X-Git-Url: https://git.sesse.net/?a=blobdiff_plain;f=src%2Fpawns.cpp;h=70fb6f23782a3ef7cce021f22258bc18a60791c9;hb=HEAD;hp=7edaa6e1bb786bfa42ff341352f3d153b280e417;hpb=95ba7f78d5e025499ec8124e37e9f3b769660e4a;p=stockfish
diff --git a/src/pawns.cpp b/src/pawns.cpp
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-/*
- 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) 2015-2019 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
- 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 .
-*/
-
-#include
-
-#include "bitboard.h"
-#include "pawns.h"
-#include "position.h"
-#include "thread.h"
-
-namespace {
-
- #define V Value
- #define S(mg, eg) make_score(mg, eg)
-
- // Pawn penalties
- constexpr Score Backward = S( 9, 24);
- constexpr Score Doubled = S(11, 56);
- constexpr Score Isolated = S( 5, 15);
-
- // Connected pawn bonus
- constexpr int Connected[RANK_NB] = { 0, 13, 24, 18, 65, 100, 175, 330 };
-
- // 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) }
- };
-
- // 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.
- constexpr Value UnblockedStorm[int(FILE_NB) / 2][RANK_NB] = {
- { V( 89), V(107), V(123), 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) }
- };
-
- #undef S
- #undef V
-
- template
- Score evaluate(const Position& pos, Pawns::Entry* e) {
-
- constexpr Color Them = (Us == WHITE ? BLACK : WHITE);
- constexpr Direction Up = (Us == WHITE ? NORTH : SOUTH);
-
- Bitboard b, neighbours, stoppers, doubled, support, phalanx;
- Bitboard lever, leverPush;
- Square s;
- bool opposed, backward;
- Score score = SCORE_ZERO;
- const Square* pl = pos.squares(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(ourPawns);
- e->pawnsOnSquares[Us][BLACK] = popcount(ourPawns & DarkSquares);
- e->pawnsOnSquares[Us][WHITE] = pos.count(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_span(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);
- 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 be safely advanced.
- backward = !(ourPawns & pawn_attack_span(Them, s + Up))
- && (stoppers & (leverPush | (s + Up)));
-
- // 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)
- && (support || !more_than_one(lever))
- && popcount(phalanx) >= popcount(leverPush))
- e->passedPawns[Us] |= s;
-
- else if ( stoppers == square_bb(s + Up)
- && relative_rank(Us, s) >= RANK_5)
- {
- b = shift(support) & ~theirPawns;
- while (b)
- if (!more_than_one(theirPawns & PawnAttacks[Us][pop_lsb(&b)]))
- e->passedPawns[Us] |= s;
- }
-
- // Score this pawn
- if (support | phalanx)
- {
- int r = relative_rank(Us, s);
- int v = phalanx ? Connected[r] + Connected[r + 1] : 2 * Connected[r];
- v = 17 * popcount(support) + (v >> (opposed + 1));
- score += make_score(v, v * (r - 2) / 4);
- }
- else if (!neighbours)
- score -= Isolated, e->weakUnopposed[Us] += !opposed;
-
- else if (backward)
- score -= Backward, e->weakUnopposed[Us] += !opposed;
-
- if (doubled && !support)
- score -= Doubled;
- }
-
- return score;
- }
-
-} // namespace
-
-namespace Pawns {
-
-/// 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(pos, e);
- e->scores[BLACK] = evaluate(pos, e);
- e->passedCount= popcount(e->passedPawns[WHITE] | e->passedPawns[BLACK]);
-
- return e;
-}
-
-
-/// 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
-Value Entry::evaluate_shelter(const Position& pos, Square ksq) {
-
- constexpr Color Them = (Us == WHITE ? BLACK : WHITE);
- constexpr Direction Down = (Us == WHITE ? SOUTH : NORTH);
- constexpr Bitboard BlockRanks = (Us == WHITE ? Rank1BB | Rank2BB : Rank8BB | Rank7BB);
-
- Bitboard b = pos.pieces(PAWN) & ~forward_ranks_bb(Them, ksq);
- Bitboard ourPawns = b & pos.pieces(Us);
- Bitboard theirPawns = b & pos.pieces(Them);
-
- Value safety = (shift(theirPawns) & (FileABB | FileHBB) & BlockRanks & ksq) ?
- Value(374) : Value(5);
-
- 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);
- Rank ourRank = b ? relative_rank(Us, backmost_sq(Us, b)) : RANK_1;
-
- b = theirPawns & file_bb(f);
- Rank theirRank = b ? relative_rank(Us, frontmost_sq(Them, b)) : RANK_1;
-
- int d = std::min(f, ~f);
- safety += ShelterStrength[d][ourRank];
- safety -= (ourRank && (ourRank == theirRank - 1)) ? 66 * (theirRank == RANK_3)
- : UnblockedStorm[d][theirRank];
- }
-
- 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
-Score Entry::do_king_safety(const Position& pos) {
-
- Square ksq = pos.square(Us);
- kingSquares[Us] = ksq;
- castlingRights[Us] = pos.castling_rights(Us);
- int minKingPawnDistance = 0;
-
- Bitboard pawns = pos.pieces(Us, PAWN);
- if (pawns)
- while (!(DistanceRingBB[ksq][++minKingPawnDistance] & pawns)) {}
-
- Value bonus = evaluate_shelter(pos, ksq);
-
- // If we can castle use the bonus after the castling if it is bigger
- if (pos.can_castle(Us | KING_SIDE))
- bonus = std::max(bonus, evaluate_shelter(pos, relative_square(Us, SQ_G1)));
-
- if (pos.can_castle(Us | QUEEN_SIDE))
- bonus = std::max(bonus, evaluate_shelter(pos, relative_square(Us, SQ_C1)));
-
- return make_score(bonus, -16 * minKingPawnDistance);
-}
-
-// Explicit template instantiation
-template Score Entry::do_king_safety(const Position& pos);
-template Score Entry::do_king_safety(const Position& pos);
-
-} // namespace Pawns