+++ /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) 2015-2020 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)
-
- // Pawn penalties
- constexpr Score Backward = S( 9, 24);
- constexpr Score Doubled = S(11, 56);
- constexpr Score Isolated = S( 5, 15);
- constexpr Score WeakLever = S( 0, 56);
- constexpr Score WeakUnopposed = S(13, 27);
-
- constexpr Score BlockedStorm[RANK_NB] = {S( 0, 0), S( 0, 0), S( 76, 78), S(-10, 15), S(-7, 10), S(-4, 6), S(-1, 2)};
-
- // 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) }
- };
-
- // 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( 85), V(-289), V(-166), V(97), V(50), V( 45), V( 50) },
- { V( 46), V( -25), V( 122), V(45), V(37), V(-10), V( 20) },
- { V( -6), V( 51), V( 168), V(34), V(-2), V(-22), V(-14) },
- { V(-15), V( -11), V( 101), V( 4), V(11), V(-15), V(-29) }
- };
-
- #undef S
- #undef V
-
- template<Color Us>
- Score evaluate(const Position& pos, Pawns::Entry* e) {
-
- constexpr Color Them = ~Us;
- constexpr Direction Up = pawn_push(Us);
-
- Bitboard neighbours, stoppers, support, phalanx, opposed;
- Bitboard lever, leverPush, blocked;
- Square s;
- bool backward, passed, doubled;
- Score score = SCORE_ZERO;
- const Square* pl = pos.squares<PAWN>(Us);
-
- Bitboard ourPawns = pos.pieces( Us, PAWN);
- Bitboard theirPawns = pos.pieces(Them, PAWN);
-
- Bitboard doubleAttackThem = pawn_double_attacks_bb<Them>(theirPawns);
-
- e->passedPawns[Us] = 0;
- e->kingSquares[Us] = SQ_NONE;
- e->pawnAttacks[Us] = e->pawnAttacksSpan[Us] = pawn_attacks_bb<Us>(ourPawns);
- e->blockedCount += popcount(shift<Up>(ourPawns) & (theirPawns | doubleAttackThem));
-
- // 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);
- blocked = theirPawns & (s + Up);
- stoppers = theirPawns & passed_pawn_span(Us, s);
- lever = theirPawns & pawn_attacks_bb(Us, s);
- leverPush = theirPawns & pawn_attacks_bb(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.
- backward = !(neighbours & forward_ranks_bb(Them, s + Up))
- && (leverPush | blocked);
-
- // Compute additional span if pawn is not backward nor blocked
- if (!backward && !blocked)
- e->pawnAttacksSpan[Us] |= pawn_attack_span(Us, s);
-
- // 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.
- // (Refined in Evaluation::passed)
- passed = !(stoppers ^ lever)
- || ( !(stoppers ^ leverPush)
- && popcount(phalanx) >= popcount(leverPush))
- || ( stoppers == blocked && r >= RANK_5
- && (shift<Up>(support) & ~(theirPawns | doubleAttackThem)));
-
- passed &= !(forward_file_bb(Us, s) & ourPawns);
-
- // Passed pawns will be properly scored later in evaluation when we have
- // full attack info.
- if (passed)
- e->passedPawns[Us] |= s;
-
- // Score this pawn
- if (support | phalanx)
- {
- int v = Connected[r] * (4 + 2 * bool(phalanx) - 2 * bool(opposed) - bool(blocked)) / 2
- + 21 * popcount(support);
-
- score += make_score(v, v * (r - 2) / 4);
- }
-
- else if (!neighbours)
- {
- score -= Isolated
- + WeakUnopposed * !opposed;
-
- if ( (ourPawns & forward_file_bb(Them, s))
- && popcount(opposed) == 1
- && !(theirPawns & adjacent_files_bb(s)))
- score -= Doubled;
- }
-
- else if (backward)
- score -= Backward
- + WeakUnopposed * !opposed;
-
- if (!support)
- score -= Doubled * doubled
- + WeakLever * more_than_one(lever);
- }
-
- 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->blockedCount = 0;
- e->scores[WHITE] = evaluate<WHITE>(pos, e);
- e->scores[BLACK] = evaluate<BLACK>(pos, e);
-
- 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<Color Us>
-Score Entry::evaluate_shelter(const Position& pos, Square ksq) {
-
- constexpr Color Them = ~Us;
-
- Bitboard b = pos.pieces(PAWN) & ~forward_ranks_bb(Them, ksq);
- Bitboard ourPawns = b & pos.pieces(Us) & ~pawnAttacks[Them];
- Bitboard theirPawns = b & pos.pieces(Them);
-
- Score bonus = make_score(5, 5);
-
- File center = Utility::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;
-
- b = theirPawns & file_bb(f);
- int theirRank = b ? relative_rank(Us, frontmost_sq(Them, b)) : 0;
-
- int d = edge_distance(f);
- bonus += make_score(ShelterStrength[d][ourRank], 0);
-
- if (ourRank && (ourRank == theirRank - 1))
- bonus -= BlockedStorm[theirRank];
- else
- bonus -= make_score(UnblockedStorm[d][theirRank], 0);
- }
-
- return 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.
-
-template<Color Us>
-Score Entry::do_king_safety(const Position& pos) {
-
- Square ksq = pos.square<KING>(Us);
- kingSquares[Us] = ksq;
- castlingRights[Us] = pos.castling_rights(Us);
- auto compare = [](Score a, Score b) { return mg_value(a) < mg_value(b); };
-
- Score shelter = evaluate_shelter<Us>(pos, ksq);
-
- // If we can castle use the bonus after castling if it is bigger
-
- if (pos.can_castle(Us & KING_SIDE))
- shelter = std::max(shelter, evaluate_shelter<Us>(pos, relative_square(Us, SQ_G1)), compare);
-
- if (pos.can_castle(Us & QUEEN_SIDE))
- shelter = std::max(shelter, evaluate_shelter<Us>(pos, relative_square(Us, SQ_C1)), compare);
-
- // In endgame we like to bring our king near our closest pawn
- Bitboard pawns = pos.pieces(Us, PAWN);
- int minPawnDist = 6;
-
- if (pawns & attacks_bb<KING>(ksq))
- minPawnDist = 1;
- else while (pawns)
- minPawnDist = std::min(minPawnDist, distance(ksq, pop_lsb(&pawns)));
-
- return shelter - 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