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
Stockfish is free software: you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
namespace Trace {
- enum Term { // First 8 entries are for PieceType
+ enum Term { // The first 8 entries are for PieceType
MATERIAL = 8, IMBALANCE, MOBILITY, THREAT, PASSED, SPACE, TOTAL, TERM_NB
};
// which attack a square in the kingRing of the enemy king.
int kingAttackersCount[COLOR_NB];
- // kingAttackersWeight[color] is the sum of the "weight" of the pieces of the
+ // kingAttackersWeight[color] is the sum of the "weights" of the pieces of the
// given color which attack a square in the kingRing of the enemy king. The
// weights of the individual piece types are given by the elements in the
// KingAttackWeights array.
enum { PawnStructure, PassedPawns, Space, KingSafety };
const struct Weight { int mg, eg; } Weights[] = {
- {214, 203}, {193, 262}, {47, 0}, {330, 0}
- };
+ {214, 203}, {193, 262}, {47, 0}, {330, 0} };
Score operator*(Score s, const Weight& w) {
return make_score(mg_value(s) * w.mg / 256, eg_value(s) * w.eg / 256);
{ S( 8, 2), S(13, 4) } // Bishops
};
- // Threat[minor/rook][attacked PieceType] contains
+ // RookOnFile[semiopen/open] contains bonuses for each rook when there is no
+ // friendly pawn on the rook file.
+ const Score RookOnFile[2] = { S(19, 10), S(43, 21) };
+
+ // ThreatBySafePawn[PieceType] contains bonuses according to which piece
+ // type is attacked by a pawn which is protected or is not attacked.
+ const Score ThreatBySafePawn[PIECE_TYPE_NB] = {
+ S(0, 0), S(0, 0), S(176, 139), S(131, 127), S(217, 218), S(203, 215) };
+
+ // Threat[by minor/by rook][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 Threat[2][PIECE_TYPE_NB] = {
- { S(0, 0), S(0, 33), S(45, 43), S(46, 47), S(72, 107), S(48,118) }, // Minor attacks
- { S(0, 0), S(0, 25), S(40, 62), S(40, 59), S( 0, 34), S(35, 48) } // Rook attacks
+ // Attacks on lesser pieces which are pawn-defended are not considered.
+ const Score Threat[][PIECE_TYPE_NB] = {
+ { S(0, 0), S(0, 33), S(45, 43), S(46, 47), S(72,107), S(48,118) }, // by Minor
+ { S(0, 0), S(0, 25), S(40, 62), S(40, 59), S( 0, 34), S(35, 48) } // by Rook
};
- // ThreatenedByPawn[PieceType] contains a penalty according to which piece
- // type is attacked by a pawn.
- const Score ThreatenedByPawn[PIECE_TYPE_NB] = {
- S(0, 0), S(0, 0), S(176, 139), S(131, 127), S(217, 218), S(203, 215)
- };
+ // ThreatByKing[on one/on many] contains bonuses for King attacks on
+ // pawns or pieces which are not pawn-defended.
+ const Score ThreatByKing[2] = { 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.
{ V(7), V(14), V(37), V(63), V(134), V(189) }
};
- // PassedFile[File] contains a bonus according to the file of a passed pawn.
- const Score PassedFile[] = {
- S( 12, 10), S( 3, 10), S( 1, -8), S(-27, -12),
- S(-27, -12), S( 1, -8), S( 3, 10), S( 12, 10)
+ // PassedFile[File] contains a bonus according to the file of a passed pawn
+ const Score PassedFile[FILE_NB] = {
+ S( 12, 10), S( 3, 10), S( 1, -8), S(-27,-12),
+ S(-27,-12), S( 1, -8), S( 3, 10), S( 12, 10)
};
- const Score ThreatenedByHangingPawn = S(70, 63);
-
// Assorted bonuses and penalties used by evaluation
- const Score KingOnOne = S( 3, 62);
- const Score KingOnMany = S( 9,138);
- const Score RookOnPawn = S( 7, 27);
- const Score RookOnOpenFile = S(43, 21);
- const Score RookOnSemiOpenFile = S(19, 10);
- const Score BishopPawns = S( 8, 12);
- const Score MinorBehindPawn = S(16, 0);
- const Score TrappedRook = S(92, 0);
- const Score Unstoppable = S( 0, 20);
- const Score Hanging = S(48, 28);
- const Score PawnAttackThreat = S(31, 19);
- const Score Checked = S(20, 20);
+ const Score MinorBehindPawn = S(16, 0);
+ const Score BishopPawns = S( 8, 12);
+ const Score RookOnPawn = S( 7, 27);
+ const Score TrappedRook = S(92, 0);
+ const Score Checked = S(20, 20);
+ const Score ThreatByHangingPawn = S(70, 63);
+ const Score Hanging = S(48, 28);
+ const Score ThreatByPawnPush = S(31, 19);
+ const Score Unstoppable = S( 0, 20);
// Penalty for a bishop on a1/h1 (a8/h8 for black) which is trapped by
// a friendly pawn on b2/g2 (b7/g7 for black). This can obviously only
const int KnightCheck = 14;
- // eval_init() initializes king and attack bitboards for given color
+ // eval_init() initializes king and attack bitboards for a given color
// adding pawn attacks. To be done at the beginning of the evaluation.
template<Color Us>
&& (pos.pieces(PAWN) & (s + pawn_push(Us))))
score += MinorBehindPawn;
- // Penalty for pawns on same color square of bishop
+ // 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);
{
Bitboard alignedPawns = pos.pieces(Them, PAWN) & PseudoAttacks[ROOK][s];
if (alignedPawns)
- score += popcount<Max15>(alignedPawns) * RookOnPawn;
+ score += RookOnPawn * popcount<Max15>(alignedPawns);
}
// Bonus when on an open or semi-open file
if (ei.pi->semiopen_file(Us, file_of(s)))
- score += ei.pi->semiopen_file(Them, file_of(s)) ? RookOnOpenFile : RookOnSemiOpenFile;
+ score += RookOnFile[!!ei.pi->semiopen_file(Them, file_of(s))];
- // Penalize when trapped by the king, even more if king cannot castle
- if (mob <= 3 && !ei.pi->semiopen_file(Us, file_of(s)))
+ // Penalize when trapped by the king, even more if the king cannot castle
+ else if (mob <= 3)
{
Square ksq = pos.square<KING>(Us);
if (DoTrace)
Trace::add(Pt, Us, score);
- // Recursively call evaluate_pieces() of next piece type until KING excluded
+ // Recursively call evaluate_pieces() of next piece type until KING is excluded
return score - evaluate_pieces<DoTrace, Them, NextPt>(pos, ei, mobility, mobilityArea);
}
}
// Finally, extract the king danger score from the KingDanger[]
- // array and subtract the score from evaluation.
+ // array and subtract the score from the evaluation.
score -= KingDanger[std::max(std::min(attackUnits, 399), 0)];
}
}
- // evaluate_threats() assigns bonuses according to the type of attacking piece
- // and the type of attacked one.
+ // 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) {
safeThreats = (shift_bb<Right>(b) | shift_bb<Left>(b)) & weak;
if (weak ^ safeThreats)
- score += ThreatenedByHangingPawn;
+ score += ThreatByHangingPawn;
while (safeThreats)
- score += ThreatenedByPawn[type_of(pos.piece_on(pop_lsb(&safeThreats)))];
+ score += ThreatBySafePawn[type_of(pos.piece_on(pop_lsb(&safeThreats)))];
}
// Non-pawn enemies defended by a pawn
b = weak & ei.attackedBy[Us][KING];
if (b)
- score += more_than_one(b) ? KingOnMany : KingOnOne;
+ score += ThreatByKing[more_than_one(b)];
}
// Bonus if some pawns can safely push and attack an enemy piece
& ~ei.attackedBy[Us][PAWN];
if (b)
- score += popcount<Max15>(b) * PawnAttackThreat;
+ score += ThreatByPawnPush * popcount<Max15>(b);
if (DoTrace)
Trace::add(THREAT, Us, score);
// assign a smaller bonus if the block square isn't attacked.
int k = !unsafeSquares ? 18 : !(unsafeSquares & blockSq) ? 8 : 0;
- // If the path to queen is fully defended, assign a big bonus.
+ // 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;
// evaluate_initiative() computes the initiative correction value for the
- // position, i.e. second order bonus/malus based on the known attacking/defending
+ // 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) {
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 is even more a draw.
+ // 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);
{
Bitboard b;
if ((b = ei.pi->passed_pawns(WHITE)) != 0)
- score += int(relative_rank(WHITE, frontmost_sq(WHITE, b))) * Unstoppable;
+ score += Unstoppable * int(relative_rank(WHITE, frontmost_sq(WHITE, b)));
if ((b = ei.pi->passed_pawns(BLACK)) != 0)
- score -= int(relative_rank(BLACK, frontmost_sq(BLACK, b))) * Unstoppable;
+ score -= Unstoppable * int(relative_rank(BLACK, frontmost_sq(BLACK, b)));
}
// Evaluate space for both sides, only during opening
{
Trace::add(MATERIAL, pos.psq_score());
Trace::add(IMBALANCE, ei.me->imbalance());
- Trace::add(PAWN, ei.pi->pawns_score());
+ Trace::add(PAWN, ei.pi->pawns_score() * Weights[PawnStructure]);
Trace::add(MOBILITY, mobility[WHITE], mobility[BLACK]);
Trace::add(SPACE, evaluate_space<WHITE>(pos, ei) * Weights[Space]
, evaluate_space<BLACK>(pos, ei) * Weights[Space]);
projects / stockfish / blobdiff