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https://github.com/sockspls/badfish
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Remove references to checks in MovePicker comments. Follow-up for https://github.com/official-stockfish/Stockfish/pull/5498 closes https://github.com/official-stockfish/Stockfish/pull/5516 No functional change
318 lines
9.9 KiB
C++
318 lines
9.9 KiB
C++
/*
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Stockfish, a UCI chess playing engine derived from Glaurung 2.1
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Copyright (C) 2004-2024 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 "movepick.h"
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#include <algorithm>
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#include <cassert>
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#include <utility>
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#include "bitboard.h"
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#include "position.h"
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namespace Stockfish {
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namespace {
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enum Stages {
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// generate main search moves
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MAIN_TT,
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CAPTURE_INIT,
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GOOD_CAPTURE,
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QUIET_INIT,
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GOOD_QUIET,
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BAD_CAPTURE,
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BAD_QUIET,
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// generate evasion moves
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EVASION_TT,
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EVASION_INIT,
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EVASION,
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// generate probcut moves
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PROBCUT_TT,
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PROBCUT_INIT,
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PROBCUT,
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// generate qsearch moves
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QSEARCH_TT,
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QCAPTURE_INIT,
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QCAPTURE
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};
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// Sort moves in descending order up to and including a given limit.
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// 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 decide which class of moves to emit, to help sorting the (presumably)
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// good moves first, and how important move ordering is at the current node.
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// MovePicker constructor for the main search and for the quiescence search
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MovePicker::MovePicker(const Position& p,
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Move ttm,
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Depth d,
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const ButterflyHistory* mh,
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const CapturePieceToHistory* cph,
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const PieceToHistory** ch,
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const PawnHistory* ph) :
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pos(p),
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mainHistory(mh),
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captureHistory(cph),
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continuationHistory(ch),
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pawnHistory(ph),
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ttMove(ttm),
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depth(d) {
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if (pos.checkers())
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stage = EVASION_TT + !(ttm && pos.pseudo_legal(ttm));
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else
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stage = (depth > 0 ? MAIN_TT : QSEARCH_TT) + !(ttm && pos.pseudo_legal(ttm));
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}
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// MovePicker constructor for ProbCut: we generate captures with Static Exchange
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// Evaluation (SEE) greater than or equal to the given threshold.
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MovePicker::MovePicker(const Position& p, Move ttm, int th, const CapturePieceToHistory* cph) :
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pos(p),
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captureHistory(cph),
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ttMove(ttm),
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threshold(th) {
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assert(!pos.checkers());
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stage = PROBCUT_TT
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+ !(ttm && pos.capture_stage(ttm) && pos.pseudo_legal(ttm) && pos.see_ge(ttm, threshold));
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}
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// Assigns a numerical value to each move in a list, used for sorting.
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// Captures are ordered by Most Valuable Victim (MVV), preferring captures
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// with a good history. Quiets moves are ordered using the history tables.
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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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[[maybe_unused]] Bitboard threatenedByPawn, threatenedByMinor, threatenedByRook,
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threatenedPieces;
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if constexpr (Type == QUIETS)
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{
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Color us = pos.side_to_move();
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threatenedByPawn = pos.attacks_by<PAWN>(~us);
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threatenedByMinor =
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pos.attacks_by<KNIGHT>(~us) | pos.attacks_by<BISHOP>(~us) | threatenedByPawn;
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threatenedByRook = pos.attacks_by<ROOK>(~us) | threatenedByMinor;
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// Pieces threatened by pieces of lesser material value
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threatenedPieces = (pos.pieces(us, QUEEN) & threatenedByRook)
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| (pos.pieces(us, ROOK) & threatenedByMinor)
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| (pos.pieces(us, KNIGHT, BISHOP) & threatenedByPawn);
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}
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for (auto& m : *this)
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if constexpr (Type == CAPTURES)
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m.value =
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7 * int(PieceValue[pos.piece_on(m.to_sq())])
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+ (*captureHistory)[pos.moved_piece(m)][m.to_sq()][type_of(pos.piece_on(m.to_sq()))];
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else if constexpr (Type == QUIETS)
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{
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Piece pc = pos.moved_piece(m);
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PieceType pt = type_of(pc);
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Square from = m.from_sq();
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Square to = m.to_sq();
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// histories
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m.value = (*mainHistory)[pos.side_to_move()][m.from_to()];
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m.value += 2 * (*pawnHistory)[pawn_structure_index(pos)][pc][to];
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m.value += 2 * (*continuationHistory[0])[pc][to];
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m.value += (*continuationHistory[1])[pc][to];
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m.value += (*continuationHistory[2])[pc][to] / 3;
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m.value += (*continuationHistory[3])[pc][to];
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m.value += (*continuationHistory[5])[pc][to];
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// bonus for checks
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m.value += bool(pos.check_squares(pt) & to) * 16384;
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// bonus for escaping from capture
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m.value += threatenedPieces & from ? (pt == QUEEN && !(to & threatenedByRook) ? 51700
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: pt == ROOK && !(to & threatenedByMinor) ? 25600
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: !(to & threatenedByPawn) ? 14450
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: 0)
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: 0;
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// malus for putting piece en prise
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m.value -= (pt == QUEEN ? bool(to & threatenedByRook) * 49000
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: pt == ROOK ? bool(to & threatenedByMinor) * 24335
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: bool(to & threatenedByPawn) * 14900);
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}
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else // Type == EVASIONS
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{
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if (pos.capture_stage(m))
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m.value =
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PieceValue[pos.piece_on(m.to_sq())] - type_of(pos.moved_piece(m)) + (1 << 28);
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else
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m.value = (*mainHistory)[pos.side_to_move()][m.from_to()]
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+ (*continuationHistory[0])[pos.moved_piece(m)][m.to_sq()]
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+ (*pawnHistory)[pawn_structure_index(pos)][pos.moved_piece(m)][m.to_sq()];
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}
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}
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// Returns the next move satisfying a predicate function.
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// This never returns the TT move, as it was emitted before.
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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 constexpr (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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// This is the most important method of the MovePicker class. We emit one
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// new pseudo-legal move on every call until there are no more moves left,
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// 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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auto quiet_threshold = [](Depth d) { return -3560 * d; };
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top:
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switch (stage)
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{
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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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partial_insertion_sort(cur, endMoves, std::numeric_limits<int>::min());
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++stage;
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goto top;
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case GOOD_CAPTURE :
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if (select<Next>([&]() {
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// Move losing capture to endBadCaptures to be tried later
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return pos.see_ge(*cur, -cur->value / 18) ? true
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: (*endBadCaptures++ = *cur, false);
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}))
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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 = beginBadQuiets = endBadQuiets = generate<QUIETS>(pos, cur);
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score<QUIETS>();
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partial_insertion_sort(cur, endMoves, quiet_threshold(depth));
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}
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++stage;
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[[fallthrough]];
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case GOOD_QUIET :
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if (!skipQuiets && select<Next>([]() { return true; }))
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{
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if ((cur - 1)->value > -7998 || (cur - 1)->value <= quiet_threshold(depth))
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return *(cur - 1);
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// Remaining quiets are bad
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beginBadQuiets = cur - 1;
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}
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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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if (select<Next>([]() { return true; }))
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return *(cur - 1);
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// Prepare the pointers to loop over the bad quiets
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cur = beginBadQuiets;
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endMoves = endBadQuiets;
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++stage;
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[[fallthrough]];
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case BAD_QUIET :
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if (!skipQuiets)
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return select<Next>([]() { return true; });
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return Move::none();
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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<Next>([&]() { return pos.see_ge(*cur, threshold); });
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case QCAPTURE :
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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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} // namespace Stockfish
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