/*
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
+ 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
along with this program. If not, see <http://www.gnu.org/licenses/>.
*/
+#include <algorithm>
#include <cassert>
+#include <cstring> // For std::memset
#include <iomanip>
#include <sstream>
-#include <algorithm>
-#include "bitcount.h"
+#include "bitboard.h"
#include "evaluate.h"
#include "material.h"
#include "pawns.h"
-#include "thread.h"
-#include "ucioption.h"
namespace {
- // Struct EvalInfo contains various information computed and collected
- // by the evaluation functions.
- struct EvalInfo {
+ namespace Trace {
+
+ enum Tracing {NO_TRACE, TRACE};
+
+ enum Term { // The first 8 entries are for PieceType
+ MATERIAL = 8, IMBALANCE, MOBILITY, THREAT, PASSED, SPACE, TOTAL, TERM_NB
+ };
+
+ double scores[TERM_NB][COLOR_NB][PHASE_NB];
+
+ double to_cp(Value v) { return double(v) / PawnValueEg; }
+
+ void add(int idx, Color c, Score s) {
+ scores[idx][c][MG] = to_cp(mg_value(s));
+ scores[idx][c][EG] = to_cp(eg_value(s));
+ }
+
+ void add(int idx, Score w, Score b = SCORE_ZERO) {
+ add(idx, WHITE, w); add(idx, BLACK, b);
+ }
+
+ std::ostream& operator<<(std::ostream& os, Term t) {
+
+ if (t == MATERIAL || t == IMBALANCE || t == Term(PAWN) || t == TOTAL)
+ os << " --- --- | --- --- | ";
+ else
+ os << std::setw(5) << scores[t][WHITE][MG] << " "
+ << std::setw(5) << scores[t][WHITE][EG] << " | "
+ << std::setw(5) << scores[t][BLACK][MG] << " "
+ << std::setw(5) << scores[t][BLACK][EG] << " | ";
+
+ os << std::setw(5) << scores[t][WHITE][MG] - scores[t][BLACK][MG] << " "
+ << std::setw(5) << scores[t][WHITE][EG] - scores[t][BLACK][EG] << " \n";
- // Pointers to material and pawn hash table entries
- MaterialInfo* mi;
- PawnInfo* pi;
+ return os;
+ }
+ }
+
+ using namespace Trace;
+
+ // Evaluation class contains various information computed and collected
+ // by the evaluation functions.
+ template<Tracing T = NO_TRACE>
+ class Evaluation {
+
+ public:
+ Evaluation() = delete;
+ Evaluation(const Position& p) : pos(p) {}
+ Evaluation& operator=(const Evaluation&) = delete;
+
+ Value value();
+
+ private:
+ // Evaluation helpers (used when calling value())
+ template<Color Us> void initialize();
+ template<Color Us> Score evaluate_king();
+ template<Color Us> Score evaluate_threats();
+ template<Color Us> Score evaluate_passed_pawns();
+ template<Color Us> Score evaluate_space();
+ template<Color Us, PieceType Pt> Score evaluate_pieces();
+ ScaleFactor evaluate_scale_factor(Value eg);
+ Score evaluate_initiative(Value eg);
+
+ // Data members
+ const Position& pos;
+ Material::Entry* me;
+ Pawns::Entry* pe;
+ Bitboard mobilityArea[COLOR_NB];
+ Score mobility[COLOR_NB] = { SCORE_ZERO, SCORE_ZERO };
// attackedBy[color][piece type] is a bitboard representing all squares
- // attacked by a given color and piece type, attackedBy[color][0] contains
- // all squares attacked by the given color.
- Bitboard attackedBy[2][8];
+ // attacked by a given color and piece type (can be also ALL_PIECES).
+ Bitboard attackedBy[COLOR_NB][PIECE_TYPE_NB];
+
+ // attackedBy2[color] are the squares attacked by 2 pieces of a given color,
+ // possibly via x-ray or by one pawn and one piece. Diagonal x-ray through
+ // pawn or squares attacked by 2 pawns are not explicitly added.
+ Bitboard attackedBy2[COLOR_NB];
// kingRing[color] is the zone around the king which is considered
// by the king safety evaluation. This consists of the squares directly
- // adjacent to the king, and the three (or two, for a king on an edge file)
+ // adjacent to the king, and (only for a king on its first rank) the
// squares two ranks in front of the king. For instance, if black's king
// is on g8, kingRing[BLACK] is a bitboard containing the squares f8, h8,
// f7, g7, h7, f6, g6 and h6.
- Bitboard kingRing[2];
+ Bitboard kingRing[COLOR_NB];
// kingAttackersCount[color] is the number of pieces of the given color
// which attack a square in the kingRing of the enemy king.
- int kingAttackersCount[2];
+ int kingAttackersCount[COLOR_NB];
- // kingAttackersWeight[color] is the sum of the "weight" of the pieces of the
+ // kingAttackersWeight[color] is the sum of the "weights" of the pieces of the
// given color which attack a square in the kingRing of the enemy king. The
- // weights of the individual piece types are given by the variables
- // QueenAttackWeight, RookAttackWeight, BishopAttackWeight and
- // KnightAttackWeight in evaluate.cpp
- int kingAttackersWeight[2];
-
- // kingAdjacentZoneAttacksCount[color] is the number of attacks to squares
- // directly adjacent to the king of the given color. Pieces which attack
- // more than one square are counted multiple times. For instance, if black's
- // king is on g8 and there's a white knight on g5, this knight adds
- // 2 to kingAdjacentZoneAttacksCount[BLACK].
- int kingAdjacentZoneAttacksCount[2];
+ // weights of the individual piece types are given by the elements in the
+ // KingAttackWeights array.
+ int kingAttackersWeight[COLOR_NB];
+
+ // kingAdjacentZoneAttacksCount[color] is the number of attacks by the given
+ // color to squares directly adjacent to the enemy king. Pieces which attack
+ // more than one square are counted multiple times. For instance, if there is
+ // a white knight on g5 and black's king is on g8, this white knight adds 2
+ // to kingAdjacentZoneAttacksCount[WHITE].
+ int kingAdjacentZoneAttacksCount[COLOR_NB];
};
- // Evaluation grain size, must be a power of 2
- const int GrainSize = 8;
-
- // Evaluation weights, initialized from UCI options
- enum { Mobility, PassedPawns, Space, KingDangerUs, KingDangerThem };
- Score Weights[6];
-
- typedef Value V;
+ #define V(v) Value(v)
#define S(mg, eg) make_score(mg, eg)
- // Internal evaluation weights. These are applied on top of the evaluation
- // weights read from UCI parameters. The purpose is to be able to change
- // the evaluation weights while keeping the default values of the UCI
- // parameters at 100, which looks prettier.
- //
- // Values modified by Joona Kiiski
- const Score WeightsInternal[] = {
- S(252, 344), S(216, 266), S(46, 0), S(247, 0), S(259, 0)
- };
-
- // MobilityBonus[PieceType][attacked] contains mobility bonuses for middle and
- // end game, indexed by piece type and number of attacked squares not occupied
- // by friendly pieces.
+ // MobilityBonus[PieceType-2][attacked] contains bonuses for middle and end game,
+ // indexed by piece type and number of attacked squares in the mobility area.
const Score MobilityBonus[][32] = {
- {}, {},
- { S(-38,-33), S(-25,-23), S(-12,-13), S( 0, -3), S(12, 7), S(25, 17), // Knights
- S( 31, 22), S( 38, 27), S( 38, 27) },
- { S(-25,-30), S(-11,-16), S( 3, -2), S(17, 12), S(31, 26), S(45, 40), // Bishops
- S( 57, 52), S( 65, 60), S( 71, 65), S(74, 69), S(76, 71), S(78, 73),
- S( 79, 74), S( 80, 75), S( 81, 76), S(81, 76) },
- { S(-20,-36), S(-14,-19), S( -8, -3), S(-2, 13), S( 4, 29), S(10, 46), // Rooks
- S( 14, 62), S( 19, 79), S( 23, 95), S(26,106), S(27,111), S(28,114),
- S( 29,116), S( 30,117), S( 31,118), S(32,118) },
- { S(-10,-18), S( -8,-13), S( -6, -7), S(-3, -2), S(-1, 3), S( 1, 8), // Queens
- S( 3, 13), S( 5, 19), S( 8, 23), S(10, 27), S(12, 32), S(15, 34),
- S( 16, 35), S( 17, 35), S( 18, 35), S(20, 35), S(20, 35), S(20, 35),
- S( 20, 35), S( 20, 35), S( 20, 35), S(20, 35), S(20, 35), S(20, 35),
- S( 20, 35), S( 20, 35), S( 20, 35), S(20, 35), S(20, 35), S(20, 35),
- S( 20, 35), S( 20, 35) }
+ { S(-75,-76), S(-57,-54), S( -9,-28), S( -2,-10), S( 6, 5), S( 14, 12), // Knights
+ S( 22, 26), S( 29, 29), S( 36, 29) },
+ { S(-48,-59), S(-20,-23), S( 16, -3), S( 26, 13), S( 38, 24), S( 51, 42), // Bishops
+ S( 55, 54), S( 63, 57), S( 63, 65), S( 68, 73), S( 81, 78), S( 81, 86),
+ S( 91, 88), S( 98, 97) },
+ { S(-58,-76), S(-27,-18), S(-15, 28), S(-10, 55), S( -5, 69), S( -2, 82), // Rooks
+ S( 9,112), S( 16,118), S( 30,132), S( 29,142), S( 32,155), S( 38,165),
+ S( 46,166), S( 48,169), S( 58,171) },
+ { S(-39,-36), S(-21,-15), S( 3, 8), S( 3, 18), S( 14, 34), S( 22, 54), // Queens
+ S( 28, 61), S( 41, 73), S( 43, 79), S( 48, 92), S( 56, 94), S( 60,104),
+ S( 60,113), S( 66,120), S( 67,123), S( 70,126), S( 71,133), S( 73,136),
+ S( 79,140), S( 88,143), S( 88,148), S( 99,166), S(102,170), S(102,175),
+ S(106,184), S(109,191), S(113,206), S(116,212) }
};
- // OutpostBonus[PieceType][Square] contains outpost bonuses of knights and
- // bishops, indexed by piece type and square (from white's point of view).
- const Value OutpostBonus[][64] = {
- {
- // A B C D E F G H
- V(0), V(0), V(0), V(0), V(0), V(0), V(0), V(0), // Knights
- V(0), V(0), V(0), V(0), V(0), V(0), V(0), V(0),
- V(0), V(0), V(4), V(8), V(8), V(4), V(0), V(0),
- V(0), V(4),V(17),V(26),V(26),V(17), V(4), V(0),
- V(0), V(8),V(26),V(35),V(35),V(26), V(8), V(0),
- V(0), V(4),V(17),V(17),V(17),V(17), V(4), V(0) },
- {
- V(0), V(0), V(0), V(0), V(0), V(0), V(0), V(0), // Bishops
- V(0), V(0), V(0), V(0), V(0), V(0), V(0), V(0),
- V(0), V(0), V(5), V(5), V(5), V(5), V(0), V(0),
- V(0), V(5),V(10),V(10),V(10),V(10), V(5), V(0),
- V(0),V(10),V(21),V(21),V(21),V(21),V(10), V(0),
- V(0), V(5), V(8), V(8), V(8), V(8), V(5), V(0) }
+ // Outpost[knight/bishop][supported by pawn] contains bonuses for minor
+ // pieces if they can reach an outpost square, bigger if that square is
+ // supported by a pawn. If the minor piece occupies an outpost square
+ // then score is doubled.
+ const Score Outpost[][2] = {
+ { S(22, 6), S(33, 9) }, // Knight
+ { S( 9, 2), S(14, 4) } // Bishop
};
- // ThreatBonus[attacking][attacked] contains threat bonuses according to
- // which piece type attacks which one.
- const Score ThreatBonus[][8] = {
- {}, {},
- { S(0, 0), S( 7, 39), S( 0, 0), S(24, 49), S(41,100), S(41,100) }, // KNIGHT
- { S(0, 0), S( 7, 39), S(24, 49), S( 0, 0), S(41,100), S(41,100) }, // BISHOP
- { S(0, 0), S(-1, 29), S(15, 49), S(15, 49), S( 0, 0), S(24, 49) }, // ROOK
- { S(0, 0), S(15, 39), S(15, 39), S(15, 39), S(15, 39), S( 0, 0) } // QUEEN
+ // RookOnFile[semiopen/open] contains bonuses for each rook when there is no
+ // friendly pawn on the rook file.
+ const Score RookOnFile[] = { S(20, 7), S(45, 20) };
+
+ // ThreatByMinor/ByRook[attacked PieceType] contains bonuses according to
+ // which piece type attacks which one. Attacks on lesser pieces which are
+ // pawn-defended are not considered.
+ const Score ThreatByMinor[PIECE_TYPE_NB] = {
+ S(0, 0), S(0, 33), S(45, 43), S(46, 47), S(72, 107), S(48, 118)
};
- // ThreatenedByPawnPenalty[PieceType] contains a penalty according to which
- // piece type is attacked by an enemy pawn.
- const Score ThreatenedByPawnPenalty[] = {
- S(0, 0), S(0, 0), S(56, 70), S(56, 70), S(76, 99), S(86, 118)
+ const Score ThreatByRook[PIECE_TYPE_NB] = {
+ S(0, 0), S(0, 25), S(40, 62), S(40, 59), S(0, 34), S(35, 48)
};
- #undef S
+ // ThreatByKing[on one/on many] contains bonuses for king attacks on
+ // pawns or pieces which are not pawn-defended.
+ const Score ThreatByKing[] = { S(3, 62), S(9, 138) };
- // Rooks and queens on the 7th rank (modified by Joona Kiiski)
- const Score RookOn7thBonus = make_score(47, 98);
- const Score QueenOn7thBonus = make_score(27, 54);
+ // Passed[mg/eg][Rank] contains midgame and endgame bonuses for passed pawns.
+ // We don't use a Score because we process the two components independently.
+ const Value Passed[][RANK_NB] = {
+ { V(5), V( 5), V(31), V(73), V(166), V(252) },
+ { V(7), V(14), V(38), V(73), V(166), V(252) }
+ };
- // Rooks on open files (modified by Joona Kiiski)
- const Score RookOpenFileBonus = make_score(43, 21);
- const Score RookHalfOpenFileBonus = make_score(19, 10);
+ // PassedFile[File] contains a bonus according to the file of a passed pawn
+ const Score PassedFile[FILE_NB] = {
+ S( 9, 10), S( 2, 10), S( 1, -8), S(-20,-12),
+ S(-20,-12), S( 1, -8), S( 2, 10), S( 9, 10)
+ };
- // Penalty for rooks trapped inside a friendly king which has lost the
- // right to castle.
- const Value TrappedRookPenalty = Value(180);
+ // KingProtector[PieceType-2] contains a bonus according to distance from king
+ const Score KingProtector[] = { S(-3, -5), S(-4, -3), S(-3, 0), S(-1, 1) };
+
+ // Assorted bonuses and penalties used by evaluation
+ const Score MinorBehindPawn = S( 16, 0);
+ const Score BishopPawns = S( 8, 12);
+ const Score RookOnPawn = S( 8, 24);
+ const Score TrappedRook = S( 92, 0);
+ const Score WeakQueen = S( 50, 10);
+ const Score OtherCheck = S( 10, 10);
+ const Score CloseEnemies = S( 7, 0);
+ const Score PawnlessFlank = S( 20, 80);
+ const Score ThreatByHangingPawn = S( 71, 61);
+ const Score ThreatBySafePawn = S(182,175);
+ const Score ThreatByRank = S( 16, 3);
+ const Score Hanging = S( 48, 27);
+ const Score ThreatByPawnPush = S( 38, 22);
+ const Score HinderPassedPawn = S( 7, 0);
// Penalty for a bishop on a1/h1 (a8/h8 for black) which is trapped by
// a friendly pawn on b2/g2 (b7/g7 for black). This can obviously only
// happen in Chess960 games.
- const Score TrappedBishopA1H1Penalty = make_score(100, 100);
-
- // Penalty for a minor piece that is not defended by anything
- const Score UndefendedMinorPenalty = make_score(25, 10);
-
- // The SpaceMask[Color] contains the area of the board which is considered
- // by the space evaluation. In the middle game, each side is given a bonus
- // based on how many squares inside this area are safe and available for
- // friendly minor pieces.
- const Bitboard SpaceMask[] = {
- (1ULL << SQ_C2) | (1ULL << SQ_D2) | (1ULL << SQ_E2) | (1ULL << SQ_F2) |
- (1ULL << SQ_C3) | (1ULL << SQ_D3) | (1ULL << SQ_E3) | (1ULL << SQ_F3) |
- (1ULL << SQ_C4) | (1ULL << SQ_D4) | (1ULL << SQ_E4) | (1ULL << SQ_F4),
- (1ULL << SQ_C7) | (1ULL << SQ_D7) | (1ULL << SQ_E7) | (1ULL << SQ_F7) |
- (1ULL << SQ_C6) | (1ULL << SQ_D6) | (1ULL << SQ_E6) | (1ULL << SQ_F6) |
- (1ULL << SQ_C5) | (1ULL << SQ_D5) | (1ULL << SQ_E5) | (1ULL << SQ_F5)
- };
+ const Score TrappedBishopA1H1 = S(50, 50);
- // King danger constants and variables. The king danger scores are taken
- // from the KingDangerTable[]. Various little "meta-bonuses" measuring
- // the strength of the enemy attack are added up into an integer, which
- // is used as an index to KingDangerTable[].
- //
- // KingAttackWeights[PieceType] contains king attack weights by piece type
- const int KingAttackWeights[] = { 0, 0, 2, 2, 3, 5 };
-
- // Bonuses for enemy's safe checks
- const int QueenContactCheckBonus = 6;
- const int RookContactCheckBonus = 4;
- const int QueenCheckBonus = 3;
- const int RookCheckBonus = 2;
- const int BishopCheckBonus = 1;
- const int KnightCheckBonus = 1;
-
- // InitKingDanger[Square] contains penalties based on the position of the
- // defending king, indexed by king's square (from white's point of view).
- const int InitKingDanger[] = {
- 2, 0, 2, 5, 5, 2, 0, 2,
- 2, 2, 4, 8, 8, 4, 2, 2,
- 7, 10, 12, 12, 12, 12, 10, 7,
- 15, 15, 15, 15, 15, 15, 15, 15,
- 15, 15, 15, 15, 15, 15, 15, 15,
- 15, 15, 15, 15, 15, 15, 15, 15,
- 15, 15, 15, 15, 15, 15, 15, 15,
- 15, 15, 15, 15, 15, 15, 15, 15
- };
-
- // KingDangerTable[Color][attackUnits] contains the actual king danger
- // weighted scores, indexed by color and by a calculated integer number.
- Score KingDangerTable[2][128];
-
- // TracedTerms[Color][PieceType || TracedType] contains a breakdown of the
- // evaluation terms, used when tracing.
- Score TracedScores[2][16];
- std::stringstream TraceStream;
-
- enum TracedType {
- PST = 8, IMBALANCE = 9, MOBILITY = 10, THREAT = 11,
- PASSED = 12, UNSTOPPABLE = 13, SPACE = 14, TOTAL = 15
- };
-
- // Function prototypes
- template<bool Trace>
- Value do_evaluate(const Position& pos, Value& margin);
-
- template<Color Us>
- void init_eval_info(const Position& pos, EvalInfo& ei);
-
- template<Color Us, bool Trace>
- Score evaluate_pieces_of_color(const Position& pos, EvalInfo& ei, Score& mobility);
-
- template<Color Us, bool Trace>
- Score evaluate_king(const Position& pos, EvalInfo& ei, Value margins[]);
-
- template<Color Us>
- Score evaluate_threats(const Position& pos, EvalInfo& ei);
-
- template<Color Us>
- int evaluate_space(const Position& pos, EvalInfo& ei);
-
- template<Color Us>
- Score evaluate_passed_pawns(const Position& pos, EvalInfo& ei);
-
- Score evaluate_unstoppable_pawns(const Position& pos, EvalInfo& ei);
-
- inline Score apply_weight(Score v, Score weight);
- Value scale_by_game_phase(const Score& v, Phase ph, ScaleFactor sf);
- Score weight_option(const std::string& mgOpt, const std::string& egOpt, Score internalWeight);
- double to_cp(Value v);
- void trace_add(int idx, Score term_w, Score term_b = SCORE_ZERO);
- void trace_row(const char* name, int idx);
-}
+ #undef S
+ #undef V
+ // KingAttackWeights[PieceType] contains king attack weights by piece type
+ const int KingAttackWeights[PIECE_TYPE_NB] = { 0, 0, 78, 56, 45, 11 };
-namespace Eval {
+ // Penalties for enemy's safe checks
+ const int QueenCheck = 780;
+ const int RookCheck = 880;
+ const int BishopCheck = 435;
+ const int KnightCheck = 790;
- Color RootColor;
+ // Threshold for lazy and space evaluation
+ const Value LazyThreshold = Value(1500);
+ const Value SpaceThreshold = Value(12222);
- /// evaluate() is the main evaluation function. It always computes two
- /// values, an endgame score and a middle game score, and interpolates
- /// between them based on the remaining material.
- Value evaluate(const Position& pos, Value& margin) {
- return do_evaluate<false>(pos, margin);
- }
+ // initialize() computes king and pawn attacks, and the king ring bitboard
+ // for a given color. This is done at the beginning of the evaluation.
+ template<Tracing T> template<Color Us>
+ void Evaluation<T>::initialize() {
- /// init() computes evaluation weights from the corresponding UCI parameters
- /// and setup king tables.
+ const Color Them = (Us == WHITE ? BLACK : WHITE);
+ const Square Up = (Us == WHITE ? NORTH : SOUTH);
+ const Square Down = (Us == WHITE ? SOUTH : NORTH);
+ const Bitboard LowRanks = (Us == WHITE ? Rank2BB | Rank3BB: Rank7BB | Rank6BB);
- void init() {
+ // Find our pawns on the first two ranks, and those which are blocked
+ Bitboard b = pos.pieces(Us, PAWN) & (shift<Down>(pos.pieces()) | LowRanks);
- Weights[Mobility] = weight_option("Mobility (Middle Game)", "Mobility (Endgame)", WeightsInternal[Mobility]);
- Weights[PassedPawns] = weight_option("Passed Pawns (Middle Game)", "Passed Pawns (Endgame)", WeightsInternal[PassedPawns]);
- Weights[Space] = weight_option("Space", "Space", WeightsInternal[Space]);
- Weights[KingDangerUs] = weight_option("Cowardice", "Cowardice", WeightsInternal[KingDangerUs]);
- Weights[KingDangerThem] = weight_option("Aggressiveness", "Aggressiveness", WeightsInternal[KingDangerThem]);
+ // Squares occupied by those pawns, by our king, or controlled by enemy pawns
+ // are excluded from the mobility area.
+ mobilityArea[Us] = ~(b | pos.square<KING>(Us) | pe->pawn_attacks(Them));
- // King safety is asymmetrical. Our king danger level is weighted by
- // "Cowardice" UCI parameter, instead the opponent one by "Aggressiveness".
- // If running in analysis mode, make sure we use symmetrical king safety. We
- // do this by replacing both Weights[kingDangerUs] and Weights[kingDangerThem]
- // by their average.
- if (Options["UCI_AnalyseMode"])
- Weights[KingDangerUs] = Weights[KingDangerThem] = (Weights[KingDangerUs] + Weights[KingDangerThem]) / 2;
+ // Initialise the attack bitboards with the king and pawn information
+ b = attackedBy[Us][KING] = pos.attacks_from<KING>(pos.square<KING>(Us));
+ attackedBy[Us][PAWN] = pe->pawn_attacks(Us);
- const int MaxSlope = 30;
- const int Peak = 1280;
+ attackedBy2[Us] = b & attackedBy[Us][PAWN];
+ attackedBy[Us][ALL_PIECES] = b | attackedBy[Us][PAWN];
- for (int t = 0, i = 1; i < 100; i++)
+ // Init our king safety tables only if we are going to use them
+ if (pos.non_pawn_material(Them) >= RookValueMg + KnightValueMg)
{
- t = std::min(Peak, std::min(int(0.4 * i * i), t + MaxSlope));
+ kingRing[Us] = b;
+ if (relative_rank(Us, pos.square<KING>(Us)) == RANK_1)
+ kingRing[Us] |= shift<Up>(b);
- KingDangerTable[1][i] = apply_weight(make_score(t, 0), Weights[KingDangerUs]);
- KingDangerTable[0][i] = apply_weight(make_score(t, 0), Weights[KingDangerThem]);
+ kingAttackersCount[Them] = popcount(b & pe->pawn_attacks(Them));
+ kingAdjacentZoneAttacksCount[Them] = kingAttackersWeight[Them] = 0;
}
+ else
+ kingRing[Us] = kingAttackersCount[Them] = 0;
}
- /// trace() is like evaluate() but instead of a value returns a string suitable
- /// to be print on stdout with the detailed descriptions and values of each
- /// evaluation term. Used mainly for debugging.
-
- std::string trace(const Position& pos) {
-
- Value margin;
- std::string totals;
-
- RootColor = pos.side_to_move();
+ // evaluate_pieces() assigns bonuses and penalties to the pieces of a given
+ // color and type.
- TraceStream.str("");
- TraceStream << std::showpoint << std::showpos << std::fixed << std::setprecision(2);
- memset(TracedScores, 0, 2 * 16 * sizeof(Score));
-
- do_evaluate<true>(pos, margin);
-
- totals = TraceStream.str();
- TraceStream.str("");
-
- TraceStream << std::setw(21) << "Eval term " << "| White | Black | Total \n"
- << " | MG EG | MG EG | MG EG \n"
- << "---------------------+-------------+-------------+---------------\n";
-
- trace_row("Material, PST, Tempo", PST);
- trace_row("Material imbalance", IMBALANCE);
- trace_row("Pawns", PAWN);
- trace_row("Knights", KNIGHT);
- trace_row("Bishops", BISHOP);
- trace_row("Rooks", ROOK);
- trace_row("Queens", QUEEN);
- trace_row("Mobility", MOBILITY);
- trace_row("King safety", KING);
- trace_row("Threats", THREAT);
- trace_row("Passed pawns", PASSED);
- trace_row("Unstoppable pawns", UNSTOPPABLE);
- trace_row("Space", SPACE);
-
- TraceStream << "---------------------+-------------+-------------+---------------\n";
- trace_row("Total", TOTAL);
- TraceStream << totals;
-
- return TraceStream.str();
- }
-
-} // namespace Eval
-
-
-namespace {
-
-template<bool Trace>
-Value do_evaluate(const Position& pos, Value& margin) {
-
- EvalInfo ei;
- Value margins[2];
- Score score, mobilityWhite, mobilityBlack;
-
- assert(pos.thread() >= 0 && pos.thread() < MAX_THREADS);
- assert(!pos.in_check());
-
- // Initialize score by reading the incrementally updated scores included
- // in the position object (material + piece square tables).
- score = pos.value();
-
- // margins[] store the uncertainty estimation of position's evaluation
- // that typically is used by the search for pruning decisions.
- margins[WHITE] = margins[BLACK] = VALUE_ZERO;
-
- // Probe the material hash table
- ei.mi = Threads[pos.thread()].materialTable.material_info(pos);
- score += ei.mi->material_value();
-
- // If we have a specialized evaluation function for the current material
- // configuration, call it and return.
- if (ei.mi->specialized_eval_exists())
- {
- margin = VALUE_ZERO;
- return ei.mi->evaluate(pos);
- }
-
- // Probe the pawn hash table
- ei.pi = Threads[pos.thread()].pawnTable.pawn_info(pos);
- score += ei.pi->pawns_value();
-
- // Initialize attack and king safety bitboards
- init_eval_info<WHITE>(pos, ei);
- init_eval_info<BLACK>(pos, ei);
-
- // Evaluate pieces and mobility
- score += evaluate_pieces_of_color<WHITE, Trace>(pos, ei, mobilityWhite)
- - evaluate_pieces_of_color<BLACK, Trace>(pos, ei, mobilityBlack);
-
- score += apply_weight(mobilityWhite - mobilityBlack, Weights[Mobility]);
-
- // Evaluate kings after all other pieces because we need complete attack
- // information when computing the king safety evaluation.
- score += evaluate_king<WHITE, Trace>(pos, ei, margins)
- - evaluate_king<BLACK, Trace>(pos, ei, margins);
-
- // Evaluate tactical threats, we need full attack information including king
- score += evaluate_threats<WHITE>(pos, ei)
- - evaluate_threats<BLACK>(pos, ei);
-
- // Evaluate passed pawns, we need full attack information including king
- score += evaluate_passed_pawns<WHITE>(pos, ei)
- - evaluate_passed_pawns<BLACK>(pos, ei);
-
- // If one side has only a king, check whether exists any unstoppable passed pawn
- if (!pos.non_pawn_material(WHITE) || !pos.non_pawn_material(BLACK))
- score += evaluate_unstoppable_pawns(pos, ei);
-
- // Evaluate space for both sides, only in middle-game.
- if (ei.mi->space_weight())
- {
- int s = evaluate_space<WHITE>(pos, ei) - evaluate_space<BLACK>(pos, ei);
- score += apply_weight(make_score(s * ei.mi->space_weight(), 0), Weights[Space]);
- }
-
- // Scale winning side if position is more drawish that what it appears
- ScaleFactor sf = eg_value(score) > VALUE_DRAW ? ei.mi->scale_factor(pos, WHITE)
- : ei.mi->scale_factor(pos, BLACK);
-
- // If we don't already have an unusual scale factor, check for opposite
- // colored bishop endgames, and use a lower scale for those.
- if ( ei.mi->game_phase() < PHASE_MIDGAME
- && pos.opposite_colored_bishops()
- && sf == SCALE_FACTOR_NORMAL)
- {
- // Only the two bishops ?
- if ( pos.non_pawn_material(WHITE) == BishopValueMidgame
- && pos.non_pawn_material(BLACK) == BishopValueMidgame)
- {
- // Check for KBP vs KB with only a single pawn that is almost
- // certainly a draw or at least two pawns.
- bool one_pawn = (pos.piece_count(WHITE, PAWN) + pos.piece_count(BLACK, PAWN) == 1);
- sf = one_pawn ? ScaleFactor(8) : ScaleFactor(32);
- }
- else
- // Endgame with opposite-colored bishops, but also other pieces. Still
- // a bit drawish, but not as drawish as with only the two bishops.
- sf = ScaleFactor(50);
- }
-
- // Interpolate between the middle game and the endgame score
- margin = margins[pos.side_to_move()];
- Value v = scale_by_game_phase(score, ei.mi->game_phase(), sf);
-
- // In case of tracing add all single evaluation contributions for both white and black
- if (Trace)
- {
- trace_add(PST, pos.value());
- trace_add(IMBALANCE, ei.mi->material_value());
- trace_add(PAWN, ei.pi->pawns_value());
- trace_add(MOBILITY, apply_weight(mobilityWhite, Weights[Mobility]), apply_weight(mobilityBlack, Weights[Mobility]));
- trace_add(THREAT, evaluate_threats<WHITE>(pos, ei), evaluate_threats<BLACK>(pos, ei));
- trace_add(PASSED, evaluate_passed_pawns<WHITE>(pos, ei), evaluate_passed_pawns<BLACK>(pos, ei));
- trace_add(UNSTOPPABLE, evaluate_unstoppable_pawns(pos, ei));
- Score w = make_score(ei.mi->space_weight() * evaluate_space<WHITE>(pos, ei), 0);
- Score b = make_score(ei.mi->space_weight() * evaluate_space<BLACK>(pos, ei), 0);
- trace_add(SPACE, apply_weight(w, Weights[Space]), apply_weight(b, Weights[Space]));
- trace_add(TOTAL, score);
- TraceStream << "\nUncertainty margin: White: " << to_cp(margins[WHITE])
- << ", Black: " << to_cp(margins[BLACK])
- << "\nScaling: " << std::noshowpos
- << std::setw(6) << 100.0 * ei.mi->game_phase() / 128.0 << "% MG, "
- << std::setw(6) << 100.0 * (1.0 - ei.mi->game_phase() / 128.0) << "% * "
- << std::setw(6) << (100.0 * sf) / SCALE_FACTOR_NORMAL << "% EG.\n"
- << "Total evaluation: " << to_cp(v);
- }
-
- return pos.side_to_move() == WHITE ? v : -v;
-}
-
-
- // init_eval_info() initializes king bitboards for given color adding
- // pawn attacks. To be done at the beginning of the evaluation.
-
- template<Color Us>
- void init_eval_info(const Position& pos, EvalInfo& ei) {
+ template<Tracing T> template<Color Us, PieceType Pt>
+ Score Evaluation<T>::evaluate_pieces() {
const Color Them = (Us == WHITE ? BLACK : WHITE);
+ const Bitboard OutpostRanks = (Us == WHITE ? Rank4BB | Rank5BB | Rank6BB
+ : Rank5BB | Rank4BB | Rank3BB);
+ const Square* pl = pos.squares<Pt>(Us);
- Bitboard b = ei.attackedBy[Them][KING] = pos.attacks_from<KING>(pos.king_square(Them));
- ei.attackedBy[Us][PAWN] = ei.pi->pawn_attacks(Us);
-
- // Init king safety tables only if we are going to use them
- if ( pos.piece_count(Us, QUEEN)
- && pos.non_pawn_material(Us) >= QueenValueMidgame + RookValueMidgame)
- {
- ei.kingRing[Them] = (b | (Us == WHITE ? b >> 8 : b << 8));
- b &= ei.attackedBy[Us][PAWN];
- ei.kingAttackersCount[Us] = b ? popcount<Max15>(b) / 2 : 0;
- ei.kingAdjacentZoneAttacksCount[Us] = ei.kingAttackersWeight[Us] = 0;
- } else
- ei.kingRing[Them] = ei.kingAttackersCount[Us] = 0;
- }
-
-
- // evaluate_outposts() evaluates bishop and knight outposts squares
-
- template<PieceType Piece, Color Us>
- Score evaluate_outposts(const Position& pos, EvalInfo& ei, Square s) {
-
- const Color Them = (Us == WHITE ? BLACK : WHITE);
-
- assert (Piece == BISHOP || Piece == KNIGHT);
-
- // Initial bonus based on square
- Value bonus = OutpostBonus[Piece == BISHOP][relative_square(Us, s)];
-
- // Increase bonus if supported by pawn, especially if the opponent has
- // no minor piece which can exchange the outpost piece.
- if (bonus && (ei.attackedBy[Us][PAWN] & s))
- {
- if ( !pos.pieces(KNIGHT, Them)
- && !(same_color_squares(s) & pos.pieces(BISHOP, Them)))
- bonus += bonus + bonus / 2;
- else
- bonus += bonus / 2;
- }
- return make_score(bonus, bonus);
- }
-
-
- // evaluate_pieces<>() assigns bonuses and penalties to the pieces of a given color
-
- template<PieceType Piece, Color Us, bool Trace>
- Score evaluate_pieces(const Position& pos, EvalInfo& ei, Score& mobility, Bitboard mobilityArea) {
-
- Bitboard b;
- Square s, ksq;
- int mob;
- File f;
+ Bitboard b, bb;
+ Square s;
Score score = SCORE_ZERO;
- const Color Them = (Us == WHITE ? BLACK : WHITE);
- const Square* pl = pos.piece_list(Us, Piece);
-
- ei.attackedBy[Us][Piece] = 0;
+ attackedBy[Us][Pt] = 0;
while ((s = *pl++) != SQ_NONE)
{
// Find attacked squares, including x-ray attacks for bishops and rooks
- if (Piece == KNIGHT || Piece == QUEEN)
- b = pos.attacks_from<Piece>(s);
- else if (Piece == BISHOP)
- b = attacks_bb<BISHOP>(s, pos.pieces() ^ pos.pieces(QUEEN, Us));
- else if (Piece == ROOK)
- b = attacks_bb<ROOK>(s, pos.pieces() ^ pos.pieces(ROOK, QUEEN, Us));
- else
- assert(false);
-
- ei.attackedBy[Us][Piece] |= b;
-
- if (b & ei.kingRing[Them])
- {
- ei.kingAttackersCount[Us]++;
- ei.kingAttackersWeight[Us] += KingAttackWeights[Piece];
- Bitboard bb = (b & ei.attackedBy[Them][KING]);
- if (bb)
- ei.kingAdjacentZoneAttacksCount[Us] += popcount<Max15>(bb);
- }
+ b = Pt == BISHOP ? attacks_bb<BISHOP>(s, pos.pieces() ^ pos.pieces(Us, QUEEN))
+ : Pt == ROOK ? attacks_bb< ROOK>(s, pos.pieces() ^ pos.pieces(Us, ROOK, QUEEN))
+ : pos.attacks_from<Pt>(s);
- mob = (Piece != QUEEN ? popcount<Max15>(b & mobilityArea)
- : popcount<Full >(b & mobilityArea));
+ if (pos.pinned_pieces(Us) & s)
+ b &= LineBB[pos.square<KING>(Us)][s];
- mobility += MobilityBonus[Piece][mob];
+ attackedBy2[Us] |= attackedBy[Us][ALL_PIECES] & b;
+ attackedBy[Us][ALL_PIECES] |= attackedBy[Us][Pt] |= b;
- // Add a bonus if a slider is pinning an enemy piece
- if ( (Piece == BISHOP || Piece == ROOK || Piece == QUEEN)
- && (PseudoAttacks[Piece][pos.king_square(Them)] & s))
+ if (b & kingRing[Them])
{
- b = BetweenBB[s][pos.king_square(Them)] & pos.pieces();
-
- assert(b);
-
- if (single_bit(b) && (b & pos.pieces(Them)))
- score += ThreatBonus[Piece][type_of(pos.piece_on(first_1(b)))];
+ kingAttackersCount[Us]++;
+ kingAttackersWeight[Us] += KingAttackWeights[Pt];
+ kingAdjacentZoneAttacksCount[Us] += popcount(b & attackedBy[Them][KING]);
}
- // Decrease score if we are attacked by an enemy pawn. Remaining part
- // of threat evaluation must be done later when we have full attack info.
- if (ei.attackedBy[Them][PAWN] & s)
- score -= ThreatenedByPawnPenalty[Piece];
+ int mob = popcount(b & mobilityArea[Us]);
- // Bishop and knight outposts squares
- if ( (Piece == BISHOP || Piece == KNIGHT)
- && !(pos.pieces(PAWN, Them) & attack_span_mask(Us, s)))
- score += evaluate_outposts<Piece, Us>(pos, ei, s);
+ mobility[Us] += MobilityBonus[Pt - 2][mob];
- // Queen or rook on 7th rank
- if ( (Piece == ROOK || Piece == QUEEN)
- && relative_rank(Us, s) == RANK_7
- && relative_rank(Us, pos.king_square(Them)) == RANK_8)
- {
- score += (Piece == ROOK ? RookOn7thBonus : QueenOn7thBonus);
- }
+ // Bonus for this piece as a king protector
+ score += KingProtector[Pt - 2] * distance(s, pos.square<KING>(Us));
- // Special extra evaluation for bishops
- if (Piece == BISHOP && pos.is_chess960())
+ if (Pt == BISHOP || Pt == KNIGHT)
{
- // An important Chess960 pattern: A cornered bishop blocked by
- // a friendly pawn diagonally in front of it is a very serious
- // problem, especially when that pawn is also blocked.
- if (s == relative_square(Us, SQ_A1) || s == relative_square(Us, SQ_H1))
+ // Bonus for outpost squares
+ bb = OutpostRanks & ~pe->pawn_attacks_span(Them);
+ if (bb & s)
+ score += Outpost[Pt == BISHOP][!!(attackedBy[Us][PAWN] & s)] * 2;
+ else
{
- Square d = pawn_push(Us) + (file_of(s) == FILE_A ? DELTA_E : DELTA_W);
- if (pos.piece_on(s + d) == make_piece(Us, PAWN))
- {
- if (!pos.square_is_empty(s + d + pawn_push(Us)))
- score -= 2*TrappedBishopA1H1Penalty;
- else if (pos.piece_on(s + 2*d) == make_piece(Us, PAWN))
- score -= TrappedBishopA1H1Penalty;
- else
- score -= TrappedBishopA1H1Penalty / 2;
- }
+ bb &= b & ~pos.pieces(Us);
+ if (bb)
+ score += Outpost[Pt == BISHOP][!!(attackedBy[Us][PAWN] & bb)];
}
- }
- // Special extra evaluation for rooks
- if (Piece == ROOK)
- {
- // Open and half-open files
- f = file_of(s);
- if (ei.pi->file_is_half_open(Us, f))
+ // Bonus when behind a pawn
+ if ( relative_rank(Us, s) < RANK_5
+ && (pos.pieces(PAWN) & (s + pawn_push(Us))))
+ score += MinorBehindPawn;
+
+ // Penalty for pawns on the same color square as the bishop
+ if (Pt == BISHOP)
+ score -= BishopPawns * pe->pawns_on_same_color_squares(Us, s);
+
+ // An important Chess960 pattern: A cornered bishop blocked by a friendly
+ // pawn diagonally in front of it is a very serious problem, especially
+ // when that pawn is also blocked.
+ if ( Pt == BISHOP
+ && pos.is_chess960()
+ && (s == relative_square(Us, SQ_A1) || s == relative_square(Us, SQ_H1)))
{
- if (ei.pi->file_is_half_open(Them, f))
- score += RookOpenFileBonus;
- else
- score += RookHalfOpenFileBonus;
+ Square d = pawn_push(Us) + (file_of(s) == FILE_A ? EAST : WEST);
+ if (pos.piece_on(s + d) == make_piece(Us, PAWN))
+ score -= !pos.empty(s + d + pawn_push(Us)) ? TrappedBishopA1H1 * 4
+ : pos.piece_on(s + d + d) == make_piece(Us, PAWN) ? TrappedBishopA1H1 * 2
+ : TrappedBishopA1H1;
}
+ }
- // Penalize rooks which are trapped inside a king. Penalize more if
- // king has lost right to castle.
- if (mob > 6 || ei.pi->file_is_half_open(Us, f))
- continue;
+ if (Pt == ROOK)
+ {
+ // Bonus for aligning with enemy pawns on the same rank/file
+ if (relative_rank(Us, s) >= RANK_5)
+ score += RookOnPawn * popcount(pos.pieces(Them, PAWN) & PseudoAttacks[ROOK][s]);
- ksq = pos.king_square(Us);
+ // Bonus when on an open or semi-open file
+ if (pe->semiopen_file(Us, file_of(s)))
+ score += RookOnFile[!!pe->semiopen_file(Them, file_of(s))];
- if ( file_of(ksq) >= FILE_E
- && file_of(s) > file_of(ksq)
- && (relative_rank(Us, ksq) == RANK_1 || rank_of(ksq) == rank_of(s)))
- {
- // Is there a half-open file between the king and the edge of the board?
- if (!ei.pi->has_open_file_to_right(Us, file_of(ksq)))
- score -= make_score(pos.can_castle(Us) ? (TrappedRookPenalty - mob * 16) / 2
- : (TrappedRookPenalty - mob * 16), 0);
- }
- else if ( file_of(ksq) <= FILE_D
- && file_of(s) < file_of(ksq)
- && (relative_rank(Us, ksq) == RANK_1 || rank_of(ksq) == rank_of(s)))
+ // Penalty when trapped by the king, even more if the king cannot castle
+ else if (mob <= 3)
{
- // Is there a half-open file between the king and the edge of the board?
- if (!ei.pi->has_open_file_to_left(Us, file_of(ksq)))
- score -= make_score(pos.can_castle(Us) ? (TrappedRookPenalty - mob * 16) / 2
- : (TrappedRookPenalty - mob * 16), 0);
+ Square ksq = pos.square<KING>(Us);
+
+ if ( ((file_of(ksq) < FILE_E) == (file_of(s) < file_of(ksq)))
+ && !pe->semiopen_side(Us, file_of(ksq), file_of(s) < file_of(ksq)))
+ score -= (TrappedRook - make_score(mob * 22, 0)) * (1 + !pos.can_castle(Us));
}
}
+
+ if (Pt == QUEEN)
+ {
+ // Penalty if any relative pin or discovered attack against the queen
+ Bitboard pinners;
+ if (pos.slider_blockers(pos.pieces(Them, ROOK, BISHOP), s, pinners))
+ score -= WeakQueen;
+ }
}
- if (Trace)
- TracedScores[Us][Piece] = score;
+ if (T)
+ Trace::add(Pt, Us, score);
return score;
}
- // evaluate_threats<>() assigns bonuses according to the type of attacking piece
- // and the type of attacked one.
+ // evaluate_king() assigns bonuses and penalties to a king of a given color
- template<Color Us>
- Score evaluate_threats(const Position& pos, EvalInfo& ei) {
+ const Bitboard QueenSide = FileABB | FileBBB | FileCBB | FileDBB;
+ const Bitboard CenterFiles = FileCBB | FileDBB | FileEBB | FileFBB;
+ const Bitboard KingSide = FileEBB | FileFBB | FileGBB | FileHBB;
- const Color Them = (Us == WHITE ? BLACK : WHITE);
+ const Bitboard KingFlank[FILE_NB] = {
+ QueenSide, QueenSide, QueenSide, CenterFiles, CenterFiles, KingSide, KingSide, KingSide
+ };
- Bitboard b;
- Score score = SCORE_ZERO;
+ template<Tracing T> template<Color Us>
+ Score Evaluation<T>::evaluate_king() {
- // Undefended minors get penalized even if not under attack
- Bitboard undefended = pos.pieces(Them)
- & (pos.pieces(BISHOP) | pos.pieces(KNIGHT))
- & ~ei.attackedBy[Them][0];
- if (undefended)
- score += single_bit(undefended) ? UndefendedMinorPenalty
- : UndefendedMinorPenalty * 2;
-
- // Enemy pieces not defended by a pawn and under our attack
- Bitboard weakEnemies = pos.pieces(Them)
- & ~ei.attackedBy[Them][PAWN]
- & ei.attackedBy[Us][0];
- if (!weakEnemies)
- return score;
-
- // Add bonus according to type of attacked enemy piece and to the
- // type of attacking piece, from knights to queens. Kings are not
- // considered because are already handled in king evaluation.
- for (PieceType pt1 = KNIGHT; pt1 < KING; pt1++)
+ const Color Them = (Us == WHITE ? BLACK : WHITE);
+ const Square Up = (Us == WHITE ? NORTH : SOUTH);
+ const Bitboard Camp = (Us == WHITE ? ~Bitboard(0) ^ Rank6BB ^ Rank7BB ^ Rank8BB
+ : ~Bitboard(0) ^ Rank1BB ^ Rank2BB ^ Rank3BB);
+
+ const Square ksq = pos.square<KING>(Us);
+ Bitboard kingOnlyDefended, b, b1, b2, safe, other;
+ int kingDanger;
+
+ // King shelter and enemy pawns storm
+ Score score = pe->king_safety<Us>(pos, ksq);
+
+ // Main king safety evaluation
+ if (kingAttackersCount[Them] > (1 - pos.count<QUEEN>(Them)))
{
- b = ei.attackedBy[Us][pt1] & weakEnemies;
- if (b)
- for (PieceType pt2 = PAWN; pt2 < KING; pt2++)
- if (b & pos.pieces(pt2))
- score += ThreatBonus[pt1][pt2];
- }
- return score;
- }
+ // Find the attacked squares which are defended only by our king...
+ kingOnlyDefended = attackedBy[Them][ALL_PIECES]
+ & attackedBy[Us][KING]
+ & ~attackedBy2[Us];
+
+ // ... and those which are not defended at all in the larger king ring
+ b = attackedBy[Them][ALL_PIECES] & ~attackedBy[Us][ALL_PIECES]
+ & kingRing[Us] & ~pos.pieces(Them);
+
+ // Initialize the 'kingDanger' variable, which will be transformed
+ // later into a king danger score. The initial value is based on the
+ // number and types of the enemy's attacking pieces, the number of
+ // attacked and weak squares around our king, the absence of queen and
+ // the quality of the pawn shelter (current 'score' value).
+ kingDanger = kingAttackersCount[Them] * kingAttackersWeight[Them]
+ + 102 * kingAdjacentZoneAttacksCount[Them]
+ + 201 * popcount(kingOnlyDefended)
+ + 143 * (popcount(b) + !!pos.pinned_pieces(Us))
+ - 848 * !pos.count<QUEEN>(Them)
+ - 9 * mg_value(score) / 8
+ + 40;
+
+ // Analyse the safe enemy's checks which are possible on next move
+ safe = ~pos.pieces(Them);
+ safe &= ~attackedBy[Us][ALL_PIECES] | (kingOnlyDefended & attackedBy2[Them]);
+
+ b1 = pos.attacks_from< ROOK>(ksq);
+ b2 = pos.attacks_from<BISHOP>(ksq);
+ // Enemy queen safe checks
+ if ((b1 | b2) & attackedBy[Them][QUEEN] & safe)
+ kingDanger += QueenCheck;
+
+ // For minors and rooks, also consider the square safe if attacked twice,
+ // and only defended by our queen.
+ safe |= attackedBy2[Them]
+ & ~(attackedBy2[Us] | pos.pieces(Them))
+ & attackedBy[Us][QUEEN];
+
+ // Some other potential checks are also analysed, even from squares
+ // currently occupied by the opponent own pieces, as long as the square
+ // is not attacked by our pawns, and is not occupied by a blocked pawn.
+ other = ~( attackedBy[Us][PAWN]
+ | (pos.pieces(Them, PAWN) & shift<Up>(pos.pieces(PAWN))));
+
+ // Enemy rooks safe and other checks
+ if (b1 & attackedBy[Them][ROOK] & safe)
+ kingDanger += RookCheck;
+
+ else if (b1 & attackedBy[Them][ROOK] & other)
+ score -= OtherCheck;
+
+ // Enemy bishops safe and other checks
+ if (b2 & attackedBy[Them][BISHOP] & safe)
+ kingDanger += BishopCheck;
+
+ else if (b2 & attackedBy[Them][BISHOP] & other)
+ score -= OtherCheck;
+
+ // Enemy knights safe and other checks
+ b = pos.attacks_from<KNIGHT>(ksq) & attackedBy[Them][KNIGHT];
+ if (b & safe)
+ kingDanger += KnightCheck;
+
+ else if (b & other)
+ score -= OtherCheck;
+
+ // Transform the kingDanger units into a Score, and substract it from the evaluation
+ if (kingDanger > 0)
+ score -= make_score(kingDanger * kingDanger / 4096, kingDanger / 16);
+ }
- // evaluate_pieces_of_color<>() assigns bonuses and penalties to all the
- // pieces of a given color.
+ // King tropism: firstly, find squares that opponent attacks in our king flank
+ File kf = file_of(ksq);
+ b = attackedBy[Them][ALL_PIECES] & KingFlank[kf] & Camp;
- template<Color Us, bool Trace>
- Score evaluate_pieces_of_color(const Position& pos, EvalInfo& ei, Score& mobility) {
+ assert(((Us == WHITE ? b << 4 : b >> 4) & b) == 0);
+ assert(popcount(Us == WHITE ? b << 4 : b >> 4) == popcount(b));
- const Color Them = (Us == WHITE ? BLACK : WHITE);
+ // Secondly, add the squares which are attacked twice in that flank and
+ // which are not defended by our pawns.
+ b = (Us == WHITE ? b << 4 : b >> 4)
+ | (b & attackedBy2[Them] & ~attackedBy[Us][PAWN]);
- Score score = mobility = SCORE_ZERO;
+ score -= CloseEnemies * popcount(b);
- // Do not include in mobility squares protected by enemy pawns or occupied by our pieces
- const Bitboard mobilityArea = ~(ei.attackedBy[Them][PAWN] | pos.pieces(Us));
+ // Penalty when our king is on a pawnless flank
+ if (!(pos.pieces(PAWN) & KingFlank[kf]))
+ score -= PawnlessFlank;
- score += evaluate_pieces<KNIGHT, Us, Trace>(pos, ei, mobility, mobilityArea);
- score += evaluate_pieces<BISHOP, Us, Trace>(pos, ei, mobility, mobilityArea);
- score += evaluate_pieces<ROOK, Us, Trace>(pos, ei, mobility, mobilityArea);
- score += evaluate_pieces<QUEEN, Us, Trace>(pos, ei, mobility, mobilityArea);
+ if (T)
+ Trace::add(KING, Us, score);
- // Sum up all attacked squares
- ei.attackedBy[Us][0] = ei.attackedBy[Us][PAWN] | ei.attackedBy[Us][KNIGHT]
- | ei.attackedBy[Us][BISHOP] | ei.attackedBy[Us][ROOK]
- | ei.attackedBy[Us][QUEEN] | ei.attackedBy[Us][KING];
return score;
}
- // evaluate_king<>() assigns bonuses and penalties to a king of a given color
+ // evaluate_threats() assigns bonuses according to the types of the attacking
+ // and the attacked pieces.
- template<Color Us, bool Trace>
- Score evaluate_king(const Position& pos, EvalInfo& ei, Value margins[]) {
+ template<Tracing T> template<Color Us>
+ Score Evaluation<T>::evaluate_threats() {
- const Color Them = (Us == WHITE ? BLACK : WHITE);
+ const Color Them = (Us == WHITE ? BLACK : WHITE);
+ const Square Up = (Us == WHITE ? NORTH : SOUTH);
+ const Square Left = (Us == WHITE ? NORTH_WEST : SOUTH_EAST);
+ const Square Right = (Us == WHITE ? NORTH_EAST : SOUTH_WEST);
+ const Bitboard TRank3BB = (Us == WHITE ? Rank3BB : Rank6BB);
- Bitboard undefended, b, b1, b2, safe;
- int attackUnits;
- const Square ksq = pos.king_square(Us);
+ Bitboard b, weak, defended, stronglyProtected, safeThreats;
+ Score score = SCORE_ZERO;
- // King shelter
- Score score = ei.pi->king_shelter<Us>(pos, ksq);
+ // Non-pawn enemies attacked by a pawn
+ weak = (pos.pieces(Them) ^ pos.pieces(Them, PAWN)) & attackedBy[Us][PAWN];
- // King safety. This is quite complicated, and is almost certainly far
- // from optimally tuned.
- if ( ei.kingAttackersCount[Them] >= 2
- && ei.kingAdjacentZoneAttacksCount[Them])
+ if (weak)
{
- // Find the attacked squares around the king which has no defenders
- // apart from the king itself
- undefended = ei.attackedBy[Them][0] & ei.attackedBy[Us][KING];
- undefended &= ~( ei.attackedBy[Us][PAWN] | ei.attackedBy[Us][KNIGHT]
- | ei.attackedBy[Us][BISHOP] | ei.attackedBy[Us][ROOK]
- | ei.attackedBy[Us][QUEEN]);
-
- // Initialize the 'attackUnits' variable, which is used later on as an
- // index to the KingDangerTable[] array. The initial value is based on
- // the number and types of the enemy's attacking pieces, the number of
- // attacked and undefended squares around our king, the square of the
- // king, and the quality of the pawn shelter.
- attackUnits = std::min(25, (ei.kingAttackersCount[Them] * ei.kingAttackersWeight[Them]) / 2)
- + 3 * (ei.kingAdjacentZoneAttacksCount[Them] + popcount<Max15>(undefended))
- + InitKingDanger[relative_square(Us, ksq)]
- - mg_value(ei.pi->king_shelter<Us>(pos, ksq)) / 32;
-
- // Analyse enemy's safe queen contact checks. First find undefended
- // squares around the king attacked by enemy queen...
- b = undefended & ei.attackedBy[Them][QUEEN] & ~pos.pieces(Them);
- if (b)
- {
- // ...then remove squares not supported by another enemy piece
- b &= ( ei.attackedBy[Them][PAWN] | ei.attackedBy[Them][KNIGHT]
- | ei.attackedBy[Them][BISHOP] | ei.attackedBy[Them][ROOK]);
- if (b)
- attackUnits += QueenContactCheckBonus
- * popcount<Max15>(b)
- * (Them == pos.side_to_move() ? 2 : 1);
- }
+ b = pos.pieces(Us, PAWN) & ( ~attackedBy[Them][ALL_PIECES]
+ | attackedBy[Us][ALL_PIECES]);
- // Analyse enemy's safe rook contact checks. First find undefended
- // squares around the king attacked by enemy rooks...
- b = undefended & ei.attackedBy[Them][ROOK] & ~pos.pieces(Them);
+ safeThreats = (shift<Right>(b) | shift<Left>(b)) & weak;
- // Consider only squares where the enemy rook gives check
- b &= PseudoAttacks[ROOK][ksq];
+ score += ThreatBySafePawn * popcount(safeThreats);
- if (b)
+ if (weak ^ safeThreats)
+ score += ThreatByHangingPawn;
+ }
+
+ // Squares strongly protected by the opponent, either because they attack the
+ // square with a pawn, or because they attack the square twice and we don't.
+ stronglyProtected = attackedBy[Them][PAWN]
+ | (attackedBy2[Them] & ~attackedBy2[Us]);
+
+ // Non-pawn enemies, strongly protected
+ defended = (pos.pieces(Them) ^ pos.pieces(Them, PAWN))
+ & stronglyProtected;
+
+ // Enemies not strongly protected and under our attack
+ weak = pos.pieces(Them)
+ & ~stronglyProtected
+ & attackedBy[Us][ALL_PIECES];
+
+ // Add a bonus according to the kind of attacking pieces
+ if (defended | weak)
+ {
+ b = (defended | weak) & (attackedBy[Us][KNIGHT] | attackedBy[Us][BISHOP]);
+ while (b)
{
- // ...then remove squares not supported by another enemy piece
- b &= ( ei.attackedBy[Them][PAWN] | ei.attackedBy[Them][KNIGHT]
- | ei.attackedBy[Them][BISHOP] | ei.attackedBy[Them][QUEEN]);
- if (b)
- attackUnits += RookContactCheckBonus
- * popcount<Max15>(b)
- * (Them == pos.side_to_move() ? 2 : 1);
+ Square s = pop_lsb(&b);
+ score += ThreatByMinor[type_of(pos.piece_on(s))];
+ if (type_of(pos.piece_on(s)) != PAWN)
+ score += ThreatByRank * (int)relative_rank(Them, s);
}
- // Analyse enemy's safe distance checks for sliders and knights
- safe = ~(pos.pieces(Them) | ei.attackedBy[Us][0]);
+ b = (pos.pieces(Them, QUEEN) | weak) & attackedBy[Us][ROOK];
+ while (b)
+ {
+ Square s = pop_lsb(&b);
+ score += ThreatByRook[type_of(pos.piece_on(s))];
+ if (type_of(pos.piece_on(s)) != PAWN)
+ score += ThreatByRank * (int)relative_rank(Them, s);
+ }
- b1 = pos.attacks_from<ROOK>(ksq) & safe;
- b2 = pos.attacks_from<BISHOP>(ksq) & safe;
+ score += Hanging * popcount(weak & ~attackedBy[Them][ALL_PIECES]);
- // Enemy queen safe checks
- b = (b1 | b2) & ei.attackedBy[Them][QUEEN];
+ b = weak & attackedBy[Us][KING];
if (b)
- attackUnits += QueenCheckBonus * popcount<Max15>(b);
+ score += ThreatByKing[more_than_one(b)];
+ }
- // Enemy rooks safe checks
- b = b1 & ei.attackedBy[Them][ROOK];
- if (b)
- attackUnits += RookCheckBonus * popcount<Max15>(b);
+ // Find squares where our pawns can push on the next move
+ b = shift<Up>(pos.pieces(Us, PAWN)) & ~pos.pieces();
+ b |= shift<Up>(b & TRank3BB) & ~pos.pieces();
- // Enemy bishops safe checks
- b = b2 & ei.attackedBy[Them][BISHOP];
- if (b)
- attackUnits += BishopCheckBonus * popcount<Max15>(b);
+ // Keep only the squares which are not completely unsafe
+ b &= ~attackedBy[Them][PAWN]
+ & (attackedBy[Us][ALL_PIECES] | ~attackedBy[Them][ALL_PIECES]);
- // Enemy knights safe checks
- b = pos.attacks_from<KNIGHT>(ksq) & ei.attackedBy[Them][KNIGHT] & safe;
- if (b)
- attackUnits += KnightCheckBonus * popcount<Max15>(b);
-
- // To index KingDangerTable[] attackUnits must be in [0, 99] range
- attackUnits = std::min(99, std::max(0, attackUnits));
-
- // Finally, extract the king danger score from the KingDangerTable[]
- // array and subtract the score from evaluation. Set also margins[]
- // value that will be used for pruning because this value can sometimes
- // be very big, and so capturing a single attacking piece can therefore
- // result in a score change far bigger than the value of the captured piece.
- score -= KingDangerTable[Us == Eval::RootColor][attackUnits];
- margins[Us] += mg_value(KingDangerTable[Us == Eval::RootColor][attackUnits]);
- }
+ // Add a bonus for each new pawn threats from those squares
+ b = (shift<Left>(b) | shift<Right>(b))
+ & pos.pieces(Them)
+ & ~attackedBy[Us][PAWN];
- if (Trace)
- TracedScores[Us][KING] = score;
+ score += ThreatByPawnPush * popcount(b);
+
+ if (T)
+ Trace::add(THREAT, Us, score);
return score;
}
- // evaluate_passed_pawns<>() evaluates the passed pawns of the given color
+ // evaluate_passed_pawns() evaluates the passed pawns and candidate passed
+ // pawns of the given color.
- template<Color Us>
- Score evaluate_passed_pawns(const Position& pos, EvalInfo& ei) {
+ template<Tracing T> template<Color Us>
+ Score Evaluation<T>::evaluate_passed_pawns() {
const Color Them = (Us == WHITE ? BLACK : WHITE);
+ const Square Up = (Us == WHITE ? NORTH : SOUTH);
- Bitboard b, squaresToQueen, defendedSquares, unsafeSquares, supportingPawns;
+ Bitboard b, bb, squaresToQueen, defendedSquares, unsafeSquares;
Score score = SCORE_ZERO;
- b = ei.pi->passed_pawns(Us);
+ b = pe->passed_pawns(Us);
- if (!b)
- return SCORE_ZERO;
+ while (b)
+ {
+ Square s = pop_lsb(&b);
- do {
- Square s = pop_1st_bit(&b);
+ assert(!(pos.pieces(Them, PAWN) & forward_file_bb(Us, s + Up)));
- assert(pos.pawn_is_passed(Us, s));
+ bb = forward_file_bb(Us, s) & (attackedBy[Them][ALL_PIECES] | pos.pieces(Them));
+ score -= HinderPassedPawn * popcount(bb);
- int r = int(relative_rank(Us, s) - RANK_2);
+ int r = relative_rank(Us, s) - RANK_2;
int rr = r * (r - 1);
- // Base bonus based on rank
- Value mbonus = Value(20 * rr);
- Value ebonus = Value(10 * (rr + r + 1));
+ Value mbonus = Passed[MG][r], ebonus = Passed[EG][r];
if (rr)
{
- Square blockSq = s + pawn_push(Us);
+ Square blockSq = s + Up;
- // Adjust bonus based on kings proximity
- ebonus += Value(square_distance(pos.king_square(Them), blockSq) * 5 * rr);
- ebonus -= Value(square_distance(pos.king_square(Us), blockSq) * 2 * rr);
+ // Adjust bonus based on the king's proximity
+ ebonus += distance(pos.square<KING>(Them), blockSq) * 5 * rr
+ - distance(pos.square<KING>( Us), blockSq) * 2 * rr;
// If blockSq is not the queening square then consider also a second push
- if (rank_of(blockSq) != (Us == WHITE ? RANK_8 : RANK_1))
- ebonus -= Value(square_distance(pos.king_square(Us), blockSq + pawn_push(Us)) * rr);
+ if (relative_rank(Us, blockSq) != RANK_8)
+ ebonus -= distance(pos.square<KING>(Us), blockSq + Up) * rr;
- // If the pawn is free to advance, increase bonus
- if (pos.square_is_empty(blockSq))
+ // If the pawn is free to advance, then increase the bonus
+ if (pos.empty(blockSq))
{
- squaresToQueen = squares_in_front_of(Us, s);
- defendedSquares = squaresToQueen & ei.attackedBy[Us][0];
-
- // If there is an enemy rook or queen attacking the pawn from behind,
- // add all X-ray attacks by the rook or queen. Otherwise consider only
- // the squares in the pawn's path attacked or occupied by the enemy.
- if ( (squares_in_front_of(Them, s) & pos.pieces(ROOK, QUEEN, Them))
- && (squares_in_front_of(Them, s) & pos.pieces(ROOK, QUEEN, Them) & pos.attacks_from<ROOK>(s)))
- unsafeSquares = squaresToQueen;
- else
- unsafeSquares = squaresToQueen & (ei.attackedBy[Them][0] | pos.pieces(Them));
-
- // If there aren't enemy attacks or pieces along the path to queen give
- // huge bonus. Even bigger if we protect the pawn's path.
- if (!unsafeSquares)
- ebonus += Value(rr * (squaresToQueen == defendedSquares ? 17 : 15));
- else
- // OK, there are enemy attacks or pieces (but not pawns). Are those
- // squares which are attacked by the enemy also attacked by us ?
- // If yes, big bonus (but smaller than when there are no enemy attacks),
- // if no, somewhat smaller bonus.
- ebonus += Value(rr * ((unsafeSquares & defendedSquares) == unsafeSquares ? 13 : 8));
- }
- } // rr != 0
+ // If there is a rook or queen attacking/defending the pawn from behind,
+ // consider all the squaresToQueen. Otherwise consider only the squares
+ // in the pawn's path attacked or occupied by the enemy.
+ defendedSquares = unsafeSquares = squaresToQueen = forward_file_bb(Us, s);
- // Increase the bonus if the passed pawn is supported by a friendly pawn
- // on the same rank and a bit smaller if it's on the previous rank.
- supportingPawns = pos.pieces(PAWN, Us) & adjacent_files_bb(file_of(s));
- if (supportingPawns & rank_bb(s))
- ebonus += Value(r * 20);
-
- else if (supportingPawns & rank_bb(s - pawn_push(Us)))
- ebonus += Value(r * 12);
-
- // Rook pawns are a special case: They are sometimes worse, and
- // sometimes better than other passed pawns. It is difficult to find
- // good rules for determining whether they are good or bad. For now,
- // we try the following: Increase the value for rook pawns if the
- // other side has no pieces apart from a knight, and decrease the
- // value if the other side has a rook or queen.
- if (file_of(s) == FILE_A || file_of(s) == FILE_H)
- {
- if (pos.non_pawn_material(Them) <= KnightValueMidgame)
- ebonus += ebonus / 4;
- else if (pos.pieces(ROOK, QUEEN, Them))
- ebonus -= ebonus / 4;
- }
- score += make_score(mbonus, ebonus);
+ bb = forward_file_bb(Them, s) & pos.pieces(ROOK, QUEEN) & pos.attacks_from<ROOK>(s);
- } while (b);
-
- // Add the scores to the middle game and endgame eval
- return apply_weight(score, Weights[PassedPawns]);
- }
+ if (!(pos.pieces(Us) & bb))
+ defendedSquares &= attackedBy[Us][ALL_PIECES];
+ if (!(pos.pieces(Them) & bb))
+ unsafeSquares &= attackedBy[Them][ALL_PIECES] | pos.pieces(Them);
- // evaluate_unstoppable_pawns() evaluates the unstoppable passed pawns for both sides, this is quite
- // conservative and returns a winning score only when we are very sure that the pawn is winning.
+ // If there aren't any enemy attacks, assign a big bonus. Otherwise
+ // assign a smaller bonus if the block square isn't attacked.
+ int k = !unsafeSquares ? 18 : !(unsafeSquares & blockSq) ? 8 : 0;
- Score evaluate_unstoppable_pawns(const Position& pos, EvalInfo& ei) {
-
- Bitboard b, b2, blockers, supporters, queeningPath, candidates;
- Square s, blockSq, queeningSquare;
- Color c, winnerSide, loserSide;
- bool pathDefended, opposed;
- int pliesToGo, movesToGo, oppMovesToGo, sacptg, blockersCount, minKingDist, kingptg, d;
- int pliesToQueen[] = { 256, 256 };
-
- // Step 1. Hunt for unstoppable passed pawns. If we find at least one,
- // record how many plies are required for promotion.
- for (c = WHITE; c <= BLACK; c++)
- {
- // Skip if other side has non-pawn pieces
- if (pos.non_pawn_material(~c))
- continue;
+ // If the path to the queen is fully defended, assign a big bonus.
+ // Otherwise assign a smaller bonus if the block square is defended.
+ if (defendedSquares == squaresToQueen)
+ k += 6;
- b = ei.pi->passed_pawns(c);
+ else if (defendedSquares & blockSq)
+ k += 4;
- while (b)
- {
- s = pop_1st_bit(&b);
- queeningSquare = relative_square(c, make_square(file_of(s), RANK_8));
- queeningPath = squares_in_front_of(c, s);
+ mbonus += k * rr, ebonus += k * rr;
+ }
+ else if (pos.pieces(Us) & blockSq)
+ mbonus += rr + r * 2, ebonus += rr + r * 2;
+ } // rr != 0
- // Compute plies to queening and check direct advancement
- movesToGo = rank_distance(s, queeningSquare) - int(relative_rank(c, s) == RANK_2);
- oppMovesToGo = square_distance(pos.king_square(~c), queeningSquare) - int(c != pos.side_to_move());
- pathDefended = ((ei.attackedBy[c][0] & queeningPath) == queeningPath);
+ // Scale down bonus for candidate passers which need more than one
+ // pawn push to become passed or have a pawn in front of them.
+ if (!pos.pawn_passed(Us, s + Up) || (pos.pieces(PAWN) & forward_file_bb(Us, s)))
+ mbonus /= 2, ebonus /= 2;
- if (movesToGo >= oppMovesToGo && !pathDefended)
- continue;
+ score += make_score(mbonus, ebonus) + PassedFile[file_of(s)];
+ }
- // Opponent king cannot block because path is defended and position
- // is not in check. So only friendly pieces can be blockers.
- assert(!pos.in_check());
- assert((queeningPath & pos.pieces()) == (queeningPath & pos.pieces(c)));
+ if (T)
+ Trace::add(PASSED, Us, score);
- // Add moves needed to free the path from friendly pieces and retest condition
- movesToGo += popcount<Max15>(queeningPath & pos.pieces(c));
+ return score;
+ }
- if (movesToGo >= oppMovesToGo && !pathDefended)
- continue;
- pliesToGo = 2 * movesToGo - int(c == pos.side_to_move());
- pliesToQueen[c] = std::min(pliesToQueen[c], pliesToGo);
- }
- }
-
- // Step 2. If either side cannot promote at least three plies before the other side then situation
- // becomes too complex and we give up. Otherwise we determine the possibly "winning side"
- if (abs(pliesToQueen[WHITE] - pliesToQueen[BLACK]) < 3)
- return SCORE_ZERO;
+ // evaluate_space() computes the space evaluation for a given side. The
+ // space evaluation is a simple bonus based on the number of safe squares
+ // available for minor pieces on the central four files on ranks 2--4. Safe
+ // squares one, two or three squares behind a friendly pawn are counted
+ // twice. Finally, the space bonus is multiplied by a weight. The aim is to
+ // improve play on game opening.
- winnerSide = (pliesToQueen[WHITE] < pliesToQueen[BLACK] ? WHITE : BLACK);
- loserSide = ~winnerSide;
+ template<Tracing T> template<Color Us>
+ Score Evaluation<T>::evaluate_space() {
- // Step 3. Can the losing side possibly create a new passed pawn and thus prevent the loss?
- b = candidates = pos.pieces(PAWN, loserSide);
+ const Color Them = (Us == WHITE ? BLACK : WHITE);
+ const Bitboard SpaceMask =
+ Us == WHITE ? CenterFiles & (Rank2BB | Rank3BB | Rank4BB)
+ : CenterFiles & (Rank7BB | Rank6BB | Rank5BB);
- while (b)
- {
- s = pop_1st_bit(&b);
+ // Find the safe squares for our pieces inside the area defined by
+ // SpaceMask. A square is unsafe if it is attacked by an enemy
+ // pawn, or if it is undefended and attacked by an enemy piece.
+ Bitboard safe = SpaceMask
+ & ~pos.pieces(Us, PAWN)
+ & ~attackedBy[Them][PAWN]
+ & (attackedBy[Us][ALL_PIECES] | ~attackedBy[Them][ALL_PIECES]);
- // Compute plies from queening
- queeningSquare = relative_square(loserSide, make_square(file_of(s), RANK_8));
- movesToGo = rank_distance(s, queeningSquare) - int(relative_rank(loserSide, s) == RANK_2);
- pliesToGo = 2 * movesToGo - int(loserSide == pos.side_to_move());
+ // Find all squares which are at most three squares behind some friendly pawn
+ Bitboard behind = pos.pieces(Us, PAWN);
+ behind |= (Us == WHITE ? behind >> 8 : behind << 8);
+ behind |= (Us == WHITE ? behind >> 16 : behind << 16);
- // Check if (without even considering any obstacles) we're too far away or doubled
- if ( pliesToQueen[winnerSide] + 3 <= pliesToGo
- || (squares_in_front_of(loserSide, s) & pos.pieces(PAWN, loserSide)))
- candidates ^= s;
- }
+ // Since SpaceMask[Us] is fully on our half of the board...
+ assert(unsigned(safe >> (Us == WHITE ? 32 : 0)) == 0);
- // If any candidate is already a passed pawn it _may_ promote in time. We give up.
- if (candidates & ei.pi->passed_pawns(loserSide))
- return SCORE_ZERO;
+ // ...count safe + (behind & safe) with a single popcount.
+ int bonus = popcount((Us == WHITE ? safe << 32 : safe >> 32) | (behind & safe));
+ int weight = pos.count<ALL_PIECES>(Us) - 2 * pe->open_files();
- // Step 4. Check new passed pawn creation through king capturing and pawn sacrifices
- b = candidates;
+ return make_score(bonus * weight * weight / 16, 0);
+ }
- while (b)
- {
- s = pop_1st_bit(&b);
- sacptg = blockersCount = 0;
- minKingDist = kingptg = 256;
- // Compute plies from queening
- queeningSquare = relative_square(loserSide, make_square(file_of(s), RANK_8));
- movesToGo = rank_distance(s, queeningSquare) - int(relative_rank(loserSide, s) == RANK_2);
- pliesToGo = 2 * movesToGo - int(loserSide == pos.side_to_move());
+ // evaluate_initiative() computes the initiative correction value for the
+ // position, i.e., second order bonus/malus based on the known attacking/defending
+ // status of the players.
- // Generate list of blocking pawns and supporters
- supporters = adjacent_files_bb(file_of(s)) & candidates;
- opposed = squares_in_front_of(loserSide, s) & pos.pieces(PAWN, winnerSide);
- blockers = passed_pawn_mask(loserSide, s) & pos.pieces(PAWN, winnerSide);
+ template<Tracing T>
+ Score Evaluation<T>::evaluate_initiative(Value eg) {
- assert(blockers);
+ int kingDistance = distance<File>(pos.square<KING>(WHITE), pos.square<KING>(BLACK))
+ - distance<Rank>(pos.square<KING>(WHITE), pos.square<KING>(BLACK));
+ bool bothFlanks = (pos.pieces(PAWN) & QueenSide) && (pos.pieces(PAWN) & KingSide);
- // How many plies does it take to remove all the blocking pawns?
- while (blockers)
- {
- blockSq = pop_1st_bit(&blockers);
- movesToGo = 256;
+ // Compute the initiative bonus for the attacking side
+ int initiative = 8 * (pe->pawn_asymmetry() + kingDistance - 17) + 12 * pos.count<PAWN>() + 16 * bothFlanks;
- // Check pawns that can give support to overcome obstacle, for instance
- // black pawns: a4, b4 white: b2 then pawn in b4 is giving support.
- if (!opposed)
- {
- b2 = supporters & in_front_bb(winnerSide, blockSq + pawn_push(winnerSide));
+ // Now apply the bonus: note that we find the attacking side by extracting
+ // the sign of the endgame value, and that we carefully cap the bonus so
+ // that the endgame score will never change sign after the bonus.
+ int v = ((eg > 0) - (eg < 0)) * std::max(initiative, -abs(eg));
- while (b2) // This while-loop could be replaced with LSB/MSB (depending on color)
- {
- d = square_distance(blockSq, pop_1st_bit(&b2)) - 2;
- movesToGo = std::min(movesToGo, d);
- }
- }
+ return make_score(0, v);
+ }
- // Check pawns that can be sacrificed against the blocking pawn
- b2 = attack_span_mask(winnerSide, blockSq) & candidates & ~(1ULL << s);
- while (b2) // This while-loop could be replaced with LSB/MSB (depending on color)
- {
- d = square_distance(blockSq, pop_1st_bit(&b2)) - 2;
- movesToGo = std::min(movesToGo, d);
- }
+ // evaluate_scale_factor() computes the scale factor for the winning side
- // If obstacle can be destroyed with an immediate pawn exchange / sacrifice,
- // it's not a real obstacle and we have nothing to add to pliesToGo.
- if (movesToGo <= 0)
- continue;
+ template<Tracing T>
+ ScaleFactor Evaluation<T>::evaluate_scale_factor(Value eg) {
- // Plies needed to sacrifice against all the blocking pawns
- sacptg += movesToGo * 2;
- blockersCount++;
+ Color strongSide = eg > VALUE_DRAW ? WHITE : BLACK;
+ ScaleFactor sf = me->scale_factor(pos, strongSide);
- // Plies needed for the king to capture all the blocking pawns
- d = square_distance(pos.king_square(loserSide), blockSq);
- minKingDist = std::min(minKingDist, d);
- kingptg = (minKingDist + blockersCount) * 2;
+ // If we don't already have an unusual scale factor, check for certain
+ // types of endgames, and use a lower scale for those.
+ if (sf == SCALE_FACTOR_NORMAL || sf == SCALE_FACTOR_ONEPAWN)
+ {
+ if (pos.opposite_bishops())
+ {
+ // Endgame with opposite-colored bishops and no other pieces (ignoring pawns)
+ // is almost a draw, in case of KBP vs KB, it is even more a draw.
+ if ( pos.non_pawn_material(WHITE) == BishopValueMg
+ && pos.non_pawn_material(BLACK) == BishopValueMg)
+ return more_than_one(pos.pieces(PAWN)) ? ScaleFactor(31) : ScaleFactor(9);
+
+ // Endgame with opposite-colored bishops, but also other pieces. Still
+ // a bit drawish, but not as drawish as with only the two bishops.
+ return ScaleFactor(46);
}
-
- // Check if pawn sacrifice plan _may_ save the day
- if (pliesToQueen[winnerSide] + 3 > pliesToGo + sacptg)
- return SCORE_ZERO;
-
- // Check if king capture plan _may_ save the day (contains some false positives)
- if (pliesToQueen[winnerSide] + 3 > pliesToGo + kingptg)
- return SCORE_ZERO;
+ // Endings where weaker side can place his king in front of the opponent's
+ // pawns are drawish.
+ else if ( abs(eg) <= BishopValueEg
+ && pos.count<PAWN>(strongSide) <= 2
+ && !pos.pawn_passed(~strongSide, pos.square<KING>(~strongSide)))
+ return ScaleFactor(37 + 7 * pos.count<PAWN>(strongSide));
}
- // Winning pawn is unstoppable and will promote as first, return big score
- Score score = make_score(0, (Value) 0x500 - 0x20 * pliesToQueen[winnerSide]);
- return winnerSide == WHITE ? score : -score;
+ return sf;
}
- // evaluate_space() computes the space evaluation for a given side. The
- // space evaluation is a simple bonus based on the number of safe squares
- // available for minor pieces on the central four files on ranks 2--4. Safe
- // squares one, two or three squares behind a friendly pawn are counted
- // twice. Finally, the space bonus is scaled by a weight taken from the
- // material hash table. The aim is to improve play on game opening.
- template<Color Us>
- int evaluate_space(const Position& pos, EvalInfo& ei) {
+ // value() is the main function of the class. It computes the various parts of
+ // the evaluation and returns the value of the position from the point of view
+ // of the side to move.
- const Color Them = (Us == WHITE ? BLACK : WHITE);
+ template<Tracing T>
+ Value Evaluation<T>::value() {
- // Find the safe squares for our pieces inside the area defined by
- // SpaceMask[]. A square is unsafe if it is attacked by an enemy
- // pawn, or if it is undefended and attacked by an enemy piece.
- Bitboard safe = SpaceMask[Us]
- & ~pos.pieces(PAWN, Us)
- & ~ei.attackedBy[Them][PAWN]
- & (ei.attackedBy[Us][0] | ~ei.attackedBy[Them][0]);
+ assert(!pos.checkers());
- // Find all squares which are at most three squares behind some friendly pawn
- Bitboard behind = pos.pieces(PAWN, Us);
- behind |= (Us == WHITE ? behind >> 8 : behind << 8);
- behind |= (Us == WHITE ? behind >> 16 : behind << 16);
+ // Probe the material hash table
+ me = Material::probe(pos);
- return popcount<Max15>(safe) + popcount<Max15>(behind & safe);
- }
+ // If we have a specialized evaluation function for the current material
+ // configuration, call it and return.
+ if (me->specialized_eval_exists())
+ return me->evaluate(pos);
+ // Initialize score by reading the incrementally updated scores included in
+ // the position object (material + piece square tables) and the material
+ // imbalance. Score is computed internally from the white point of view.
+ Score score = pos.psq_score() + me->imbalance();
- // apply_weight() applies an evaluation weight to a value trying to prevent overflow
+ // Probe the pawn hash table
+ pe = Pawns::probe(pos);
+ score += pe->pawns_score();
- inline Score apply_weight(Score v, Score w) {
- return make_score((int(mg_value(v)) * mg_value(w)) / 0x100,
- (int(eg_value(v)) * eg_value(w)) / 0x100);
- }
+ // Early exit if score is high
+ Value v = (mg_value(score) + eg_value(score)) / 2;
+ if (abs(v) > LazyThreshold)
+ return pos.side_to_move() == WHITE ? v : -v;
+ // Main evaluation begins here
- // scale_by_game_phase() interpolates between a middle game and an endgame score,
- // based on game phase. It also scales the return value by a ScaleFactor array.
+ initialize<WHITE>();
+ initialize<BLACK>();
- Value scale_by_game_phase(const Score& v, Phase ph, ScaleFactor sf) {
+ score += evaluate_pieces<WHITE, KNIGHT>() - evaluate_pieces<BLACK, KNIGHT>();
+ score += evaluate_pieces<WHITE, BISHOP>() - evaluate_pieces<BLACK, BISHOP>();
+ score += evaluate_pieces<WHITE, ROOK >() - evaluate_pieces<BLACK, ROOK >();
+ score += evaluate_pieces<WHITE, QUEEN >() - evaluate_pieces<BLACK, QUEEN >();
- assert(mg_value(v) > -VALUE_INFINITE && mg_value(v) < VALUE_INFINITE);
- assert(eg_value(v) > -VALUE_INFINITE && eg_value(v) < VALUE_INFINITE);
- assert(ph >= PHASE_ENDGAME && ph <= PHASE_MIDGAME);
+ score += mobility[WHITE] - mobility[BLACK];
- int ev = (eg_value(v) * int(sf)) / SCALE_FACTOR_NORMAL;
- int result = (mg_value(v) * int(ph) + ev * int(128 - ph)) / 128;
- return Value((result + GrainSize / 2) & ~(GrainSize - 1));
- }
+ score += evaluate_king<WHITE>()
+ - evaluate_king<BLACK>();
+ score += evaluate_threats<WHITE>()
+ - evaluate_threats<BLACK>();
- // weight_option() computes the value of an evaluation weight, by combining
- // two UCI-configurable weights (midgame and endgame) with an internal weight.
+ score += evaluate_passed_pawns<WHITE>()
+ - evaluate_passed_pawns<BLACK>();
- Score weight_option(const std::string& mgOpt, const std::string& egOpt, Score internalWeight) {
+ if (pos.non_pawn_material() >= SpaceThreshold)
+ score += evaluate_space<WHITE>()
+ - evaluate_space<BLACK>();
- // Scale option value from 100 to 256
- int mg = Options[mgOpt] * 256 / 100;
- int eg = Options[egOpt] * 256 / 100;
+ score += evaluate_initiative(eg_value(score));
- return apply_weight(make_score(mg, eg), internalWeight);
- }
+ // Interpolate between a middlegame and a (scaled by 'sf') endgame score
+ ScaleFactor sf = evaluate_scale_factor(eg_value(score));
+ v = mg_value(score) * int(me->game_phase())
+ + eg_value(score) * int(PHASE_MIDGAME - me->game_phase()) * sf / SCALE_FACTOR_NORMAL;
+
+ v /= int(PHASE_MIDGAME);
+ // In case of tracing add all remaining individual evaluation terms
+ if (T)
+ {
+ Trace::add(MATERIAL, pos.psq_score());
+ Trace::add(IMBALANCE, me->imbalance());
+ Trace::add(PAWN, pe->pawns_score());
+ Trace::add(MOBILITY, mobility[WHITE], mobility[BLACK]);
+ if (pos.non_pawn_material() >= SpaceThreshold)
+ Trace::add(SPACE, evaluate_space<WHITE>()
+ , evaluate_space<BLACK>());
+ Trace::add(TOTAL, score);
+ }
- // A couple of little helpers used by tracing code, to_cp() converts a value to
- // a double in centipawns scale, trace_add() stores white and black scores.
+ return (pos.side_to_move() == WHITE ? v : -v) + Eval::Tempo; // Side to move point of view
+ }
- double to_cp(Value v) { return double(v) / double(PawnValueMidgame); }
+} // namespace
- void trace_add(int idx, Score wScore, Score bScore) {
- TracedScores[WHITE][idx] = wScore;
- TracedScores[BLACK][idx] = bScore;
- }
+/// evaluate() is the evaluator for the outer world. It returns a static evaluation
+/// of the position from the point of view of the side to move.
+Value Eval::evaluate(const Position& pos)
+{
+ return Evaluation<>(pos).value();
+}
- // trace_row() is an helper function used by tracing code to register the
- // values of a single evaluation term.
-
- void trace_row(const char* name, int idx) {
-
- Score wScore = TracedScores[WHITE][idx];
- Score bScore = TracedScores[BLACK][idx];
-
- switch (idx) {
- case PST: case IMBALANCE: case PAWN: case UNSTOPPABLE: case TOTAL:
- TraceStream << std::setw(20) << name << " | --- --- | --- --- | "
- << std::setw(6) << to_cp(mg_value(wScore)) << " "
- << std::setw(6) << to_cp(eg_value(wScore)) << " \n";
- break;
- default:
- TraceStream << std::setw(20) << name << " | " << std::noshowpos
- << std::setw(5) << to_cp(mg_value(wScore)) << " "
- << std::setw(5) << to_cp(eg_value(wScore)) << " | "
- << std::setw(5) << to_cp(mg_value(bScore)) << " "
- << std::setw(5) << to_cp(eg_value(bScore)) << " | "
- << std::showpos
- << std::setw(6) << to_cp(mg_value(wScore - bScore)) << " "
- << std::setw(6) << to_cp(eg_value(wScore - bScore)) << " \n";
- }
- }
+/// trace() is like evaluate(), but instead of returning a value, it returns
+/// a string (suitable for outputting to stdout) that contains the detailed
+/// descriptions and values of each evaluation term. Useful for debugging.
+
+std::string Eval::trace(const Position& pos) {
+
+ std::memset(scores, 0, sizeof(scores));
+
+ Value v = Evaluation<TRACE>(pos).value();
+ v = pos.side_to_move() == WHITE ? v : -v; // White's point of view
+
+ std::stringstream ss;
+ ss << std::showpoint << std::noshowpos << std::fixed << std::setprecision(2)
+ << " Eval term | White | Black | Total \n"
+ << " | MG EG | MG EG | MG EG \n"
+ << "----------------+-------------+-------------+-------------\n"
+ << " Material | " << Term(MATERIAL)
+ << " Imbalance | " << Term(IMBALANCE)
+ << " Pawns | " << Term(PAWN)
+ << " Knights | " << Term(KNIGHT)
+ << " Bishops | " << Term(BISHOP)
+ << " Rooks | " << Term(ROOK)
+ << " Queens | " << Term(QUEEN)
+ << " Mobility | " << Term(MOBILITY)
+ << " King safety | " << Term(KING)
+ << " Threats | " << Term(THREAT)
+ << " Passed pawns | " << Term(PASSED)
+ << " Space | " << Term(SPACE)
+ << "----------------+-------------+-------------+-------------\n"
+ << " Total | " << Term(TOTAL);
+
+ ss << "\nTotal Evaluation: " << to_cp(v) << " (white side)\n";
+
+ return ss.str();
}