that refer to more then one material
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// distribution. Should be probed after the specialized ones.
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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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mi->scalingFunction[WHITE] = &ScaleKBPsK[WHITE];
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if (is_KBPsKs<BLACK>(pos))
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mi->scalingFunction[BLACK] = &ScaleKBPsK[BLACK];
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if (is_KQKRPs<WHITE>(pos))
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mi->scalingFunction[WHITE] = &ScaleKQKRPs[WHITE];
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else if (is_KQKRPs<BLACK>(pos))
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mi->scalingFunction[BLACK] = &ScaleKQKRPs[BLACK];
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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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if (npm_w + npm_b == VALUE_ZERO)
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{
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if (pos.piece_count(BLACK, PAWN) == 0)
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{
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assert(pos.piece_count(WHITE, PAWN) >= 2);
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mi->scalingFunction[WHITE] = &ScaleKPsK[WHITE];
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}
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else if (pos.piece_count(WHITE, PAWN) == 0)
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{
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assert(pos.piece_count(BLACK, PAWN) >= 2);
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mi->scalingFunction[BLACK] = &ScaleKPsK[BLACK];
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}
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else if (pos.piece_count(WHITE, PAWN) == 1 && pos.piece_count(BLACK, PAWN) == 1)
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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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mi->scalingFunction[WHITE] = &ScaleKPKP[WHITE];
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mi->scalingFunction[BLACK] = &ScaleKPKP[BLACK];
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}
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}
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// No pawns makes it difficult to win, even with a material advantage
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if (pos.piece_count(WHITE, PAWN) == 0 && npm_w - npm_b <= BishopValueMidgame)
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{
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mi->factor[WHITE] = uint8_t
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(npm_w == npm_b || npm_w < RookValueMidgame ? 0 : NoPawnsSF[Min(pos.piece_count(WHITE, BISHOP), 2)]);
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}
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if (pos.piece_count(BLACK, PAWN) == 0 && npm_b - npm_w <= BishopValueMidgame)
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{
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mi->factor[BLACK] = uint8_t
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(npm_w == npm_b || npm_b < RookValueMidgame ? 0 : NoPawnsSF[Min(pos.piece_count(BLACK, BISHOP), 2)]);
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}
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// Compute the space weight
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if (npm_w + npm_b >= 2 * QueenValueMidgame + 4 * RookValueMidgame + 2 * KnightValueMidgame)
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{
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int minorPieceCount = pos.piece_count(WHITE, KNIGHT) + pos.piece_count(WHITE, BISHOP)
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+ pos.piece_count(BLACK, KNIGHT) + pos.piece_count(BLACK, BISHOP);
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mi->spaceWeight = minorPieceCount * minorPieceCount;
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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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// for the bishop pair "extended piece", this allow us to be more flexible
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// in defining bishop pair bonuses.
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const int pieceCount[2][8] = {
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{ pos.piece_count(WHITE, BISHOP) > 1, pos.piece_count(WHITE, PAWN), pos.piece_count(WHITE, KNIGHT),
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pos.piece_count(WHITE, BISHOP) , pos.piece_count(WHITE, ROOK), pos.piece_count(WHITE, QUEEN) },
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{ pos.piece_count(BLACK, BISHOP) > 1, pos.piece_count(BLACK, PAWN), pos.piece_count(BLACK, KNIGHT),
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pos.piece_count(BLACK, BISHOP) , pos.piece_count(BLACK, ROOK), pos.piece_count(BLACK, QUEEN) } };
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mi->value = int16_t((imbalance<WHITE>(pieceCount) - imbalance<BLACK>(pieceCount)) / 16);
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return mi;
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}
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/// MaterialInfoTable::imbalance() calculates imbalance comparing piece count of each
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/// piece type for both colors.
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template<Color Us>
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int MaterialInfoTable::imbalance(const int pieceCount[][8]) {
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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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// Redundancy of major pieces, formula based on Kaufman's paper
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// "The Evaluation of Material Imbalances in Chess"
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if (pieceCount[Us][ROOK] > 0)
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value -= RedundantRookPenalty * (pieceCount[Us][ROOK] - 1)
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+ RedundantQueenPenalty * pieceCount[Us][QUEEN];
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// Second-degree polynomial material imbalance by Tord Romstad
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for (pt1 = PIECE_TYPE_NONE; pt1 <= QUEEN; pt1++)
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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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for (pt2 = PIECE_TYPE_NONE; pt2 <= pt1; pt2++)
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v += QuadraticCoefficientsSameColor[pt1][pt2] * pieceCount[Us][pt2]
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+ QuadraticCoefficientsOppositeColor[pt1][pt2] * pieceCount[Them][pt2];
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value += pc * v;
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}
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return value;
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}
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/// MaterialInfoTable::game_phase() calculates the phase given the current
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/// position. Because the phase is strictly a function of the material, it
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/// is stored in MaterialInfo.
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Phase MaterialInfoTable::game_phase(const Position& pos) {
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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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