/*
Stockfish, a UCI chess playing engine derived from Glaurung 2.1
Copyright (C) 2004-2008 Tord Romstad (Glaurung author)
- Copyright (C) 2008-2009 Marco Costalba
+ Copyright (C) 2008-2015 Marco Costalba, Joona Kiiski, Tord Romstad
+ Copyright (C) 2015-2019 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/>.
*/
-
-////
-//// Includes
-////
-
+#include <algorithm>
#include <cassert>
-#include <cstring>
-#include "bitcount.h"
+#include "bitboard.h"
#include "pawns.h"
#include "position.h"
-
-
-////
-//// Local definitions
-////
+#include "thread.h"
namespace {
- /// Constants and variables
-
- // Doubled pawn penalty by file, middle game
- const Value DoubledPawnMidgamePenalty[8] = {
- Value(13), Value(20), Value(23), Value(23),
- Value(23), Value(23), Value(20), Value(13)
+ #define V Value
+ #define S(mg, eg) make_score(mg, eg)
+
+ // Pawn penalties
+ constexpr Score Backward = S( 9, 24);
+ constexpr Score BlockedStorm = S(82, 82);
+ constexpr Score Doubled = S(11, 56);
+ constexpr Score Isolated = S( 5, 15);
+ constexpr Score WeakLever = S( 0, 56);
+ constexpr Score WeakUnopposed = S(13, 27);
+
+ // Connected pawn bonus
+ constexpr int Connected[RANK_NB] = { 0, 7, 8, 12, 29, 48, 86 };
+
+ // Strength of pawn shelter for our king by [distance from edge][rank].
+ // RANK_1 = 0 is used for files where we have no pawn, or pawn is behind our king.
+ constexpr Value ShelterStrength[int(FILE_NB) / 2][RANK_NB] = {
+ { V( -6), V( 81), V( 93), V( 58), V( 39), V( 18), V( 25) },
+ { V(-43), V( 61), V( 35), V(-49), V(-29), V(-11), V( -63) },
+ { V(-10), V( 75), V( 23), V( -2), V( 32), V( 3), V( -45) },
+ { V(-39), V(-13), V(-29), V(-52), V(-48), V(-67), V(-166) }
};
- // Doubled pawn penalty by file, endgame
- const Value DoubledPawnEndgamePenalty[8] = {
- Value(43), Value(48), Value(48), Value(48),
- Value(48), Value(48), Value(48), Value(43)
+ // Danger of enemy pawns moving toward our king by [distance from edge][rank].
+ // RANK_1 = 0 is used for files where the enemy has no pawn, or their pawn
+ // is behind our king. Note that UnblockedStorm[0][1-2] accommodate opponent pawn
+ // on edge, likely blocked by our king.
+ constexpr Value UnblockedStorm[int(FILE_NB) / 2][RANK_NB] = {
+ { V( 89), V(-285), V(-185), V(93), V(57), V( 45), V( 51) },
+ { V( 44), V( -18), V( 123), V(46), V(39), V( -7), V( 23) },
+ { V( 4), V( 52), V( 162), V(37), V( 7), V(-14), V( -2) },
+ { V(-10), V( -14), V( 90), V(15), V( 2), V( -7), V(-16) }
};
- // Isolated pawn penalty by file, middle game
- const Value IsolatedPawnMidgamePenalty[8] = {
- Value(25), Value(36), Value(40), Value(40),
- Value(40), Value(40), Value(36), Value(25)
- };
+ #undef S
+ #undef V
- // Isolated pawn penalty by file, endgame
- const Value IsolatedPawnEndgamePenalty[8] = {
- Value(30), Value(35), Value(35), Value(35),
- Value(35), Value(35), Value(35), Value(30)
- };
+ template<Color Us>
+ Score evaluate(const Position& pos, Pawns::Entry* e) {
- // Backward pawn penalty by file, middle game
- const Value BackwardPawnMidgamePenalty[8] = {
- Value(20), Value(29), Value(33), Value(33),
- Value(33), Value(33), Value(29), Value(20)
- };
+ constexpr Color Them = (Us == WHITE ? BLACK : WHITE);
+ constexpr Direction Up = (Us == WHITE ? NORTH : SOUTH);
- // Backward pawn penalty by file, endgame
- const Value BackwardPawnEndgamePenalty[8] = {
- Value(28), Value(31), Value(31), Value(31),
- Value(31), Value(31), Value(31), Value(28)
- };
+ Bitboard neighbours, stoppers, support, phalanx, opposed;
+ Bitboard lever, leverPush;
+ Square s;
+ bool backward, passed, doubled;
+ Score score = SCORE_ZERO;
+ const Square* pl = pos.squares<PAWN>(Us);
- // Pawn chain membership bonus by file, middle game
- const Value ChainMidgameBonus[8] = {
- Value(11), Value(13), Value(13), Value(14),
- Value(14), Value(13), Value(13), Value(11)
- };
+ Bitboard ourPawns = pos.pieces( Us, PAWN);
+ Bitboard theirPawns = pos.pieces(Them, PAWN);
- // Pawn chain membership bonus by file, endgame
- const Value ChainEndgameBonus[8] = {
- Value(-1), Value(-1), Value(-1), Value(-1),
- Value(-1), Value(-1), Value(-1), Value(-1)
- };
+ Bitboard doubleAttackThem = pawn_double_attacks_bb<Them>(theirPawns);
- // Candidate passed pawn bonus by rank, middle game
- const Value CandidateMidgameBonus[8] = {
- Value( 0), Value( 6), Value(6), Value(14),
- Value(34), Value(83), Value(0), Value( 0)
- };
+ e->passedPawns[Us] = e->pawnAttacksSpan[Us] = 0;
+ e->kingSquares[Us] = SQ_NONE;
+ e->pawnAttacks[Us] = pawn_attacks_bb<Us>(ourPawns);
- // Candidate passed pawn bonus by rank, endgame
- const Value CandidateEndgameBonus[8] = {
- Value( 0), Value( 13), Value(13), Value(29),
- Value(68), Value(166), Value( 0), Value( 0)
- };
+ // 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));
+
+ Rank r = relative_rank(Us, s);
+
+ // Flag the pawn
+ opposed = theirPawns & forward_file_bb(Us, s);
+ stoppers = theirPawns & passed_pawn_span(Us, s);
+ lever = theirPawns & PawnAttacks[Us][s];
+ leverPush = theirPawns & PawnAttacks[Us][s + Up];
+ doubled = ourPawns & (s - Up);
+ neighbours = ourPawns & adjacent_files_bb(s);
+ phalanx = neighbours & rank_bb(s);
+ support = 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 safely advance. Phalanx and isolated
+ // pawns will be excluded when the pawn is scored.
+ backward = !(neighbours & forward_ranks_bb(Them, s))
+ && (stoppers & (leverPush | (s + Up)));
+
+ // Span of backward pawns and span behind opposing pawns are not included
+ // in the pawnAttacksSpan bitboard.
+ if (!backward || phalanx)
+ {
+ if (opposed)
+ e->pawnAttacksSpan[Us] |= pawn_attack_span(Us, s) &
+ ~pawn_attack_span(Us, frontmost_sq(Them, opposed));
+ else
+ e->pawnAttacksSpan[Us] |= pawn_attack_span(Us, s);
+ }
- // Pawn storm tables for positions with opposite castling
- const int QStormTable[64] = {
- 0, 0, 0, 0, 0, 0, 0, 0,
- -22,-22,-22,-14,-6, 0, 0, 0,
- -6,-10,-10,-10,-6, 0, 0, 0,
- 4, 12, 16, 12, 4, 0, 0, 0,
- 16, 23, 23, 16, 0, 0, 0, 0,
- 23, 31, 31, 23, 0, 0, 0, 0,
- 23, 31, 31, 23, 0, 0, 0, 0,
- 0, 0, 0, 0, 0, 0, 0, 0
- };
+ // A pawn is passed if one of the three following conditions is true:
+ // (a) there is no stoppers except some levers
+ // (b) the only stoppers are the leverPush, but we outnumber them
+ // (c) there is only one front stopper which can be levered.
+ passed = !(stoppers ^ lever)
+ || ( !(stoppers ^ leverPush)
+ && popcount(phalanx) >= popcount(leverPush))
+ || ( stoppers == square_bb(s + Up) && r >= RANK_5
+ && (shift<Up>(support) & ~(theirPawns | doubleAttackThem)));
+
+ // Passed pawns will be properly scored later in evaluation when we have
+ // full attack info.
+ if (passed)
+ e->passedPawns[Us] |= s;
- const int KStormTable[64] = {
- 0, 0, 0, 0, 0, 0, 0, 0,
- 0, 0, 0,-10,-19,-28,-33,-33,
- 0, 0, 0,-10,-15,-19,-24,-24,
- 0, 0, 0, 0, 1, 1, 1, 1,
- 0, 0, 0, 0, 1, 10, 19, 19,
- 0, 0, 0, 0, 1, 19, 31, 27,
- 0, 0, 0, 0, 0, 22, 31, 22,
- 0, 0, 0, 0, 0, 0, 0, 0
- };
+ // Score this pawn
+ if (support | phalanx)
+ {
+ int v = Connected[r] * (2 + bool(phalanx) - bool(opposed))
+ + 21 * popcount(support);
- // Pawn storm open file bonuses by file
- const int16_t KStormOpenFileBonus[8] = { 31, 31, 18, 0, 0, 0, 0, 0 };
- const int16_t QStormOpenFileBonus[8] = { 0, 0, 0, 0, 0, 26, 42, 26 };
+ score += make_score(v, v * (r - 2) / 4);
+ }
- // Pawn storm lever bonuses by file
- const int StormLeverBonus[8] = { -8, -8, -13, 0, 0, -13, -8, -8 };
+ else if (!neighbours)
+ score -= Isolated
+ + WeakUnopposed * !opposed;
-}
+ else if (backward)
+ score -= Backward
+ + WeakUnopposed * !opposed;
+ if (!support)
+ score -= Doubled * doubled
+ + WeakLever * more_than_one(lever);
+ }
-////
-//// Functions
-////
+ return score;
+ }
-/// Constructor
+} // namespace
-PawnInfoTable::PawnInfoTable(unsigned numOfEntries) {
+namespace Pawns {
- size = numOfEntries;
- entries = new PawnInfo[size];
- if (!entries)
- {
- std::cerr << "Failed to allocate " << (numOfEntries * sizeof(PawnInfo))
- << " bytes for pawn hash table." << std::endl;
- Application::exit_with_failure();
- }
-}
+/// 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.
+Entry* probe(const Position& pos) {
-/// Destructor
+ Key key = pos.pawn_key();
+ Entry* e = pos.this_thread()->pawnsTable[key];
-PawnInfoTable::~PawnInfoTable() {
- delete [] entries;
-}
+ if (e->key == key)
+ return e;
+ e->key = key;
+ e->scores[WHITE] = evaluate<WHITE>(pos, e);
+ e->scores[BLACK] = evaluate<BLACK>(pos, e);
-/// PawnInfo::clear() resets to zero the PawnInfo entry. Note that
-/// kingSquares[] is initialized to SQ_NONE instead.
+ return e;
+}
-void PawnInfo::clear() {
- memset(this, 0, sizeof(PawnInfo));
- kingSquares[WHITE] = kingSquares[BLACK] = SQ_NONE;
-}
+/// Entry::evaluate_shelter() calculates the shelter bonus and the storm
+/// penalty for a king, looking at the king file and the two closest files.
+template<Color Us>
+Score Entry::evaluate_shelter(const Position& pos, Square ksq) {
-/// 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 a hash table, so we don't have to recompute everything when
-/// the same pawn structure occurs again.
+ constexpr Color Them = (Us == WHITE ? BLACK : WHITE);
-PawnInfo* PawnInfoTable::get_pawn_info(const Position& pos) {
+ Bitboard b = pos.pieces(PAWN) & ~forward_ranks_bb(Them, ksq);
+ Bitboard ourPawns = b & pos.pieces(Us);
+ Bitboard theirPawns = b & pos.pieces(Them);
- assert(pos.is_ok());
+ Score bonus = make_score(5, 5);
- Key key = pos.get_pawn_key();
- int index = int(key & (size - 1));
- PawnInfo* pi = entries + index;
+ File center = clamp(file_of(ksq), FILE_B, FILE_G);
+ for (File f = File(center - 1); f <= File(center + 1); ++f)
+ {
+ b = ourPawns & file_bb(f);
+ int ourRank = b ? relative_rank(Us, frontmost_sq(Them, b)) : 0;
- // 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;
+ b = theirPawns & file_bb(f);
+ int theirRank = b ? relative_rank(Us, frontmost_sq(Them, b)) : 0;
- // Clear the PawnInfo object, and set the key
- pi->clear();
- pi->key = key;
+ File d = map_to_queenside(f);
+ bonus += make_score(ShelterStrength[d][ourRank], 0);
- Value mgValue[2] = {Value(0), Value(0)};
- Value egValue[2] = {Value(0), Value(0)};
+ if (ourRank && (ourRank == theirRank - 1))
+ bonus -= BlockedStorm * int(theirRank == RANK_3);
+ else
+ bonus -= make_score(UnblockedStorm[d][theirRank], 0);
+ }
- // Calculate pawn attacks
- pi->pawnAttacks[WHITE] = ((pos.pieces(PAWN, WHITE) << 9) & ~FileABB) | ((pos.pieces(PAWN, WHITE) << 7) & ~FileHBB);
- pi->pawnAttacks[BLACK] = ((pos.pieces(PAWN, BLACK) >> 7) & ~FileABB) | ((pos.pieces(PAWN, BLACK) >> 9) & ~FileHBB);
+ return bonus;
+}
- // Loop through the pawns for both colors
- for (Color us = WHITE; us <= BLACK; us++)
- {
- Color them = opposite_color(us);
- Bitboard ourPawns = pos.pieces(PAWN, us);
- Bitboard theirPawns = pos.pieces(PAWN, them);
- Bitboard pawns = ourPawns;
-
- // Initialize pawn storm scores by giving bonuses for open files
- for (File f = FILE_A; f <= FILE_H; f++)
- if (!(pawns & file_bb(f)))
- {
- pi->ksStormValue[us] += KStormOpenFileBonus[f];
- pi->qsStormValue[us] += QStormOpenFileBonus[f];
- pi->halfOpenFiles[us] |= (1 << f);
- }
- // Loop through all pawns of the current color and score each pawn
- while (pawns)
- {
- Square s = pop_1st_bit(&pawns);
- File f = square_file(s);
- Rank r = square_rank(s);
-
- assert(pos.piece_on(s) == piece_of_color_and_type(us, PAWN));
-
- // Passed, isolated or doubled pawn?
- bool passed = Position::pawn_is_passed(theirPawns, us, s);
- bool isolated = Position::pawn_is_isolated(ourPawns, s);
- bool doubled = Position::pawn_is_doubled(ourPawns, us, s);
-
- // We calculate kingside and queenside pawn storm
- // scores for both colors. These are used when evaluating
- // middle game positions with opposite side castling.
- //
- // Each pawn is given a base score given by a piece square table
- // (KStormTable[] or QStormTable[]). Pawns which seem to have good
- // chances of creating an open file by exchanging itself against an
- // enemy pawn on an adjacent file gets an additional bonus.
-
- // Kingside pawn storms
- int bonus = KStormTable[relative_square(us, s)];
- if (f >= FILE_F)
- {
- Bitboard b = outpost_mask(us, s) & theirPawns & (FileFBB | FileGBB | FileHBB);
- while (b)
- {
- Square s2 = pop_1st_bit(&b);
- if (!(theirPawns & neighboring_files_bb(s2) & rank_bb(s2)))
- {
- // The enemy pawn has no pawn beside itself, which makes it
- // particularly vulnerable. Big bonus, especially against a
- // weakness on the rook file.
- if (square_file(s2) == FILE_H)
- bonus += 4*StormLeverBonus[f] - 8*square_distance(s, s2);
- else
- bonus += 2*StormLeverBonus[f] - 4*square_distance(s, s2);
- } else
- // There is at least one enemy pawn beside the enemy pawn we look
- // at, which means that the pawn has somewhat better chances of
- // defending itself by advancing. Smaller bonus.
- bonus += StormLeverBonus[f] - 2*square_distance(s, s2);
- }
- }
- pi->ksStormValue[us] += bonus;
+/// 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.
- // Queenside pawn storms
- bonus = QStormTable[relative_square(us, s)];
- if (f <= FILE_C)
- {
- Bitboard b = outpost_mask(us, s) & theirPawns & (FileABB | FileBBB | FileCBB);
- while (b)
- {
- Square s2 = pop_1st_bit(&b);
- if (!(theirPawns & neighboring_files_bb(s2) & rank_bb(s2)))
- {
- // The enemy pawn has no pawn beside itself, which makes it
- // particularly vulnerable. Big bonus, especially against a
- // weakness on the rook file.
- if (square_file(s2) == FILE_A)
- bonus += 4*StormLeverBonus[f] - 16*square_distance(s, s2);
- else
- bonus += 2*StormLeverBonus[f] - 8*square_distance(s, s2);
- } else
- // There is at least one enemy pawn beside the enemy pawn we look
- // at, which means that the pawn has somewhat better chances of
- // defending itself by advancing. Smaller bonus.
- bonus += StormLeverBonus[f] - 4*square_distance(s, s2);
- }
- }
- pi->qsStormValue[us] += bonus;
-
- // Member of a pawn chain (but not the backward one)? We could speed up
- // the test a little by introducing an array of masks indexed by color
- // and square for doing the test, but because everything is hashed,
- // it probably won't make any noticable difference.
- bool chain = ourPawns
- & neighboring_files_bb(f)
- & (rank_bb(r) | rank_bb(r - (us == WHITE ? 1 : -1)));
-
- // Test for backward pawn
- //
- // If the pawn is passed, isolated, or member of a pawn chain
- // it cannot be backward. If can capture an enemy pawn or if
- // there are friendly pawns behind on neighboring files it cannot
- // be backward either.
-
- bool backward;
- if ( (passed | isolated | chain)
- || (ourPawns & behind_bb(us, r) & neighboring_files_bb(f))
- || (pos.attacks_from<PAWN>(s, us) & theirPawns))
- backward = false;
- else
- {
- // 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.
- Bitboard b = pos.attacks_from<PAWN>(s, us);
- if (us == WHITE)
- {
- for ( ; !(b & (ourPawns | theirPawns)); b <<= 8);
- backward = (b | (b << 8)) & theirPawns;
- }
- else
- {
- for ( ; !(b & (ourPawns | theirPawns)); b >>= 8);
- backward = (b | (b >> 8)) & theirPawns;
- }
- }
+template<Color Us>
+Score Entry::do_king_safety(const Position& pos) {
- // Test for candidate passed pawn
- bool candidate;
- candidate = !passed
- && !(theirPawns & file_bb(f))
- && ( count_1s_max_15(neighboring_files_bb(f) & (behind_bb(us, r) | rank_bb(r)) & ourPawns)
- - count_1s_max_15(neighboring_files_bb(f) & in_front_bb(us, r) & theirPawns)
- >= 0);
+ Square ksq = pos.square<KING>(Us);
+ kingSquares[Us] = ksq;
+ castlingRights[Us] = pos.castling_rights(Us);
- // In order to prevent doubled passed pawns from receiving a too big
- // bonus, only the frontmost passed pawn on each file is considered as
- // a true passed pawn.
- if (passed && (ourPawns & squares_in_front_of(us, s)))
- passed = false;
+ Score shelters[3] = { evaluate_shelter<Us>(pos, ksq),
+ make_score(-VALUE_INFINITE, 0),
+ make_score(-VALUE_INFINITE, 0) };
- // Score this pawn
- if (passed)
- set_bit(&(pi->passedPawns), s);
+ // If we can castle use the bonus after castling if it is bigger
+ if (pos.can_castle(Us & KING_SIDE))
+ shelters[1] = evaluate_shelter<Us>(pos, relative_square(Us, SQ_G1));
- if (isolated)
- {
- mgValue[us] -= IsolatedPawnMidgamePenalty[f];
- egValue[us] -= IsolatedPawnEndgamePenalty[f];
- if (!(theirPawns & file_bb(f)))
- {
- mgValue[us] -= IsolatedPawnMidgamePenalty[f] / 2;
- egValue[us] -= IsolatedPawnEndgamePenalty[f] / 2;
- }
- }
- if (doubled)
- {
- mgValue[us] -= DoubledPawnMidgamePenalty[f];
- egValue[us] -= DoubledPawnEndgamePenalty[f];
- }
- if (backward)
- {
- mgValue[us] -= BackwardPawnMidgamePenalty[f];
- egValue[us] -= BackwardPawnEndgamePenalty[f];
- if (!(theirPawns & file_bb(f)))
- {
- mgValue[us] -= BackwardPawnMidgamePenalty[f] / 2;
- egValue[us] -= BackwardPawnEndgamePenalty[f] / 2;
- }
- }
- if (chain)
- {
- mgValue[us] += ChainMidgameBonus[f];
- egValue[us] += ChainEndgameBonus[f];
- }
- if (candidate)
- {
- mgValue[us] += CandidateMidgameBonus[relative_rank(us, s)];
- egValue[us] += CandidateEndgameBonus[relative_rank(us, s)];
- }
- } // while(pawns)
- } // for(colors)
+ if (pos.can_castle(Us & QUEEN_SIDE))
+ shelters[2] = evaluate_shelter<Us>(pos, relative_square(Us, SQ_C1));
- pi->mgValue = int16_t(mgValue[WHITE] - mgValue[BLACK]);
- pi->egValue = int16_t(egValue[WHITE] - egValue[BLACK]);
- return pi;
-}
+ for (int i : {1, 2})
+ if (mg_value(shelters[i]) > mg_value(shelters[0]))
+ shelters[0] = shelters[i];
+ // In endgame we like to bring our king near our closest pawn
+ Bitboard pawns = pos.pieces(Us, PAWN);
+ int minPawnDist = pawns ? 8 : 0;
-/// PawnInfo::updateShelter calculates and caches king shelter. It is called
-/// only when king square changes, about 20% of total get_king_shelter() calls.
-int PawnInfo::updateShelter(const Position& pos, Color c, Square ksq) {
+ if (pawns & PseudoAttacks[KING][ksq])
+ minPawnDist = 1;
+ else while (pawns)
+ minPawnDist = std::min(minPawnDist, distance(ksq, pop_lsb(&pawns)));
- unsigned shelter = 0;
- Bitboard pawns = pos.pieces(PAWN, c) & this_and_neighboring_files_bb(ksq);
- unsigned r = ksq & (7 << 3);
- for (int i = 1, k = (c ? -8 : 8); i < 4; i++)
- {
- r += k;
- shelter += BitCount8Bit[(pawns >> r) & 0xFF] * (128 >> i);
- }
- kingSquares[c] = ksq;
- kingShelters[c] = shelter;
- return shelter;
+ return shelters[0] - make_score(0, 16 * minPawnDist);
}
+
+// Explicit template instantiation
+template Score Entry::do_king_safety<WHITE>(const Position& pos);
+template Score Entry::do_king_safety<BLACK>(const Position& pos);
+
+} // namespace Pawns
projects / stockfish / blobdiff