/*
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
+ Copyright (C) 2004-2024 The Stockfish developers (see AUTHORS file)
Stockfish is free software: you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
along with this program. If not, see <http://www.gnu.org/licenses/>.
*/
-#include <cassert>
-
#include "movepick.h"
-namespace {
+#include <algorithm>
+#include <cassert>
+#include <utility>
+
+#include "bitboard.h"
+#include "position.h"
- enum Stages {
- MAIN_TT, CAPTURE_INIT, GOOD_CAPTURE, REFUTATION, QUIET_INIT, QUIET, BAD_CAPTURE,
- EVASION_TT, EVASION_INIT, EVASION,
- PROBCUT_TT, PROBCUT_INIT, PROBCUT,
- QSEARCH_TT, QCAPTURE_INIT, QCAPTURE, QCHECK_INIT, QCHECK
- };
+namespace Stockfish {
- // Helper filter used with select()
- const auto Any = [](){ return true; };
+namespace {
- // partial_insertion_sort() sorts moves in descending order up to and including
- // a given limit. The order of moves smaller than the limit is left unspecified.
- void partial_insertion_sort(ExtMove* begin, ExtMove* end, int limit) {
+enum Stages {
+ // generate main search moves
+ MAIN_TT,
+ CAPTURE_INIT,
+ GOOD_CAPTURE,
+ QUIET_INIT,
+ GOOD_QUIET,
+ BAD_CAPTURE,
+ BAD_QUIET,
+
+ // generate evasion moves
+ EVASION_TT,
+ EVASION_INIT,
+ EVASION,
+
+ // generate probcut moves
+ PROBCUT_TT,
+ PROBCUT_INIT,
+ PROBCUT,
+
+ // generate qsearch moves
+ QSEARCH_TT,
+ QCAPTURE_INIT,
+ QCAPTURE
+};
+
+// Sort moves in descending order up to and including a given limit.
+// The order of moves smaller than the limit is left unspecified.
+void partial_insertion_sort(ExtMove* begin, ExtMove* end, int limit) {
for (ExtMove *sortedEnd = begin, *p = begin + 1; p < end; ++p)
if (p->value >= limit)
{
ExtMove tmp = *p, *q;
- *p = *++sortedEnd;
+ *p = *++sortedEnd;
for (q = sortedEnd; q != begin && *(q - 1) < tmp; --q)
*q = *(q - 1);
*q = tmp;
}
- }
-
-} // namespace
-
-
-/// Constructors of the MovePicker class. As arguments we pass information
-/// to help it to return the (presumably) good moves first, to decide which
-/// moves to return (in the quiescence search, for instance, we only want to
-/// search captures, promotions, and some checks) and how important good move
-/// ordering is at the current node.
-
-/// MovePicker constructor for the main search
-MovePicker::MovePicker(const Position& p, Move ttm, Depth d, const ButterflyHistory* mh,
- const CapturePieceToHistory* cph, const PieceToHistory** ch, Move cm, Move* killers)
- : pos(p), mainHistory(mh), captureHistory(cph), continuationHistory(ch),
- refutations{{killers[0], 0}, {killers[1], 0}, {cm, 0}}, depth(d) {
+}
- assert(d > DEPTH_ZERO);
+} // namespace
+
+
+// Constructors of the MovePicker class. As arguments, we pass information
+// to decide which class of moves to emit, to help sorting the (presumably)
+// good moves first, and how important move ordering is at the current node.
+
+// MovePicker constructor for the main search and for the quiescence search
+MovePicker::MovePicker(const Position& p,
+ Move ttm,
+ Depth d,
+ const ButterflyHistory* mh,
+ const CapturePieceToHistory* cph,
+ const PieceToHistory** ch,
+ const PawnHistory* ph) :
+ pos(p),
+ mainHistory(mh),
+ captureHistory(cph),
+ continuationHistory(ch),
+ pawnHistory(ph),
+ ttMove(ttm),
+ depth(d) {
+
+ if (pos.checkers())
+ stage = EVASION_TT + !(ttm && pos.pseudo_legal(ttm));
+
+ else
+ stage = (depth > 0 ? MAIN_TT : QSEARCH_TT) + !(ttm && pos.pseudo_legal(ttm));
+}
- stage = pos.checkers() ? EVASION_TT : MAIN_TT;
- ttMove = ttm && pos.pseudo_legal(ttm) ? ttm : MOVE_NONE;
- stage += (ttMove == MOVE_NONE);
+// MovePicker constructor for ProbCut: we generate captures with Static Exchange
+// Evaluation (SEE) greater than or equal to the given threshold.
+MovePicker::MovePicker(const Position& p, Move ttm, int th, const CapturePieceToHistory* cph) :
+ pos(p),
+ captureHistory(cph),
+ ttMove(ttm),
+ threshold(th) {
+ assert(!pos.checkers());
+
+ stage = PROBCUT_TT
+ + !(ttm && pos.capture_stage(ttm) && pos.pseudo_legal(ttm) && pos.see_ge(ttm, threshold));
}
-/// MovePicker constructor for quiescence search
-MovePicker::MovePicker(const Position& p, Move ttm, Depth d, const ButterflyHistory* mh,
- const CapturePieceToHistory* cph, const PieceToHistory** ch, Square rs)
- : pos(p), mainHistory(mh), captureHistory(cph), continuationHistory(ch), recaptureSquare(rs), depth(d) {
+// Assigns a numerical value to each move in a list, used for sorting.
+// Captures are ordered by Most Valuable Victim (MVV), preferring captures
+// with a good history. Quiets moves are ordered using the history tables.
+template<GenType Type>
+void MovePicker::score() {
- assert(d <= DEPTH_ZERO);
+ static_assert(Type == CAPTURES || Type == QUIETS || Type == EVASIONS, "Wrong type");
- stage = pos.checkers() ? EVASION_TT : QSEARCH_TT;
- ttMove = ttm
- && pos.pseudo_legal(ttm)
- && (depth > DEPTH_QS_RECAPTURES || to_sq(ttm) == recaptureSquare) ? ttm : MOVE_NONE;
- stage += (ttMove == MOVE_NONE);
-}
+ [[maybe_unused]] Bitboard threatenedByPawn, threatenedByMinor, threatenedByRook,
+ threatenedPieces;
+ if constexpr (Type == QUIETS)
+ {
+ Color us = pos.side_to_move();
-/// MovePicker constructor for ProbCut: we generate captures with SEE greater
-/// than or equal to the given threshold.
-MovePicker::MovePicker(const Position& p, Move ttm, Value th, const CapturePieceToHistory* cph)
- : pos(p), captureHistory(cph), threshold(th) {
+ threatenedByPawn = pos.attacks_by<PAWN>(~us);
+ threatenedByMinor =
+ pos.attacks_by<KNIGHT>(~us) | pos.attacks_by<BISHOP>(~us) | threatenedByPawn;
+ threatenedByRook = pos.attacks_by<ROOK>(~us) | threatenedByMinor;
- assert(!pos.checkers());
+ // Pieces threatened by pieces of lesser material value
+ threatenedPieces = (pos.pieces(us, QUEEN) & threatenedByRook)
+ | (pos.pieces(us, ROOK) & threatenedByMinor)
+ | (pos.pieces(us, KNIGHT, BISHOP) & threatenedByPawn);
+ }
- stage = PROBCUT_TT;
- ttMove = ttm
- && pos.pseudo_legal(ttm)
- && pos.capture(ttm)
- && pos.see_ge(ttm, threshold) ? ttm : MOVE_NONE;
- stage += (ttMove == MOVE_NONE);
-}
+ for (auto& m : *this)
+ if constexpr (Type == CAPTURES)
+ m.value =
+ 7 * int(PieceValue[pos.piece_on(m.to_sq())])
+ + (*captureHistory)[pos.moved_piece(m)][m.to_sq()][type_of(pos.piece_on(m.to_sq()))];
-/// MovePicker::score() assigns a numerical value to each move in a list, used
-/// for sorting. Captures are ordered by Most Valuable Victim (MVV), preferring
-/// captures with a good history. Quiets moves are ordered using the histories.
-template<GenType Type>
-void MovePicker::score() {
+ else if constexpr (Type == QUIETS)
+ {
+ Piece pc = pos.moved_piece(m);
+ PieceType pt = type_of(pc);
+ Square from = m.from_sq();
+ Square to = m.to_sq();
+
+ // histories
+ m.value = (*mainHistory)[pos.side_to_move()][m.from_to()];
+ m.value += 2 * (*pawnHistory)[pawn_structure_index(pos)][pc][to];
+ m.value += 2 * (*continuationHistory[0])[pc][to];
+ m.value += (*continuationHistory[1])[pc][to];
+ m.value += (*continuationHistory[2])[pc][to] / 3;
+ m.value += (*continuationHistory[3])[pc][to];
+ m.value += (*continuationHistory[5])[pc][to];
+
+ // bonus for checks
+ m.value += bool(pos.check_squares(pt) & to) * 16384;
+
+ // bonus for escaping from capture
+ m.value += threatenedPieces & from ? (pt == QUEEN && !(to & threatenedByRook) ? 51700
+ : pt == ROOK && !(to & threatenedByMinor) ? 25600
+ : !(to & threatenedByPawn) ? 14450
+ : 0)
+ : 0;
+
+ // malus for putting piece en prise
+ m.value -= (pt == QUEEN ? bool(to & threatenedByRook) * 49000
+ : pt == ROOK ? bool(to & threatenedByMinor) * 24335
+ : bool(to & threatenedByPawn) * 14900);
+ }
- static_assert(Type == CAPTURES || Type == QUIETS || Type == EVASIONS, "Wrong type");
-
- for (auto& m : *this)
- if (Type == CAPTURES)
- m.value = PieceValue[MG][pos.piece_on(to_sq(m))]
- + (*captureHistory)[pos.moved_piece(m)][to_sq(m)][type_of(pos.piece_on(to_sq(m)))] / 8;
-
- else if (Type == QUIETS)
- m.value = (*mainHistory)[pos.side_to_move()][from_to(m)]
- + (*continuationHistory[0])[pos.moved_piece(m)][to_sq(m)]
- + (*continuationHistory[1])[pos.moved_piece(m)][to_sq(m)]
- + (*continuationHistory[3])[pos.moved_piece(m)][to_sq(m)];
-
- else // Type == EVASIONS
- {
- if (pos.capture(m))
- m.value = PieceValue[MG][pos.piece_on(to_sq(m))]
- - Value(type_of(pos.moved_piece(m)));
- else
- m.value = (*mainHistory)[pos.side_to_move()][from_to(m)]
- + (*continuationHistory[0])[pos.moved_piece(m)][to_sq(m)]
- - (1 << 28);
- }
+ else // Type == EVASIONS
+ {
+ if (pos.capture_stage(m))
+ m.value =
+ PieceValue[pos.piece_on(m.to_sq())] - type_of(pos.moved_piece(m)) + (1 << 28);
+ else
+ m.value = (*mainHistory)[pos.side_to_move()][m.from_to()]
+ + (*continuationHistory[0])[pos.moved_piece(m)][m.to_sq()]
+ + (*pawnHistory)[pawn_structure_index(pos)][pos.moved_piece(m)][m.to_sq()];
+ }
}
-/// MovePicker::select() returns the next move satisfying a predicate function.
-/// It never returns the TT move.
+// Returns the next move satisfying a predicate function.
+// This never returns the TT move, as it was emitted before.
template<MovePicker::PickType T, typename Pred>
Move MovePicker::select(Pred filter) {
- while (cur < endMoves)
- {
- if (T == Best)
- std::swap(*cur, *std::max_element(cur, endMoves));
+ while (cur < endMoves)
+ {
+ if constexpr (T == Best)
+ std::swap(*cur, *std::max_element(cur, endMoves));
- move = *cur++;
+ if (*cur != ttMove && filter())
+ return *cur++;
- if (move != ttMove && filter())
- return move;
- }
- return move = MOVE_NONE;
+ cur++;
+ }
+ return Move::none();
}
-/// MovePicker::next_move() is the most important method of the MovePicker class. It
-/// returns a new pseudo legal move every time it is called until there are no more
-/// moves left, picking the move with the highest score from a list of generated moves.
+// This is the most important method of the MovePicker class. We emit one
+// new pseudo-legal move on every call until there are no more moves left,
+// picking the move with the highest score from a list of generated moves.
Move MovePicker::next_move(bool skipQuiets) {
+ auto quiet_threshold = [](Depth d) { return -3560 * d; };
+
top:
- switch (stage) {
-
- case MAIN_TT:
- case EVASION_TT:
- case QSEARCH_TT:
- case PROBCUT_TT:
- ++stage;
- return ttMove;
-
- case CAPTURE_INIT:
- case PROBCUT_INIT:
- case QCAPTURE_INIT:
- cur = endBadCaptures = moves;
- endMoves = generate<CAPTURES>(pos, cur);
-
- score<CAPTURES>();
- ++stage;
- goto top;
-
- case GOOD_CAPTURE:
- if (select<Best>([&](){
- return pos.see_ge(move, Value(-55 * (cur-1)->value / 1024)) ?
- // Move losing capture to endBadCaptures to be tried later
- true : (*endBadCaptures++ = move, false); }))
- return move;
-
- // Prepare the pointers to loop over the refutations array
- cur = std::begin(refutations);
- endMoves = std::end(refutations);
-
- // If the countermove is the same as a killer, skip it
- if ( refutations[0].move == refutations[2].move
- || refutations[1].move == refutations[2].move)
- --endMoves;
-
- ++stage;
- /* fallthrough */
-
- case REFUTATION:
- if (select<Next>([&](){ return move != MOVE_NONE
- && !pos.capture(move)
- && pos.pseudo_legal(move); }))
- return move;
- ++stage;
- /* fallthrough */
-
- case QUIET_INIT:
- cur = endBadCaptures;
- endMoves = generate<QUIETS>(pos, cur);
-
- score<QUIETS>();
- partial_insertion_sort(cur, endMoves, -4000 * depth / ONE_PLY);
- ++stage;
- /* fallthrough */
-
- case QUIET:
- if ( !skipQuiets
- && select<Next>([&](){return move != refutations[0]
- && move != refutations[1]
- && move != refutations[2];}))
- return move;
-
- // Prepare the pointers to loop over the bad captures
- cur = moves;
- endMoves = endBadCaptures;
-
- ++stage;
- /* fallthrough */
-
- case BAD_CAPTURE:
- return select<Next>(Any);
-
- case EVASION_INIT:
- cur = moves;
- endMoves = generate<EVASIONS>(pos, cur);
-
- score<EVASIONS>();
- ++stage;
- /* fallthrough */
-
- case EVASION:
- return select<Best>(Any);
-
- case PROBCUT:
- return select<Best>([&](){ return pos.see_ge(move, threshold); });
-
- case QCAPTURE:
- if (select<Best>([&](){ return depth > DEPTH_QS_RECAPTURES
- || to_sq(move) == recaptureSquare; }))
- return move;
-
- // If we did not find any move and we do not try checks, we have finished
- if (depth != DEPTH_QS_CHECKS)
- return MOVE_NONE;
-
- ++stage;
- /* fallthrough */
-
- case QCHECK_INIT:
- cur = moves;
- endMoves = generate<QUIET_CHECKS>(pos, cur);
-
- ++stage;
- /* fallthrough */
-
- case QCHECK:
- return select<Next>(Any);
- }
-
- assert(false);
- return MOVE_NONE; // Silence warning
+ switch (stage)
+ {
+
+ case MAIN_TT :
+ case EVASION_TT :
+ case QSEARCH_TT :
+ case PROBCUT_TT :
+ ++stage;
+ return ttMove;
+
+ case CAPTURE_INIT :
+ case PROBCUT_INIT :
+ case QCAPTURE_INIT :
+ cur = endBadCaptures = moves;
+ endMoves = generate<CAPTURES>(pos, cur);
+
+ score<CAPTURES>();
+ partial_insertion_sort(cur, endMoves, std::numeric_limits<int>::min());
+ ++stage;
+ goto top;
+
+ case GOOD_CAPTURE :
+ if (select<Next>([&]() {
+ // Move losing capture to endBadCaptures to be tried later
+ return pos.see_ge(*cur, -cur->value / 18) ? true
+ : (*endBadCaptures++ = *cur, false);
+ }))
+ return *(cur - 1);
+
+ ++stage;
+ [[fallthrough]];
+
+ case QUIET_INIT :
+ if (!skipQuiets)
+ {
+ cur = endBadCaptures;
+ endMoves = beginBadQuiets = endBadQuiets = generate<QUIETS>(pos, cur);
+
+ score<QUIETS>();
+ partial_insertion_sort(cur, endMoves, quiet_threshold(depth));
+ }
+
+ ++stage;
+ [[fallthrough]];
+
+ case GOOD_QUIET :
+ if (!skipQuiets && select<Next>([]() { return true; }))
+ {
+ if ((cur - 1)->value > -7998 || (cur - 1)->value <= quiet_threshold(depth))
+ return *(cur - 1);
+
+ // Remaining quiets are bad
+ beginBadQuiets = cur - 1;
+ }
+
+ // Prepare the pointers to loop over the bad captures
+ cur = moves;
+ endMoves = endBadCaptures;
+
+ ++stage;
+ [[fallthrough]];
+
+ case BAD_CAPTURE :
+ if (select<Next>([]() { return true; }))
+ return *(cur - 1);
+
+ // Prepare the pointers to loop over the bad quiets
+ cur = beginBadQuiets;
+ endMoves = endBadQuiets;
+
+ ++stage;
+ [[fallthrough]];
+
+ case BAD_QUIET :
+ if (!skipQuiets)
+ return select<Next>([]() { return true; });
+
+ return Move::none();
+
+ case EVASION_INIT :
+ cur = moves;
+ endMoves = generate<EVASIONS>(pos, cur);
+
+ score<EVASIONS>();
+ ++stage;
+ [[fallthrough]];
+
+ case EVASION :
+ return select<Best>([]() { return true; });
+
+ case PROBCUT :
+ return select<Next>([&]() { return pos.see_ge(*cur, threshold); });
+
+ case QCAPTURE :
+ return select<Next>([]() { return true; });
+ }
+
+ assert(false);
+ return Move::none(); // Silence warning
}
+
+} // namespace Stockfish
projects / stockfish / blobdiff