#include <algorithm>

#include <cassert>

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

#include <iomanip>

#include <sstream>

#include "bitboard.h"

#include "evaluate.h"

#include "material.h"

#include "pawns.h"

namespace {

const Bitboard Center = (FileDBB | FileEBB) & (Rank4BB | Rank5BB);

const Bitboard QueenSide = FileABB | FileBBB | FileCBB | FileDBB;

const Bitboard CenterFiles = FileCBB | FileDBB | FileEBB | FileFBB;

const Bitboard KingSide = FileEBB | FileFBB | FileGBB | FileHBB;

const Bitboard KingFlank[FILE_NB] = {

QueenSide, QueenSide, QueenSide, CenterFiles, CenterFiles, KingSide, KingSide, KingSide

};

namespace Trace {

enum Tracing {NO_TRACE, TRACE};

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

MATERIAL = 8, IMBALANCE, MOBILITY, THREAT, PASSED, SPACE, INITIATIVE, 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 == INITIATIVE || 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";

return os;

}

}

using namespace Trace;

// Evaluation class contains various information computed and collected

// by the evaluation functions.

template<Tracing T = NO_TRACE>

class Evaluation {

};

#define V(v) Value(v)

#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.

const Score MobilityBonus[][32] = {

{ 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) }

};

// 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(36,12) }, // Knight

{ S( 9, 2), S(15, 5) } // Bishop

};

// 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)

};

const Score ThreatByRook[PIECE_TYPE_NB] = {

S(0, 0), S(0, 25), S(40, 62), S(40, 59), S(0, 34), S(35, 48)

};

// 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) };

// 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) }

};

// 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)

};

// 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 LongRangedBishop = S( 22, 0);

const Score RookOnPawn = S( 8, 24);

const Score TrappedRook = S( 92, 0);

const Score WeakQueen = S( 50, 10);

const Score CloseEnemies = S( 7, 0);

const Score PawnlessFlank = S( 20, 80);

const Score ThreatBySafePawn = S(192,175);

const Score ThreatByRank = S( 16, 3);

const Score Hanging = S( 48, 27);

const Score WeakUnopposedPawn = S( 5, 25);

const Score ThreatByPawnPush = S( 38, 22);

const Score ThreatByAttackOnQueen = S( 38, 22);

const Score HinderPassedPawn = S( 7, 0);

const Score TrappedBishopA1H1 = S( 50, 50);

#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 };

// Penalties for enemy's safe checks

const int QueenSafeCheck = 780;

const int RookSafeCheck = 880;

const int BishopSafeCheck = 435;

const int KnightSafeCheck = 790;

// Threshold for lazy and space evaluation

const Value LazyThreshold = Value(1500);

const Value SpaceThreshold = Value(12222);

// 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() {

const Color Them = (Us == WHITE ? BLACK : WHITE);

const Direction Up = (Us == WHITE ? NORTH : SOUTH);

const Direction Down = (Us == WHITE ? SOUTH : NORTH);

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

// Find our pawns on the first two ranks, and those which are blocked

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

// 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));

// 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);

attackedBy2[Us] = b & attackedBy[Us][PAWN];

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

// Init our king safety tables only if we are going to use them

if (pos.non_pawn_material(Them) >= RookValueMg + KnightValueMg)

{

kingRing[Us] = b;

if (relative_rank(Us, pos.square<KING>(Us)) == RANK_1)

kingRing[Us] |= shift<Up>(b);

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

kingAdjacentZoneAttacksCount[Them] = kingAttackersWeight[Them] = 0;

}

else

kingRing[Us] = kingAttackersCount[Them] = 0;

}

// evaluate_pieces() assigns bonuses and penalties to the pieces of a given

// color and type.

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, bb;

Square s;

Score score = SCORE_ZERO;

attackedBy[Us][Pt] = 0;

if (Pt == QUEEN)

attackedBy[Us][QUEEN_DIAGONAL] = 0;

while ((s = *pl++) != SQ_NONE)

{

// 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))

: pos.attacks_from<Pt>(s);

if (pos.pinned_pieces(Us) & s)

b &= LineBB[pos.square<KING>(Us)][s];

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

attackedBy[Us][ALL_PIECES] |= attackedBy[Us][Pt] |= b;

if (Pt == QUEEN)

attackedBy[Us][QUEEN_DIAGONAL] |= b & PseudoAttacks[BISHOP][s];

if (b & kingRing[Them])

{

kingAttackersCount[Us]++;

kingAttackersWeight[Us] += KingAttackWeights[Pt];

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

}

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

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

// Bonus for this piece as a king protector

score += KingProtector[Pt - 2] * distance(s, pos.square<KING>(Us));

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

{

// Bonus for outpost squares

bb = OutpostRanks & ~pe->pawn_attacks_span(Them);

if (bb & s)

score += Outpost[Pt == BISHOP][bool(attackedBy[Us][PAWN] & s)] * 2;

else

{

bb &= b & ~pos.pieces(Us);

if (bb)

score += Outpost[Pt == BISHOP][bool(attackedBy[Us][PAWN] & bb)];

}

// Bonus when behind a pawn

if ( relative_rank(Us, s) < RANK_5

&& (pos.pieces(PAWN) & (s + pawn_push(Us))))

score += MinorBehindPawn;

if (Pt == BISHOP)

{

// Penalty for pawns on the same color square as the bishop

score -= BishopPawns * pe->pawns_on_same_color_squares(Us, s);

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

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

score += LongRangedBishop;

}

// 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)))

{

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)) ? TrappedBishopA1H1 * 4

: pos.piece_on(s + d + d) == make_piece(Us, PAWN) ? TrappedBishopA1H1 * 2

: TrappedBishopA1H1;

}

}

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]);

// Bonus when on an open or semi-open file

if (pe->semiopen_file(Us, file_of(s)))

score += RookOnFile[bool(pe->semiopen_file(Them, file_of(s)))];

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

else if (mob <= 3)

{

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 (T)

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

return score;

}

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

template<Tracing T> template<Color Us>

Score Evaluation<T>::evaluate_king() {

const Color Them = (Us == WHITE ? BLACK : WHITE);

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

: AllSquares ^ Rank1BB ^ Rank2BB ^ Rank3BB);

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

Bitboard weak, b, b1, b2, safe, unsafeChecks;

// 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)))

{

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

weak = attackedBy[Them][ALL_PIECES]

& ~attackedBy2[Us]

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

int kingDanger = unsafeChecks = 0;

// 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 queen safe checks

if ((b1 | b2) & attackedBy[Them][QUEEN] & safe & ~attackedBy[Us][QUEEN])

kingDanger += QueenSafeCheck;

b1 &= attackedBy[Them][ROOK];

b2 &= attackedBy[Them][BISHOP];

// Enemy rooks checks

if (b1 & safe)

kingDanger += RookSafeCheck;

else

unsafeChecks |= b1;

// Enemy bishops checks

if (b2 & safe)

kingDanger += BishopSafeCheck;

else

unsafeChecks |= b2;

// Enemy knights checks

b = pos.attacks_from<KNIGHT>(ksq) & attackedBy[Them][KNIGHT];

if (b & safe)

kingDanger += KnightSafeCheck;

else

unsafeChecks |= b;

// Unsafe or occupied checking squares will also be considered, as long as

// the square is in the attacker's mobility area.

unsafeChecks &= mobilityArea[Them];

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

+ 102 * kingAdjacentZoneAttacksCount[Them]

+ 191 * popcount(kingRing[Us] & weak)

+ 143 * popcount(pos.pinned_pieces(Us) | unsafeChecks)

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

- 9 * mg_value(score) / 8

+ 40;

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

if (kingDanger > 0)

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

}

// 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;

assert(((Us == WHITE ? b << 4 : b >> 4) & b) == 0);

assert(popcount(Us == WHITE ? b << 4 : b >> 4) == popcount(b));

// 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 -= CloseEnemies * popcount(b);

// Penalty when our king is on a pawnless flank

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

score -= PawnlessFlank;

if (T)

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

return score;

}

// evaluate_threats() assigns bonuses according to the types of the attacking

// and the attacked pieces.

template<Tracing T> template<Color Us>

Score Evaluation<T>::evaluate_threats() {

const Color Them = (Us == WHITE ? BLACK : WHITE);

const Direction Up = (Us == WHITE ? NORTH : SOUTH);

const Direction Left = (Us == WHITE ? NORTH_WEST : SOUTH_EAST);

const Direction Right = (Us == WHITE ? NORTH_EAST : SOUTH_WEST);

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

Bitboard b, weak, defended, stronglyProtected, safeThreats;

Score score = SCORE_ZERO;

// Non-pawn enemies attacked by a pawn

weak = (pos.pieces(Them) ^ pos.pieces(Them, PAWN)) & attackedBy[Us][PAWN];

if (weak)

{

b = pos.pieces(Us, PAWN) & ( ~attackedBy[Them][ALL_PIECES]

| attackedBy[Us][ALL_PIECES]);

safeThreats = (shift<Right>(b) | shift<Left>(b)) & weak;

score += ThreatBySafePawn * popcount(safeThreats);

}

// 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)

{

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);

}

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);

}

score += Hanging * popcount(weak & ~attackedBy[Them][ALL_PIECES]);

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

if (b)

score += ThreatByKing[more_than_one(b)];

}

// Bonus for opponent unopposed weak pawns

if (pos.pieces(Us, ROOK, QUEEN))

score += WeakUnopposedPawn * pe->weak_unopposed(Them);

// 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 not completely unsafe

b &= ~attackedBy[Them][PAWN]

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

// Add a bonus for each new pawn threats from those squares

b = (shift<Left>(b) | shift<Right>(b))

& pos.pieces(Them)

& ~attackedBy[Us][PAWN];

score += ThreatByPawnPush * popcount(b);

// Add a bonus for safe slider attack threats on opponent queen

safeThreats = ~pos.pieces(Us) & ~attackedBy2[Them] & attackedBy2[Us];

b = (attackedBy[Us][BISHOP] & attackedBy[Them][QUEEN_DIAGONAL])

| (attackedBy[Us][ROOK ] & attackedBy[Them][QUEEN] & ~attackedBy[Them][QUEEN_DIAGONAL]);

score += ThreatByAttackOnQueen * popcount(b & safeThreats);

if (T)

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

return score;

}

// evaluate_passed_pawns() evaluates the passed pawns and candidate passed

// pawns of the given color.

template<Tracing T> template<Color Us>

Score Evaluation<T>::evaluate_passed_pawns() {

const Color Them = (Us == WHITE ? BLACK : WHITE);

const Direction Up = (Us == WHITE ? NORTH : SOUTH);

Bitboard b, bb, squaresToQueen, defendedSquares, unsafeSquares;

Score score = SCORE_ZERO;

b = pe->passed_pawns(Us);

while (b)

{

Square s = pop_lsb(&b);

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

bb = forward_file_bb(Us, s) & (attackedBy[Them][ALL_PIECES] | pos.pieces(Them));

score -= HinderPassedPawn * popcount(bb);

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 + Up;

// 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 + Up) * 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_file_bb(Us, s);

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

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

defendedSquares &= attackedBy[Us][ALL_PIECES];

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

unsafeSquares &= 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

// 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;

score += make_score(mbonus, ebonus) + PassedFile[file_of(s)];

}

if (T)

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

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<Tracing T> template<Color Us>

Score Evaluation<T>::evaluate_space() {

const Color Them = (Us == WHITE ? BLACK : WHITE);

const Bitboard SpaceMask =

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

: CenterFiles & (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)

& ~attackedBy[Them][PAWN]

& (attackedBy[Us][ALL_PIECES] | ~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<ALL_PIECES>(Us) - 2 * pe->open_files();

return make_score(bonus * weight * weight / 16, 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.

template<Tracing T>

Score Evaluation<T>::evaluate_initiative(Value eg) {

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);

// Compute the initiative bonus for the attacking side

int initiative = 8 * (pe->pawn_asymmetry() + kingDistance - 17) + 12 * pos.count<PAWN>() + 16 * bothFlanks;

// 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));

if (T)

Trace::add(INITIATIVE, make_score(0, v));

return make_score(0, v);

}

// evaluate_scale_factor() computes the scale factor for the winning side

template<Tracing T>

ScaleFactor Evaluation<T>::evaluate_scale_factor(Value eg) {

Color strongSide = eg > VALUE_DRAW ? WHITE : BLACK;

ScaleFactor sf = 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 (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);

}

// 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));

}

return sf;

}

// 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() + Eval::Contempt;

// Probe the pawn hash table

pe = Pawns::probe(pos);

score += pe->pawns_score();

// 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

initialize<WHITE>();

initialize<BLACK>();

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 >();

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

score += evaluate_king<WHITE>()

- evaluate_king<BLACK>();

score += evaluate_threats<WHITE>()

- evaluate_threats<BLACK>();

score += evaluate_passed_pawns<WHITE>()

- evaluate_passed_pawns<BLACK>();

if (pos.non_pawn_material() >= SpaceThreshold)

score += evaluate_space<WHITE>()

- evaluate_space<BLACK>();

score += evaluate_initiative(eg_value(score));

// 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);

}

return pos.side_to_move() == WHITE ? v : -v; // Side to move point of view

}

} // namespace

Score Eval::Contempt = SCORE_ZERO;

Value Eval::evaluate(const Position& pos)

{

return Evaluation<>(pos).value() + Eval::Tempo;

}

std::string Eval::trace(const Position& pos) {

}