/*
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) 2008-2013 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
along with this program. If not, see <http://www.gnu.org/licenses/>.
*/
-
-////
-//// Includes
-////
-
+#include <algorithm>
#include <cassert>
+#include "bitboard.h"
#include "bitcount.h"
#include "pawns.h"
#include "position.h"
-
-////
-//// Local definitions
-////
-
namespace {
- /// Constants and variables
-
- // Doubled pawn penalty by file, middle game.
- const Value DoubledPawnMidgamePenalty[8] = {
- Value(20), Value(30), Value(34), Value(34),
- Value(34), Value(34), Value(30), Value(20)
+ #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) }};
+
+ // 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) }};
+
+ // 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)
};
- // Doubled pawn penalty by file, endgame.
- const Value DoubledPawnEndgamePenalty[8] = {
- Value(35), Value(40), Value(40), Value(40),
- Value(40), Value(40), Value(40), Value(35)
+ // 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)
};
- // Isolated pawn penalty by file, middle game.
- const Value IsolatedPawnMidgamePenalty[8] = {
- Value(20), Value(30), Value(34), Value(34),
- Value(34), Value(34), Value(30), Value(20)
- };
+ // Weakness of our pawn shelter in front of the king indexed by [king pawn][rank]
+ const Value ShelterWeakness[2][RANK_NB] =
+ { { V(141), V(0), V(38), V(102), V(128), V(141), V(141) },
+ { V( 61), V(0), V(16), V( 44), V( 56), V( 61), V( 61) } };
+
+ // Danger of enemy pawns moving toward our king indexed by [pawn blocked][rank]
+ const Value StormDanger[2][RANK_NB] =
+ { { V(26), V(0), V(128), V(51), V(26) },
+ { V(13), 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.
+ const Value MaxSafetyBonus = V(263);
+
+ #undef S
+ #undef V
+
+ template<Color Us>
+ Score evaluate(const Position& pos, Pawns::Entry* e) {
+
+ const Color Them = (Us == WHITE ? BLACK : WHITE);
+ const Square Up = (Us == WHITE ? DELTA_N : DELTA_S);
+ const Square Right = (Us == WHITE ? DELTA_NE : DELTA_SW);
+ const Square Left = (Us == WHITE ? DELTA_NW : DELTA_SE);
+
+ Bitboard b;
+ Square s;
+ File f;
+ Rank r;
+ bool passed, isolated, doubled, opposed, chain, backward, candidate;
+ Score value = SCORE_ZERO;
+ const Square* pl = pos.list<PAWN>(Us);
+
+ Bitboard ourPawns = pos.pieces(Us, PAWN);
+ Bitboard theirPawns = pos.pieces(Them, PAWN);
+
+ e->passedPawns[Us] = 0;
+ e->kingSquares[Us] = SQ_NONE;
+ e->semiopenFiles[Us] = 0xFF;
+ e->pawnAttacks[Us] = shift_bb<Right>(ourPawns) | shift_bb<Left>(ourPawns);
+ e->pawnsOnSquares[Us][BLACK] = popcount<Max15>(ourPawns & BlackSquares);
+ e->pawnsOnSquares[Us][WHITE] = pos.count<PAWN>(Us) - e->pawnsOnSquares[Us][BLACK];
- // Isolated pawn penalty by file, endgame.
- const Value IsolatedPawnEndgamePenalty[8] = {
- Value(35), Value(40), Value(40), Value(40),
- Value(40), Value(40), Value(40), Value(35)
- };
+ // 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));
- // Backward pawn penalty by file, middle game.
- const Value BackwardPawnMidgamePenalty[8] = {
- Value(16), Value(24), Value(27), Value(27),
- Value(27), Value(27), Value(24), Value(16)
- };
+ f = file_of(s);
+ r = rank_of(s);
- // Backward pawn penalty by file, endgame.
- const Value BackwardPawnEndgamePenalty[8] = {
- Value(28), Value(32), Value(32), Value(32),
- Value(32), Value(32), Value(32), Value(28)
- };
+ // This file cannot be semi-open
+ e->semiopenFiles[Us] &= ~(1 << f);
- // Pawn chain membership bonus by file, middle game.
- const Value ChainMidgameBonus[8] = {
- Value(14), Value(16), Value(17), Value(18),
- Value(18), Value(17), Value(16), Value(14)
- };
+ // Our rank plus previous one. Used for chain detection
+ b = rank_bb(r) | rank_bb(Us == WHITE ? r - Rank(1) : r + Rank(1));
- // Pawn chain membership bonus by file, endgame.
- const Value ChainEndgameBonus[8] = {
- Value(16), Value(16), Value(16), Value(16),
- Value(16), Value(16), Value(16), Value(16)
- };
+ // 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));
- // Candidate passed pawn bonus by rank, middle game.
- const Value CandidateMidgameBonus[8] = {
- Value( 0), Value(12), Value(12), Value(20),
- Value(40), Value(90), Value( 0), Value( 0)
- };
+ // 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 adjacent files
+ // or if can capture an enemy pawn it cannot be backward either.
+ if ( !(passed | isolated | chain)
+ && !(ourPawns & pawn_attack_span(Them, s))
+ && !(pos.attacks_from<PAWN>(s, Us) & theirPawns))
+ {
+ // We now know that there are no friendly pawns beside or behind this
+ // pawn on adjacent files. We now check whether the pawn is
+ // backward by looking in the forward direction on the adjacent
+ // files, and seeing whether we meet a friendly or an enemy pawn first.
+ b = pos.attacks_from<PAWN>(s, Us);
- // Candidate passed pawn bonus by rank, endgame.
- const Value CandidateEndgameBonus[8] = {
- Value( 0), Value(24), Value(24), Value(40),
- Value(80), Value(180), Value(0), Value( 0)
- };
+ // 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)))
+ b = shift_bb<Up>(b);
- // Pawn storm tables for positions with opposite castling:
- const int QStormTable[64] = {
- 0, 0, 0, 0, 0, 0, 0, 0,
- -22,-22,-22,-13,-4, 0, 0, 0,
- -4, -9, -9, -9,-4, 0, 0, 0,
- 9, 18, 22, 18, 9, 0, 0, 0,
- 22, 31, 31, 22, 0, 0, 0, 0,
- 31, 40, 40, 31, 0, 0, 0, 0,
- 31, 40, 40, 31, 0, 0, 0, 0,
- 0, 0, 0, 0, 0, 0, 0, 0
- };
+ // 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 | shift_bb<Up>(b)) & theirPawns;
+ }
- const int KStormTable[64] = {
- 0, 0, 0, 0, 0, 0, 0, 0,
- 0, 0, 0,-4,-13,-22,-27,-27,
- 0, 0, 0,-4, -9,-13,-18,-18,
- 0, 0, 0, 0, 9, 9, 9, 9,
- 0, 0, 0, 0, 9, 18, 27, 27,
- 0, 0, 0, 0, 9, 27, 40, 36,
- 0, 0, 0, 0, 0, 31, 40, 31,
- 0, 0, 0, 0, 0, 0, 0, 0
- };
+ assert(opposed | passed | (pawn_attack_span(Us, s) & theirPawns));
- // Pawn storm open file bonuses by file
- const int16_t KStormOpenFileBonus[8] = { 45, 45, 30, 0, 0, 0, 0, 0 };
- const int16_t QStormOpenFileBonus[8] = { 0, 0, 0, 0, 0, 30, 45, 30 };
+ // 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);
- // Pawn storm lever bonuses by file
- const int StormLeverBonus[8] = { 20, 20, 10, 0, 0, 10, 20, 20 };
+ // 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)
+ e->passedPawns[Us] |= s;
-}
+ // Score this pawn
+ if (isolated)
+ value -= Isolated[opposed][f];
+ if (doubled)
+ value -= Doubled[opposed][f];
-////
-//// Functions
-////
+ if (backward)
+ value -= Backward[opposed][f];
-/// Constructor
+ if (chain)
+ value += ChainMember[f];
-PawnInfoTable::PawnInfoTable(unsigned numOfEntries) {
+ if (candidate)
+ value += CandidatePassed[relative_rank(Us, s)];
+ }
- size = numOfEntries;
- entries = new PawnInfo[size];
- if (entries == NULL)
- {
- std::cerr << "Failed to allocate " << (numOfEntries * sizeof(PawnInfo))
- << " bytes for pawn hash table." << std::endl;
- Application::exit_with_failure();
+ return value;
}
-}
+} // namespace
-/// Destructor
+namespace Pawns {
-PawnInfoTable::~PawnInfoTable() {
- delete [] entries;
-}
+/// 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.
+Entry* probe(const Position& pos, Table& entries) {
-/// 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.
+ Key key = pos.pawn_key();
+ Entry* e = entries[key];
-PawnInfo *PawnInfoTable::get_pawn_info(const Position &pos) {
+ if (e->key == key)
+ return e;
+
+ e->key = key;
+ e->value = evaluate<WHITE>(pos, e) - evaluate<BLACK>(pos, e);
+ return e;
+}
- assert(pos.is_ok());
- Key key = pos.get_pawn_key();
- int index = int(key & (size - 1));
- PawnInfo *pi = entries + index;
+/// Entry::shelter_storm() calculates shelter and storm penalties for the file
+/// the king is on, as well as the two adjacent files.
- // 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;
+template<Color Us>
+Value Entry::shelter_storm(const Position& pos, Square ksq) {
- // Clear the PawnInfo object, and set the key
- pi->clear();
- pi->key = key;
+ const Color Them = (Us == WHITE ? BLACK : WHITE);
- Value mgValue[2] = {Value(0), Value(0)};
- Value egValue[2] = {Value(0), Value(0)};
+ Value safety = MaxSafetyBonus;
+ Bitboard b = pos.pieces(PAWN) & (in_front_bb(Us, rank_of(ksq)) | rank_bb(ksq));
+ Bitboard ourPawns = b & pos.pieces(Us) & ~rank_bb(ksq);
+ Bitboard theirPawns = b & pos.pieces(Them);
+ Rank rkUs, rkThem;
+ File kf = file_of(ksq);
- // Loop through the pawns for both colors
- for (Color us = WHITE; us <= BLACK; us++)
+ kf = (kf == FILE_A) ? FILE_B : (kf == FILE_H) ? FILE_G : kf;
+
+ for (int f = kf - 1; f <= kf + 1; f++)
{
- Color them = opposite_color(us);
- Bitboard ourPawns = pos.pawns(us);
- Bitboard theirPawns = pos.pawns(them);
- Bitboard pawns = ourPawns;
- int bonus;
-
- // Initialize pawn storm scores by giving bonuses for open files
- for (File f = FILE_A; f <= FILE_H; f++)
- if (pos.file_is_half_open(us, f))
- {
- pi->ksStormValue[us] += KStormOpenFileBonus[f];
- pi->qsStormValue[us] += QStormOpenFileBonus[f];
- }
+ // Shelter penalty is higher for the pawn in front of the king
+ b = ourPawns & FileBB[f];
+ rkUs = b ? rank_of(Us == WHITE ? lsb(b) : ~msb(b)) : RANK_1;
+ safety -= ShelterWeakness[f != kf][rkUs];
+
+ // Storm danger is smaller if enemy pawn is blocked
+ b = theirPawns & FileBB[f];
+ rkThem = b ? rank_of(Us == WHITE ? lsb(b) : ~msb(b)) : RANK_1;
+ safety -= StormDanger[rkThem == rkUs + 1][rkThem];
+ }
- // Loop through all pawns of the current color and score each pawn
- while (pawns)
- {
- bool passed, doubled, isolated, backward, chain, candidate;
- 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));
-
- // The file containing the pawn is not half open
- pi->halfOpenFiles[us] &= ~(1 << f);
-
- // Passed, isolated or doubled pawn?
- passed = pos.pawn_is_passed(us, s);
- isolated = pos.pawn_is_isolated(us, s);
- doubled = pos.pawn_is_doubled(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
- 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;
+ return safety;
+}
- // 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.
- chain = ourPawns
- & neighboring_files_bb(f)
- & (rank_bb(r) | rank_bb(r - (us == WHITE ? 1 : -1)));
+/// 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.
- // 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.
- if ( passed
- || isolated
- || chain
- || (pos.pawn_attacks(us, s) & theirPawns)
- || (ourPawns & behind_bb(us, r) & neighboring_files_bb(f)))
- 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;
- if (us == WHITE)
- {
- for (b = pos.pawn_attacks(us, s); !(b & (ourPawns | theirPawns)); b <<= 8);
- backward = (b | (b << 8)) & theirPawns;
- }
- else
- {
- for (b = pos.pawn_attacks(us, s); !(b & (ourPawns | theirPawns)); b >>= 8);
- backward = (b | (b >> 8)) & theirPawns;
- }
- }
+template<Color Us>
+Score Entry::update_safety(const Position& pos, Square ksq) {
- // Test for candidate passed pawn
- candidate = !passed
- && pos.file_is_half_open(them, 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);
-
- // 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)))
- {
- // candidate = true;
- passed = false;
- }
+ kingSquares[Us] = ksq;
+ castleRights[Us] = pos.can_castle(Us);
+ minKPdistance[Us] = 0;
- // Score this pawn
- Value mv = Value(0), ev = Value(0);
- if (isolated)
- {
- mv -= IsolatedPawnMidgamePenalty[f];
- ev -= IsolatedPawnEndgamePenalty[f];
- if (pos.file_is_half_open(them, f))
- {
- mv -= IsolatedPawnMidgamePenalty[f] / 2;
- ev -= IsolatedPawnEndgamePenalty[f] / 2;
- }
- }
- if (doubled)
- {
- mv -= DoubledPawnMidgamePenalty[f];
- ev -= DoubledPawnEndgamePenalty[f];
- }
- if (backward)
- {
- mv -= BackwardPawnMidgamePenalty[f];
- ev -= BackwardPawnEndgamePenalty[f];
- if (pos.file_is_half_open(them, f))
- {
- mv -= BackwardPawnMidgamePenalty[f] / 2;
- ev -= BackwardPawnEndgamePenalty[f] / 2;
- }
- }
- if (chain)
- {
- mv += ChainMidgameBonus[f];
- ev += ChainEndgameBonus[f];
- }
- if (candidate)
- {
- mv += CandidateMidgameBonus[relative_rank(us, s)];
- ev += CandidateEndgameBonus[relative_rank(us, s)];
- }
+ Bitboard pawns = pos.pieces(Us, PAWN);
+ if (pawns)
+ while (!(DistanceRingsBB[ksq][minKPdistance[Us]++] & pawns)) {}
- mgValue[us] += mv;
- egValue[us] += ev;
+ if (relative_rank(Us, ksq) > RANK_4)
+ return kingSafety[Us] = make_score(0, -16 * minKPdistance[Us]);
- // If the pawn is passed, set the square of the pawn in the passedPawns
- // bitboard
- if (passed)
- set_bit(&(pi->passedPawns), s);
- } // while(pawns)
- } // for(colors)
+ Value bonus = shelter_storm<Us>(pos, ksq);
- pi->mgValue = int16_t(mgValue[WHITE] - mgValue[BLACK]);
- pi->egValue = int16_t(egValue[WHITE] - egValue[BLACK]);
- return pi;
+ // If we can castle use the bonus after the castle if is bigger
+ if (pos.can_castle(make_castle_right(Us, KING_SIDE)))
+ bonus = std::max(bonus, shelter_storm<Us>(pos, relative_square(Us, SQ_G1)));
+
+ if (pos.can_castle(make_castle_right(Us, QUEEN_SIDE)))
+ bonus = std::max(bonus, shelter_storm<Us>(pos, relative_square(Us, SQ_C1)));
+
+ return kingSafety[Us] = 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);
+
+} // namespace Pawns
projects / stockfish / blobdiff