X-Git-Url: https://git.sesse.net/?a=blobdiff_plain;ds=sidebyside;f=src%2Fmaterial.cpp;h=8b659ecc2f612b1571d1fddf8e6cc478982e0329;hb=83e829c9dc900dcb00d673417062f4193481ff36;hp=9818fdce54c904b3378537b2b0f114caf221a597;hpb=5dc23121215039938a9ef4e59ae934312774571c;p=stockfish
diff --git a/src/material.cpp b/src/material.cpp
index 9818fdce..8b659ecc 100644
--- a/src/material.cpp
+++ b/src/material.cpp
@@ -1,7 +1,8 @@
/*
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) 2015-2017 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
@@ -17,391 +18,211 @@
along with this program. If not, see .
*/
-
-////
-//// Includes
-////
-
+#include // For std::min
#include
+#include // 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 KPKMaterialKey, KKPMaterialKey;
- Key KBNKMaterialKey, KKBNMaterialKey;
- Key KRKPMaterialKey, KPKRMaterialKey;
- Key KRKBMaterialKey, KBKRMaterialKey;
- Key KRKNMaterialKey, KNKRMaterialKey;
- Key KQKRMaterialKey, KRKQMaterialKey;
- Key KRPKRMaterialKey, KRKRPMaterialKey;
- Key KRPPKRPMaterialKey, KRPKRPPMaterialKey;
- Key KNNKMaterialKey, KKNNMaterialKey;
- Key KBPKBMaterialKey, KBKBPMaterialKey;
- Key KBPKNMaterialKey, KNKBPMaterialKey;
- Key KNPKMaterialKey, KKNPMaterialKey;
- Key KPKPMaterialKey;
+ // Polynomial material imbalance parameters
+
+ const int QuadraticOurs[][PIECE_TYPE_NB] = {
+ // OUR PIECES
+ // pair pawn knight bishop rook queen
+ {1667 }, // Bishop pair
+ { 40, 0 }, // Pawn
+ { 32, 255, -3 }, // Knight OUR PIECES
+ { 0, 104, 4, 0 }, // Bishop
+ { -26, -2, 47, 105, -149 }, // Rook
+ {-189, 24, 117, 133, -134, -10 } // Queen
+ };
+
+ const 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
+ };
+
+ // 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 EvaluateKXK[] = { Endgame(WHITE), Endgame(BLACK) };
+
+ Endgame ScaleKBPsK[] = { Endgame(WHITE), Endgame(BLACK) };
+ Endgame ScaleKQKRPs[] = { Endgame(WHITE), Endgame(BLACK) };
+ Endgame ScaleKPsK[] = { Endgame(WHITE), Endgame(BLACK) };
+ Endgame ScaleKPKP[] = { Endgame(WHITE), Endgame(BLACK) };
+
+ // 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_KBPsKs(const Position& pos, Color us) {
+ return pos.non_pawn_material(us) == BishopValueMg
+ && pos.count(us) == 1
+ && pos.count(us) >= 1;
+ }
+
+ bool is_KQKRPs(const Position& pos, Color us) {
+ return !pos.count(us)
+ && pos.non_pawn_material(us) == QueenValueMg
+ && pos.count(us) == 1
+ && pos.count(~us) == 1
+ && pos.count(~us) >= 1;
+ }
+
+ /// imbalance() calculates the imbalance by comparing the piece count of each
+ /// piece type for both colors.
+ template
+ int imbalance(const int pieceCount[][PIECE_TYPE_NB]) {
+
+ const Color Them = (Us == WHITE ? BLACK : WHITE);
+
+ int bonus = 0;
+
+ // 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;
+
+ for (int pt2 = NO_PIECE_TYPE; pt2 <= pt1; ++pt2)
+ v += QuadraticOurs[pt1][pt2] * pieceCount[Us][pt2]
+ + QuadraticTheirs[pt1][pt2] * pieceCount[Them][pt2];
+
+ bonus += pieceCount[Us][pt1] * v;
+ }
-}
+ return bonus;
+ }
+} // namespace
-////
-//// Functions
-////
-
-/// 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.
-
-void MaterialInfo::init() {
- KPKMaterialKey = Position::zobMaterial[WHITE][PAWN][1];
- KKPMaterialKey = Position::zobMaterial[BLACK][PAWN][1];
- KBNKMaterialKey =
- Position::zobMaterial[WHITE][BISHOP][1] ^
- Position::zobMaterial[WHITE][KNIGHT][1];
- KKBNMaterialKey =
- Position::zobMaterial[BLACK][BISHOP][1] ^
- Position::zobMaterial[BLACK][KNIGHT][1];
- KRKPMaterialKey =
- Position::zobMaterial[WHITE][ROOK][1] ^
- Position::zobMaterial[BLACK][PAWN][1];
- KPKRMaterialKey =
- Position::zobMaterial[WHITE][PAWN][1] ^
- Position::zobMaterial[BLACK][ROOK][1];
- KRKBMaterialKey =
- Position::zobMaterial[WHITE][ROOK][1] ^
- Position::zobMaterial[BLACK][BISHOP][1];
- KBKRMaterialKey =
- Position::zobMaterial[WHITE][BISHOP][1] ^
- Position::zobMaterial[BLACK][ROOK][1];
- KRKNMaterialKey =
- Position::zobMaterial[WHITE][ROOK][1] ^
- Position::zobMaterial[BLACK][KNIGHT][1];
- KNKRMaterialKey =
- Position::zobMaterial[WHITE][KNIGHT][1] ^
- Position::zobMaterial[BLACK][ROOK][1];
- KQKRMaterialKey =
- Position::zobMaterial[WHITE][QUEEN][1] ^
- Position::zobMaterial[BLACK][ROOK][1];
- KRKQMaterialKey =
- Position::zobMaterial[WHITE][ROOK][1] ^
- Position::zobMaterial[BLACK][QUEEN][1];
- KRPKRMaterialKey =
- Position::zobMaterial[WHITE][ROOK][1] ^
- Position::zobMaterial[WHITE][PAWN][1] ^
- Position::zobMaterial[BLACK][ROOK][1];
- KRKRPMaterialKey =
- Position::zobMaterial[WHITE][ROOK][1] ^
- Position::zobMaterial[BLACK][ROOK][1] ^
- Position::zobMaterial[BLACK][PAWN][1];
- KRPPKRPMaterialKey =
- Position::zobMaterial[WHITE][ROOK][1] ^
- Position::zobMaterial[WHITE][PAWN][1] ^
- Position::zobMaterial[WHITE][PAWN][2] ^
- Position::zobMaterial[BLACK][ROOK][1] ^
- Position::zobMaterial[BLACK][PAWN][1];
- KRPKRPPMaterialKey =
- Position::zobMaterial[WHITE][ROOK][1] ^
- Position::zobMaterial[WHITE][PAWN][1] ^
- Position::zobMaterial[BLACK][ROOK][1] ^
- Position::zobMaterial[BLACK][PAWN][1] ^
- Position::zobMaterial[BLACK][PAWN][2];
- KNNKMaterialKey =
- Position::zobMaterial[WHITE][KNIGHT][1] ^
- Position::zobMaterial[WHITE][KNIGHT][2];
- KKNNMaterialKey =
- Position::zobMaterial[BLACK][KNIGHT][1] ^
- Position::zobMaterial[BLACK][KNIGHT][2];
- KBPKBMaterialKey =
- Position::zobMaterial[WHITE][BISHOP][1] ^
- Position::zobMaterial[WHITE][PAWN][1] ^
- Position::zobMaterial[BLACK][BISHOP][1];
- KBKBPMaterialKey =
- Position::zobMaterial[WHITE][BISHOP][1] ^
- Position::zobMaterial[BLACK][BISHOP][1] ^
- Position::zobMaterial[BLACK][PAWN][1];
- KBPKNMaterialKey =
- Position::zobMaterial[WHITE][BISHOP][1] ^
- Position::zobMaterial[WHITE][PAWN][1] ^
- Position::zobMaterial[BLACK][KNIGHT][1];
- KNKBPMaterialKey =
- Position::zobMaterial[WHITE][KNIGHT][1] ^
- Position::zobMaterial[BLACK][BISHOP][1] ^
- Position::zobMaterial[BLACK][PAWN][1];
- KNPKMaterialKey =
- Position::zobMaterial[WHITE][KNIGHT][1] ^
- Position::zobMaterial[WHITE][PAWN][1];
- KKNPMaterialKey =
- Position::zobMaterial[BLACK][KNIGHT][1] ^
- Position::zobMaterial[BLACK][PAWN][1];
- KPKPMaterialKey =
- Position::zobMaterial[WHITE][PAWN][1] ^
- Position::zobMaterial[BLACK][PAWN][1];
-}
+namespace Material {
+/// 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.
-/// Constructor for the MaterialInfoTable class.
+Entry* probe(const Position& pos) {
-MaterialInfoTable::MaterialInfoTable(unsigned numOfEntries) {
- size = numOfEntries;
- entries = new MaterialInfo[size];
- if(entries == NULL) {
- std::cerr << "Failed to allocate " << (numOfEntries * sizeof(MaterialInfo))
- << " bytes for material hash table." << std::endl;
- exit(EXIT_FAILURE);
- }
- this->clear();
-}
+ Key key = pos.material_key();
+ Entry* e = pos.this_thread()->materialTable[key];
+ if (e->key == key)
+ return e;
-/// Destructor for the MaterialInfoTable class.
+ std::memset(e, 0, sizeof(Entry));
+ e->key = key;
+ e->factor[WHITE] = e->factor[BLACK] = (uint8_t)SCALE_FACTOR_NORMAL;
-MaterialInfoTable::~MaterialInfoTable() {
- delete [] entries;
-}
+ Value npm_w = pos.non_pawn_material(WHITE);
+ Value npm_b = pos.non_pawn_material(BLACK);
+ Value npm = std::max(EndgameLimit, std::min(npm_w + npm_b, MidgameLimit));
+ // Map total non-pawn material into [PHASE_ENDGAME, PHASE_MIDGAME]
+ e->gamePhase = Phase(((npm - EndgameLimit) * PHASE_MIDGAME) / (MidgameLimit - EndgameLimit));
-/// MaterialInfoTable::clear() clears a material hash table by setting
-/// all entries to 0.
+ // 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 = pos.this_thread()->endgames.probe(key)) != nullptr)
+ return e;
-void MaterialInfoTable::clear() {
- memset(entries, 0, size * sizeof(MaterialInfo));
-}
+ for (Color c = WHITE; c <= BLACK; ++c)
+ if (is_KXK(pos, c))
+ {
+ e->evaluationFunction = &EvaluateKXK[c];
+ return e;
+ }
+ // OK, we didn't find any special evaluation function for the current material
+ // configuration. Is there a suitable specialized scaling function?
+ EndgameBase* sf;
-/// 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.
-
-MaterialInfo *MaterialInfoTable::get_material_info(const Position &pos) {
- 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;
-
- // Clear the MaterialInfo object, and set its key:
- mi->clear();
- mi->key = key;
-
- // A special case before looking for a specialized evaluation function:
- // KNN vs K is a draw:
- if(key == KNNKMaterialKey || key == KKNNMaterialKey) {
- mi->factor[WHITE] = mi->factor[BLACK] = 0;
- return mi;
+ if ((sf = pos.this_thread()->endgames.probe(key)) != nullptr)
+ {
+ 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(key == KPKMaterialKey) {
- mi->evaluationFunction = &EvaluateKPK;
- return mi;
- }
- else if(key == KKPMaterialKey) {
- mi->evaluationFunction = &EvaluateKKP;
- return mi;
- }
- else if(key == KBNKMaterialKey) {
- mi->evaluationFunction = &EvaluateKBNK;
- return mi;
- }
- else if(key == KKBNMaterialKey) {
- mi->evaluationFunction = &EvaluateKKBN;
- return mi;
- }
- else if(key == KRKPMaterialKey) {
- mi->evaluationFunction = &EvaluateKRKP;
- return mi;
- }
- else if(key == KPKRMaterialKey) {
- mi->evaluationFunction = &EvaluateKPKR;
- return mi;
- }
- else if(key == KRKBMaterialKey) {
- mi->evaluationFunction = &EvaluateKRKB;
- return mi;
- }
- else if(key == KBKRMaterialKey) {
- mi->evaluationFunction = &EvaluateKBKR;
- return mi;
- }
- else if(key == KRKNMaterialKey) {
- mi->evaluationFunction = &EvaluateKRKN;
- return mi;
- }
- else if(key == KNKRMaterialKey) {
- mi->evaluationFunction = &EvaluateKNKR;
- return mi;
- }
- else if(key == KQKRMaterialKey) {
- mi->evaluationFunction = &EvaluateKQKR;
- return mi;
- }
- else if(key == KRKQMaterialKey) {
- mi->evaluationFunction = &EvaluateKRKQ;
- 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) {
- mi->evaluationFunction = &EvaluateKKX;
- return mi;
- }
+ // 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; c <= BLACK; ++c)
+ {
+ if (is_KBPsKs(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.
-
- if(key == KRPKRMaterialKey) {
- mi->scalingFunction[WHITE] = &ScaleKRPKR;
- return mi;
- }
- if(key == KRKRPMaterialKey) {
- mi->scalingFunction[BLACK] = &ScaleKRKRP;
- return mi;
- }
- if(key == KRPPKRPMaterialKey) {
- mi->scalingFunction[WHITE] = &ScaleKRPPKRP;
- return mi;
- }
- else if(key == KRPKRPPMaterialKey) {
- mi->scalingFunction[BLACK] = &ScaleKRPKRPP;
- return mi;
- }
- if(key == KBPKBMaterialKey) {
- mi->scalingFunction[WHITE] = &ScaleKBPKB;
- return mi;
- }
- if(key == KBKBPMaterialKey) {
- mi->scalingFunction[BLACK] = &ScaleKBKBP;
- return mi;
- }
- if(key == KBPKNMaterialKey) {
- mi->scalingFunction[WHITE] = &ScaleKBPKN;
- return mi;
- }
- if(key == KNKBPMaterialKey) {
- mi->scalingFunction[BLACK] = &ScaleKNKBP;
- return mi;
- }
- if(key == KNPKMaterialKey) {
- mi->scalingFunction[WHITE] = &ScaleKNPK;
- return mi;
- }
- if(key == KKNPMaterialKey) {
- mi->scalingFunction[BLACK] = &ScaleKKNP;
- 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(pos.piece_count(BLACK, PAWN) == 0) {
- assert(pos.piece_count(WHITE, PAWN) >= 2);
- mi->scalingFunction[WHITE] = &ScaleKPsK;
- }
- else if(pos.piece_count(WHITE, PAWN) == 0) {
- assert(pos.piece_count(BLACK, PAWN) >= 2);
- mi->scalingFunction[BLACK] = &ScaleKKPs;
- }
- else if(pos.piece_count(WHITE, PAWN) == 1 && pos.piece_count(BLACK, PAWN) == 1) {
- mi->scalingFunction[WHITE] = &ScaleKPKPw;
- mi->scalingFunction[BLACK] = &ScaleKPKPb;
- }
- }
+ if (npm_w + npm_b == VALUE_ZERO && pos.pieces(PAWN)) // Only pawns on the board
+ {
+ if (!pos.count(BLACK))
+ {
+ assert(pos.count(WHITE) >= 2);
- // Evaluate the material balance.
-
- Color c;
- int sign;
- Value egValue = Value(0), 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)))
- mi->factor[c] = 0;
- else if(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;
- }
+ e->scalingFunction[WHITE] = &ScaleKPsK[WHITE];
}
- }
+ else if (!pos.count(WHITE))
+ {
+ assert(pos.count(BLACK) >= 2);
- // Bishop pair:
- if(pos.piece_count(c, BISHOP) >= 2) {
- mgValue += sign * BishopPairMidgameBonus;
- egValue += sign * BishopPairEndgameBonus;
- }
+ e->scalingFunction[BLACK] = &ScaleKPsK[BLACK];
+ }
+ else if (pos.count(WHITE) == 1 && pos.count(BLACK) == 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];
+ }
+ }
- // 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;
- }
+ // 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(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(BLACK) && npm_b - npm_w <= BishopValueMg)
+ e->factor[BLACK] = uint8_t(npm_b < RookValueMg ? SCALE_FACTOR_DRAW :
+ npm_w <= BishopValueMg ? 4 : 14);
- mi->mgValue = int16_t(mgValue);
- mi->egValue = int16_t(egValue);
+ if (pos.count(WHITE) == 1 && npm_w - npm_b <= BishopValueMg)
+ e->factor[WHITE] = (uint8_t) SCALE_FACTOR_ONEPAWN;
- return mi;
+ if (pos.count(BLACK) == 1 && npm_b - npm_w <= BishopValueMg)
+ e->factor[BLACK] = (uint8_t) SCALE_FACTOR_ONEPAWN;
+
+ // 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(WHITE) > 1, pos.count(WHITE), pos.count(WHITE),
+ pos.count(WHITE) , pos.count(WHITE), pos.count(WHITE) },
+ { pos.count(BLACK) > 1, pos.count(BLACK), pos.count(BLACK),
+ pos.count(BLACK) , pos.count(BLACK), pos.count(BLACK) } };
+
+ e->value = int16_t((imbalance(PieceCount) - imbalance(PieceCount)) / 16);
+ return e;
}
+
+} // namespace Material