/*
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] = {
- S(11,-1), S(13,-1), S(13,-1), S(14,-1),
- S(14,-1), S(13,-1), S(13,-1), S(11,-1)
- };
-
- // 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)
- };
-
- // 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] = {
- { 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) }};
+ S(33, 31), S(33, 31), S(29, 31), S(20, 28) } };
+
+ // Connected pawn bonus by opposed, phalanx flags and rank
+ Score Connected[2][2][RANK_NB];
+
+ // 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) };
+
+ // Unsupported pawn penalty
+ const Score UnsupportedPawnPenalty = S(20, 10);
+
+ // Weakness of our pawn shelter in front of the king by [distance from edge][rank]
+ const Value ShelterWeakness[][RANK_NB] = {
+ { V(101), V(10), V(24), V(68), V(90), V( 95), V(102) },
+ { V(105), V( 1), V(30), V(76), V(95), V(100), V(105) },
+ { V( 99), V( 0), V(32), V(72), V(92), V(101), V(100) },
+ { V( 94), V( 1), V(31), V(68), V(89), V( 98), V(106) } };
+
+ // Danger of enemy pawns moving toward our king by [type][distance from edge][rank]
+ const Value StormDanger[][4][RANK_NB] = {
+ { { V( 0), V( 61), V( 128), V(47), V(27) },
+ { V( 0), V( 66), V( 131), V(49), V(27) },
+ { V( 0), V( 62), V( 126), V(52), V(23) },
+ { V( 0), V( 63), V( 128), V(52), V(26) } },
+ { { V(25), V( 33), V( 95), V(39), V(21) },
+ { V(24), V( 33), V( 97), V(42), V(22) },
+ { V(24), V( 33), V( 93), V(35), V(23) },
+ { V(26), V( 27), V( 96), V(37), V(22) } },
+ { { V( 0), V( 0), V( 80), V(14), V( 8) },
+ { V( 0), V( 0), V( 163), V(28), V(12) },
+ { V( 0), V( 0), V( 163), V(25), V(15) },
+ { V( 0), V( 0), V( 161), V(24), V(14) } },
+ { { V( 0), V(-300), V(-300), V(54), V(23) },
+ { V( 0), V( 67), V( 128), V(46), V(24) },
+ { V( 0), V( 64), V( 130), V(50), V(29) },
+ { V( 0), V( 63), V( 127), V(51), V(24) } } };
// 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.
- const Value MaxSafetyBonus = V(263);
+ // in front of the king and no enemy pawn on the horizon.
+ const Value MaxSafetyBonus = V(261);
#undef S
#undef V
const Square Right = (Us == WHITE ? DELTA_NE : DELTA_SW);
const Square Left = (Us == WHITE ? DELTA_NW : DELTA_SE);
- Bitboard b;
+ Bitboard b, p, doubled, connected;
Square s;
- File f;
- bool passed, isolated, doubled, opposed, chain, backward, candidate;
+ bool passed, isolated, opposed, phalanx, backward, 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 ourPawns = pos.pieces(Us , PAWN);
Bitboard theirPawns = pos.pieces(Them, PAWN);
- e->passedPawns[Us] = e->candidatePawns[Us] = 0;
+ e->passedPawns[Us] = 0;
e->kingSquares[Us] = SQ_NONE;
e->semiopenFiles[Us] = 0xFF;
e->pawnAttacks[Us] = shift_bb<Right>(ourPawns) | shift_bb<Left>(ourPawns);
{
assert(pos.piece_on(s) == make_piece(Us, PAWN));
- f = file_of(s);
+ File f = file_of(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));
- // 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) & (rank_bb(s) | p);
+ phalanx = connected & rank_bb(s);
+ 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
- // 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
- // advance and if the number of friendly pawns beside or behind this
- // pawn on adjacent files is higher or equal than 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
- && popcount<Max15>(b) >= popcount<Max15>(pawn_attack_span(Us, s) & theirPawns);
-
// Passed pawns will be properly scored in evaluation because we need
// full attack info to evaluate passed pawns. Only the frontmost passed
// pawn on each file is considered a true passed pawn.
if (isolated)
value -= Isolated[opposed][f];
+ if (unsupported && !isolated)
+ value -= UnsupportedPawnPenalty;
+
if (doubled)
- value -= Doubled[opposed][f];
+ value -= Doubled[f] / distance<Rank>(s, frontmost_sq(Us, doubled));
if (backward)
value -= Backward[opposed][f];
- if (chain)
- value += ChainMember[f];
-
- if (candidate)
- {
- value += CandidatePassed[relative_rank(Us, s)];
+ if (connected)
+ value += Connected[opposed][phalanx][relative_rank(Us, s)];
- if (!doubled)
- e->candidatePawns[Us] |= s;
- }
+ if (lever)
+ value += Lever[relative_rank(Us, s)];
}
+ b = e->semiopenFiles[Us] ^ 0xFF;
+ e->pawnSpan[Us] = b ? int(msb(b) - lsb(b)) : 0;
+
return value;
}
namespace Pawns {
-/// 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
+/// init() initializes some tables used by evaluation. Instead of hard-coded
+/// tables, when makes sense, we prefer to calculate them with a formula to
+/// reduce independent parameters and to allow easier tuning and better insight.
+
+void init()
+{
+ static const int Seed[RANK_NB] = { 0, 6, 15, 10, 57, 75, 135, 258 };
+
+ for (int opposed = 0; opposed <= 1; ++opposed)
+ for (int phalanx = 0; phalanx <= 1; ++phalanx)
+ for (Rank r = RANK_2; r < RANK_8; ++r)
+ {
+ int bonus = Seed[r] + (phalanx ? (Seed[r + 1] - Seed[r]) / 2 : 0);
+ Connected[opposed][phalanx][r] = make_score(bonus / 2, bonus >> opposed);
+ }
+}
+
+
+/// 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) {
const Color Them = (Us == WHITE ? BLACK : WHITE);
- Value safety = MaxSafetyBonus;
+ enum { NoFriendlyPawn, Unblocked, BlockedByPawn, BlockedByKing };
+
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;
- File kf = std::max(FILE_B, std::min(FILE_G, file_of(ksq)));
+ Value safety = MaxSafetyBonus;
+ File center = std::max(FILE_B, std::min(FILE_G, file_of(ksq)));
- for (int f = kf - 1; f <= kf + 1; ++f)
+ for (File f = center - File(1); f <= center + File(1); ++f)
{
- b = ourPawns & FileBB[f];
- rkUs = b ? relative_rank(Us, backmost_sq(Us, b)) : RANK_1;
- safety -= ShelterWeakness[rkUs];
-
- b = theirPawns & FileBB[f];
- rkThem = b ? relative_rank(Us, frontmost_sq(Them, b)) : RANK_1;
- safety -= StormDanger[rkUs == RANK_1 ? 0 : rkThem == rkUs + 1 ? 2 : 1][rkThem];
+ b = ourPawns & file_bb(f);
+ Rank rkUs = b ? relative_rank(Us, backmost_sq(Us, b)) : RANK_1;
+
+ b = theirPawns & file_bb(f);
+ Rank rkThem = b ? relative_rank(Us, frontmost_sq(Them, b)) : RANK_1;
+
+ safety -= ShelterWeakness[std::min(f, FILE_H - f)][rkUs]
+ + StormDanger
+ [f == file_of(ksq) && rkThem == relative_rank(Us, ksq) + 1 ? BlockedByKing :
+ rkUs == RANK_1 ? NoFriendlyPawn :
+ rkThem == rkUs + 1 ? BlockedByPawn : Unblocked]
+ [std::min(f, FILE_H - f)][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);
- minKPdistance[Us] = 0;
+ castlingRights[Us] = pos.can_castle(Us);
+ minKingPawnDistance[Us] = 0;
Bitboard pawns = pos.pieces(Us, PAWN);
if (pawns)
- while (!(DistanceRingsBB[ksq][minKPdistance[Us]++] & pawns)) {}
+ while (!(DistanceRingsBB[ksq][minKingPawnDistance[Us]++] & pawns)) {}
if (relative_rank(Us, ksq) > RANK_4)
- return kingSafety[Us] = make_score(0, -16 * minKPdistance[Us]);
+ return make_score(0, -16 * minKingPawnDistance[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 * minKingPawnDistance[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