/*
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
{ 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 and rank (initialized by formula)
- Score ChainMember[FILE_NB][RANK_NB];
+ // 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) };
+ // Levers bonus by rank
+ const Score Lever[RANK_NB] = {
+ S( 0, 0), S( 0, 0), S(0, 0), S(0, 0),
+ S(20,20), S(40,40), 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] =
{ V(100), V(0), V(27), V(73), V(92), V(101), V(101) };
// Danger of enemy pawns moving toward our king indexed by
// [no friendly pawn | pawn unblocked | pawn blocked][rank of enemy pawn]
- const Value StormDanger[3][RANK_NB] = {
+ const Value StormDanger[][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(160), 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 horizon.
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;
- bool passed, isolated, doubled, opposed, chain, backward, candidate;
+ bool passed, isolated, opposed, connected, backward, candidate, unsupported, lever;
Score value = SCORE_ZERO;
const Square* pl = pos.list<PAWN>(Us);
+ const Bitboard* pawnAttacksBB = StepAttacksBB[make_piece(Us, PAWN)];
Bitboard ourPawns = pos.pieces(Us, PAWN);
Bitboard theirPawns = pos.pieces(Them, PAWN);
// 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));
+ lever = theirPawns & pawnAttacksBB[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
+ // 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 | chain)
+ if ( (passed | isolated | connected)
|| (ourPawns & pawn_attack_span(Them, s))
|| (pos.attacks_from<PAWN>(s, Us) & theirPawns))
backward = false;
if (isolated)
value -= Isolated[opposed][f];
+ if (unsupported && !isolated)
+ value -= UnsupportedPawnPenalty;
+
if (doubled)
- value -= Doubled[f];
+ value -= Doubled[f] / rank_distance(s, lsb(doubled));
if (backward)
value -= Backward[opposed][f];
- if (chain)
- value += ChainMember[f][relative_rank(Us, s)];
+ if (connected)
+ value += Connected[f][relative_rank(Us, s)];
+
+ if (lever)
+ value += Lever[relative_rank(Us, s)];
if (candidate)
{
}
}
+ b = e->semiopenFiles[Us] ^ 0xFF;
+ e->pawnSpan[Us] = b ? int(msb(b) - lsb(b)) : 0;
+
// 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));
- }
+ value += PawnsFileSpan * e->pawnSpan[Us];
return value;
}
void init() {
- const int chainByFile[8] = { 1, 3, 3, 4, 4, 3, 3, 1 };
- int bonus;
+ const int bonusByFile[] = { 1, 3, 3, 4, 4, 3, 3, 1 };
for (Rank r = RANK_1; r < RANK_8; ++r)
for (File f = FILE_A; f <= FILE_H; ++f)
{
- bonus = r * (r-1) * (r-2) + chainByFile[f] * (r/2 + 1);
- ChainMember[f][r] = make_score(bonus, bonus);
+ int bonus = r * (r - 1) * (r - 2) + bonusByFile[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
+/// probe() takes a position 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.
Entry* probe(const Position& pos, Table& entries) {
Value Entry::shelter_storm(const Position& pos, Square ksq) {
const Color Them = (Us == WHITE ? BLACK : WHITE);
+ const Bitboard Edges = (FileABB | FileHBB) & (Rank2BB | Rank3BB);
- Value safety = MaxSafetyBonus;
Bitboard b = pos.pieces(PAWN) & (in_front_bb(Us, rank_of(ksq)) | rank_bb(ksq));
Bitboard ourPawns = b & pos.pieces(Us);
Bitboard theirPawns = b & pos.pieces(Them);
- Rank rkUs, rkThem;
+ Value safety = MaxSafetyBonus;
File kf = std::max(FILE_B, std::min(FILE_G, file_of(ksq)));
for (File f = kf - File(1); f <= kf + File(1); ++f)
{
b = ourPawns & file_bb(f);
- rkUs = b ? relative_rank(Us, backmost_sq(Us, b)) : RANK_1;
- safety -= ShelterWeakness[rkUs];
+ Rank rkUs = b ? relative_rank(Us, backmost_sq(Us, b)) : RANK_1;
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];
+ Rank rkThem = b ? relative_rank(Us, frontmost_sq(Them, b)) : RANK_1;
+
+ if ( (Edges & make_square(f, rkThem))
+ && file_of(ksq) == f
+ && relative_rank(Us, ksq) == rkThem - 1)
+ safety += 200;
+ else
+ safety -= ShelterWeakness[rkUs]
+ + StormDanger[rkUs == RANK_1 ? 0 :
+ rkThem != rkUs + 1 ? 1 : 2][rkThem];
}
return safety;
}
-/// Entry::update_safety() calculates and caches a bonus for king safety.
-/// It is called only when king square changes, which is 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;
- castlingFlags[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 castling if it is bigger
- if (pos.can_castle(make_castling_flag(Us, KING_SIDE)))
+ 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_castling_flag(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