/*
Stockfish, a UCI chess playing engine derived from Glaurung 2.1
Copyright (C) 2004-2008 Tord Romstad (Glaurung author)
- Copyright (C) 2008-2010 Marco Costalba, Joona Kiiski, Tord Romstad
+ Copyright (C) 2008-2015 Marco Costalba, Joona Kiiski, Tord Romstad
+ Copyright (C) 2015-2018 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
along with this program. If not, see <http://www.gnu.org/licenses/>.
*/
+#include <algorithm>
#include <cassert>
#include "bitboard.h"
-#include "bitcount.h"
#include "pawns.h"
#include "position.h"
+#include "thread.h"
namespace {
+ #define V Value
#define S(mg, eg) make_score(mg, eg)
- // Doubled pawn penalty by opposed flag and file
- const Score DoubledPawnPenalty[2][8] = {
- { 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) }};
-
- // Isolated pawn penalty by opposed flag and file
- const Score IsolatedPawnPenalty[2][8] = {
- { 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) }};
-
- // Backward pawn penalty by opposed flag and file
- const Score BackwardPawnPenalty[2][8] = {
- { 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 ChainBonus[8] = {
- S(11,-1), S(13,-1), S(13,-1), S(14,-1),
- S(14,-1), S(13,-1), S(13,-1), S(11,-1)
+ // Isolated pawn penalty
+ const Score Isolated = S(13, 18);
+
+ // Backward pawn penalty
+ const Score Backward = S(24, 12);
+
+ // Connected pawn bonus by opposed, phalanx, #support and rank
+ Score Connected[2][2][3][RANK_NB];
+
+ // Doubled pawn penalty
+ const Score Doubled = S(18, 38);
+
+ // Weakness of our pawn shelter in front of the king by [isKingFile][distance from edge][rank].
+ // RANK_1 = 0 is used for files where we have no pawns or our pawn is behind our king.
+ const Value ShelterWeakness[][int(FILE_NB) / 2][RANK_NB] = {
+ { { V( 98), V(20), V(11), V(42), V( 83), V( 84), V(101) }, // Not On King file
+ { V(103), V( 8), V(33), V(86), V( 87), V(105), V(113) },
+ { V(100), V( 2), V(65), V(95), V( 59), V( 89), V(115) },
+ { V( 72), V( 6), V(52), V(74), V( 83), V( 84), V(112) } },
+ { { V(105), V(19), V( 3), V(27), V( 85), V( 93), V( 84) }, // On King file
+ { V(121), V( 7), V(33), V(95), V(112), V( 86), V( 72) },
+ { V(121), V(26), V(65), V(90), V( 65), V( 76), V(117) },
+ { V( 79), V( 0), V(45), V(65), V( 94), V( 92), V(105) } }
};
- // Candidate passed pawn bonus by rank
- const Score CandidateBonus[8] = {
- S( 0, 0), S( 6, 13), S(6,13), S(14,29),
- S(34,68), S(83,166), S(0, 0), S( 0, 0)
+ // Danger of enemy pawns moving toward our king by [type][distance from edge][rank].
+ // For the unopposed and unblocked cases, RANK_1 = 0 is used when opponent has
+ // no pawn on the given file, or their pawn is behind our king.
+ const Value StormDanger[][4][RANK_NB] = {
+ { { V( 0), V(-290), V(-274), V(57), V(41) }, // BlockedByKing
+ { V( 0), V( 60), V( 144), V(39), V(13) },
+ { V( 0), V( 65), V( 141), V(41), V(34) },
+ { V( 0), V( 53), V( 127), V(56), V(14) } },
+ { { V( 4), V( 73), V( 132), V(46), V(31) }, // Unopposed
+ { V( 1), V( 64), V( 143), V(26), V(13) },
+ { V( 1), V( 47), V( 110), V(44), V(24) },
+ { V( 0), V( 72), V( 127), V(50), V(31) } },
+ { { V( 0), V( 0), V( 79), V(23), V( 1) }, // BlockedByPawn
+ { V( 0), V( 0), V( 148), V(27), V( 2) },
+ { V( 0), V( 0), V( 161), V(16), V( 1) },
+ { V( 0), V( 0), V( 171), V(22), V(15) } },
+ { { V(22), V( 45), V( 104), V(62), V( 6) }, // Unblocked
+ { V(31), V( 30), V( 99), V(39), V(19) },
+ { V(23), V( 29), V( 96), V(41), V(15) },
+ { V(21), V( 23), V( 116), V(41), V(15) } }
};
+ // 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 Value MaxSafetyBonus = V(258);
+
#undef S
-}
+ #undef V
+
+ template<Color Us>
+ Score evaluate(const Position& pos, Pawns::Entry* e) {
+
+ const Color Them = (Us == WHITE ? BLACK : WHITE);
+ const Direction Up = (Us == WHITE ? NORTH : SOUTH);
+
+ Bitboard b, neighbours, stoppers, doubled, supported, phalanx;
+ Bitboard lever, leverPush;
+ Square s;
+ bool opposed, backward;
+ Score score = SCORE_ZERO;
+ const Square* pl = pos.squares<PAWN>(Us);
+
+ Bitboard ourPawns = pos.pieces( Us, PAWN);
+ Bitboard theirPawns = pos.pieces(Them, PAWN);
+
+ e->passedPawns[Us] = e->pawnAttacksSpan[Us] = e->weakUnopposed[Us] = 0;
+ e->semiopenFiles[Us] = 0xFF;
+ e->kingSquares[Us] = SQ_NONE;
+ e->pawnAttacks[Us] = pawn_attacks_bb<Us>(ourPawns);
+ e->pawnsOnSquares[Us][BLACK] = popcount(ourPawns & DarkSquares);
+ e->pawnsOnSquares[Us][WHITE] = pos.count<PAWN>(Us) - e->pawnsOnSquares[Us][BLACK];
+
+ // Loop through all pawns of the current color and score each pawn
+ while ((s = *pl++) != SQ_NONE)
+ {
+ assert(pos.piece_on(s) == make_piece(Us, PAWN));
+
+ File f = file_of(s);
+
+ e->semiopenFiles[Us] &= ~(1 << f);
+ e->pawnAttacksSpan[Us] |= pawn_attack_span(Us, s);
+
+ // Flag the pawn
+ opposed = theirPawns & forward_file_bb(Us, s);
+ stoppers = theirPawns & passed_pawn_mask(Us, s);
+ lever = theirPawns & PawnAttacks[Us][s];
+ leverPush = theirPawns & PawnAttacks[Us][s + Up];
+ doubled = ourPawns & (s - Up);
+ neighbours = ourPawns & adjacent_files_bb(f);
+ phalanx = neighbours & rank_bb(s);
+ supported = neighbours & rank_bb(s - Up);
+
+ // A pawn is backward when it is behind all pawns of the same color on the
+ // adjacent files and cannot be safely advanced.
+ if (!neighbours || lever || relative_rank(Us, s) >= RANK_5)
+ backward = false;
+ else
+ {
+ // Find the backmost rank with neighbours or stoppers
+ b = rank_bb(backmost_sq(Us, neighbours | stoppers));
+
+ // The pawn is backward when it cannot safely progress to that rank:
+ // either there is a stopper in the way on this rank, or there is a
+ // stopper on adjacent file which controls the way to that rank.
+ backward = (b | shift<Up>(b & adjacent_files_bb(f))) & stoppers;
+
+ assert(!(backward && (forward_ranks_bb(Them, s + Up) & neighbours)));
+ }
+
+ // Passed pawns will be properly scored in evaluation because we need
+ // full attack info to evaluate them. Include also not passed pawns
+ // which could become passed after one or two pawn pushes when are
+ // not attacked more times than defended.
+ if ( !(stoppers ^ lever ^ leverPush)
+ && !(ourPawns & forward_file_bb(Us, s))
+ && popcount(supported) >= popcount(lever)
+ && popcount(phalanx) >= popcount(leverPush))
+ e->passedPawns[Us] |= s;
+
+ else if ( stoppers == SquareBB[s + Up]
+ && relative_rank(Us, s) >= RANK_5)
+ {
+ b = shift<Up>(supported) & ~theirPawns;
+ while (b)
+ if (!more_than_one(theirPawns & PawnAttacks[Us][pop_lsb(&b)]))
+ e->passedPawns[Us] |= s;
+ }
+
+ // Score this pawn
+ if (supported | phalanx)
+ score += Connected[opposed][bool(phalanx)][popcount(supported)][relative_rank(Us, s)];
+
+ else if (!neighbours)
+ score -= Isolated, e->weakUnopposed[Us] += !opposed;
+
+ else if (backward)
+ score -= Backward, e->weakUnopposed[Us] += !opposed;
+
+ if (doubled && !supported)
+ score -= Doubled;
+ }
+
+ return score;
+ }
+
+} // namespace
+
+namespace Pawns {
+
+/// Pawns::init() initializes some tables needed by evaluation. Instead of using
+/// 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() {
-/// PawnInfoTable::get_pawn_info() takes a position object as input, computes
-/// a PawnInfo object, and returns a pointer to it. The result is also stored
-/// in an hash table, so we don't have to recompute everything when the same
-/// pawn structure occurs again.
+ static const int Seed[RANK_NB] = { 0, 13, 24, 18, 76, 100, 175, 330 };
+
+ for (int opposed = 0; opposed <= 1; ++opposed)
+ for (int phalanx = 0; phalanx <= 1; ++phalanx)
+ for (int support = 0; support <= 2; ++support)
+ for (Rank r = RANK_2; r < RANK_8; ++r)
+ {
+ int v = 17 * support;
+ v += (Seed[r] + (phalanx ? (Seed[r + 1] - Seed[r]) / 2 : 0)) >> opposed;
+
+ Connected[opposed][phalanx][support][r] = make_score(v, v * (r - 2) / 4);
+ }
+}
-PawnInfo* PawnInfoTable::get_pawn_info(const Position& pos) const {
- assert(pos.is_ok());
+/// Pawns::probe() looks up the current position's pawns configuration in
+/// the pawns hash table. It returns a pointer to the Entry if the position
+/// is found. Otherwise a new Entry is computed and stored there, so we don't
+/// have to recompute all when the same pawns configuration occurs again.
- Key key = pos.get_pawn_key();
- PawnInfo* pi = probe(key);
+Entry* probe(const Position& pos) {
- // If pi->key matches the position's pawn hash key, it means that we
- // have analysed this pawn structure before, and we can simply return
- // the information we found the last time instead of recomputing it.
- if (pi->key == key)
- return pi;
+ Key key = pos.pawn_key();
+ Entry* e = pos.this_thread()->pawnsTable[key];
- // Initialize PawnInfo entry
- pi->key = key;
- pi->passedPawns[WHITE] = pi->passedPawns[BLACK] = 0;
- pi->kingSquares[WHITE] = pi->kingSquares[BLACK] = SQ_NONE;
- pi->halfOpenFiles[WHITE] = pi->halfOpenFiles[BLACK] = 0xFF;
+ if (e->key == key)
+ return e;
- // Calculate pawn attacks
- Bitboard wPawns = pos.pieces(PAWN, WHITE);
- Bitboard bPawns = pos.pieces(PAWN, BLACK);
- pi->pawnAttacks[WHITE] = ((wPawns << 9) & ~FileABB) | ((wPawns << 7) & ~FileHBB);
- pi->pawnAttacks[BLACK] = ((bPawns >> 7) & ~FileABB) | ((bPawns >> 9) & ~FileHBB);
+ e->key = key;
+ e->scores[WHITE] = evaluate<WHITE>(pos, e);
+ e->scores[BLACK] = evaluate<BLACK>(pos, e);
+ e->openFiles = popcount(e->semiopenFiles[WHITE] & e->semiopenFiles[BLACK]);
+ e->asymmetry = popcount( (e->passedPawns[WHITE] | e->passedPawns[BLACK])
+ | (e->semiopenFiles[WHITE] ^ e->semiopenFiles[BLACK]));
- // Evaluate pawns for both colors
- pi->value = evaluate_pawns<WHITE>(pos, wPawns, bPawns, pi)
- - evaluate_pawns<BLACK>(pos, bPawns, wPawns, pi);
- return pi;
+ return e;
}
-/// PawnInfoTable::evaluate_pawns() evaluates each pawn of the given color
+/// Entry::shelter_storm() calculates shelter and storm penalties for the file
+/// the king is on, as well as the two closest files.
template<Color Us>
-Score PawnInfoTable::evaluate_pawns(const Position& pos, Bitboard ourPawns,
- Bitboard theirPawns, PawnInfo* pi) {
-
- const BitCountType Max15 = CpuIs64Bit ? CNT64_MAX15 : CNT32_MAX15;
- const Color Them = (Us == WHITE ? BLACK : WHITE);
-
- Bitboard b;
- Square s;
- File f;
- Rank r;
- bool passed, isolated, doubled, opposed, chain, backward, candidate;
- Score value = SCORE_ZERO;
- const Square* ptr = pos.piece_list_begin(Us, PAWN);
-
- // Loop through all pawns of the current color and score each pawn
- while ((s = *ptr++) != SQ_NONE)
+Value Entry::shelter_storm(const Position& pos, Square ksq) {
+
+ constexpr Color Them = (Us == WHITE ? BLACK : WHITE);
+ constexpr Bitboard ShelterMask =
+ Us == WHITE ? make_bitboard(SQ_A2, SQ_B3, SQ_C2, SQ_F2, SQ_G3, SQ_H2)
+ : make_bitboard(SQ_A7, SQ_B6, SQ_C7, SQ_F7, SQ_G6, SQ_H7);
+ constexpr Bitboard StormMask =
+ Us == WHITE ? make_bitboard(SQ_A3, SQ_C3, SQ_F3, SQ_H3)
+ : make_bitboard(SQ_A6, SQ_C6, SQ_F6, SQ_H6);
+
+ enum { BlockedByKing, Unopposed, BlockedByPawn, Unblocked };
+
+ File center = std::max(FILE_B, std::min(FILE_G, file_of(ksq)));
+ Bitboard b = pos.pieces(PAWN)
+ & (forward_ranks_bb(Us, ksq) | rank_bb(ksq))
+ & (adjacent_files_bb(center) | file_bb(center));
+ Bitboard ourPawns = b & pos.pieces(Us);
+ Bitboard theirPawns = b & pos.pieces(Them);
+ Value safety = MaxSafetyBonus;
+
+ for (File f = File(center - 1); f <= File(center + 1); ++f)
{
- assert(pos.piece_on(s) == make_piece(Us, PAWN));
-
- f = square_file(s);
- r = square_rank(s);
-
- // This file cannot be half open
- pi->halfOpenFiles[Us] &= ~(1 << f);
-
- // Our rank plus previous one. Used for chain detection
- b = rank_bb(r) | rank_bb(Us == WHITE ? r - Rank(1) : r + Rank(1));
-
- // Flag the pawn as passed, isolated, doubled or member of a pawn
- // chain (but not the backward one).
- passed = !(theirPawns & passed_pawn_mask(Us, s));
- doubled = ourPawns & squares_in_front_of(Us, s);
- opposed = theirPawns & squares_in_front_of(Us, s);
- isolated = !(ourPawns & neighboring_files_bb(f));
- chain = ourPawns & neighboring_files_bb(f) & b;
-
- // Test for backward pawn
- backward = false;
-
- // If the pawn is passed, isolated, or member of a pawn chain it cannot
- // be backward. If there are friendly pawns behind on neighboring files
- // or if can capture an enemy pawn it cannot be backward either.
- if ( !(passed | isolated | chain)
- && !(ourPawns & attack_span_mask(Them, s))
- && !(pos.attacks_from<PAWN>(s, Us) & theirPawns))
- {
- // We now know that there are no friendly pawns beside or behind this
- // pawn on neighboring files. We now check whether the pawn is
- // backward by looking in the forward direction on the neighboring
- // files, and seeing whether we meet a friendly or an enemy pawn first.
- b = pos.attacks_from<PAWN>(s, Us);
-
- // Note that we are sure to find something because pawn is not passed
- // nor isolated, so loop is potentially infinite, but it isn't.
- while (!(b & (ourPawns | theirPawns)))
- Us == WHITE ? b <<= 8 : b >>= 8;
-
- // The friendly pawn needs to be at least two ranks closer than the
- // enemy pawn in order to help the potentially backward pawn advance.
- backward = (b | (Us == WHITE ? b << 8 : b >> 8)) & theirPawns;
- }
-
- assert(opposed | passed | (attack_span_mask(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 neighboring files is higher or equal than the number of
- // enemy pawns in the forward direction on the neighboring files.
- candidate = !(opposed | passed | backward | isolated)
- && (b = attack_span_mask(Them, s + pawn_push(Us)) & ourPawns) != EmptyBoardBB
- && count_1s<Max15>(b) >= count_1s<Max15>(attack_span_mask(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 (passed && !doubled)
- set_bit(&(pi->passedPawns[Us]), s);
-
- // Score this pawn
- if (isolated)
- value -= IsolatedPawnPenalty[opposed][f];
-
- if (doubled)
- value -= DoubledPawnPenalty[opposed][f];
-
- if (backward)
- value -= BackwardPawnPenalty[opposed][f];
-
- if (chain)
- value += ChainBonus[f];
-
- if (candidate)
- value += CandidateBonus[relative_rank(Us, s)];
+ 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;
+
+ int d = std::min(f, ~f);
+ safety -= ShelterWeakness[f == file_of(ksq)][d][rkUs]
+ + StormDanger
+ [f == file_of(ksq) && rkThem == relative_rank(Us, ksq) + 1 ? BlockedByKing :
+ rkUs == RANK_1 ? Unopposed :
+ rkThem == rkUs + 1 ? BlockedByPawn : Unblocked]
+ [d][rkThem];
}
- return value;
+
+ if (popcount((ourPawns & ShelterMask) | (theirPawns & StormMask)) == 5)
+ safety += Value(300);
+
+ return safety;
}
-/// PawnInfo::updateShelter() calculates and caches king shelter. It is called
-/// only when king square changes, about 20% of total king_shelter() 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 PawnInfo::updateShelter(const Position& pos, Square ksq) {
+Score Entry::do_king_safety(const Position& pos, Square ksq) {
- const int Shift = (Us == WHITE ? 8 : -8);
+ kingSquares[Us] = ksq;
+ castlingRights[Us] = pos.can_castle(Us);
+ int minKingPawnDistance = 0;
- Bitboard pawns;
- int r, shelter = 0;
+ Bitboard pawns = pos.pieces(Us, PAWN);
+ if (pawns)
+ while (!(DistanceRingBB[ksq][minKingPawnDistance++] & pawns)) {}
- if (relative_rank(Us, ksq) <= RANK_4)
- {
- pawns = pos.pieces(PAWN, Us) & this_and_neighboring_files_bb(ksq);
- r = ksq & (7 << 3);
- for (int i = 0; i < 3; i++)
- {
- r += Shift;
- shelter += BitCount8Bit[(pawns >> r) & 0xFF] * (64 >> i);
- }
- }
- kingSquares[Us] = ksq;
- kingShelters[Us] = make_score(shelter, 0);
- return kingShelters[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(MakeCastling<Us, KING_SIDE>::right))
+ bonus = std::max(bonus, shelter_storm<Us>(pos, relative_square(Us, SQ_G1)));
+
+ if (pos.can_castle(MakeCastling<Us, QUEEN_SIDE>::right))
+ bonus = std::max(bonus, shelter_storm<Us>(pos, relative_square(Us, SQ_C1)));
+
+ return make_score(bonus, -16 * minKingPawnDistance);
}
// Explicit template instantiation
-template Score PawnInfo::updateShelter<WHITE>(const Position& pos, Square ksq);
-template Score PawnInfo::updateShelter<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