/*
Stockfish, a UCI chess playing engine derived from Glaurung 2.1
Copyright (C) 2004-2008 Tord Romstad (Glaurung author)
- Copyright (C) 2008-2013 Marco Costalba, Joona Kiiski, Tord Romstad
+ Copyright (C) 2008-2014 Marco Costalba, Joona Kiiski, 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
#define V Value
#define S(mg, eg) make_score(mg, eg)
- // Doubled pawn penalty by opposed flag and file
- const Score Doubled[2][FILE_NB] = {
- { S(13, 43), S(20, 48), S(23, 48), S(23, 48),
- S(23, 48), S(23, 48), S(20, 48), S(13, 43) },
- { S(13, 43), S(20, 48), S(23, 48), S(23, 48),
- S(23, 48), S(23, 48), S(20, 48), S(13, 43) }};
+ // Doubled pawn penalty by file
+ const Score Doubled[FILE_NB] = {
+ S(13, 43), S(20, 48), S(23, 48), S(23, 48),
+ S(23, 48), S(23, 48), S(20, 48), S(13, 43) };
// Isolated pawn penalty by opposed flag and file
const Score Isolated[2][FILE_NB] = {
{ S(37, 45), S(54, 52), S(60, 52), S(60, 52),
S(60, 52), S(60, 52), S(54, 52), S(37, 45) },
{ S(25, 30), S(36, 35), S(40, 35), S(40, 35),
- S(40, 35), S(40, 35), S(36, 35), S(25, 30) }};
+ S(40, 35), S(40, 35), S(36, 35), S(25, 30) } };
// Backward pawn penalty by opposed flag and file
const Score Backward[2][FILE_NB] = {
{ S(30, 42), S(43, 46), S(49, 46), S(49, 46),
S(49, 46), S(49, 46), S(43, 46), S(30, 42) },
{ S(20, 28), S(29, 31), S(33, 31), S(33, 31),
- S(33, 31), S(33, 31), S(29, 31), S(20, 28) }};
-
- // Pawn chain membership bonus by file
- const Score ChainMember[FILE_NB][RANK_NB] = {
- { S(0, 0), S(14, 0), S(16, 4), S(18, 9), S(56, 56), S(104, 208), S(236, 472) },
- { S(0, 0), S(16, 0), S(18, 5), S(20, 10), S(60, 60), S(108, 216), S(240, 480) },
- { S(0, 0), S(16, 0), S(18, 5), S(20, 10), S(60, 60), S(108, 216), S(240, 480) },
- { S(0, 0), S(17, 0), S(19, 6), S(22, 11), S(66, 66), S(118, 236), S(254, 508) },
- { S(0, 0), S(17, 0), S(19, 6), S(22, 11), S(66, 66), S(118, 236), S(254, 508) },
- { S(0, 0), S(16, 0), S(18, 5), S(20, 10), S(60, 60), S(108, 216), S(240, 480) },
- { S(0, 0), S(16, 0), S(18, 5), S(20, 10), S(60, 60), S(108, 216), S(240, 480) },
- { S(0, 0), S(14, 0), S(16, 4), S(18, 9), S(56, 56), S(104, 208), S(236, 472) }
- };
+ S(33, 31), S(33, 31), S(29, 31), S(20, 28) } };
+
+ // Connected pawn bonus by file and rank (initialized by formula)
+ Score Connected[FILE_NB][RANK_NB];
// Candidate passed pawn bonus by rank
const Score CandidatePassed[RANK_NB] = {
S( 0, 0), S( 6, 13), S(6,13), S(14,29),
- S(34,68), S(83,166), S(0, 0), S( 0, 0)
- };
+ S(34,68), S(83,166), S(0, 0), S( 0, 0) };
+
+ // Bonus for file distance of the two outermost pawns
+ const Score PawnsFileSpan = S(0, 15);
+
+ // Unsupported pawn penalty
+ const Score UnsupportedPawnPenalty = S(20, 10);
// Weakness of our pawn shelter in front of the king indexed by [rank]
const Value ShelterWeakness[RANK_NB] =
const Value StormDanger[3][RANK_NB] = {
{ V( 0), V(64), V(128), V(51), V(26) },
{ V(26), V(32), V( 96), V(38), V(20) },
- { V( 0), V( 0), V( 64), V(25), V(13) }};
+ { V( 0), V( 0), V( 64), V(25), V(13) } };
// Max bonus for king safety. Corresponds to start position with all the pawns
- // in front of the king and no enemy pawn on the horizont.
+ // in front of the king and no enemy pawn on the horizon.
const Value MaxSafetyBonus = V(263);
#undef S
const Square Right = (Us == WHITE ? DELTA_NE : DELTA_SW);
const Square Left = (Us == WHITE ? DELTA_NW : DELTA_SE);
- Bitboard b;
+ Bitboard b, p, doubled;
Square s;
File f;
- Rank r;
- bool passed, isolated, doubled, opposed, chain, backward, candidate;
+ bool passed, isolated, opposed, connected, backward, candidate, unsupported;
Score value = SCORE_ZERO;
const Square* pl = pos.list<PAWN>(Us);
assert(pos.piece_on(s) == make_piece(Us, PAWN));
f = file_of(s);
- r = relative_rank(Us, s);
// This file cannot be semi-open
e->semiopenFiles[Us] &= ~(1 << f);
- // Our rank plus previous one. Used for chain detection
- b = rank_bb(s) | rank_bb(s - pawn_push(Us));
+ // Previous rank
+ p = rank_bb(s - pawn_push(Us));
+
+ // Our rank plus previous one
+ b = rank_bb(s) | p;
- // Flag the pawn as passed, isolated, doubled or member of a pawn
- // chain (but not the backward one).
- chain = ourPawns & adjacent_files_bb(f) & b;
- isolated = !(ourPawns & adjacent_files_bb(f));
- doubled = ourPawns & forward_bb(Us, s);
- opposed = theirPawns & forward_bb(Us, s);
- passed = !(theirPawns & passed_pawn_mask(Us, s));
+ // Flag the pawn as passed, isolated, doubled,
+ // unsupported or connected (but not the backward one).
+ connected = ourPawns & adjacent_files_bb(f) & b;
+ unsupported = !(ourPawns & adjacent_files_bb(f) & p);
+ isolated = !(ourPawns & adjacent_files_bb(f));
+ doubled = ourPawns & forward_bb(Us, s);
+ opposed = theirPawns & forward_bb(Us, s);
+ passed = !(theirPawns & passed_pawn_mask(Us, s));
// Test for backward pawn.
- // If the pawn is passed, isolated, or member of a pawn chain it cannot
- // be backward. If there are friendly pawns behind on adjacent files
- // or if can capture an enemy pawn it cannot be backward either.
- if ( (passed | isolated | chain)
+ // If the pawn is passed, isolated, or connected it cannot be
+ // backward. If there are friendly pawns behind on adjacent files
+ // or if it can capture an enemy pawn it cannot be backward either.
+ if ( (passed | isolated | connected)
|| (ourPawns & pawn_attack_span(Them, s))
|| (pos.attacks_from<PAWN>(s, Us) & theirPawns))
backward = false;
assert(opposed | passed | (pawn_attack_span(Us, s) & theirPawns));
- // A not passed pawn is a candidate to become passed if it is free to
+ // A not-passed pawn is a candidate to become passed, if it is free to
// advance and if the number of friendly pawns beside or behind this
- // pawn on adjacent files is higher or equal than the number of
+ // pawn on adjacent files is higher than or equal to the number of
// enemy pawns in the forward direction on the adjacent files.
candidate = !(opposed | passed | backward | isolated)
&& (b = pawn_attack_span(Them, s + pawn_push(Us)) & ourPawns) != 0
if (isolated)
value -= Isolated[opposed][f];
+ if (unsupported && !isolated)
+ value -= UnsupportedPawnPenalty;
+
if (doubled)
- value -= Doubled[opposed][f];
+ value -= Doubled[f] / rank_distance(s, lsb(doubled));
if (backward)
value -= Backward[opposed][f];
- if (chain)
- value += opposed ? ChainMember[f][r] / 2 : ChainMember[f][r];
+ if (connected)
+ value += Connected[f][relative_rank(Us, s)];
if (candidate)
{
- value += CandidatePassed[r];
+ value += CandidatePassed[relative_rank(Us, s)];
if (!doubled)
e->candidatePawns[Us] |= s;
}
}
+ // In endgame it's better to have pawns on both wings. So give a bonus according
+ // to file distance between left and right outermost pawns.
+ if (pos.count<PAWN>(Us) > 1)
+ {
+ b = e->semiopenFiles[Us] ^ 0xFF;
+ value += PawnsFileSpan * int(msb(b) - lsb(b));
+ }
+
return value;
}
namespace Pawns {
+/// init() initializes some tables by formula instead of hard-coding their values
+
+void init() {
+
+ const int bonusesByFile[8] = { 1, 3, 3, 4, 4, 3, 3, 1 };
+ int bonus;
+
+ for (Rank r = RANK_1; r < RANK_8; ++r)
+ for (File f = FILE_A; f <= FILE_H; ++f)
+ {
+ bonus = r * (r-1) * (r-2) + bonusesByFile[f] * (r/2 + 1);
+ Connected[f][r] = make_score(bonus, bonus);
+ }
+}
+
+
/// probe() takes a position object as input, computes a Entry object, and returns
/// a pointer to it. The result is also stored in a hash table, so we don't have
/// to recompute everything when the same pawn structure occurs again.
Value Entry::shelter_storm(const Position& pos, Square ksq) {
const Color Them = (Us == WHITE ? BLACK : WHITE);
+ static const Bitboard MiddleEdges = (FileABB | FileHBB) & (Rank2BB | Rank3BB);
Value safety = MaxSafetyBonus;
Bitboard b = pos.pieces(PAWN) & (in_front_bb(Us, rank_of(ksq)) | rank_bb(ksq));
Rank rkUs, rkThem;
File kf = std::max(FILE_B, std::min(FILE_G, file_of(ksq)));
- for (int f = kf - 1; f <= kf + 1; ++f)
+ for (File f = kf - File(1); f <= kf + File(1); ++f)
{
- b = ourPawns & FileBB[f];
+ b = ourPawns & file_bb(f);
rkUs = b ? relative_rank(Us, backmost_sq(Us, b)) : RANK_1;
- safety -= ShelterWeakness[rkUs];
- b = theirPawns & FileBB[f];
+ b = theirPawns & file_bb(f);
rkThem = b ? relative_rank(Us, frontmost_sq(Them, b)) : RANK_1;
- safety -= StormDanger[rkUs == RANK_1 ? 0 : rkThem == rkUs + 1 ? 2 : 1][rkThem];
+
+ if ( (MiddleEdges & make_square(f, rkThem))
+ && file_of(ksq) == f
+ && relative_rank(Us, ksq) == rkThem - 1)
+ safety += Value(200);
+ else
+ safety -= ShelterWeakness[rkUs]
+ + StormDanger[rkUs == RANK_1 ? 0 : rkThem == rkUs + 1 ? 2 : 1][rkThem];
}
return safety;
}
-/// Entry::update_safety() calculates and caches a bonus for king safety. It is
-/// called only when king square changes, about 20% of total king_safety() calls.
+/// Entry::do_king_safety() calculates a bonus for king safety. It is called only
+/// when king square changes, which is about 20% of total king_safety() calls.
template<Color Us>
-Score Entry::update_safety(const Position& pos, Square ksq) {
+Score Entry::do_king_safety(const Position& pos, Square ksq) {
kingSquares[Us] = ksq;
- castleRights[Us] = pos.can_castle(Us);
+ castlingRights[Us] = pos.can_castle(Us);
minKPdistance[Us] = 0;
Bitboard pawns = pos.pieces(Us, PAWN);
while (!(DistanceRingsBB[ksq][minKPdistance[Us]++] & pawns)) {}
if (relative_rank(Us, ksq) > RANK_4)
- return kingSafety[Us] = make_score(0, -16 * minKPdistance[Us]);
+ return make_score(0, -16 * minKPdistance[Us]);
Value bonus = shelter_storm<Us>(pos, ksq);
- // If we can castle use the bonus after the castle if is bigger
- if (pos.can_castle(make_castle_right(Us, KING_SIDE)))
+ // If we can castle use the bonus after the castling if it is bigger
+ if (pos.can_castle(MakeCastling<Us, KING_SIDE>::right))
bonus = std::max(bonus, shelter_storm<Us>(pos, relative_square(Us, SQ_G1)));
- if (pos.can_castle(make_castle_right(Us, QUEEN_SIDE)))
+ if (pos.can_castle(MakeCastling<Us, QUEEN_SIDE>::right))
bonus = std::max(bonus, shelter_storm<Us>(pos, relative_square(Us, SQ_C1)));
- return kingSafety[Us] = make_score(bonus, -16 * minKPdistance[Us]);
+ return make_score(bonus, -16 * minKPdistance[Us]);
}
// Explicit template instantiation
-template Score Entry::update_safety<WHITE>(const Position& pos, Square ksq);
-template Score Entry::update_safety<BLACK>(const Position& pos, Square ksq);
+template Score Entry::do_king_safety<WHITE>(const Position& pos, Square ksq);
+template Score Entry::do_king_safety<BLACK>(const Position& pos, Square ksq);
} // namespace Pawns
projects / stockfish / blobdiff