896 lines
35 KiB
C++
896 lines
35 KiB
C++
/*
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Stockfish, a UCI chess playing engine derived from Glaurung 2.1
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Copyright (C) 2004-2008 Tord Romstad (Glaurung author)
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Copyright (C) 2008-2015 Marco Costalba, Joona Kiiski, Tord Romstad
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Copyright (C) 2015-2016 Marco Costalba, Joona Kiiski, Gary Linscott, Tord Romstad
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Stockfish is free software: you can redistribute it and/or modify
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it under the terms of the GNU General Public License as published by
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the Free Software Foundation, either version 3 of the License, or
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(at your option) any later version.
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Stockfish is distributed in the hope that it will be useful,
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but WITHOUT ANY WARRANTY; without even the implied warranty of
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MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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GNU General Public License for more details.
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You should have received a copy of the GNU General Public License
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along with this program. If not, see <http://www.gnu.org/licenses/>.
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*/
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#include <algorithm>
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#include <cassert>
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#include <cstring> // For std::memset
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#include <iomanip>
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#include <sstream>
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#include "bitboard.h"
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#include "evaluate.h"
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#include "material.h"
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#include "pawns.h"
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namespace {
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namespace Trace {
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enum Term { // The first 8 entries are for PieceType
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MATERIAL = 8, IMBALANCE, MOBILITY, THREAT, PASSED, SPACE, TOTAL, TERM_NB
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};
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double scores[TERM_NB][COLOR_NB][PHASE_NB];
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double to_cp(Value v) { return double(v) / PawnValueEg; }
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void add(int idx, Color c, Score s) {
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scores[idx][c][MG] = to_cp(mg_value(s));
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scores[idx][c][EG] = to_cp(eg_value(s));
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}
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void add(int idx, Score w, Score b = SCORE_ZERO) {
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add(idx, WHITE, w); add(idx, BLACK, b);
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}
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std::ostream& operator<<(std::ostream& os, Term t) {
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if (t == MATERIAL || t == IMBALANCE || t == Term(PAWN) || t == TOTAL)
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os << " --- --- | --- --- | ";
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else
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os << std::setw(5) << scores[t][WHITE][MG] << " "
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<< std::setw(5) << scores[t][WHITE][EG] << " | "
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<< std::setw(5) << scores[t][BLACK][MG] << " "
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<< std::setw(5) << scores[t][BLACK][EG] << " | ";
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os << std::setw(5) << scores[t][WHITE][MG] - scores[t][BLACK][MG] << " "
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<< std::setw(5) << scores[t][WHITE][EG] - scores[t][BLACK][EG] << " \n";
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return os;
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}
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}
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using namespace Trace;
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// Struct EvalInfo contains various information computed and collected
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// by the evaluation functions.
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struct EvalInfo {
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// attackedBy[color][piece type] is a bitboard representing all squares
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// attacked by a given color and piece type (can be also ALL_PIECES).
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Bitboard attackedBy[COLOR_NB][PIECE_TYPE_NB];
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// kingRing[color] is the zone around the king which is considered
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// by the king safety evaluation. This consists of the squares directly
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// adjacent to the king, and the three (or two, for a king on an edge file)
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// squares two ranks in front of the king. For instance, if black's king
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// is on g8, kingRing[BLACK] is a bitboard containing the squares f8, h8,
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// f7, g7, h7, f6, g6 and h6.
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Bitboard kingRing[COLOR_NB];
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// kingAttackersCount[color] is the number of pieces of the given color
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// which attack a square in the kingRing of the enemy king.
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int kingAttackersCount[COLOR_NB];
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// kingAttackersWeight[color] is the sum of the "weights" of the pieces of the
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// given color which attack a square in the kingRing of the enemy king. The
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// weights of the individual piece types are given by the elements in the
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// KingAttackWeights array.
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int kingAttackersWeight[COLOR_NB];
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// kingAdjacentZoneAttacksCount[color] is the number of attacks by the given
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// color to squares directly adjacent to the enemy king. Pieces which attack
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// more than one square are counted multiple times. For instance, if there is
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// a white knight on g5 and black's king is on g8, this white knight adds 2
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// to kingAdjacentZoneAttacksCount[WHITE].
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int kingAdjacentZoneAttacksCount[COLOR_NB];
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Bitboard pinnedPieces[COLOR_NB];
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Material::Entry* me;
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Pawns::Entry* pi;
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};
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#define V(v) Value(v)
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#define S(mg, eg) make_score(mg, eg)
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// MobilityBonus[PieceType][attacked] contains bonuses for middle and end
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// game, indexed by piece type and number of attacked squares in the MobilityArea.
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const Score MobilityBonus[][32] = {
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{}, {},
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{ S(-75,-76), S(-56,-54), S(- 9,-26), S( -2,-10), S( 6, 5), S( 15, 11), // Knights
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S( 22, 26), S( 30, 28), S( 36, 29) },
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{ S(-48,-58), S(-21,-19), S( 16, -2), S( 26, 12), S( 37, 22), S( 51, 42), // Bishops
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S( 54, 54), S( 63, 58), S( 65, 63), S( 71, 70), S( 79, 74), S( 81, 86),
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S( 92, 90), S( 97, 94) },
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{ S(-56,-78), S(-25,-18), S(-11, 26), S( -5, 55), S( -4, 70), S( -1, 81), // Rooks
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S( 8,109), S( 14,120), S( 21,128), S( 23,143), S( 31,154), S( 32,160),
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S( 43,165), S( 49,168), S( 59,169) },
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{ S(-40,-35), S(-25,-12), S( 2, 7), S( 4, 19), S( 14, 37), S( 24, 55), // Queens
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S( 25, 62), S( 40, 76), S( 43, 79), S( 47, 87), S( 54, 94), S( 56,102),
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S( 60,111), S( 70,116), S( 72,118), S( 73,122), S( 75,128), S( 77,130),
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S( 85,133), S( 94,136), S( 99,140), S(108,157), S(112,158), S(113,161),
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S(118,174), S(119,177), S(123,191), S(128,199) }
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};
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// Outpost[knight/bishop][supported by pawn] contains bonuses for knights and
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// bishops outposts, bigger if outpost piece is supported by a pawn.
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const Score Outpost[][2] = {
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{ S(43,11), S(65,20) }, // Knights
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{ S(20, 3), S(29, 8) } // Bishops
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};
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// ReachableOutpost[knight/bishop][supported by pawn] contains bonuses for
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// knights and bishops which can reach an outpost square in one move, bigger
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// if outpost square is supported by a pawn.
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const Score ReachableOutpost[][2] = {
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{ S(21, 5), S(35, 8) }, // Knights
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{ S( 8, 0), S(14, 4) } // Bishops
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};
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// RookOnFile[semiopen/open] contains bonuses for each rook when there is no
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// friendly pawn on the rook file.
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const Score RookOnFile[2] = { S(20, 7), S(45, 20) };
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// ThreatBySafePawn[PieceType] contains bonuses according to which piece
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// type is attacked by a pawn which is protected or is not attacked.
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const Score ThreatBySafePawn[PIECE_TYPE_NB] = {
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S(0, 0), S(0, 0), S(176, 139), S(131, 127), S(217, 218), S(203, 215) };
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// Threat[by minor/by rook][attacked PieceType] contains
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// bonuses according to which piece type attacks which one.
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// Attacks on lesser pieces which are pawn-defended are not considered.
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const Score Threat[][PIECE_TYPE_NB] = {
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{ S(0, 0), S(0, 33), S(45, 43), S(46, 47), S(72,107), S(48,118) }, // by Minor
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{ S(0, 0), S(0, 25), S(40, 62), S(40, 59), S( 0, 34), S(35, 48) } // by Rook
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};
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// ThreatByKing[on one/on many] contains bonuses for King attacks on
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// pawns or pieces which are not pawn-defended.
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const Score ThreatByKing[2] = { S(3, 62), S(9, 138) };
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// Passed[mg/eg][Rank] contains midgame and endgame bonuses for passed pawns.
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// We don't use a Score because we process the two components independently.
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const Value Passed[][RANK_NB] = {
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{ V(5), V( 5), V(31), V(73), V(166), V(252) },
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{ V(7), V(14), V(38), V(73), V(166), V(252) }
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};
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// PassedFile[File] contains a bonus according to the file of a passed pawn
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const Score PassedFile[FILE_NB] = {
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S( 9, 10), S( 2, 10), S( 1, -8), S(-20,-12),
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S(-20,-12), S( 1, -8), S( 2, 10), S( 9, 10)
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};
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// Assorted bonuses and penalties used by evaluation
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const Score MinorBehindPawn = S(16, 0);
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const Score BishopPawns = S( 8, 12);
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const Score RookOnPawn = S( 8, 24);
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const Score TrappedRook = S(92, 0);
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const Score SafeCheck = S(20, 20);
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const Score OtherCheck = S(10, 10);
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const Score ThreatByHangingPawn = S(71, 61);
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const Score LooseEnemies = S( 0, 25);
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const Score Hanging = S(48, 27);
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const Score ThreatByPawnPush = S(38, 22);
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const Score Unstoppable = S( 0, 20);
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// Penalty for a bishop on a1/h1 (a8/h8 for black) which is trapped by
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// a friendly pawn on b2/g2 (b7/g7 for black). This can obviously only
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// happen in Chess960 games.
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const Score TrappedBishopA1H1 = S(50, 50);
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#undef S
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#undef V
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// King danger constants and variables. The king danger scores are looked-up
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// in KingDanger[]. Various little "meta-bonuses" measuring the strength
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// of the enemy attack are added up into an integer, which is used as an
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// index to KingDanger[].
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Score KingDanger[512];
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// KingAttackWeights[PieceType] contains king attack weights by piece type
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const int KingAttackWeights[PIECE_TYPE_NB] = { 0, 0, 7, 5, 4, 1 };
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// Penalties for enemy's safe checks
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const int QueenContactCheck = 89;
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const int QueenCheck = 52;
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const int RookCheck = 45;
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const int BishopCheck = 5;
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const int KnightCheck = 17;
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// eval_init() initializes king and attack bitboards for a given color
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// adding pawn attacks. To be done at the beginning of the evaluation.
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template<Color Us>
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void eval_init(const Position& pos, EvalInfo& ei) {
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const Color Them = (Us == WHITE ? BLACK : WHITE);
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const Square Down = (Us == WHITE ? DELTA_S : DELTA_N);
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ei.pinnedPieces[Us] = pos.pinned_pieces(Us);
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Bitboard b = ei.attackedBy[Them][KING] = pos.attacks_from<KING>(pos.square<KING>(Them));
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ei.attackedBy[Them][ALL_PIECES] |= b;
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ei.attackedBy[Us][ALL_PIECES] |= ei.attackedBy[Us][PAWN] = ei.pi->pawn_attacks(Us);
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// Init king safety tables only if we are going to use them
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if (pos.non_pawn_material(Us) >= QueenValueMg)
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{
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ei.kingRing[Them] = b | shift_bb<Down>(b);
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b &= ei.attackedBy[Us][PAWN];
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ei.kingAttackersCount[Us] = popcount(b);
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ei.kingAdjacentZoneAttacksCount[Us] = ei.kingAttackersWeight[Us] = 0;
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}
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else
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ei.kingRing[Them] = ei.kingAttackersCount[Us] = 0;
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}
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// evaluate_pieces() assigns bonuses and penalties to the pieces of a given
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// color and type.
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template<bool DoTrace, Color Us = WHITE, PieceType Pt = KNIGHT>
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Score evaluate_pieces(const Position& pos, EvalInfo& ei, Score* mobility,
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const Bitboard* mobilityArea) {
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Bitboard b, bb;
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Square s;
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Score score = SCORE_ZERO;
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const PieceType NextPt = (Us == WHITE ? Pt : PieceType(Pt + 1));
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const Color Them = (Us == WHITE ? BLACK : WHITE);
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const Bitboard OutpostRanks = (Us == WHITE ? Rank4BB | Rank5BB | Rank6BB
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: Rank5BB | Rank4BB | Rank3BB);
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const Square* pl = pos.squares<Pt>(Us);
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ei.attackedBy[Us][Pt] = 0;
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while ((s = *pl++) != SQ_NONE)
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{
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// Find attacked squares, including x-ray attacks for bishops and rooks
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b = Pt == BISHOP ? attacks_bb<BISHOP>(s, pos.pieces() ^ pos.pieces(Us, QUEEN))
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: Pt == ROOK ? attacks_bb< ROOK>(s, pos.pieces() ^ pos.pieces(Us, ROOK, QUEEN))
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: pos.attacks_from<Pt>(s);
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if (ei.pinnedPieces[Us] & s)
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b &= LineBB[pos.square<KING>(Us)][s];
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ei.attackedBy[Us][ALL_PIECES] |= ei.attackedBy[Us][Pt] |= b;
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if (b & ei.kingRing[Them])
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{
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ei.kingAttackersCount[Us]++;
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ei.kingAttackersWeight[Us] += KingAttackWeights[Pt];
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ei.kingAdjacentZoneAttacksCount[Us] += popcount(b & ei.attackedBy[Them][KING]);
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}
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if (Pt == QUEEN)
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b &= ~( ei.attackedBy[Them][KNIGHT]
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| ei.attackedBy[Them][BISHOP]
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| ei.attackedBy[Them][ROOK]);
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int mob = popcount(b & mobilityArea[Us]);
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mobility[Us] += MobilityBonus[Pt][mob];
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if (Pt == BISHOP || Pt == KNIGHT)
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{
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// Bonus for outpost squares
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bb = OutpostRanks & ~ei.pi->pawn_attacks_span(Them);
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if (bb & s)
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score += Outpost[Pt == BISHOP][!!(ei.attackedBy[Us][PAWN] & s)];
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else
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{
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bb &= b & ~pos.pieces(Us);
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if (bb)
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score += ReachableOutpost[Pt == BISHOP][!!(ei.attackedBy[Us][PAWN] & bb)];
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}
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// Bonus when behind a pawn
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if ( relative_rank(Us, s) < RANK_5
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&& (pos.pieces(PAWN) & (s + pawn_push(Us))))
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score += MinorBehindPawn;
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// Penalty for pawns on the same color square as the bishop
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if (Pt == BISHOP)
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score -= BishopPawns * ei.pi->pawns_on_same_color_squares(Us, s);
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// An important Chess960 pattern: A cornered bishop blocked by a friendly
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// pawn diagonally in front of it is a very serious problem, especially
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// when that pawn is also blocked.
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if ( Pt == BISHOP
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&& pos.is_chess960()
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&& (s == relative_square(Us, SQ_A1) || s == relative_square(Us, SQ_H1)))
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{
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Square d = pawn_push(Us) + (file_of(s) == FILE_A ? DELTA_E : DELTA_W);
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if (pos.piece_on(s + d) == make_piece(Us, PAWN))
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score -= !pos.empty(s + d + pawn_push(Us)) ? TrappedBishopA1H1 * 4
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: pos.piece_on(s + d + d) == make_piece(Us, PAWN) ? TrappedBishopA1H1 * 2
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: TrappedBishopA1H1;
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}
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}
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if (Pt == ROOK)
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{
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// Bonus for aligning with enemy pawns on the same rank/file
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if (relative_rank(Us, s) >= RANK_5)
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score += RookOnPawn * popcount(pos.pieces(Them, PAWN) & PseudoAttacks[ROOK][s]);
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// Bonus when on an open or semi-open file
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if (ei.pi->semiopen_file(Us, file_of(s)))
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score += RookOnFile[!!ei.pi->semiopen_file(Them, file_of(s))];
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// Penalize when trapped by the king, even more if the king cannot castle
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else if (mob <= 3)
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{
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Square ksq = pos.square<KING>(Us);
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if ( ((file_of(ksq) < FILE_E) == (file_of(s) < file_of(ksq)))
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&& (rank_of(ksq) == rank_of(s) || relative_rank(Us, ksq) == RANK_1)
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&& !ei.pi->semiopen_side(Us, file_of(ksq), file_of(s) < file_of(ksq)))
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score -= (TrappedRook - make_score(mob * 22, 0)) * (1 + !pos.can_castle(Us));
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}
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}
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}
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if (DoTrace)
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Trace::add(Pt, Us, score);
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// Recursively call evaluate_pieces() of next piece type until KING is excluded
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return score - evaluate_pieces<DoTrace, Them, NextPt>(pos, ei, mobility, mobilityArea);
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}
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template<>
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Score evaluate_pieces<false, WHITE, KING>(const Position&, EvalInfo&, Score*, const Bitboard*) { return SCORE_ZERO; }
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template<>
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Score evaluate_pieces< true, WHITE, KING>(const Position&, EvalInfo&, Score*, const Bitboard*) { return SCORE_ZERO; }
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// evaluate_king() assigns bonuses and penalties to a king of a given color
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template<Color Us, bool DoTrace>
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Score evaluate_king(const Position& pos, const EvalInfo& ei) {
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const Color Them = (Us == WHITE ? BLACK : WHITE);
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const Square Up = (Us == WHITE ? DELTA_N : DELTA_S);
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Bitboard undefended, b, b1, b2, safe, other;
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int attackUnits;
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const Square ksq = pos.square<KING>(Us);
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// King shelter and enemy pawns storm
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Score score = ei.pi->king_safety<Us>(pos, ksq);
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// Main king safety evaluation
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if (ei.kingAttackersCount[Them])
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{
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// Find the attacked squares which are defended only by the king...
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undefended = ei.attackedBy[Them][ALL_PIECES]
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& ei.attackedBy[Us][KING]
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& ~( ei.attackedBy[Us][PAWN] | ei.attackedBy[Us][KNIGHT]
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| ei.attackedBy[Us][BISHOP] | ei.attackedBy[Us][ROOK]
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| ei.attackedBy[Us][QUEEN]);
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// ... and those which are not defended at all in the larger king ring
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b = ei.attackedBy[Them][ALL_PIECES] & ~ei.attackedBy[Us][ALL_PIECES]
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& ei.kingRing[Us] & ~pos.pieces(Them);
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// Initialize the 'attackUnits' variable, which is used later on as an
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// index into the KingDanger[] array. The initial value is based on the
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// number and types of the enemy's attacking pieces, the number of
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// attacked and undefended squares around our king and the quality of
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// the pawn shelter (current 'score' value).
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attackUnits = std::min(72, ei.kingAttackersCount[Them] * ei.kingAttackersWeight[Them])
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+ 9 * ei.kingAdjacentZoneAttacksCount[Them]
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+ 27 * popcount(undefended)
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+ 11 * (popcount(b) + !!ei.pinnedPieces[Us])
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- 64 * !pos.count<QUEEN>(Them)
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- mg_value(score) / 8;
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// Analyse the enemy's safe queen contact checks. Firstly, find the
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// undefended squares around the king reachable by the enemy queen...
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b = undefended & ei.attackedBy[Them][QUEEN] & ~pos.pieces(Them);
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if (b)
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{
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// ...and then remove squares not supported by another enemy piece
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b &= ei.attackedBy[Them][PAWN] | ei.attackedBy[Them][KNIGHT]
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| ei.attackedBy[Them][BISHOP] | ei.attackedBy[Them][ROOK]
|
|
| ei.attackedBy[Them][KING];
|
|
|
|
attackUnits += QueenContactCheck * popcount(b);
|
|
}
|
|
|
|
// Analyse the safe enemy's checks which are possible on next move...
|
|
safe = ~(ei.attackedBy[Us][ALL_PIECES] | pos.pieces(Them));
|
|
|
|
// ... and some other potential checks, only requiring the square to be
|
|
// safe from pawn-attacks, and not being occupied by a blocked pawn.
|
|
other = ~( ei.attackedBy[Us][PAWN]
|
|
| (pos.pieces(Them, PAWN) & shift_bb<Up>(pos.pieces(PAWN))));
|
|
|
|
b1 = pos.attacks_from<ROOK >(ksq);
|
|
b2 = pos.attacks_from<BISHOP>(ksq);
|
|
|
|
// Enemy queen safe checks
|
|
if ((b1 | b2) & ei.attackedBy[Them][QUEEN] & safe)
|
|
attackUnits += QueenCheck, score -= SafeCheck;
|
|
|
|
// Enemy rooks safe and other checks
|
|
if (b1 & ei.attackedBy[Them][ROOK] & safe)
|
|
attackUnits += RookCheck, score -= SafeCheck;
|
|
|
|
else if (b1 & ei.attackedBy[Them][ROOK] & other)
|
|
score -= OtherCheck;
|
|
|
|
// Enemy bishops safe and other checks
|
|
if (b2 & ei.attackedBy[Them][BISHOP] & safe)
|
|
attackUnits += BishopCheck, score -= SafeCheck;
|
|
|
|
else if (b2 & ei.attackedBy[Them][BISHOP] & other)
|
|
score -= OtherCheck;
|
|
|
|
// Enemy knights safe and other checks
|
|
b = pos.attacks_from<KNIGHT>(ksq) & ei.attackedBy[Them][KNIGHT];
|
|
if (b & safe)
|
|
attackUnits += KnightCheck, score -= SafeCheck;
|
|
|
|
else if (b & other)
|
|
score -= OtherCheck;
|
|
|
|
// Finally, extract the king danger score from the KingDanger[]
|
|
// array and subtract the score from the evaluation.
|
|
score -= KingDanger[std::max(std::min(attackUnits, 399), 0)];
|
|
}
|
|
|
|
if (DoTrace)
|
|
Trace::add(KING, Us, score);
|
|
|
|
return score;
|
|
}
|
|
|
|
|
|
// evaluate_threats() assigns bonuses according to the types of the attacking
|
|
// and the attacked pieces.
|
|
|
|
template<Color Us, bool DoTrace>
|
|
Score evaluate_threats(const Position& pos, const EvalInfo& ei) {
|
|
|
|
const Color Them = (Us == WHITE ? BLACK : WHITE);
|
|
const Square Up = (Us == WHITE ? DELTA_N : DELTA_S);
|
|
const Square Left = (Us == WHITE ? DELTA_NW : DELTA_SE);
|
|
const Square Right = (Us == WHITE ? DELTA_NE : DELTA_SW);
|
|
const Bitboard TRank2BB = (Us == WHITE ? Rank2BB : Rank7BB);
|
|
const Bitboard TRank7BB = (Us == WHITE ? Rank7BB : Rank2BB);
|
|
|
|
enum { Minor, Rook };
|
|
|
|
Bitboard b, weak, defended, safeThreats;
|
|
Score score = SCORE_ZERO;
|
|
|
|
// Small bonus if the opponent has loose pawns or pieces
|
|
if ( (pos.pieces(Them) ^ pos.pieces(Them, QUEEN, KING))
|
|
& ~(ei.attackedBy[Us][ALL_PIECES] | ei.attackedBy[Them][ALL_PIECES]))
|
|
score += LooseEnemies;
|
|
|
|
// Non-pawn enemies attacked by a pawn
|
|
weak = (pos.pieces(Them) ^ pos.pieces(Them, PAWN)) & ei.attackedBy[Us][PAWN];
|
|
|
|
if (weak)
|
|
{
|
|
b = pos.pieces(Us, PAWN) & ( ~ei.attackedBy[Them][ALL_PIECES]
|
|
| ei.attackedBy[Us][ALL_PIECES]);
|
|
|
|
safeThreats = (shift_bb<Right>(b) | shift_bb<Left>(b)) & weak;
|
|
|
|
if (weak ^ safeThreats)
|
|
score += ThreatByHangingPawn;
|
|
|
|
while (safeThreats)
|
|
score += ThreatBySafePawn[type_of(pos.piece_on(pop_lsb(&safeThreats)))];
|
|
}
|
|
|
|
// Non-pawn enemies defended by a pawn
|
|
defended = (pos.pieces(Them) ^ pos.pieces(Them, PAWN)) & ei.attackedBy[Them][PAWN];
|
|
|
|
// Enemies not defended by a pawn and under our attack
|
|
weak = pos.pieces(Them)
|
|
& ~ei.attackedBy[Them][PAWN]
|
|
& ei.attackedBy[Us][ALL_PIECES];
|
|
|
|
// Add a bonus according to the kind of attacking pieces
|
|
if (defended | weak)
|
|
{
|
|
b = (defended | weak) & (ei.attackedBy[Us][KNIGHT] | ei.attackedBy[Us][BISHOP]);
|
|
while (b)
|
|
score += Threat[Minor][type_of(pos.piece_on(pop_lsb(&b)))];
|
|
|
|
b = (pos.pieces(Them, QUEEN) | weak) & ei.attackedBy[Us][ROOK];
|
|
while (b)
|
|
score += Threat[Rook ][type_of(pos.piece_on(pop_lsb(&b)))];
|
|
|
|
score += Hanging * popcount(weak & ~ei.attackedBy[Them][ALL_PIECES]);
|
|
|
|
b = weak & ei.attackedBy[Us][KING];
|
|
if (b)
|
|
score += ThreatByKing[more_than_one(b)];
|
|
}
|
|
|
|
// Bonus if some pawns can safely push and attack an enemy piece
|
|
b = pos.pieces(Us, PAWN) & ~TRank7BB;
|
|
b = shift_bb<Up>(b | (shift_bb<Up>(b & TRank2BB) & ~pos.pieces()));
|
|
|
|
b &= ~pos.pieces()
|
|
& ~ei.attackedBy[Them][PAWN]
|
|
& (ei.attackedBy[Us][ALL_PIECES] | ~ei.attackedBy[Them][ALL_PIECES]);
|
|
|
|
b = (shift_bb<Left>(b) | shift_bb<Right>(b))
|
|
& pos.pieces(Them)
|
|
& ~ei.attackedBy[Us][PAWN];
|
|
|
|
score += ThreatByPawnPush * popcount(b);
|
|
|
|
if (DoTrace)
|
|
Trace::add(THREAT, Us, score);
|
|
|
|
return score;
|
|
}
|
|
|
|
|
|
// evaluate_passed_pawns() evaluates the passed pawns of the given color
|
|
|
|
template<Color Us, bool DoTrace>
|
|
Score evaluate_passed_pawns(const Position& pos, const EvalInfo& ei) {
|
|
|
|
const Color Them = (Us == WHITE ? BLACK : WHITE);
|
|
|
|
Bitboard b, squaresToQueen, defendedSquares, unsafeSquares;
|
|
Score score = SCORE_ZERO;
|
|
|
|
b = ei.pi->passed_pawns(Us);
|
|
|
|
while (b)
|
|
{
|
|
Square s = pop_lsb(&b);
|
|
|
|
assert(pos.pawn_passed(Us, s));
|
|
|
|
int r = relative_rank(Us, s) - RANK_2;
|
|
int rr = r * (r - 1);
|
|
|
|
Value mbonus = Passed[MG][r], ebonus = Passed[EG][r];
|
|
|
|
if (rr)
|
|
{
|
|
Square blockSq = s + pawn_push(Us);
|
|
|
|
// 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 (relative_rank(Us, blockSq) != RANK_8)
|
|
ebonus -= distance(pos.square<KING>(Us), blockSq + pawn_push(Us)) * rr;
|
|
|
|
// If the pawn is free to advance, then increase the bonus
|
|
if (pos.empty(blockSq))
|
|
{
|
|
// 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_bb(Us, s);
|
|
|
|
Bitboard bb = forward_bb(Them, s) & pos.pieces(ROOK, QUEEN) & pos.attacks_from<ROOK>(s);
|
|
|
|
if (!(pos.pieces(Us) & bb))
|
|
defendedSquares &= ei.attackedBy[Us][ALL_PIECES];
|
|
|
|
if (!(pos.pieces(Them) & bb))
|
|
unsafeSquares &= ei.attackedBy[Them][ALL_PIECES] | pos.pieces(Them);
|
|
|
|
// 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;
|
|
|
|
// 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;
|
|
|
|
else if (defendedSquares & blockSq)
|
|
k += 4;
|
|
|
|
mbonus += k * rr, ebonus += k * rr;
|
|
}
|
|
else if (pos.pieces(Us) & blockSq)
|
|
mbonus += rr + r * 2, ebonus += rr + r * 2;
|
|
} // rr != 0
|
|
|
|
score += make_score(mbonus, ebonus) + PassedFile[file_of(s)];
|
|
}
|
|
|
|
if (DoTrace)
|
|
Trace::add(PASSED, Us, score);
|
|
|
|
// Add the scores to the middlegame and endgame eval
|
|
return score;
|
|
}
|
|
|
|
|
|
// 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.
|
|
template<Color Us>
|
|
Score evaluate_space(const Position& pos, const EvalInfo& ei) {
|
|
|
|
const Color Them = (Us == WHITE ? BLACK : WHITE);
|
|
const Bitboard SpaceMask =
|
|
Us == WHITE ? (FileCBB | FileDBB | FileEBB | FileFBB) & (Rank2BB | Rank3BB | Rank4BB)
|
|
: (FileCBB | FileDBB | FileEBB | FileFBB) & (Rank7BB | Rank6BB | Rank5BB);
|
|
|
|
// 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)
|
|
& ~ei.attackedBy[Them][PAWN]
|
|
& (ei.attackedBy[Us][ALL_PIECES] | ~ei.attackedBy[Them][ALL_PIECES]);
|
|
|
|
// 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);
|
|
|
|
// Since SpaceMask[Us] is fully on our half of the board...
|
|
assert(unsigned(safe >> (Us == WHITE ? 32 : 0)) == 0);
|
|
|
|
// ...count safe + (behind & safe) with a single popcount
|
|
int bonus = popcount((Us == WHITE ? safe << 32 : safe >> 32) | (behind & safe));
|
|
int weight = pos.count<KNIGHT>(Us) + pos.count<BISHOP>(Us)
|
|
+ pos.count<KNIGHT>(Them) + pos.count<BISHOP>(Them);
|
|
|
|
return make_score(bonus * weight * weight * 2 / 11, 0);
|
|
}
|
|
|
|
|
|
// 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.
|
|
Score evaluate_initiative(const Position& pos, int asymmetry, Value eg) {
|
|
|
|
int kingDistance = distance<File>(pos.square<KING>(WHITE), pos.square<KING>(BLACK))
|
|
- distance<Rank>(pos.square<KING>(WHITE), pos.square<KING>(BLACK));
|
|
int pawns = pos.count<PAWN>(WHITE) + pos.count<PAWN>(BLACK);
|
|
|
|
// Compute the initiative bonus for the attacking side
|
|
int initiative = 8 * (asymmetry + kingDistance - 15) + 12 * pawns;
|
|
|
|
// 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 be divided by more than two.
|
|
int value = ((eg > 0) - (eg < 0)) * std::max(initiative, -abs(eg / 2));
|
|
|
|
return make_score(0, value);
|
|
}
|
|
|
|
|
|
// evaluate_scale_factor() computes the scale factor for the winning side
|
|
ScaleFactor evaluate_scale_factor(const Position& pos, const EvalInfo& ei, Value eg) {
|
|
|
|
Color strongSide = eg > VALUE_DRAW ? WHITE : BLACK;
|
|
ScaleFactor sf = ei.me->scale_factor(pos, strongSide);
|
|
|
|
// If we don't already have an unusual scale factor, check for certain
|
|
// types of endgames, and use a lower scale for those.
|
|
if ( ei.me->game_phase() < PHASE_MIDGAME
|
|
&& (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)
|
|
sf = 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.
|
|
else
|
|
sf = ScaleFactor(46 * sf / SCALE_FACTOR_NORMAL);
|
|
}
|
|
// Endings where weaker side can place his king in front of the opponent's
|
|
// pawns are drawish.
|
|
else if ( abs(eg) <= BishopValueEg
|
|
&& ei.pi->pawn_span(strongSide) <= 1
|
|
&& !pos.pawn_passed(~strongSide, pos.square<KING>(~strongSide)))
|
|
sf = ei.pi->pawn_span(strongSide) ? ScaleFactor(51) : ScaleFactor(37);
|
|
}
|
|
|
|
return sf;
|
|
}
|
|
|
|
} // namespace
|
|
|
|
|
|
/// evaluate() is the main evaluation function. It returns a static evaluation
|
|
/// of the position from the point of view of the side to move.
|
|
|
|
template<bool DoTrace>
|
|
Value Eval::evaluate(const Position& pos) {
|
|
|
|
assert(!pos.checkers());
|
|
|
|
EvalInfo ei;
|
|
Score score, mobility[COLOR_NB] = { SCORE_ZERO, SCORE_ZERO };
|
|
|
|
// Initialize score by reading the incrementally updated scores included in
|
|
// the position object (material + piece square tables). Score is computed
|
|
// internally from the white point of view.
|
|
score = pos.psq_score();
|
|
|
|
// Probe the material hash table
|
|
ei.me = Material::probe(pos);
|
|
score += ei.me->imbalance();
|
|
|
|
// If we have a specialized evaluation function for the current material
|
|
// configuration, call it and return.
|
|
if (ei.me->specialized_eval_exists())
|
|
return ei.me->evaluate(pos);
|
|
|
|
// Probe the pawn hash table
|
|
ei.pi = Pawns::probe(pos);
|
|
score += ei.pi->pawns_score();
|
|
|
|
// Initialize attack and king safety bitboards
|
|
ei.attackedBy[WHITE][ALL_PIECES] = ei.attackedBy[BLACK][ALL_PIECES] = 0;
|
|
eval_init<WHITE>(pos, ei);
|
|
eval_init<BLACK>(pos, ei);
|
|
|
|
// Pawns blocked or on ranks 2 and 3 will be excluded from the mobility area
|
|
Bitboard blockedPawns[] = {
|
|
pos.pieces(WHITE, PAWN) & (shift_bb<DELTA_S>(pos.pieces()) | Rank2BB | Rank3BB),
|
|
pos.pieces(BLACK, PAWN) & (shift_bb<DELTA_N>(pos.pieces()) | Rank7BB | Rank6BB)
|
|
};
|
|
|
|
// Do not include in mobility area squares protected by enemy pawns, or occupied
|
|
// by our blocked pawns or king.
|
|
Bitboard mobilityArea[] = {
|
|
~(ei.attackedBy[BLACK][PAWN] | blockedPawns[WHITE] | pos.square<KING>(WHITE)),
|
|
~(ei.attackedBy[WHITE][PAWN] | blockedPawns[BLACK] | pos.square<KING>(BLACK))
|
|
};
|
|
|
|
// Evaluate all pieces but king and pawns
|
|
score += evaluate_pieces<DoTrace>(pos, ei, mobility, mobilityArea);
|
|
score += mobility[WHITE] - mobility[BLACK];
|
|
|
|
// Evaluate kings after all other pieces because we need full attack
|
|
// information when computing the king safety evaluation.
|
|
score += evaluate_king<WHITE, DoTrace>(pos, ei)
|
|
- evaluate_king<BLACK, DoTrace>(pos, ei);
|
|
|
|
// Evaluate tactical threats, we need full attack information including king
|
|
score += evaluate_threats<WHITE, DoTrace>(pos, ei)
|
|
- evaluate_threats<BLACK, DoTrace>(pos, ei);
|
|
|
|
// Evaluate passed pawns, we need full attack information including king
|
|
score += evaluate_passed_pawns<WHITE, DoTrace>(pos, ei)
|
|
- evaluate_passed_pawns<BLACK, DoTrace>(pos, ei);
|
|
|
|
// If both sides have only pawns, score for potential unstoppable pawns
|
|
if (!pos.non_pawn_material(WHITE) && !pos.non_pawn_material(BLACK))
|
|
{
|
|
Bitboard b;
|
|
if ((b = ei.pi->passed_pawns(WHITE)) != 0)
|
|
score += Unstoppable * int(relative_rank(WHITE, frontmost_sq(WHITE, b)));
|
|
|
|
if ((b = ei.pi->passed_pawns(BLACK)) != 0)
|
|
score -= Unstoppable * int(relative_rank(BLACK, frontmost_sq(BLACK, b)));
|
|
}
|
|
|
|
// Evaluate space for both sides, only during opening
|
|
if (pos.non_pawn_material(WHITE) + pos.non_pawn_material(BLACK) >= 12222)
|
|
score += evaluate_space<WHITE>(pos, ei)
|
|
- evaluate_space<BLACK>(pos, ei);
|
|
|
|
// Evaluate position potential for the winning side
|
|
score += evaluate_initiative(pos, ei.pi->pawn_asymmetry(), eg_value(score));
|
|
|
|
// Evaluate scale factor for the winning side
|
|
ScaleFactor sf = evaluate_scale_factor(pos, ei, eg_value(score));
|
|
|
|
// Interpolate between a middlegame and a (scaled by 'sf') endgame score
|
|
Value v = mg_value(score) * int(ei.me->game_phase())
|
|
+ eg_value(score) * int(PHASE_MIDGAME - ei.me->game_phase()) * sf / SCALE_FACTOR_NORMAL;
|
|
|
|
v /= int(PHASE_MIDGAME);
|
|
|
|
// In case of tracing add all remaining individual evaluation terms
|
|
if (DoTrace)
|
|
{
|
|
Trace::add(MATERIAL, pos.psq_score());
|
|
Trace::add(IMBALANCE, ei.me->imbalance());
|
|
Trace::add(PAWN, ei.pi->pawns_score());
|
|
Trace::add(MOBILITY, mobility[WHITE], mobility[BLACK]);
|
|
Trace::add(SPACE, evaluate_space<WHITE>(pos, ei)
|
|
, evaluate_space<BLACK>(pos, ei));
|
|
Trace::add(TOTAL, score);
|
|
}
|
|
|
|
return (pos.side_to_move() == WHITE ? v : -v) + Eval::Tempo; // Side to move point of view
|
|
}
|
|
|
|
// Explicit template instantiations
|
|
template Value Eval::evaluate<true >(const Position&);
|
|
template Value Eval::evaluate<false>(const Position&);
|
|
|
|
|
|
/// 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 = evaluate<true>(pos);
|
|
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)
|
|
<< " Bishop | " << 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();
|
|
}
|
|
|
|
|
|
/// init() computes evaluation weights, usually at startup
|
|
|
|
void Eval::init() {
|
|
|
|
const int MaxSlope = 322;
|
|
const int Peak = 47410;
|
|
int t = 0;
|
|
|
|
for (int i = 0; i < 400; ++i)
|
|
{
|
|
t = std::min(Peak, std::min(i * i - 16, t + MaxSlope));
|
|
KingDanger[i] = make_score(t * 268 / 7700, 0);
|
|
}
|
|
}
|