+++ /dev/null
-/*
- Stockfish, a UCI chess playing engine derived from Glaurung 2.1
- Copyright (C) 2004-2008 Tord Romstad (Glaurung author)
- 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
- the Free Software Foundation, either version 3 of the License, or
- (at your option) any later version.
-
- Stockfish is distributed in the hope that it will be useful,
- but WITHOUT ANY WARRANTY; without even the implied warranty of
- MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
- GNU General Public License for more details.
-
- You should have received a copy of the GNU General Public License
- along with this program. If not, see <http://www.gnu.org/licenses/>.
-*/
-
-#include <algorithm>
-#include <cassert>
-
-#include "bitboard.h"
-#include "pawns.h"
-#include "position.h"
-#include "thread.h"
-
-namespace {
-
- #define V Value
- #define S(mg, eg) make_score(mg, eg)
-
- // 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) } }
- };
-
- // 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() {
-
- 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);
- }
-}
-
-
-/// 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) {
-
- Key key = pos.pawn_key();
- Entry* e = pos.this_thread()->pawnsTable[key];
-
- if (e->key == key)
- return e;
-
- 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]));
-
- return e;
-}
-
-
-/// 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>
-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)
- {
- 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];
- }
-
- if (popcount((ourPawns & ShelterMask) | (theirPawns & StormMask)) == 5)
- safety += Value(300);
-
- return safety;
-}
-
-
-/// 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::do_king_safety(const Position& pos, Square ksq) {
-
- kingSquares[Us] = ksq;
- castlingRights[Us] = pos.can_castle(Us);
- int minKingPawnDistance = 0;
-
- Bitboard pawns = pos.pieces(Us, PAWN);
- if (pawns)
- while (!(DistanceRingBB[ksq][minKingPawnDistance++] & pawns)) {}
-
- 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 Entry::do_king_safety<WHITE>(const Position& pos, Square ksq);
-template Score Entry::do_king_safety<BLACK>(const Position& pos, Square ksq);
-
-} // namespace Pawns