mirror of
https://github.com/sockspls/badfish
synced 2025-04-30 00:33:09 +00:00
87586b3d0c
- "discovered check" (instead of "discovery check") - "en passant" (instead of "en-passant") - "pseudo-legal" before a noun (instead of "pseudo legal") - "3-fold" (instead of "3fold") closes https://github.com/official-stockfish/Stockfish/pull/3294 No functional change.
265 lines
8.7 KiB
C++
265 lines
8.7 KiB
C++
/*
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Stockfish, a UCI chess playing engine derived from Glaurung 2.1
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Copyright (C) 2004-2021 The Stockfish developers (see AUTHORS file)
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Stockfish is free software: you can redistribute it and/or modify
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it under the terms of the GNU General Public License as published by
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the Free Software Foundation, either version 3 of the License, or
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(at your option) any later version.
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Stockfish is distributed in the hope that it will be useful,
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but WITHOUT ANY WARRANTY; without even the implied warranty of
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MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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GNU General Public License for more details.
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You should have received a copy of the GNU General Public License
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along with this program. If not, see <http://www.gnu.org/licenses/>.
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*/
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#include <cassert>
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#include "movepick.h"
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namespace {
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enum Stages {
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MAIN_TT, CAPTURE_INIT, GOOD_CAPTURE, REFUTATION, QUIET_INIT, QUIET, BAD_CAPTURE,
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EVASION_TT, EVASION_INIT, EVASION,
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PROBCUT_TT, PROBCUT_INIT, PROBCUT,
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QSEARCH_TT, QCAPTURE_INIT, QCAPTURE, QCHECK_INIT, QCHECK
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};
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// partial_insertion_sort() sorts moves in descending order up to and including
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// a given limit. The order of moves smaller than the limit is left unspecified.
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void partial_insertion_sort(ExtMove* begin, ExtMove* end, int limit) {
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for (ExtMove *sortedEnd = begin, *p = begin + 1; p < end; ++p)
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if (p->value >= limit)
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{
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ExtMove tmp = *p, *q;
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*p = *++sortedEnd;
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for (q = sortedEnd; q != begin && *(q - 1) < tmp; --q)
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*q = *(q - 1);
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*q = tmp;
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}
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}
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} // namespace
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/// Constructors of the MovePicker class. As arguments we pass information
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/// to help it to return the (presumably) good moves first, to decide which
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/// moves to return (in the quiescence search, for instance, we only want to
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/// search captures, promotions, and some checks) and how important good move
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/// ordering is at the current node.
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/// MovePicker constructor for the main search
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MovePicker::MovePicker(const Position& p, Move ttm, Depth d, const ButterflyHistory* mh, const LowPlyHistory* lp,
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const CapturePieceToHistory* cph, const PieceToHistory** ch, Move cm, const Move* killers, int pl)
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: pos(p), mainHistory(mh), lowPlyHistory(lp), captureHistory(cph), continuationHistory(ch),
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ttMove(ttm), refutations{{killers[0], 0}, {killers[1], 0}, {cm, 0}}, depth(d), ply(pl) {
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assert(d > 0);
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stage = (pos.checkers() ? EVASION_TT : MAIN_TT) +
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!(ttm && pos.pseudo_legal(ttm));
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}
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/// MovePicker constructor for quiescence search
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MovePicker::MovePicker(const Position& p, Move ttm, Depth d, const ButterflyHistory* mh,
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const CapturePieceToHistory* cph, const PieceToHistory** ch, Square rs)
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: pos(p), mainHistory(mh), captureHistory(cph), continuationHistory(ch), ttMove(ttm), recaptureSquare(rs), depth(d) {
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assert(d <= 0);
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stage = (pos.checkers() ? EVASION_TT : QSEARCH_TT) +
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!( ttm
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&& (pos.checkers() || depth > DEPTH_QS_RECAPTURES || to_sq(ttm) == recaptureSquare)
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&& pos.pseudo_legal(ttm));
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}
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/// MovePicker constructor for ProbCut: we generate captures with SEE greater
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/// than or equal to the given threshold.
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MovePicker::MovePicker(const Position& p, Move ttm, Value th, const CapturePieceToHistory* cph)
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: pos(p), captureHistory(cph), ttMove(ttm), threshold(th) {
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assert(!pos.checkers());
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stage = PROBCUT_TT + !(ttm && pos.capture(ttm)
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&& pos.pseudo_legal(ttm)
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&& pos.see_ge(ttm, threshold));
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}
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/// MovePicker::score() assigns a numerical value to each move in a list, used
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/// for sorting. Captures are ordered by Most Valuable Victim (MVV), preferring
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/// captures with a good history. Quiets moves are ordered using the histories.
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template<GenType Type>
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void MovePicker::score() {
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static_assert(Type == CAPTURES || Type == QUIETS || Type == EVASIONS, "Wrong type");
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for (auto& m : *this)
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if (Type == CAPTURES)
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m.value = int(PieceValue[MG][pos.piece_on(to_sq(m))]) * 6
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+ (*captureHistory)[pos.moved_piece(m)][to_sq(m)][type_of(pos.piece_on(to_sq(m)))];
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else if (Type == QUIETS)
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m.value = (*mainHistory)[pos.side_to_move()][from_to(m)]
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+ 2 * (*continuationHistory[0])[pos.moved_piece(m)][to_sq(m)]
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+ 2 * (*continuationHistory[1])[pos.moved_piece(m)][to_sq(m)]
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+ 2 * (*continuationHistory[3])[pos.moved_piece(m)][to_sq(m)]
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+ (*continuationHistory[5])[pos.moved_piece(m)][to_sq(m)]
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+ (ply < MAX_LPH ? std::min(4, depth / 3) * (*lowPlyHistory)[ply][from_to(m)] : 0);
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else // Type == EVASIONS
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{
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if (pos.capture(m))
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m.value = PieceValue[MG][pos.piece_on(to_sq(m))]
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- Value(type_of(pos.moved_piece(m)));
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else
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m.value = (*mainHistory)[pos.side_to_move()][from_to(m)]
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+ (*continuationHistory[0])[pos.moved_piece(m)][to_sq(m)]
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- (1 << 28);
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}
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}
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/// MovePicker::select() returns the next move satisfying a predicate function.
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/// It never returns the TT move.
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template<MovePicker::PickType T, typename Pred>
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Move MovePicker::select(Pred filter) {
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while (cur < endMoves)
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{
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if (T == Best)
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std::swap(*cur, *std::max_element(cur, endMoves));
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if (*cur != ttMove && filter())
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return *cur++;
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cur++;
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}
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return MOVE_NONE;
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}
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/// MovePicker::next_move() is the most important method of the MovePicker class. It
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/// returns a new pseudo-legal move every time it is called until there are no more
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/// moves left, picking the move with the highest score from a list of generated moves.
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Move MovePicker::next_move(bool skipQuiets) {
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top:
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switch (stage) {
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case MAIN_TT:
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case EVASION_TT:
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case QSEARCH_TT:
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case PROBCUT_TT:
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++stage;
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return ttMove;
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case CAPTURE_INIT:
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case PROBCUT_INIT:
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case QCAPTURE_INIT:
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cur = endBadCaptures = moves;
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endMoves = generate<CAPTURES>(pos, cur);
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score<CAPTURES>();
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++stage;
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goto top;
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case GOOD_CAPTURE:
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if (select<Best>([&](){
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return pos.see_ge(*cur, Value(-69 * cur->value / 1024)) ?
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// Move losing capture to endBadCaptures to be tried later
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true : (*endBadCaptures++ = *cur, false); }))
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return *(cur - 1);
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// Prepare the pointers to loop over the refutations array
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cur = std::begin(refutations);
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endMoves = std::end(refutations);
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// If the countermove is the same as a killer, skip it
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if ( refutations[0].move == refutations[2].move
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|| refutations[1].move == refutations[2].move)
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--endMoves;
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++stage;
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[[fallthrough]];
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case REFUTATION:
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if (select<Next>([&](){ return *cur != MOVE_NONE
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&& !pos.capture(*cur)
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&& pos.pseudo_legal(*cur); }))
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return *(cur - 1);
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++stage;
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[[fallthrough]];
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case QUIET_INIT:
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if (!skipQuiets)
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{
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cur = endBadCaptures;
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endMoves = generate<QUIETS>(pos, cur);
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score<QUIETS>();
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partial_insertion_sort(cur, endMoves, -3000 * depth);
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}
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++stage;
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[[fallthrough]];
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case QUIET:
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if ( !skipQuiets
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&& select<Next>([&](){return *cur != refutations[0].move
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&& *cur != refutations[1].move
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&& *cur != refutations[2].move;}))
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return *(cur - 1);
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// Prepare the pointers to loop over the bad captures
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cur = moves;
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endMoves = endBadCaptures;
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++stage;
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[[fallthrough]];
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case BAD_CAPTURE:
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return select<Next>([](){ return true; });
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case EVASION_INIT:
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cur = moves;
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endMoves = generate<EVASIONS>(pos, cur);
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score<EVASIONS>();
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++stage;
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[[fallthrough]];
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case EVASION:
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return select<Best>([](){ return true; });
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case PROBCUT:
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return select<Best>([&](){ return pos.see_ge(*cur, threshold); });
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case QCAPTURE:
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if (select<Best>([&](){ return depth > DEPTH_QS_RECAPTURES
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|| to_sq(*cur) == recaptureSquare; }))
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return *(cur - 1);
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// If we did not find any move and we do not try checks, we have finished
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if (depth != DEPTH_QS_CHECKS)
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return MOVE_NONE;
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++stage;
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[[fallthrough]];
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case QCHECK_INIT:
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cur = moves;
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endMoves = generate<QUIET_CHECKS>(pos, cur);
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++stage;
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[[fallthrough]];
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case QCHECK:
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return select<Next>([](){ return true; });
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}
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assert(false);
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return MOVE_NONE; // Silence warning
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}
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