+++ /dev/null
-/*
- Stockfish, a UCI chess playing engine derived from Glaurung 2.1
- Copyright (C) 2004-2008 Tord Romstad (Glaurung author)
- Copyright (C) 2008-2012 Marco Costalba, Joona Kiiski, Tord Romstad
-
- Stockfish is free software: you can redistribute it and/or modify
- it under the terms of the GNU General Public License as published by
- the Free Software Foundation, either version 3 of the License, or
- (at your option) any later version.
-
- Stockfish is distributed in the hope that it will be useful,
- but WITHOUT ANY WARRANTY; without even the implied warranty of
- MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
- GNU General Public License for more details.
-
- You should have received a copy of the GNU General Public License
- along with this program. If not, see <http://www.gnu.org/licenses/>.
-*/
-
-#include <algorithm>
-#include <cassert>
-#include <cstring>
-
-#include "material.h"
-
-using namespace std;
-
-namespace {
-
- // Values modified by Joona Kiiski
- const Value MidgameLimit = Value(15581);
- const Value EndgameLimit = Value(3998);
-
- // Scale factors used when one side has no more pawns
- const int NoPawnsSF[4] = { 6, 12, 32 };
-
- // Polynomial material balance parameters
- const Value RedundantQueenPenalty = Value(320);
- const Value RedundantRookPenalty = Value(554);
-
- const int LinearCoefficients[6] = { 1617, -162, -1172, -190, 105, 26 };
-
- const int QuadraticCoefficientsSameColor[][8] = {
- { 7, 7, 7, 7, 7, 7 }, { 39, 2, 7, 7, 7, 7 }, { 35, 271, -4, 7, 7, 7 },
- { 7, 25, 4, 7, 7, 7 }, { -27, -2, 46, 100, 56, 7 }, { 58, 29, 83, 148, -3, -25 } };
-
- const int QuadraticCoefficientsOppositeColor[][8] = {
- { 41, 41, 41, 41, 41, 41 }, { 37, 41, 41, 41, 41, 41 }, { 10, 62, 41, 41, 41, 41 },
- { 57, 64, 39, 41, 41, 41 }, { 50, 40, 23, -22, 41, 41 }, { 106, 101, 3, 151, 171, 41 } };
-
- // Endgame evaluation and scaling functions accessed direcly and not through
- // the function maps because correspond to more then one material hash key.
- Endgame<KmmKm> EvaluateKmmKm[] = { Endgame<KmmKm>(WHITE), Endgame<KmmKm>(BLACK) };
- Endgame<KXK> EvaluateKXK[] = { Endgame<KXK>(WHITE), Endgame<KXK>(BLACK) };
-
- Endgame<KBPsK> ScaleKBPsK[] = { Endgame<KBPsK>(WHITE), Endgame<KBPsK>(BLACK) };
- Endgame<KQKRPs> ScaleKQKRPs[] = { Endgame<KQKRPs>(WHITE), Endgame<KQKRPs>(BLACK) };
- Endgame<KPsK> ScaleKPsK[] = { Endgame<KPsK>(WHITE), Endgame<KPsK>(BLACK) };
- Endgame<KPKP> ScaleKPKP[] = { Endgame<KPKP>(WHITE), Endgame<KPKP>(BLACK) };
-
- // Helper templates used to detect a given material distribution
- template<Color Us> bool is_KXK(const Position& pos) {
- const Color Them = (Us == WHITE ? BLACK : WHITE);
- return pos.non_pawn_material(Them) == VALUE_ZERO
- && pos.piece_count(Them, PAWN) == 0
- && pos.non_pawn_material(Us) >= RookValueMidgame;
- }
-
- template<Color Us> bool is_KBPsKs(const Position& pos) {
- return pos.non_pawn_material(Us) == BishopValueMidgame
- && pos.piece_count(Us, BISHOP) == 1
- && pos.piece_count(Us, PAWN) >= 1;
- }
-
- template<Color Us> bool is_KQKRPs(const Position& pos) {
- const Color Them = (Us == WHITE ? BLACK : WHITE);
- return pos.piece_count(Us, PAWN) == 0
- && pos.non_pawn_material(Us) == QueenValueMidgame
- && pos.piece_count(Us, QUEEN) == 1
- && pos.piece_count(Them, ROOK) == 1
- && pos.piece_count(Them, PAWN) >= 1;
- }
-
-} // namespace
-
-
-/// MaterialTable::probe() takes a position object as input, looks up a MaterialEntry
-/// object, and returns a pointer to it. If the material configuration is not
-/// already present in the table, it is computed and stored there, so we don't
-/// have to recompute everything when the same material configuration occurs again.
-
-MaterialEntry* MaterialTable::probe(const Position& pos) {
-
- Key key = pos.material_key();
- MaterialEntry* e = entries[key];
-
- // If e->key matches the position's material hash key, it means that we
- // have analysed this material configuration before, and we can simply
- // return the information we found the last time instead of recomputing it.
- if (e->key == key)
- return e;
-
- memset(e, 0, sizeof(MaterialEntry));
- e->key = key;
- e->factor[WHITE] = e->factor[BLACK] = (uint8_t)SCALE_FACTOR_NORMAL;
- e->gamePhase = MaterialTable::game_phase(pos);
-
- // Let's look if we have a specialized evaluation function for this
- // particular material configuration. First we look for a fixed
- // configuration one, then a generic one if previous search failed.
- if ((e->evaluationFunction = endgames.probe<Value>(key)) != NULL)
- return e;
-
- if (is_KXK<WHITE>(pos))
- {
- e->evaluationFunction = &EvaluateKXK[WHITE];
- return e;
- }
-
- if (is_KXK<BLACK>(pos))
- {
- e->evaluationFunction = &EvaluateKXK[BLACK];
- return e;
- }
-
- if (!pos.pieces(PAWN) && !pos.pieces(ROOK) && !pos.pieces(QUEEN))
- {
- // Minor piece endgame with at least one minor piece per side and
- // no pawns. Note that the case KmmK is already handled by KXK.
- assert((pos.pieces(KNIGHT, WHITE) | pos.pieces(BISHOP, WHITE)));
- assert((pos.pieces(KNIGHT, BLACK) | pos.pieces(BISHOP, BLACK)));
-
- if ( pos.piece_count(WHITE, BISHOP) + pos.piece_count(WHITE, KNIGHT) <= 2
- && pos.piece_count(BLACK, BISHOP) + pos.piece_count(BLACK, KNIGHT) <= 2)
- {
- e->evaluationFunction = &EvaluateKmmKm[pos.side_to_move()];
- return e;
- }
- }
-
- // OK, we didn't find any special evaluation function for the current
- // material configuration. Is there a suitable scaling function?
- //
- // We face problems when there are several conflicting applicable
- // scaling functions and we need to decide which one to use.
- EndgameBase<ScaleFactor>* sf;
-
- if ((sf = endgames.probe<ScaleFactor>(key)) != NULL)
- {
- e->scalingFunction[sf->color()] = sf;
- return e;
- }
-
- // Generic scaling functions that refer to more then one material
- // distribution. Should be probed after the specialized ones.
- // Note that these ones don't return after setting the function.
- if (is_KBPsKs<WHITE>(pos))
- e->scalingFunction[WHITE] = &ScaleKBPsK[WHITE];
-
- if (is_KBPsKs<BLACK>(pos))
- e->scalingFunction[BLACK] = &ScaleKBPsK[BLACK];
-
- if (is_KQKRPs<WHITE>(pos))
- e->scalingFunction[WHITE] = &ScaleKQKRPs[WHITE];
-
- else if (is_KQKRPs<BLACK>(pos))
- e->scalingFunction[BLACK] = &ScaleKQKRPs[BLACK];
-
- Value npm_w = pos.non_pawn_material(WHITE);
- Value npm_b = pos.non_pawn_material(BLACK);
-
- if (npm_w + npm_b == VALUE_ZERO)
- {
- if (pos.piece_count(BLACK, PAWN) == 0)
- {
- assert(pos.piece_count(WHITE, PAWN) >= 2);
- e->scalingFunction[WHITE] = &ScaleKPsK[WHITE];
- }
- else if (pos.piece_count(WHITE, PAWN) == 0)
- {
- assert(pos.piece_count(BLACK, PAWN) >= 2);
- e->scalingFunction[BLACK] = &ScaleKPsK[BLACK];
- }
- else if (pos.piece_count(WHITE, PAWN) == 1 && pos.piece_count(BLACK, PAWN) == 1)
- {
- // This is a special case because we set scaling functions
- // for both colors instead of only one.
- e->scalingFunction[WHITE] = &ScaleKPKP[WHITE];
- e->scalingFunction[BLACK] = &ScaleKPKP[BLACK];
- }
- }
-
- // No pawns makes it difficult to win, even with a material advantage
- if (pos.piece_count(WHITE, PAWN) == 0 && npm_w - npm_b <= BishopValueMidgame)
- {
- e->factor[WHITE] = (uint8_t)
- (npm_w == npm_b || npm_w < RookValueMidgame ? 0 : NoPawnsSF[std::min(pos.piece_count(WHITE, BISHOP), 2)]);
- }
-
- if (pos.piece_count(BLACK, PAWN) == 0 && npm_b - npm_w <= BishopValueMidgame)
- {
- e->factor[BLACK] = (uint8_t)
- (npm_w == npm_b || npm_b < RookValueMidgame ? 0 : NoPawnsSF[std::min(pos.piece_count(BLACK, BISHOP), 2)]);
- }
-
- // Compute the space weight
- if (npm_w + npm_b >= 2 * QueenValueMidgame + 4 * RookValueMidgame + 2 * KnightValueMidgame)
- {
- int minorPieceCount = pos.piece_count(WHITE, KNIGHT) + pos.piece_count(WHITE, BISHOP)
- + pos.piece_count(BLACK, KNIGHT) + pos.piece_count(BLACK, BISHOP);
-
- e->spaceWeight = minorPieceCount * minorPieceCount;
- }
-
- // Evaluate the material imbalance. We use PIECE_TYPE_NONE as a place holder
- // for the bishop pair "extended piece", this allow us to be more flexible
- // in defining bishop pair bonuses.
- const int pieceCount[2][8] = {
- { pos.piece_count(WHITE, BISHOP) > 1, pos.piece_count(WHITE, PAWN), pos.piece_count(WHITE, KNIGHT),
- pos.piece_count(WHITE, BISHOP) , pos.piece_count(WHITE, ROOK), pos.piece_count(WHITE, QUEEN) },
- { pos.piece_count(BLACK, BISHOP) > 1, pos.piece_count(BLACK, PAWN), pos.piece_count(BLACK, KNIGHT),
- pos.piece_count(BLACK, BISHOP) , pos.piece_count(BLACK, ROOK), pos.piece_count(BLACK, QUEEN) } };
-
- e->value = (int16_t)((imbalance<WHITE>(pieceCount) - imbalance<BLACK>(pieceCount)) / 16);
- return e;
-}
-
-
-/// MaterialTable::imbalance() calculates imbalance comparing piece count of each
-/// piece type for both colors.
-
-template<Color Us>
-int MaterialTable::imbalance(const int pieceCount[][8]) {
-
- const Color Them = (Us == WHITE ? BLACK : WHITE);
-
- int pt1, pt2, pc, v;
- int value = 0;
-
- // Redundancy of major pieces, formula based on Kaufman's paper
- // "The Evaluation of Material Imbalances in Chess"
- if (pieceCount[Us][ROOK] > 0)
- value -= RedundantRookPenalty * (pieceCount[Us][ROOK] - 1)
- + RedundantQueenPenalty * pieceCount[Us][QUEEN];
-
- // Second-degree polynomial material imbalance by Tord Romstad
- for (pt1 = NO_PIECE_TYPE; pt1 <= QUEEN; pt1++)
- {
- pc = pieceCount[Us][pt1];
- if (!pc)
- continue;
-
- v = LinearCoefficients[pt1];
-
- for (pt2 = NO_PIECE_TYPE; pt2 <= pt1; pt2++)
- v += QuadraticCoefficientsSameColor[pt1][pt2] * pieceCount[Us][pt2]
- + QuadraticCoefficientsOppositeColor[pt1][pt2] * pieceCount[Them][pt2];
-
- value += pc * v;
- }
- return value;
-}
-
-
-/// MaterialTable::game_phase() calculates the phase given the current
-/// position. Because the phase is strictly a function of the material, it
-/// is stored in MaterialEntry.
-
-Phase MaterialTable::game_phase(const Position& pos) {
-
- Value npm = pos.non_pawn_material(WHITE) + pos.non_pawn_material(BLACK);
-
- return npm >= MidgameLimit ? PHASE_MIDGAME
- : npm <= EndgameLimit ? PHASE_ENDGAME
- : Phase(((npm - EndgameLimit) * 128) / (MidgameLimit - EndgameLimit));
-}