/*
Stockfish, a UCI chess playing engine derived from Glaurung 2.1
Copyright (C) 2004-2008 Tord Romstad (Glaurung author)
- Copyright (C) 2008 Marco Costalba
+ Copyright (C) 2008-2015 Marco Costalba, Joona Kiiski, Tord Romstad
+ Copyright (C) 2015-2020 Marco Costalba, Joona Kiiski, Gary Linscott, 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
along with this program. If not, see <http://www.gnu.org/licenses/>.
*/
-
-////
-//// Includes
-////
-
#include <cassert>
-#include <map>
+#include <cstring> // For std::memset
#include "material.h"
+#include "thread.h"
-
-////
-//// Local definitions
-////
+using namespace std;
namespace {
- const Value BishopPairMidgameBonus = Value(100);
- const Value BishopPairEndgameBonus = Value(100);
-
- Key KNNKMaterialKey, KKNNMaterialKey;
-
- struct ScalingInfo
- {
- Color col;
- ScalingFunction* fun;
+ // Polynomial material imbalance parameters
+
+ constexpr int QuadraticOurs[][PIECE_TYPE_NB] = {
+ // OUR PIECES
+ // pair pawn knight bishop rook queen
+ {1438 }, // Bishop pair
+ { 40, 38 }, // Pawn
+ { 32, 255, -62 }, // Knight OUR PIECES
+ { 0, 104, 4, 0 }, // Bishop
+ { -26, -2, 47, 105, -208 }, // Rook
+ {-189, 24, 117, 133, -134, -6 } // Queen
};
-}
-
-////
-//// Classes
-////
-
-class EndgameFunctions {
+ constexpr int QuadraticTheirs[][PIECE_TYPE_NB] = {
+ // THEIR PIECES
+ // pair pawn knight bishop rook queen
+ { 0 }, // Bishop pair
+ { 36, 0 }, // Pawn
+ { 9, 63, 0 }, // Knight OUR PIECES
+ { 59, 65, 42, 0 }, // Bishop
+ { 46, 39, 24, -24, 0 }, // Rook
+ { 97, 100, -42, 137, 268, 0 } // Queen
+ };
-public:
- EndgameFunctions();
- EndgameEvaluationFunction* getEEF(Key key);
- ScalingInfo getESF(Key key);
+ // Endgame evaluation and scaling functions are accessed directly and not through
+ // the function maps because they correspond to more than one material hash key.
+ Endgame<KXK> EvaluateKXK[] = { Endgame<KXK>(WHITE), Endgame<KXK>(BLACK) };
-private:
- void add(Key k, EndgameEvaluationFunction* f);
- void add(Key k, Color c, ScalingFunction* f);
+ 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) };
- std::map<Key, EndgameEvaluationFunction*> EEFmap;
- std::map<Key, ScalingInfo> ESFmap;
-};
+ // Helper used to detect a given material distribution
+ bool is_KXK(const Position& pos, Color us) {
+ return !more_than_one(pos.pieces(~us))
+ && pos.non_pawn_material(us) >= RookValueMg;
+ }
+ bool is_KBPsK(const Position& pos, Color us) {
+ return pos.non_pawn_material(us) == BishopValueMg
+ && pos.count<PAWN >(us) >= 1;
+ }
-////
-//// Functions
-////
+ bool is_KQKRPs(const Position& pos, Color us) {
+ return !pos.count<PAWN>(us)
+ && pos.non_pawn_material(us) == QueenValueMg
+ && pos.count<ROOK>(~us) == 1
+ && pos.count<PAWN>(~us) >= 1;
+ }
-/// MaterialInfo::init() is called during program initialization. It
-/// precomputes material hash keys for a few basic endgames, in order
-/// to make it easy to recognize such endgames when they occur.
+ /// imbalance() calculates the imbalance by comparing the piece count of each
+ /// piece type for both colors.
+ template<Color Us>
+ int imbalance(const int pieceCount[][PIECE_TYPE_NB]) {
-void MaterialInfo::init() {
+ constexpr Color Them = (Us == WHITE ? BLACK : WHITE);
- typedef Key ZM[2][8][16];
- const ZM& z = Position::zobMaterial;
+ int bonus = 0;
- KNNKMaterialKey = z[WHITE][KNIGHT][1] ^ z[WHITE][KNIGHT][2];
- KKNNMaterialKey = z[BLACK][KNIGHT][1] ^ z[BLACK][KNIGHT][2];
-}
+ // Second-degree polynomial material imbalance, by Tord Romstad
+ for (int pt1 = NO_PIECE_TYPE; pt1 <= QUEEN; ++pt1)
+ {
+ if (!pieceCount[Us][pt1])
+ continue;
+ int v = 0;
-/// Constructor for the MaterialInfoTable class
+ for (int pt2 = NO_PIECE_TYPE; pt2 <= pt1; ++pt2)
+ v += QuadraticOurs[pt1][pt2] * pieceCount[Us][pt2]
+ + QuadraticTheirs[pt1][pt2] * pieceCount[Them][pt2];
-MaterialInfoTable::MaterialInfoTable(unsigned int numOfEntries) {
+ bonus += pieceCount[Us][pt1] * v;
+ }
- size = numOfEntries;
- entries = new MaterialInfo[size];
- funcs = new EndgameFunctions();
- if (!entries || !funcs)
- {
- std::cerr << "Failed to allocate " << (numOfEntries * sizeof(MaterialInfo))
- << " bytes for material hash table." << std::endl;
- exit(EXIT_FAILURE);
+ return bonus;
}
- clear();
-}
+} // namespace
-/// Destructor for the MaterialInfoTable class
+namespace Material {
-MaterialInfoTable::~MaterialInfoTable() {
-
- delete [] entries;
- delete funcs;
-}
+/// Material::probe() looks up the current position's material configuration in
+/// the material hash table. It returns a pointer to the Entry if the position
+/// is found. Otherwise a new Entry is computed and stored there, so we don't
+/// have to recompute all when the same material configuration occurs again.
+Entry* probe(const Position& pos) {
-/// MaterialInfoTable::clear() clears a material hash table by setting
-/// all entries to 0.
+ Key key = pos.material_key();
+ Entry* e = pos.this_thread()->materialTable[key];
-void MaterialInfoTable::clear() {
+ if (e->key == key)
+ return e;
- memset(entries, 0, size * sizeof(MaterialInfo));
-}
+ std::memset(e, 0, sizeof(Entry));
+ e->key = key;
+ e->factor[WHITE] = e->factor[BLACK] = (uint8_t)SCALE_FACTOR_NORMAL;
+ Value npm_w = pos.non_pawn_material(WHITE);
+ Value npm_b = pos.non_pawn_material(BLACK);
+ Value npm = clamp(npm_w + npm_b, EndgameLimit, MidgameLimit);
-/// MaterialInfoTable::get_material_info() takes a position object as input,
-/// computes or looks up a MaterialInfo object, and returns a pointer to it.
-/// If the material configuration is not already present in the table, it
-/// is stored there, so we don't have to recompute everything when the
-/// same material configuration occurs again.
+ // Map total non-pawn material into [PHASE_ENDGAME, PHASE_MIDGAME]
+ e->gamePhase = Phase(((npm - EndgameLimit) * PHASE_MIDGAME) / (MidgameLimit - EndgameLimit));
-MaterialInfo *MaterialInfoTable::get_material_info(const Position& pos) {
+ // Let's look if we have a specialized evaluation function for this particular
+ // material configuration. Firstly we look for a fixed configuration one, then
+ // for a generic one if the previous search failed.
+ if ((e->evaluationFunction = Endgames::probe<Value>(key)) != nullptr)
+ return e;
- Key key = pos.get_material_key();
- int index = key & (size - 1);
- MaterialInfo* mi = entries + index;
-
- // If mi->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 (mi->key == key)
- return mi;
+ for (Color c : { WHITE, BLACK })
+ if (is_KXK(pos, c))
+ {
+ e->evaluationFunction = &EvaluateKXK[c];
+ return e;
+ }
- // Clear the MaterialInfo object, and set its key
- mi->clear();
- mi->key = key;
+ // OK, we didn't find any special evaluation function for the current material
+ // configuration. Is there a suitable specialized scaling function?
+ const auto* sf = Endgames::probe<ScaleFactor>(key);
- // A special case before looking for a specialized evaluation function
- // KNN vs K is a draw.
- if (key == KNNKMaterialKey || key == KKNNMaterialKey)
+ if (sf)
{
- mi->factor[WHITE] = mi->factor[BLACK] = 0;
- return mi;
+ e->scalingFunction[sf->strongSide] = sf; // Only strong color assigned
+ return e;
}
- // Let's look if we have a specialized evaluation function for this
- // particular material configuration.
- if ((mi->evaluationFunction = funcs->getEEF(key)) != NULL)
- return mi;
-
- else if ( pos.non_pawn_material(BLACK) == Value(0)
- && pos.piece_count(BLACK, PAWN) == 0
- && pos.non_pawn_material(WHITE) >= RookValueEndgame)
- {
- mi->evaluationFunction = &EvaluateKXK;
- return mi;
- }
- else if ( pos.non_pawn_material(WHITE) == Value(0)
- && pos.piece_count(WHITE, PAWN) == 0
- && pos.non_pawn_material(BLACK) >= RookValueEndgame)
+ // We didn't find any specialized scaling function, so fall back on generic
+ // ones that refer to more than one material distribution. Note that in this
+ // case we don't return after setting the function.
+ for (Color c : { WHITE, BLACK })
{
- mi->evaluationFunction = &EvaluateKKX;
- return mi;
- }
+ if (is_KBPsK(pos, c))
+ e->scalingFunction[c] = &ScaleKBPsK[c];
- // OK, we didn't find any special evaluation function for the current
- // material configuration. Is there a suitable scaling function?
- //
- // The code below is rather messy, and it could easily get worse later,
- // if we decide to add more special cases. We face problems when there
- // are several conflicting applicable scaling functions and we need to
- // decide which one to use.
- ScalingInfo si = funcs->getESF(key);
- if (si.fun != NULL)
- {
- mi->scalingFunction[si.col] = si.fun;
- return mi;
+ else if (is_KQKRPs(pos, c))
+ e->scalingFunction[c] = &ScaleKQKRPs[c];
}
- if ( pos.non_pawn_material(WHITE) == BishopValueMidgame
- && pos.piece_count(WHITE, BISHOP) == 1
- && pos.piece_count(WHITE, PAWN) >= 1)
- mi->scalingFunction[WHITE] = &ScaleKBPK;
-
- if ( pos.non_pawn_material(BLACK) == BishopValueMidgame
- && pos.piece_count(BLACK, BISHOP) == 1
- && pos.piece_count(BLACK, PAWN) >= 1)
- mi->scalingFunction[BLACK] = &ScaleKKBP;
-
- if ( pos.piece_count(WHITE, PAWN) == 0
- && pos.non_pawn_material(WHITE) == QueenValueMidgame
- && pos.piece_count(WHITE, QUEEN) == 1
- && pos.piece_count(BLACK, ROOK) == 1
- && pos.piece_count(BLACK, PAWN) >= 1)
- mi->scalingFunction[WHITE] = &ScaleKQKRP;
-
- else if ( pos.piece_count(BLACK, PAWN) == 0
- && pos.non_pawn_material(BLACK) == QueenValueMidgame
- && pos.piece_count(BLACK, QUEEN) == 1
- && pos.piece_count(WHITE, ROOK) == 1
- && pos.piece_count(WHITE, PAWN) >= 1)
- mi->scalingFunction[BLACK] = &ScaleKRPKQ;
-
- if (pos.non_pawn_material(WHITE) + pos.non_pawn_material(BLACK) == Value(0))
+ if (npm_w + npm_b == VALUE_ZERO && pos.pieces(PAWN)) // Only pawns on the board
{
- if (pos.piece_count(BLACK, PAWN) == 0)
+ if (!pos.count<PAWN>(BLACK))
{
- assert(pos.piece_count(WHITE, PAWN) >= 2);
- mi->scalingFunction[WHITE] = &ScaleKPsK;
+ assert(pos.count<PAWN>(WHITE) >= 2);
+
+ e->scalingFunction[WHITE] = &ScaleKPsK[WHITE];
}
- else if (pos.piece_count(WHITE, PAWN) == 0)
+ else if (!pos.count<PAWN>(WHITE))
{
- assert(pos.piece_count(BLACK, PAWN) >= 2);
- mi->scalingFunction[BLACK] = &ScaleKKPs;
+ assert(pos.count<PAWN>(BLACK) >= 2);
+
+ e->scalingFunction[BLACK] = &ScaleKPsK[BLACK];
}
- else if (pos.piece_count(WHITE, PAWN) == 1 && pos.piece_count(BLACK, PAWN) == 1)
+ else if (pos.count<PAWN>(WHITE) == 1 && pos.count<PAWN>(BLACK) == 1)
{
- mi->scalingFunction[WHITE] = &ScaleKPKPw;
- mi->scalingFunction[BLACK] = &ScaleKPKPb;
+ // 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];
}
}
- // Evaluate the material balance
-
- Color c;
- int sign;
- Value egValue = Value(0);
- Value mgValue = Value(0);
-
- for (c = WHITE, sign = 1; c <= BLACK; c++, sign = -sign)
- {
- // No pawns makes it difficult to win, even with a material advantage
- if ( pos.piece_count(c, PAWN) == 0
- && pos.non_pawn_material(c) - pos.non_pawn_material(opposite_color(c)) <= BishopValueMidgame)
- {
- if ( pos.non_pawn_material(c) == pos.non_pawn_material(opposite_color(c))
- || pos.non_pawn_material(c) < RookValueMidgame)
- mi->factor[c] = 0;
- else
- {
- switch (pos.piece_count(c, BISHOP)) {
- case 2:
- mi->factor[c] = 32;
- break;
- case 1:
- mi->factor[c] = 12;
- break;
- case 0:
- mi->factor[c] = 6;
- break;
- }
- }
- }
-
- // Bishop pair
- if (pos.piece_count(c, BISHOP) >= 2)
- {
- mgValue += sign * BishopPairMidgameBonus;
- egValue += sign * BishopPairEndgameBonus;
- }
-
- // Knights are stronger when there are many pawns on the board. The
- // formula is taken from Larry Kaufman's paper "The Evaluation of Material
- // Imbalances in Chess":
- // http://mywebpages.comcast.net/danheisman/Articles/evaluation_of_material_imbalance.htm
- mgValue += sign * Value(pos.piece_count(c, KNIGHT)*(pos.piece_count(c, PAWN)-5)*16);
- egValue += sign * Value(pos.piece_count(c, KNIGHT)*(pos.piece_count(c, PAWN)-5)*16);
-
- // Redundancy of major pieces, again based on Kaufman's paper:
- if (pos.piece_count(c, ROOK) >= 1)
- {
- Value v = Value((pos.piece_count(c, ROOK) - 1) * 32 + pos.piece_count(c, QUEEN) * 16);
- mgValue -= sign * v;
- egValue -= sign * v;
- }
- }
-
- mi->mgValue = int16_t(mgValue);
- mi->egValue = int16_t(egValue);
- return mi;
+ // Zero or just one pawn makes it difficult to win, even with a small material
+ // advantage. This catches some trivial draws like KK, KBK and KNK and gives a
+ // drawish scale factor for cases such as KRKBP and KmmKm (except for KBBKN).
+ if (!pos.count<PAWN>(WHITE) && npm_w - npm_b <= BishopValueMg)
+ e->factor[WHITE] = uint8_t(npm_w < RookValueMg ? SCALE_FACTOR_DRAW :
+ npm_b <= BishopValueMg ? 4 : 14);
+
+ if (!pos.count<PAWN>(BLACK) && npm_b - npm_w <= BishopValueMg)
+ e->factor[BLACK] = uint8_t(npm_b < RookValueMg ? SCALE_FACTOR_DRAW :
+ npm_w <= BishopValueMg ? 4 : 14);
+
+ // Evaluate the material imbalance. We use PIECE_TYPE_NONE as a place holder
+ // for the bishop pair "extended piece", which allows us to be more flexible
+ // in defining bishop pair bonuses.
+ const int pieceCount[COLOR_NB][PIECE_TYPE_NB] = {
+ { pos.count<BISHOP>(WHITE) > 1, pos.count<PAWN>(WHITE), pos.count<KNIGHT>(WHITE),
+ pos.count<BISHOP>(WHITE) , pos.count<ROOK>(WHITE), pos.count<QUEEN >(WHITE) },
+ { pos.count<BISHOP>(BLACK) > 1, pos.count<PAWN>(BLACK), pos.count<KNIGHT>(BLACK),
+ pos.count<BISHOP>(BLACK) , pos.count<ROOK>(BLACK), pos.count<QUEEN >(BLACK) } };
+
+ e->value = int16_t((imbalance<WHITE>(pieceCount) - imbalance<BLACK>(pieceCount)) / 16);
+ return e;
}
-
-/// EndgameFunctions members definition. This helper class is used to
-/// store the maps of end game and scaling functions that MaterialInfoTable
-/// will query for each key. The maps are constant, and are populated only
-/// at construction. Being per thread avoids to use locks to access them.
-
-EndgameFunctions::EndgameFunctions() {
-
- typedef Key ZM[2][8][16];
- const ZM& z = Position::zobMaterial;
-
- static const Color W = WHITE;
- static const Color B = BLACK;
-
- KNNKMaterialKey = z[W][KNIGHT][1] ^ z[W][KNIGHT][2];
- KKNNMaterialKey = z[B][KNIGHT][1] ^ z[B][KNIGHT][2];
-
- add(z[W][PAWN][1], &EvaluateKPK);
- add(z[B][PAWN][1], &EvaluateKKP);
-
- add(z[W][BISHOP][1] ^ z[W][KNIGHT][1], &EvaluateKBNK);
- add(z[B][BISHOP][1] ^ z[B][KNIGHT][1], &EvaluateKKBN);
- add(z[W][ROOK][1] ^ z[B][PAWN][1], &EvaluateKRKP);
- add(z[W][PAWN][1] ^ z[B][ROOK][1], &EvaluateKPKR);
- add(z[W][ROOK][1] ^ z[B][BISHOP][1], &EvaluateKRKB);
- add(z[W][BISHOP][1] ^ z[B][ROOK][1], &EvaluateKBKR);
- add(z[W][ROOK][1] ^ z[B][KNIGHT][1], &EvaluateKRKN);
- add(z[W][KNIGHT][1] ^ z[B][ROOK][1], &EvaluateKNKR);
- add(z[W][QUEEN][1] ^ z[B][ROOK][1], &EvaluateKQKR);
- add(z[W][ROOK][1] ^ z[B][QUEEN][1], &EvaluateKRKQ);
-
- add(z[W][KNIGHT][1] ^ z[W][PAWN][1], W, &ScaleKNPK);
- add(z[B][KNIGHT][1] ^ z[B][PAWN][1], B, &ScaleKKNP);
-
- add(z[W][ROOK][1] ^ z[W][PAWN][1] ^ z[B][ROOK][1] , W, &ScaleKRPKR);
- add(z[W][ROOK][1] ^ z[B][ROOK][1] ^ z[B][PAWN][1] , B, &ScaleKRKRP);
- add(z[W][BISHOP][1] ^ z[W][PAWN][1] ^ z[B][BISHOP][1], W, &ScaleKBPKB);
- add(z[W][BISHOP][1] ^ z[B][BISHOP][1] ^ z[B][PAWN][1] , B, &ScaleKBKBP);
- add(z[W][BISHOP][1] ^ z[W][PAWN][1] ^ z[B][KNIGHT][1], W, &ScaleKBPKN);
- add(z[W][KNIGHT][1] ^ z[B][BISHOP][1] ^ z[B][PAWN][1] , B, &ScaleKNKBP);
-
- add(z[W][ROOK][1] ^ z[W][PAWN][1] ^ z[W][PAWN][2] ^ z[B][ROOK][1] ^ z[B][PAWN][1], W, &ScaleKRPPKRP);
- add(z[W][ROOK][1] ^ z[W][PAWN][1] ^ z[B][ROOK][1] ^ z[B][PAWN][1] ^ z[B][PAWN][2], B, &ScaleKRPKRPP);
-}
-
-void EndgameFunctions::add(Key k, EndgameEvaluationFunction* f) {
-
- EEFmap.insert(std::pair<Key, EndgameEvaluationFunction*>(k, f));
-}
-
-void EndgameFunctions::add(Key k, Color c, ScalingFunction* f) {
-
- ScalingInfo s = {c, f};
- ESFmap.insert(std::pair<Key, ScalingInfo>(k, s));
-}
-
-EndgameEvaluationFunction* EndgameFunctions::getEEF(Key key) {
-
- EndgameEvaluationFunction* f = NULL;
- std::map<Key, EndgameEvaluationFunction*>::iterator it(EEFmap.find(key));
- if (it != EEFmap.end())
- f = it->second;
-
- return f;
-}
-
-ScalingInfo EndgameFunctions::getESF(Key key) {
-
- ScalingInfo si = {WHITE, NULL};
- std::map<Key, ScalingInfo>::iterator it(ESFmap.find(key));
- if (it != ESFmap.end())
- si = it->second;
-
- return si;
-}
+} // namespace Material