Stockfish, a UCI chess playing engine derived from Glaurung 2.1
Copyright (C) 2004-2008 Tord Romstad (Glaurung author)
Copyright (C) 2008-2015 Marco Costalba, Joona Kiiski, Tord Romstad
- Copyright (C) 2015-2016 Marco Costalba, Joona Kiiski, Gary Linscott, Tord Romstad
+ Copyright (C) 2015-2017 Marco Costalba, Joona Kiiski, Gary Linscott, Tord Romstad
Stockfish is free software: you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
// by the evaluation functions.
struct EvalInfo {
+ Material::Entry* me;
+ Pawns::Entry* pe;
+ Bitboard mobilityArea[COLOR_NB];
+
// attackedBy[color][piece type] is a bitboard representing all squares
// attacked by a given color and piece type (can be also ALL_PIECES).
Bitboard attackedBy[COLOR_NB][PIECE_TYPE_NB];
// a white knight on g5 and black's king is on g8, this white knight adds 2
// to kingAdjacentZoneAttacksCount[WHITE].
int kingAdjacentZoneAttacksCount[COLOR_NB];
-
- Bitboard pinnedPieces[COLOR_NB];
- Material::Entry* me;
- Pawns::Entry* pi;
};
#define V(v) Value(v)
#define S(mg, eg) make_score(mg, eg)
- // MobilityBonus[PieceType][attacked] contains bonuses for middle and end
- // game, indexed by piece type and number of attacked squares in the MobilityArea.
+ // MobilityBonus[PieceType][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(-56,-54), S( -9,-26), S( -2,-10), S( 6, 5), S( 15, 11), // Knights
S(118,174), S(119,177), S(123,191), S(128,199) }
};
- // Outpost[knight/bishop][supported by pawn] contains bonuses for knights and
- // bishops outposts, bigger if outpost piece is supported by a pawn.
+ // 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(43,11), S(65,20) }, // Knights
- { S(20, 3), S(29, 8) } // Bishops
- };
-
- // ReachableOutpost[knight/bishop][supported by pawn] contains bonuses for
- // knights and bishops which can reach an outpost square in one move, bigger
- // if outpost square is supported by a pawn.
- const Score ReachableOutpost[][2] = {
- { S(21, 5), S(35, 8) }, // Knights
- { S( 8, 0), S(14, 4) } // Bishops
+ { S(22, 6), S(33, 9) }, // Knight
+ { S( 9, 2), S(14, 4) } // Bishop
};
// RookOnFile[semiopen/open] contains bonuses for each rook when there is no
const int BishopCheck = 588;
const int KnightCheck = 924;
+ // Threshold for lazy evaluation
+ const Value LazyThreshold = Value(1500);
// eval_init() initializes king and attack bitboards for a given color
// adding pawn attacks. To be done at the beginning of the evaluation.
void eval_init(const Position& pos, EvalInfo& ei) {
const Color Them = (Us == WHITE ? BLACK : WHITE);
+ const Square Up = (Us == WHITE ? NORTH : SOUTH);
const Square Down = (Us == WHITE ? SOUTH : NORTH);
+ const Bitboard LowRanks = (Us == WHITE ? Rank2BB | Rank3BB: Rank7BB | Rank6BB);
- ei.pinnedPieces[Us] = pos.pinned_pieces(Us);
- Bitboard b = ei.attackedBy[Them][KING];
- ei.attackedBy[Them][ALL_PIECES] |= b;
- ei.attackedBy[Us][ALL_PIECES] |= ei.attackedBy[Us][PAWN] = ei.pi->pawn_attacks(Us);
- ei.attackedBy2[Us] = ei.attackedBy[Us][PAWN] & ei.attackedBy[Us][KING];
+ // Find our pawns on the first two ranks, and those which are blocked
+ Bitboard b = pos.pieces(Us, PAWN) & (shift<Down>(pos.pieces()) | LowRanks);
- // Init king safety tables only if we are going to use them
- if (pos.non_pawn_material(Us) >= QueenValueMg)
+ // Squares occupied by those pawns, by our king, or controlled by enemy pawns
+ // are excluded from the mobility area.
+ ei.mobilityArea[Us] = ~(b | pos.square<KING>(Us) | ei.pe->pawn_attacks(Them));
+
+ // Initialise the attack bitboards with the king and pawn information
+ b = ei.attackedBy[Us][KING] = pos.attacks_from<KING>(pos.square<KING>(Us));
+ ei.attackedBy[Us][PAWN] = ei.pe->pawn_attacks(Us);
+
+ ei.attackedBy2[Us] = b & ei.attackedBy[Us][PAWN];
+ ei.attackedBy[Us][ALL_PIECES] = b | ei.attackedBy[Us][PAWN];
+
+ // Init our king safety tables only if we are going to use them
+ if (pos.non_pawn_material(Them) >= QueenValueMg)
{
- ei.kingRing[Them] = b | shift<Down>(b);
- ei.kingAttackersCount[Us] = popcount(b & ei.attackedBy[Us][PAWN]);
- ei.kingAdjacentZoneAttacksCount[Us] = ei.kingAttackersWeight[Us] = 0;
+ ei.kingRing[Us] = b | shift<Up>(b);
+ ei.kingAttackersCount[Them] = popcount(b & ei.pe->pawn_attacks(Them));
+ ei.kingAdjacentZoneAttacksCount[Them] = ei.kingAttackersWeight[Them] = 0;
}
else
- ei.kingRing[Them] = ei.kingAttackersCount[Us] = 0;
+ ei.kingRing[Us] = ei.kingAttackersCount[Them] = 0;
}
// color and type.
template<bool DoTrace, Color Us = WHITE, PieceType Pt = KNIGHT>
- Score evaluate_pieces(const Position& pos, EvalInfo& ei, Score* mobility,
- const Bitboard* mobilityArea) {
+ Score evaluate_pieces(const Position& pos, EvalInfo& ei, Score* mobility) {
+
const PieceType NextPt = (Us == WHITE ? Pt : PieceType(Pt + 1));
const Color Them = (Us == WHITE ? BLACK : WHITE);
const Bitboard OutpostRanks = (Us == WHITE ? Rank4BB | Rank5BB | Rank6BB
: Pt == ROOK ? attacks_bb< ROOK>(s, pos.pieces() ^ pos.pieces(Us, ROOK, QUEEN))
: pos.attacks_from<Pt>(s);
- if (ei.pinnedPieces[Us] & s)
+ if (pos.pinned_pieces(Us) & s)
b &= LineBB[pos.square<KING>(Us)][s];
ei.attackedBy2[Us] |= ei.attackedBy[Us][ALL_PIECES] & b;
| ei.attackedBy[Them][BISHOP]
| ei.attackedBy[Them][ROOK]);
- int mob = popcount(b & mobilityArea[Us]);
+ int mob = popcount(b & ei.mobilityArea[Us]);
mobility[Us] += MobilityBonus[Pt][mob];
if (Pt == BISHOP || Pt == KNIGHT)
{
// Bonus for outpost squares
- bb = OutpostRanks & ~ei.pi->pawn_attacks_span(Them);
+ bb = OutpostRanks & ~ei.pe->pawn_attacks_span(Them);
if (bb & s)
- score += Outpost[Pt == BISHOP][!!(ei.attackedBy[Us][PAWN] & s)];
+ score += Outpost[Pt == BISHOP][!!(ei.attackedBy[Us][PAWN] & s)] * 2;
else
{
bb &= b & ~pos.pieces(Us);
if (bb)
- score += ReachableOutpost[Pt == BISHOP][!!(ei.attackedBy[Us][PAWN] & bb)];
+ score += Outpost[Pt == BISHOP][!!(ei.attackedBy[Us][PAWN] & bb)];
}
// Bonus when behind a pawn
// Penalty for pawns on the same color square as the bishop
if (Pt == BISHOP)
- score -= BishopPawns * ei.pi->pawns_on_same_color_squares(Us, s);
+ score -= BishopPawns * ei.pe->pawns_on_same_color_squares(Us, s);
// An important Chess960 pattern: A cornered bishop blocked by a friendly
// pawn diagonally in front of it is a very serious problem, especially
score += RookOnPawn * popcount(pos.pieces(Them, PAWN) & PseudoAttacks[ROOK][s]);
// Bonus when on an open or semi-open file
- if (ei.pi->semiopen_file(Us, file_of(s)))
- score += RookOnFile[!!ei.pi->semiopen_file(Them, file_of(s))];
+ if (ei.pe->semiopen_file(Us, file_of(s)))
+ score += RookOnFile[!!ei.pe->semiopen_file(Them, file_of(s))];
- // Penalize when trapped by the king, even more if the king cannot castle
+ // 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)))
- && !ei.pi->semiopen_side(Us, file_of(ksq), file_of(s) < file_of(ksq)))
+ && !ei.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));
}
}
Trace::add(Pt, Us, score);
// Recursively call evaluate_pieces() of next piece type until KING is excluded
- return score - evaluate_pieces<DoTrace, Them, NextPt>(pos, ei, mobility, mobilityArea);
+ return score - evaluate_pieces<DoTrace, Them, NextPt>(pos, ei, mobility);
}
template<>
- Score evaluate_pieces<false, WHITE, KING>(const Position&, EvalInfo&, Score*, const Bitboard*) { return SCORE_ZERO; }
+ Score evaluate_pieces<false, WHITE, KING>(const Position&, EvalInfo&, Score*) { return SCORE_ZERO; }
template<>
- Score evaluate_pieces< true, WHITE, KING>(const Position&, EvalInfo&, Score*, const Bitboard*) { return SCORE_ZERO; }
+ Score evaluate_pieces< true, WHITE, KING>(const Position&, EvalInfo&, Score*) { return SCORE_ZERO; }
// evaluate_king() assigns bonuses and penalties to a king of a given color
int kingDanger;
// King shelter and enemy pawns storm
- Score score = ei.pi->king_safety<Us>(pos, ksq);
+ Score score = ei.pe->king_safety<Us>(pos, ksq);
// Main king safety evaluation
if (ei.kingAttackersCount[Them])
{
- // Find the attacked squares which are defended only by the king...
+ // Find the attacked squares which are defended only by our king...
undefended = ei.attackedBy[Them][ALL_PIECES]
& ei.attackedBy[Us][KING]
& ~ei.attackedBy2[Us];
kingDanger = std::min(807, ei.kingAttackersCount[Them] * ei.kingAttackersWeight[Them])
+ 101 * ei.kingAdjacentZoneAttacksCount[Them]
+ 235 * popcount(undefended)
- + 134 * (popcount(b) + !!ei.pinnedPieces[Us])
+ + 134 * (popcount(b) + !!pos.pinned_pieces(Us))
- 717 * !pos.count<QUEEN>(Them)
- 7 * mg_value(score) / 5 - 5;
// Analyse the enemy's safe queen contact checks. Firstly, find the
- // undefended squares around the king reachable by the enemy queen...
+ // undefended squares around our king reachable by the enemy queen...
b = undefended & ei.attackedBy[Them][QUEEN] & ~pos.pieces(Them);
- // ...and keep squares supported by another enemy piece
+ // ...and keep squares supported by another enemy piece.
kingDanger += QueenContactCheck * popcount(b & ei.attackedBy2[Them]);
- // Analyse the safe enemy's checks which are possible on next move...
+ // 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<Up>(pos.pieces(PAWN))));
-
b1 = pos.attacks_from<ROOK >(ksq);
b2 = pos.attacks_from<BISHOP>(ksq);
if ((b1 | b2) & ei.attackedBy[Them][QUEEN] & safe)
kingDanger += QueenCheck;
- // For other pieces, also consider the square safe if attacked twice,
- // and only defended by a queen.
+ // For minors and rooks, also consider the square safe if attacked twice,
+ // and only defended by our queen.
safe |= ei.attackedBy2[Them]
& ~(ei.attackedBy2[Us] | pos.pieces(Them))
& ei.attackedBy[Us][QUEEN];
+ // Some other potential checks are also analysed, even from squares
+ // currently occupied by the opponent own pieces, as long as the square
+ // is not attacked by our pawns, and is not occupied by a blocked pawn.
+ other = ~( ei.attackedBy[Us][PAWN]
+ | (pos.pieces(Them, PAWN) & shift<Up>(pos.pieces(PAWN))));
+
// Enemy rooks safe and other checks
if (b1 & ei.attackedBy[Them][ROOK] & safe)
kingDanger += RookCheck;
else if (b & other)
score -= OtherCheck;
- // Compute the king danger score and subtract it from the evaluation
+ // Transform the kingDanger units into a Score, and substract it from the evaluation
if (kingDanger > 0)
score -= make_score(std::min(kingDanger * kingDanger / 4096, 2 * int(BishopValueMg)), 0);
}
}
- // evaluate_passed_pawns() evaluates the passed pawns of the given color
+ // evaluate_passer_pawns() evaluates the passed pawns and candidate passed
+ // pawns of the given color.
template<Color Us, bool DoTrace>
- Score evaluate_passed_pawns(const Position& pos, const EvalInfo& ei) {
+ Score evaluate_passer_pawns(const Position& pos, const EvalInfo& ei) {
const Color Them = (Us == WHITE ? BLACK : WHITE);
Bitboard b, bb, squaresToQueen, defendedSquares, unsafeSquares;
Score score = SCORE_ZERO;
- b = ei.pi->passed_pawns(Us);
+ b = ei.pe->passed_pawns(Us);
while (b)
{
Square s = pop_lsb(&b);
- assert(pos.pawn_passed(Us, s));
assert(!(pos.pieces(PAWN) & forward_bb(Us, s)));
bb = forward_bb(Us, s) & (ei.attackedBy[Them][ALL_PIECES] | pos.pieces(Them));
if (!pos.non_pawn_material(Them))
ebonus += 20;
+ // Scale down bonus for candidate passers which need more than one pawn
+ // push to become passed.
+ if (!pos.pawn_passed(Us, s + pawn_push(Us)))
+ mbonus /= 2, ebonus /= 2;
+
score += make_score(mbonus, ebonus) + PassedFile[file_of(s)];
}
// 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
+ // ...count safe + (behind & safe) with a single popcount.
int bonus = popcount((Us == WHITE ? safe << 32 : safe >> 32) | (behind & safe));
bonus = std::min(16, bonus);
- int weight = pos.count<ALL_PIECES>(Us) - 2 * ei.pi->open_files();
+ int weight = pos.count<ALL_PIECES>(Us) - 2 * ei.pe->open_files();
return make_score(bonus * weight * weight / 18, 0);
}
assert(!pos.checkers());
Score mobility[COLOR_NB] = { SCORE_ZERO, SCORE_ZERO };
+ Value v;
EvalInfo ei;
// Probe the material hash table
Score score = pos.psq_score() + ei.me->imbalance();
// Probe the pawn hash table
- ei.pi = Pawns::probe(pos);
- score += ei.pi->pawns_score();
+ ei.pe = Pawns::probe(pos);
+ score += ei.pe->pawns_score();
+
+ // Early exit if score is high
+ v = (mg_value(score) + eg_value(score)) / 2;
+ if (abs(v) > LazyThreshold)
+ return pos.side_to_move() == WHITE ? v : -v;
// Initialize attack and king safety bitboards
- ei.attackedBy[WHITE][ALL_PIECES] = ei.attackedBy[BLACK][ALL_PIECES] = 0;
- ei.attackedBy[WHITE][KING] = pos.attacks_from<KING>(pos.square<KING>(WHITE));
- ei.attackedBy[BLACK][KING] = pos.attacks_from<KING>(pos.square<KING>(BLACK));
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<SOUTH>(pos.pieces()) | Rank2BB | Rank3BB),
- pos.pieces(BLACK, PAWN) & (shift<NORTH>(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 += evaluate_pieces<DoTrace>(pos, ei, mobility);
score += mobility[WHITE] - mobility[BLACK];
// Evaluate kings after all other pieces because we need full attack
- 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);
+ score += evaluate_passer_pawns<WHITE, DoTrace>(pos, ei)
+ - evaluate_passer_pawns<BLACK, DoTrace>(pos, ei);
// Evaluate space for both sides, only during opening
if (pos.non_pawn_material(WHITE) + pos.non_pawn_material(BLACK) >= 12222)
- evaluate_space<BLACK>(pos, ei);
// Evaluate position potential for the winning side
- score += evaluate_initiative(pos, ei.pi->pawn_asymmetry(), eg_value(score));
+ score += evaluate_initiative(pos, ei.pe->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 = 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);
{
Trace::add(MATERIAL, pos.psq_score());
Trace::add(IMBALANCE, ei.me->imbalance());
- Trace::add(PAWN, ei.pi->pawns_score());
+ Trace::add(PAWN, ei.pe->pawns_score());
Trace::add(MOBILITY, mobility[WHITE], mobility[BLACK]);
if (pos.non_pawn_material(WHITE) + pos.non_pawn_material(BLACK) >= 12222)
Trace::add(SPACE, evaluate_space<WHITE>(pos, ei)
projects / stockfish / blobdiff