#include <algorithm>

#include <cassert>

#include <cstdlib>

#include <cstring> // For std::memset

#include <fstream>

#include <iomanip>

#include <sstream>

#include <iostream>

#include <streambuf>

#include <vector>

#include "bitboard.h"

#include "evaluate.h"

#include "material.h"

#include "misc.h"

#include "pawns.h"

#include "thread.h"

#include "uci.h"

#include "incbin/incbin.h"

#if !defined(_MSC_VER) && !defined(NNUE_EMBEDDING_OFF)

INCBIN(EmbeddedNNUE, EvalFileDefaultName);

#else

const unsigned char gEmbeddedNNUEData[1] = {0x0};

const unsigned char *const gEmbeddedNNUEEnd = &gEmbeddedNNUEData[1];

const unsigned int gEmbeddedNNUESize = 1;

#endif

using namespace std;

using namespace Eval::NNUE;

namespace Eval {

bool useNNUE;

string eval_file_loaded = "None";

/// init_NNUE() tries to load a nnue network at startup time, or when the engine

/// receives a UCI command "setoption name EvalFile value nn-[a-z0-9]{12}.nnue"

/// The name of the nnue network is always retrieved from the EvalFile option.

/// We search the given network in three locations: internally (the default

/// network may be embedded in the binary), in the active working directory and

/// in the engine directory. Distro packagers may define the DEFAULT_NNUE_DIRECTORY

/// variable to have the engine search in a special directory in their distro.

void init_NNUE() {

}

/// verify_NNUE() verifies that the last net used was loaded successfully

void verify_NNUE() {

}

}

namespace Trace {

enum Tracing { NO_TRACE, TRACE };

enum Term { // The first 8 entries are reserved for PieceType

MATERIAL = 8, IMBALANCE, MOBILITY, THREAT, PASSED, SPACE, WINNABLE, TOTAL, TERM_NB

};

Score scores[TERM_NB][COLOR_NB];

double to_cp(Value v) { return double(v) / PawnValueEg; }

void add(int idx, Color c, Score s) {

scores[idx][c] = s;

}

void add(int idx, Score w, Score b = SCORE_ZERO) {

scores[idx][WHITE] = w;

scores[idx][BLACK] = b;

}

std::ostream& operator<<(std::ostream& os, Score s) {

os << std::setw(5) << to_cp(mg_value(s)) << " "

<< std::setw(5) << to_cp(eg_value(s));

return os;

}

std::ostream& operator<<(std::ostream& os, Term t) {

if (t == MATERIAL || t == IMBALANCE || t == WINNABLE || t == TOTAL)

os << " ---- ----" << " | " << " ---- ----";

else

os << scores[t][WHITE] << " | " << scores[t][BLACK];

os << " | " << scores[t][WHITE] - scores[t][BLACK] << "\n";

return os;

}

}

using namespace Trace;

namespace {

// Threshold for lazy and space evaluation

constexpr Value LazyThreshold1 = Value(1400);

constexpr Value LazyThreshold2 = Value(1300);

constexpr Value SpaceThreshold = Value(12222);

constexpr Value NNUEThreshold1 = Value(550);

constexpr Value NNUEThreshold2 = Value(150);

// KingAttackWeights[PieceType] contains king attack weights by piece type

constexpr int KingAttackWeights[PIECE_TYPE_NB] = { 0, 0, 81, 52, 44, 10 };

// SafeCheck[PieceType][single/multiple] contains safe check bonus by piece type,

// higher if multiple safe checks are possible for that piece type.

constexpr int SafeCheck[][2] = {

{}, {}, {792, 1283}, {645, 967}, {1084, 1897}, {772, 1119}

};

#define S(mg, eg) make_score(mg, eg)

// MobilityBonus[PieceType-2][attacked] contains bonuses for middle and end game,

// indexed by piece type and number of attacked squares in the mobility area.

constexpr Score MobilityBonus[][32] = {

{ S(-62,-81), S(-53,-56), S(-12,-31), S( -4,-16), S( 3, 5), S( 13, 11), // Knight

S( 22, 17), S( 28, 20), S( 33, 25) },

{ S(-48,-59), S(-20,-23), S( 16, -3), S( 26, 13), S( 38, 24), S( 51, 42), // Bishop

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(-60,-78), S(-20,-17), S( 2, 23), S( 3, 39), S( 3, 70), S( 11, 99), // Rook

S( 22,103), S( 31,121), S( 40,134), S( 40,139), S( 41,158), S( 48,164),

S( 57,168), S( 57,169), S( 62,172) },

{ S(-30,-48), S(-12,-30), S( -8, -7), S( -9, 19), S( 20, 40), S( 23, 55), // Queen

S( 23, 59), S( 35, 75), S( 38, 78), S( 53, 96), S( 64, 96), S( 65,100),

S( 65,121), S( 66,127), S( 67,131), S( 67,133), S( 72,136), S( 72,141),

S( 77,147), S( 79,150), S( 93,151), S(108,168), S(108,168), S(108,171),

S(110,182), S(114,182), S(114,192), S(116,219) }

};

// KingProtector[knight/bishop] contains penalty for each distance unit to own king

constexpr Score KingProtector[] = { S(8, 9), S(6, 9) };

// Outpost[knight/bishop] contains bonuses for each knight or bishop occupying a

// pawn protected square on rank 4 to 6 which is also safe from a pawn attack.

constexpr Score Outpost[] = { S(56, 34), S(31, 23) };

// PassedRank[Rank] contains a bonus according to the rank of a passed pawn

constexpr Score PassedRank[RANK_NB] = {

S(0, 0), S(9, 28), S(15, 31), S(17, 39), S(64, 70), S(171, 177), S(277, 260)

};

// RookOnFile[semiopen/open] contains bonuses for each rook when there is

// no (friendly) pawn on the rook file.

constexpr Score RookOnFile[] = { S(19, 7), S(48, 27) };

// 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.

constexpr Score ThreatByMinor[PIECE_TYPE_NB] = {

S(0, 0), S(5, 32), S(55, 41), S(77, 56), S(89, 119), S(79, 162)

};

constexpr Score ThreatByRook[PIECE_TYPE_NB] = {

S(0, 0), S(3, 44), S(37, 68), S(42, 60), S(0, 39), S(58, 43)

};

// Assorted bonuses and penalties

constexpr Score BadOutpost = S( -7, 36);

constexpr Score BishopOnKingRing = S( 24, 0);

constexpr Score BishopPawns = S( 3, 7);

constexpr Score BishopXRayPawns = S( 4, 5);

constexpr Score CorneredBishop = S( 50, 50);

constexpr Score FlankAttacks = S( 8, 0);

constexpr Score Hanging = S( 69, 36);

constexpr Score KnightOnQueen = S( 16, 11);

constexpr Score LongDiagonalBishop = S( 45, 0);

constexpr Score MinorBehindPawn = S( 18, 3);

constexpr Score PassedFile = S( 11, 8);

constexpr Score PawnlessFlank = S( 17, 95);

constexpr Score ReachableOutpost = S( 31, 22);

constexpr Score RestrictedPiece = S( 7, 7);

constexpr Score RookOnKingRing = S( 16, 0);

constexpr Score RookOnQueenFile = S( 6, 11);

constexpr Score SliderOnQueen = S( 60, 18);

constexpr Score ThreatByKing = S( 24, 89);

constexpr Score ThreatByPawnPush = S( 48, 39);

constexpr Score ThreatBySafePawn = S(173, 94);

constexpr Score TrappedRook = S( 55, 13);

constexpr Score WeakQueenProtection = S( 14, 0);

constexpr Score WeakQueen = S( 56, 15);

#undef S

// Evaluation class computes and stores attacks tables and other working data

template<Tracing T>

class Evaluation {

};

// Evaluation::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() {

constexpr Color Them = ~Us;

constexpr Direction Up = pawn_push(Us);

constexpr Direction Down = -Up;

constexpr Bitboard LowRanks = (Us == WHITE ? Rank2BB | Rank3BB : Rank7BB | Rank6BB);

const Square ksq = pos.square<KING>(Us);

Bitboard dblAttackByPawn = pawn_double_attacks_bb<Us>(pos.pieces(Us, PAWN));

// Find our pawns that are blocked or on the first two ranks

Bitboard b = pos.pieces(Us, PAWN) & (shift<Down>(pos.pieces()) | LowRanks);

// Squares occupied by those pawns, by our king or queen, by blockers to attacks on our king

// or controlled by enemy pawns are excluded from the mobility area.

mobilityArea[Us] = ~(b | pos.pieces(Us, KING, QUEEN) | pos.blockers_for_king(Us) | pe->pawn_attacks(Them));

// Initialize attackedBy[] for king and pawns

attackedBy[Us][KING] = attacks_bb<KING>(ksq);

attackedBy[Us][PAWN] = pe->pawn_attacks(Us);

attackedBy[Us][ALL_PIECES] = attackedBy[Us][KING] | attackedBy[Us][PAWN];

attackedBy2[Us] = dblAttackByPawn | (attackedBy[Us][KING] & attackedBy[Us][PAWN]);

// Init our king safety tables

Square s = make_square(std::clamp(file_of(ksq), FILE_B, FILE_G),

std::clamp(rank_of(ksq), RANK_2, RANK_7));

kingRing[Us] = attacks_bb<KING>(s) | s;

kingAttackersCount[Them] = popcount(kingRing[Us] & pe->pawn_attacks(Them));

kingAttacksCount[Them] = kingAttackersWeight[Them] = 0;

// Remove from kingRing[] the squares defended by two pawns

kingRing[Us] &= ~dblAttackByPawn;

}

// Evaluation::pieces() scores pieces of a given color and type

template<Tracing T> template<Color Us, PieceType Pt>

Score Evaluation<T>::pieces() {

constexpr Color Them = ~Us;

constexpr Direction Down = -pawn_push(Us);

constexpr Bitboard OutpostRanks = (Us == WHITE ? Rank4BB | Rank5BB | Rank6BB

: Rank5BB | Rank4BB | Rank3BB);

const Square* pl = pos.squares<Pt>(Us);

Bitboard b, bb;

Score score = SCORE_ZERO;

attackedBy[Us][Pt] = 0;

for (Square s = *pl; s != SQ_NONE; s = *++pl)

{

// Find attacked squares, including x-ray attacks for bishops and rooks

b = Pt == BISHOP ? attacks_bb<BISHOP>(s, pos.pieces() ^ pos.pieces(QUEEN))

: Pt == ROOK ? attacks_bb< ROOK>(s, pos.pieces() ^ pos.pieces(QUEEN) ^ pos.pieces(Us, ROOK))

: attacks_bb<Pt>(s, pos.pieces());

if (pos.blockers_for_king(Us) & s)

b &= line_bb(pos.square<KING>(Us), s);

attackedBy2[Us] |= attackedBy[Us][ALL_PIECES] & b;

attackedBy[Us][Pt] |= b;

attackedBy[Us][ALL_PIECES] |= b;

if (b & kingRing[Them])

{

kingAttackersCount[Us]++;

kingAttackersWeight[Us] += KingAttackWeights[Pt];

kingAttacksCount[Us] += popcount(b & attackedBy[Them][KING]);

}

else if (Pt == ROOK && (file_bb(s) & kingRing[Them]))

score += RookOnKingRing;

else if (Pt == BISHOP && (attacks_bb<BISHOP>(s, pos.pieces(PAWN)) & kingRing[Them]))

score += BishopOnKingRing;

int mob = popcount(b & mobilityArea[Us]);

mobility[Us] += MobilityBonus[Pt - 2][mob];

if (Pt == BISHOP || Pt == KNIGHT)

{

// Bonus if the piece is on an outpost square or can reach one

// Reduced bonus for knights (BadOutpost) if few relevant targets

bb = OutpostRanks & (attackedBy[Us][PAWN] | shift<Down>(pos.pieces(PAWN)))

& ~pe->pawn_attacks_span(Them);

Bitboard targets = pos.pieces(Them) & ~pos.pieces(PAWN);

if ( Pt == KNIGHT

&& bb & s & ~CenterFiles // on a side outpost

&& !(b & targets) // no relevant attacks

&& (!more_than_one(targets & (s & QueenSide ? QueenSide : KingSide))))

score += BadOutpost;

else if (bb & s)

score += Outpost[Pt == BISHOP];

else if (Pt == KNIGHT && bb & b & ~pos.pieces(Us))

score += ReachableOutpost;

// Bonus for a knight or bishop shielded by pawn

if (shift<Down>(pos.pieces(PAWN)) & s)

score += MinorBehindPawn;

// Penalty if the piece is far from the king

score -= KingProtector[Pt == BISHOP] * distance(pos.square<KING>(Us), s);

if (Pt == BISHOP)

{

// Penalty according to the number of our pawns on the same color square as the

// bishop, bigger when the center files are blocked with pawns and smaller

// when the bishop is outside the pawn chain.

Bitboard blocked = pos.pieces(Us, PAWN) & shift<Down>(pos.pieces());

score -= BishopPawns * pos.pawns_on_same_color_squares(Us, s)

* (!(attackedBy[Us][PAWN] & s) + popcount(blocked & CenterFiles));

// Penalty for all enemy pawns x-rayed

score -= BishopXRayPawns * popcount(attacks_bb<BISHOP>(s) & pos.pieces(Them, PAWN));

// Bonus for bishop on a long diagonal which can "see" both center squares

if (more_than_one(attacks_bb<BISHOP>(s, pos.pieces(PAWN)) & Center))

score += LongDiagonalBishop;

// 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 ( pos.is_chess960()

&& (s == relative_square(Us, SQ_A1) || s == relative_square(Us, SQ_H1)))

{

Direction 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)) ? CorneredBishop * 4

: pos.piece_on(s + d + d) == make_piece(Us, PAWN) ? CorneredBishop * 2

: CorneredBishop;

}

}

}

if (Pt == ROOK)

{

// Bonus for rook on the same file as a queen

if (file_bb(s) & pos.pieces(QUEEN))

score += RookOnQueenFile;

// Bonus for rook on an open or semi-open file

if (pos.is_on_semiopen_file(Us, s))

score += RookOnFile[pos.is_on_semiopen_file(Them, s)];

// Penalty when trapped by the king, even more if the king cannot castle

else if (mob <= 3)

{

File kf = file_of(pos.square<KING>(Us));

if ((kf < FILE_E) == (file_of(s) < kf))

score -= TrappedRook * (1 + !pos.castling_rights(Us));

}

}

if (Pt == QUEEN)

{

// Penalty if any relative pin or discovered attack against the queen

Bitboard queenPinners;

if (pos.slider_blockers(pos.pieces(Them, ROOK, BISHOP), s, queenPinners))

score -= WeakQueen;

}

}

if (T)

Trace::add(Pt, Us, score);

return score;

}

// Evaluation::king() assigns bonuses and penalties to a king of a given color

template<Tracing T> template<Color Us>

Score Evaluation<T>::king() const {

constexpr Color Them = ~Us;

constexpr Bitboard Camp = (Us == WHITE ? AllSquares ^ Rank6BB ^ Rank7BB ^ Rank8BB

: AllSquares ^ Rank1BB ^ Rank2BB ^ Rank3BB);

Bitboard weak, b1, b2, b3, safe, unsafeChecks = 0;

Bitboard rookChecks, queenChecks, bishopChecks, knightChecks;

int kingDanger = 0;

const Square ksq = pos.square<KING>(Us);

// Init the score with king shelter and enemy pawns storm

Score score = pe->king_safety<Us>(pos);

// Attacked squares defended at most once by our queen or king

weak = attackedBy[Them][ALL_PIECES]

& ~attackedBy2[Us]

& (~attackedBy[Us][ALL_PIECES] | attackedBy[Us][KING] | attackedBy[Us][QUEEN]);

// Analyse the safe enemy's checks which are possible on next move

safe = ~pos.pieces(Them);

safe &= ~attackedBy[Us][ALL_PIECES] | (weak & attackedBy2[Them]);

b1 = attacks_bb<ROOK >(ksq, pos.pieces() ^ pos.pieces(Us, QUEEN));

b2 = attacks_bb<BISHOP>(ksq, pos.pieces() ^ pos.pieces(Us, QUEEN));

// Enemy rooks checks

rookChecks = b1 & attackedBy[Them][ROOK] & safe;

if (rookChecks)

kingDanger += SafeCheck[ROOK][more_than_one(rookChecks)];

else

unsafeChecks |= b1 & attackedBy[Them][ROOK];

// Enemy queen safe checks: count them only if the checks are from squares from

// which opponent cannot give a rook check, because rook checks are more valuable.

queenChecks = (b1 | b2) & attackedBy[Them][QUEEN] & safe

& ~(attackedBy[Us][QUEEN] | rookChecks);

if (queenChecks)

kingDanger += SafeCheck[QUEEN][more_than_one(queenChecks)];

// Enemy bishops checks: count them only if they are from squares from which

// opponent cannot give a queen check, because queen checks are more valuable.

bishopChecks = b2 & attackedBy[Them][BISHOP] & safe

& ~queenChecks;

if (bishopChecks)

kingDanger += SafeCheck[BISHOP][more_than_one(bishopChecks)];

else

unsafeChecks |= b2 & attackedBy[Them][BISHOP];

// Enemy knights checks

knightChecks = attacks_bb<KNIGHT>(ksq) & attackedBy[Them][KNIGHT];

if (knightChecks & safe)

kingDanger += SafeCheck[KNIGHT][more_than_one(knightChecks & safe)];

else

unsafeChecks |= knightChecks;

// Find the squares that opponent attacks in our king flank, the squares

// which they attack twice in that flank, and the squares that we defend.

b1 = attackedBy[Them][ALL_PIECES] & KingFlank[file_of(ksq)] & Camp;

b2 = b1 & attackedBy2[Them];

b3 = attackedBy[Us][ALL_PIECES] & KingFlank[file_of(ksq)] & Camp;

int kingFlankAttack = popcount(b1) + popcount(b2);

int kingFlankDefense = popcount(b3);

kingDanger += kingAttackersCount[Them] * kingAttackersWeight[Them]

+ 185 * popcount(kingRing[Us] & weak)

+ 148 * popcount(unsafeChecks)

+ 98 * popcount(pos.blockers_for_king(Us))

+ 69 * kingAttacksCount[Them]

+ 3 * kingFlankAttack * kingFlankAttack / 8

+ mg_value(mobility[Them] - mobility[Us])

- 873 * !pos.count<QUEEN>(Them)

- 100 * bool(attackedBy[Us][KNIGHT] & attackedBy[Us][KING])

- 6 * mg_value(score) / 8

- 4 * kingFlankDefense

+ 37;

// Transform the kingDanger units into a Score, and subtract it from the evaluation

if (kingDanger > 100)

score -= make_score(kingDanger * kingDanger / 4096, kingDanger / 16);

// Penalty when our king is on a pawnless flank

if (!(pos.pieces(PAWN) & KingFlank[file_of(ksq)]))

score -= PawnlessFlank;

// Penalty if king flank is under attack, potentially moving toward the king

score -= FlankAttacks * kingFlankAttack;

if (T)

Trace::add(KING, Us, score);

return score;

}

// Evaluation::threats() assigns bonuses according to the types of the

// attacking and the attacked pieces.

template<Tracing T> template<Color Us>

Score Evaluation<T>::threats() const {

constexpr Color Them = ~Us;

constexpr Direction Up = pawn_push(Us);

constexpr Bitboard TRank3BB = (Us == WHITE ? Rank3BB : Rank6BB);

Bitboard b, weak, defended, nonPawnEnemies, stronglyProtected, safe;

Score score = SCORE_ZERO;

// Non-pawn enemies

nonPawnEnemies = pos.pieces(Them) & ~pos.pieces(PAWN);

// Squares strongly protected by the enemy, either because they defend the

// square with a pawn, or because they defend the square twice and we don't.

stronglyProtected = attackedBy[Them][PAWN]

| (attackedBy2[Them] & ~attackedBy2[Us]);

// Non-pawn enemies, strongly protected

defended = nonPawnEnemies & stronglyProtected;

// Enemies not strongly protected and under our attack

weak = pos.pieces(Them) & ~stronglyProtected & attackedBy[Us][ALL_PIECES];

// Bonus according to the kind of attacking pieces

if (defended | weak)

{

b = (defended | weak) & (attackedBy[Us][KNIGHT] | attackedBy[Us][BISHOP]);

while (b)

score += ThreatByMinor[type_of(pos.piece_on(pop_lsb(&b)))];

b = weak & attackedBy[Us][ROOK];

while (b)

score += ThreatByRook[type_of(pos.piece_on(pop_lsb(&b)))];

if (weak & attackedBy[Us][KING])

score += ThreatByKing;

b = ~attackedBy[Them][ALL_PIECES]

| (nonPawnEnemies & attackedBy2[Us]);

score += Hanging * popcount(weak & b);

// Additional bonus if weak piece is only protected by a queen

score += WeakQueenProtection * popcount(weak & attackedBy[Them][QUEEN]);

}

// Bonus for restricting their piece moves

b = attackedBy[Them][ALL_PIECES]

& ~stronglyProtected

& attackedBy[Us][ALL_PIECES];

score += RestrictedPiece * popcount(b);

// Protected or unattacked squares

safe = ~attackedBy[Them][ALL_PIECES] | attackedBy[Us][ALL_PIECES];

// Bonus for attacking enemy pieces with our relatively safe pawns

b = pos.pieces(Us, PAWN) & safe;

b = pawn_attacks_bb<Us>(b) & nonPawnEnemies;

score += ThreatBySafePawn * popcount(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();

// Keep only the squares which are relatively safe

b &= ~attackedBy[Them][PAWN] & safe;

// Bonus for safe pawn threats on the next move

b = pawn_attacks_bb<Us>(b) & nonPawnEnemies;

score += ThreatByPawnPush * popcount(b);

// Bonus for threats on the next moves against enemy queen

if (pos.count<QUEEN>(Them) == 1)

{

bool queenImbalance = pos.count<QUEEN>() == 1;

Square s = pos.square<QUEEN>(Them);

safe = mobilityArea[Us]

& ~pos.pieces(Us, PAWN)

& ~stronglyProtected;

b = attackedBy[Us][KNIGHT] & attacks_bb<KNIGHT>(s);

score += KnightOnQueen * popcount(b & safe) * (1 + queenImbalance);

b = (attackedBy[Us][BISHOP] & attacks_bb<BISHOP>(s, pos.pieces()))

| (attackedBy[Us][ROOK ] & attacks_bb<ROOK >(s, pos.pieces()));

score += SliderOnQueen * popcount(b & safe & attackedBy2[Us]) * (1 + queenImbalance);

}

if (T)

Trace::add(THREAT, Us, score);

return score;

}

// Evaluation::passed() evaluates the passed pawns and candidate passed

// pawns of the given color.

template<Tracing T> template<Color Us>

Score Evaluation<T>::passed() const {

constexpr Color Them = ~Us;

constexpr Direction Up = pawn_push(Us);

constexpr Direction Down = -Up;

auto king_proximity = [&](Color c, Square s) {

return std::min(distance(pos.square<KING>(c), s), 5);

};

Bitboard b, bb, squaresToQueen, unsafeSquares, blockedPassers, helpers;

Score score = SCORE_ZERO;

b = pe->passed_pawns(Us);

blockedPassers = b & shift<Down>(pos.pieces(Them, PAWN));

if (blockedPassers)

{

helpers = shift<Up>(pos.pieces(Us, PAWN))

& ~pos.pieces(Them)

& (~attackedBy2[Them] | attackedBy[Us][ALL_PIECES]);

// Remove blocked candidate passers that don't have help to pass

b &= ~blockedPassers

| shift<WEST>(helpers)

| shift<EAST>(helpers);

}

while (b)

{

Square s = pop_lsb(&b);

assert(!(pos.pieces(Them, PAWN) & forward_file_bb(Us, s + Up)));

int r = relative_rank(Us, s);

Score bonus = PassedRank[r];

if (r > RANK_3)

{

int w = 5 * r - 13;

Square blockSq = s + Up;

// Adjust bonus based on the king's proximity

bonus += make_score(0, ( king_proximity(Them, blockSq) * 19 / 4

- king_proximity(Us, blockSq) * 2) * w);

// If blockSq is not the queening square then consider also a second push

if (r != RANK_7)

bonus -= make_score(0, king_proximity(Us, blockSq + Up) * w);

// If the pawn is free to advance, then increase the bonus

if (pos.empty(blockSq))

{

squaresToQueen = forward_file_bb(Us, s);

unsafeSquares = passed_pawn_span(Us, s);

bb = forward_file_bb(Them, s) & pos.pieces(ROOK, QUEEN);

if (!(pos.pieces(Them) & bb))

unsafeSquares &= attackedBy[Them][ALL_PIECES];

// If there are no enemy attacks on passed pawn span, assign a big bonus.

// Otherwise assign a smaller bonus if the path to queen is not attacked

// and even smaller bonus if it is attacked but block square is not.

int k = !unsafeSquares ? 35 :

!(unsafeSquares & squaresToQueen) ? 20 :

!(unsafeSquares & blockSq) ? 9 :

0 ;

// Assign a larger bonus if the block square is defended

if ((pos.pieces(Us) & bb) || (attackedBy[Us][ALL_PIECES] & blockSq))

k += 5;

bonus += make_score(k * w, k * w);

}

} // r > RANK_3

score += bonus - PassedFile * edge_distance(file_of(s));

}

if (T)

Trace::add(PASSED, Us, score);

return score;

}

// Evaluation::space() computes a space evaluation for a given side, aiming to improve game

// play in the opening. It is based on the number of safe squares on the four central files

// on ranks 2 to 4. Completely safe squares behind a friendly pawn are counted twice.

// Finally, the space bonus is multiplied by a weight which decreases according to occupancy.

template<Tracing T> template<Color Us>

Score Evaluation<T>::space() const {

// Early exit if, for example, both queens or 6 minor pieces have been exchanged

if (pos.non_pawn_material() < SpaceThreshold)

return SCORE_ZERO;

constexpr Color Them = ~Us;

constexpr Direction Down = -pawn_push(Us);

constexpr Bitboard SpaceMask =

Us == WHITE ? CenterFiles & (Rank2BB | Rank3BB | Rank4BB)

: CenterFiles & (Rank7BB | Rank6BB | Rank5BB);

// Find the available squares for our pieces inside the area defined by SpaceMask

Bitboard safe = SpaceMask

& ~pos.pieces(Us, PAWN)

& ~attackedBy[Them][PAWN];

// Find all squares which are at most three squares behind some friendly pawn

Bitboard behind = pos.pieces(Us, PAWN);

behind |= shift<Down>(behind);

behind |= shift<Down+Down>(behind);

int bonus = popcount(safe) + popcount(behind & safe & ~attackedBy[Them][ALL_PIECES]);

int weight = pos.count<ALL_PIECES>(Us) - 3 + std::min(pe->blocked_count(), 9);

Score score = make_score(bonus * weight * weight / 16, 0);

if (T)

Trace::add(SPACE, Us, score);

return score;

}

// Evaluation::winnable() adjusts the midgame and endgame score components, based on

// the known attacking/defending status of the players. The final value is derived

// by interpolation from the midgame and endgame values.

template<Tracing T>

Value Evaluation<T>::winnable(Score score) const {

int outflanking = distance<File>(pos.square<KING>(WHITE), pos.square<KING>(BLACK))

- distance<Rank>(pos.square<KING>(WHITE), pos.square<KING>(BLACK));

bool pawnsOnBothFlanks = (pos.pieces(PAWN) & QueenSide)

&& (pos.pieces(PAWN) & KingSide);

bool almostUnwinnable = outflanking < 0

&& !pawnsOnBothFlanks;

bool infiltration = rank_of(pos.square<KING>(WHITE)) > RANK_4

|| rank_of(pos.square<KING>(BLACK)) < RANK_5;

// Compute the initiative bonus for the attacking side

int complexity = 9 * pe->passed_count()

+ 12 * pos.count<PAWN>()

+ 9 * outflanking

+ 21 * pawnsOnBothFlanks

+ 24 * infiltration

+ 51 * !pos.non_pawn_material()

- 43 * almostUnwinnable

-110 ;

Value mg = mg_value(score);

Value eg = eg_value(score);

// Now apply the bonus: note that we find the attacking side by extracting the

// sign of the midgame or endgame values, and that we carefully cap the bonus

// so that the midgame and endgame scores do not change sign after the bonus.

int u = ((mg > 0) - (mg < 0)) * std::clamp(complexity + 50, -abs(mg), 0);

int v = ((eg > 0) - (eg < 0)) * std::max(complexity, -abs(eg));

mg += u;

eg += v;

// Compute the scale factor for the winning side

Color strongSide = eg > VALUE_DRAW ? WHITE : BLACK;

int sf = me->scale_factor(pos, strongSide);

// If scale factor is not already specific, scale down via general heuristics

if (sf == SCALE_FACTOR_NORMAL)

{

if (pos.opposite_bishops())

{

if ( pos.non_pawn_material(WHITE) == BishopValueMg

&& pos.non_pawn_material(BLACK) == BishopValueMg)

sf = 18 + 4 * popcount(pe->passed_pawns(strongSide));

else

sf = 22 + 3 * pos.count<ALL_PIECES>(strongSide);

}

else if ( pos.non_pawn_material(WHITE) == RookValueMg

&& pos.non_pawn_material(BLACK) == RookValueMg

&& pos.count<PAWN>(strongSide) - pos.count<PAWN>(~strongSide) <= 1

&& bool(KingSide & pos.pieces(strongSide, PAWN)) != bool(QueenSide & pos.pieces(strongSide, PAWN))

&& (attacks_bb<KING>(pos.square<KING>(~strongSide)) & pos.pieces(~strongSide, PAWN)))

sf = 36;

else if (pos.count<QUEEN>() == 1)

sf = 37 + 3 * (pos.count<QUEEN>(WHITE) == 1 ? pos.count<BISHOP>(BLACK) + pos.count<KNIGHT>(BLACK)

: pos.count<BISHOP>(WHITE) + pos.count<KNIGHT>(WHITE));

else

sf = std::min(sf, 36 + 7 * pos.count<PAWN>(strongSide));

}

// Interpolate between the middlegame and (scaled by 'sf') endgame score

v = mg * int(me->game_phase())

+ eg * int(PHASE_MIDGAME - me->game_phase()) * ScaleFactor(sf) / SCALE_FACTOR_NORMAL;

v /= PHASE_MIDGAME;

if (T)

{

Trace::add(WINNABLE, make_score(u, eg * ScaleFactor(sf) / SCALE_FACTOR_NORMAL - eg_value(score)));

Trace::add(TOTAL, make_score(mg, eg * ScaleFactor(sf) / SCALE_FACTOR_NORMAL));

}

return Value(v);

}

// Evaluation::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.

template<Tracing T>

Value Evaluation<T>::value() {

assert(!pos.checkers());

// Probe the material hash table

me = Material::probe(pos);

// 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() + pos.this_thread()->contempt;

// Probe the pawn hash table

pe = Pawns::probe(pos);

score += pe->pawn_score(WHITE) - pe->pawn_score(BLACK);

// Early exit if score is high

auto lazy_skip = [&](Value lazyThreshold) {

return abs(mg_value(score) + eg_value(score)) / 2 > lazyThreshold + pos.non_pawn_material() / 64;

};

if (lazy_skip(LazyThreshold1))

goto make_v;

// Main evaluation begins here

initialize<WHITE>();

initialize<BLACK>();

// Pieces evaluated first (also populates attackedBy, attackedBy2).

// Note that the order of evaluation of the terms is left unspecified.

score += pieces<WHITE, KNIGHT>() - pieces<BLACK, KNIGHT>()

+ pieces<WHITE, BISHOP>() - pieces<BLACK, BISHOP>()

+ pieces<WHITE, ROOK >() - pieces<BLACK, ROOK >()

+ pieces<WHITE, QUEEN >() - pieces<BLACK, QUEEN >();

score += mobility[WHITE] - mobility[BLACK];

// More complex interactions that require fully populated attack bitboards

score += king< WHITE>() - king< BLACK>()

+ passed< WHITE>() - passed< BLACK>();

if (lazy_skip(LazyThreshold2))

goto make_v;

score += threats<WHITE>() - threats<BLACK>()

+ space< WHITE>() - space< BLACK>();

make_v:

// Derive single value from mg and eg parts of score

Value v = winnable(score);

// 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->pawn_score(WHITE), pe->pawn_score(BLACK));

Trace::add(MOBILITY, mobility[WHITE], mobility[BLACK]);

}