X-Git-Url: https://git.sesse.net/?p=stockfish;a=blobdiff_plain;f=src%2Fmovepick.cpp;h=025f5b82cdeb2ae808d23c0e75a955862b48524b;hp=e350bda839b7a073a6775669ee6fac773921d6b4;hb=bae019b53e5c2bfcf0d69b4ebfc52b4f4de762eb;hpb=049e5ca191e34b727150a27fb70018eaf89d29df diff --git a/src/movepick.cpp b/src/movepick.cpp index e350bda8..025f5b82 100644 --- a/src/movepick.cpp +++ b/src/movepick.cpp @@ -1,14 +1,14 @@ /* Stockfish, a UCI chess playing engine derived from Glaurung 2.1 Copyright (C) 2004-2008 Tord Romstad (Glaurung author) - Copyright (C) 2008-2013 Marco Costalba, Joona Kiiski, Tord Romstad + 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 @@ -21,360 +21,251 @@ #include #include "movepick.h" -#include "thread.h" namespace { - enum Sequencer { - MAIN_SEARCH, CAPTURES_S1, KILLERS_S1, QUIETS_1_S1, QUIETS_2_S1, BAD_CAPTURES_S1, - EVASION, EVASIONS_S2, - QSEARCH_0, CAPTURES_S3, QUIET_CHECKS_S3, - QSEARCH_1, CAPTURES_S4, - PROBCUT, CAPTURES_S5, - RECAPTURE, CAPTURES_S6, - STOP + 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 }; - // Our insertion sort, guaranteed to be stable, as is needed - void insertion_sort(MoveStack* begin, MoveStack* end) - { - MoveStack tmp, *p, *q; - - for (p = begin + 1; p < end; ++p) - { - tmp = *p; - for (q = p; q != begin && *(q-1) < tmp; --q) - *q = *(q-1); - *q = tmp; - } + // 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) { + + for (ExtMove *sortedEnd = begin, *p = begin + 1; p < end; ++p) + if (p->value >= limit) + { + ExtMove tmp = *p, *q; + *p = *++sortedEnd; + for (q = sortedEnd; q != begin && *(q - 1) < tmp; --q) + *q = *(q - 1); + *q = tmp; + } } - // Unary predicate used by std::partition to split positive scores from remaining - // ones so to sort separately the two sets, and with the second sort delayed. - inline bool has_positive_score(const MoveStack& ms) { return ms.score > 0; } - - // Picks and moves to the front the best move in the range [begin, end), - // it is faster than sorting all the moves in advance when moves are few, as - // normally are the possible captures. - inline MoveStack* pick_best(MoveStack* begin, MoveStack* end) - { - std::swap(*begin, *std::max_element(begin, end)); - return begin; - } -} +} // namespace /// Constructors of the MovePicker class. As arguments we pass information -/// to help it to return the presumably good moves first, to decide which +/// 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 about how important good -/// move ordering is at the current node. - -MovePicker::MovePicker(const Position& p, Move ttm, Depth d, const History& h, const Refutations& r, - Search::Stack* s, Value beta) : pos(p), Hist(h), depth(d) { - - assert(d > DEPTH_ZERO); - - captureThreshold = 0; - cur = end = moves; - endBadCaptures = moves + MAX_MOVES - 1; - ss = s; - - if (p.checkers()) - phase = EVASION; - - else - { - phase = MAIN_SEARCH; +/// search captures, promotions, and some checks) and how important good move +/// ordering is at the current node. - killers[0].move = ss->killers[0]; - killers[1].move = ss->killers[1]; - Square prevSq = to_sq((ss-1)->currentMove); - killers[2].move = r[pos.piece_on(prevSq)][prevSq]; +/// 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) { - // Consider sligtly negative captures as good if at low depth and far from beta - if (ss && ss->staticEval < beta - PawnValueMg && d < 3 * ONE_PLY) - captureThreshold = -PawnValueMg; + assert(d > 0); - // Consider negative captures as good if still enough to reach beta - else if (ss && ss->staticEval > beta) - captureThreshold = beta - ss->staticEval; - } - - ttMove = (ttm && pos.is_pseudo_legal(ttm) ? ttm : MOVE_NONE); - end += (ttMove != MOVE_NONE); + stage = pos.checkers() ? EVASION_TT : MAIN_TT; + ttMove = ttm && pos.pseudo_legal(ttm) ? ttm : MOVE_NONE; + stage += (ttMove == MOVE_NONE); } -MovePicker::MovePicker(const Position& p, Move ttm, Depth d, const History& h, - Square sq) : pos(p), Hist(h), cur(moves), end(moves) { - - assert(d <= DEPTH_ZERO); +/// 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) { - if (p.checkers()) - phase = EVASION; - - else if (d > DEPTH_QS_NO_CHECKS) - phase = QSEARCH_0; - - else if (d > DEPTH_QS_RECAPTURES) - { - phase = QSEARCH_1; + assert(d <= 0); - // Skip TT move if is not a capture or a promotion, this avoids qsearch - // tree explosion due to a possible perpetual check or similar rare cases - // when TT table is full. - if (ttm && !pos.is_capture_or_promotion(ttm)) - ttm = MOVE_NONE; - } - else - { - phase = RECAPTURE; - recaptureSquare = sq; - ttm = MOVE_NONE; - } - - ttMove = (ttm && pos.is_pseudo_legal(ttm) ? ttm : MOVE_NONE); - end += (ttMove != MOVE_NONE); + stage = pos.checkers() ? EVASION_TT : QSEARCH_TT; + ttMove = ttm + && (depth > DEPTH_QS_RECAPTURES || to_sq(ttm) == recaptureSquare) + && pos.pseudo_legal(ttm) ? ttm : MOVE_NONE; + stage += (ttMove == MOVE_NONE); } -MovePicker::MovePicker(const Position& p, Move ttm, const History& h, PieceType pt) - : pos(p), Hist(h), cur(moves), end(moves) { +/// 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) { assert(!pos.checkers()); - phase = PROBCUT; - - // In ProbCut we generate only captures better than parent's captured piece - captureThreshold = PieceValue[MG][pt]; - ttMove = (ttm && pos.is_pseudo_legal(ttm) ? ttm : MOVE_NONE); - - if (ttMove && (!pos.is_capture(ttMove) || pos.see(ttMove) <= captureThreshold)) - ttMove = MOVE_NONE; + stage = PROBCUT_TT; + ttMove = ttm + && pos.capture(ttm) + && pos.pseudo_legal(ttm) + && pos.see_ge(ttm, threshold) ? ttm : MOVE_NONE; + stage += (ttMove == MOVE_NONE); +} - end += (ttMove != MOVE_NONE); +/// 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 +void MovePicker::score() { + + static_assert(Type == CAPTURES || Type == QUIETS || Type == EVASIONS, "Wrong type"); + + for (auto& m : *this) + if (Type == CAPTURES) + m.value = int(PieceValue[MG][pos.piece_on(to_sq(m))]) * 6 + + (*captureHistory)[pos.moved_piece(m)][to_sq(m)][type_of(pos.piece_on(to_sq(m)))]; + + else if (Type == QUIETS) + m.value = (*mainHistory)[pos.side_to_move()][from_to(m)] + + 2 * (*continuationHistory[0])[pos.moved_piece(m)][to_sq(m)] + + 2 * (*continuationHistory[1])[pos.moved_piece(m)][to_sq(m)] + + 2 * (*continuationHistory[3])[pos.moved_piece(m)][to_sq(m)] + + (*continuationHistory[5])[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); + } } +/// MovePicker::select() returns the next move satisfying a predicate function. +/// It never returns the TT move. +template +Move MovePicker::select(Pred filter) { -/// score() assign a numerical move ordering score to each move in a move list. -/// The moves with highest scores will be picked first. -template<> -void MovePicker::score() { - // Winning and equal captures in the main search are ordered by MVV/LVA. - // Suprisingly, this appears to perform slightly better than SEE based - // move ordering. The reason is probably that in a position with a winning - // capture, capturing a more valuable (but sufficiently defended) piece - // first usually doesn't hurt. The opponent will have to recapture, and - // the hanging piece will still be hanging (except in the unusual cases - // where it is possible to recapture with the hanging piece). Exchanging - // big pieces before capturing a hanging piece probably helps to reduce - // the subtree size. - // In main search we want to push captures with negative SEE values to - // badCaptures[] array, but instead of doing it now we delay till when - // the move has been picked up in pick_move_from_list(), this way we save - // some SEE calls in case we get a cutoff (idea from Pablo Vazquez). - Move m; - - for (MoveStack* it = moves; it != end; ++it) + while (cur < endMoves) { - m = it->move; - it->score = PieceValue[MG][pos.piece_on(to_sq(m))] - - type_of(pos.piece_moved(m)); + if (T == Best) + std::swap(*cur, *std::max_element(cur, endMoves)); - if (type_of(m) == PROMOTION) - it->score += PieceValue[MG][promotion_type(m)] - PieceValue[MG][PAWN]; + if (*cur != ttMove && filter()) + return *cur++; - else if (type_of(m) == ENPASSANT) - it->score += PieceValue[MG][PAWN]; + cur++; } + return MOVE_NONE; } -template<> -void MovePicker::score() { +/// 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. +Move MovePicker::next_move(bool skipQuiets) { - Move m; +top: + switch (stage) { - for (MoveStack* it = moves; it != end; ++it) - { - m = it->move; - it->score = Hist[pos.piece_moved(m)][to_sq(m)]; - } -} + case MAIN_TT: + case EVASION_TT: + case QSEARCH_TT: + case PROBCUT_TT: + ++stage; + return ttMove; -template<> -void MovePicker::score() { - // Try good captures ordered by MVV/LVA, then non-captures if destination square - // is not under attack, ordered by history value, then bad-captures and quiet - // moves with a negative SEE. This last group is ordered by the SEE score. - Move m; - int seeScore; + case CAPTURE_INIT: + case PROBCUT_INIT: + case QCAPTURE_INIT: + cur = endBadCaptures = moves; + endMoves = generate(pos, cur); - for (MoveStack* it = moves; it != end; ++it) - { - m = it->move; - if ((seeScore = pos.see_sign(m)) < 0) - it->score = seeScore - History::Max; // At the bottom - - else if (pos.is_capture(m)) - it->score = PieceValue[MG][pos.piece_on(to_sq(m))] - - type_of(pos.piece_moved(m)) + History::Max; - else - it->score = Hist[pos.piece_moved(m)][to_sq(m)]; - } -} + score(); + ++stage; + goto top; + + case GOOD_CAPTURE: + if (select([&](){ + return pos.see_ge(*cur, Value(-55 * cur->value / 1024)) ? + // Move losing capture to endBadCaptures to be tried later + true : (*endBadCaptures++ = *cur, false); })) + return *(cur - 1); + + // 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([&](){ return *cur != MOVE_NONE + && !pos.capture(*cur) + && pos.pseudo_legal(*cur); })) + return *(cur - 1); + ++stage; + /* fallthrough */ + + case QUIET_INIT: + if (!skipQuiets) + { + cur = endBadCaptures; + endMoves = generate(pos, cur); + + score(); + partial_insertion_sort(cur, endMoves, -3000 * depth); + } + ++stage; + /* fallthrough */ -/// generate_next() generates, scores and sorts the next bunch of moves, when -/// there are no more moves to try for the current phase. + case QUIET: + if ( !skipQuiets + && select([&](){return *cur != refutations[0].move + && *cur != refutations[1].move + && *cur != refutations[2].move;})) + return *(cur - 1); -void MovePicker::generate_next() { + // Prepare the pointers to loop over the bad captures + cur = moves; + endMoves = endBadCaptures; - cur = moves; + ++stage; + /* fallthrough */ - switch (++phase) { + case BAD_CAPTURE: + return select([](){ return true; }); - case CAPTURES_S1: case CAPTURES_S3: case CAPTURES_S4: case CAPTURES_S5: case CAPTURES_S6: - end = generate(pos, moves); - score(); - return; - - case KILLERS_S1: - cur = killers; - end = cur + 3 - (killers[2].move == killers[0].move || killers[2].move == killers[1].move); - return; - - case QUIETS_1_S1: - endQuiets = end = generate(pos, moves); - score(); - end = std::partition(cur, end, has_positive_score); - insertion_sort(cur, end); - return; - - case QUIETS_2_S1: - cur = end; - end = endQuiets; - if (depth >= 3 * ONE_PLY) - insertion_sort(cur, end); - return; - - case BAD_CAPTURES_S1: - // Just pick them in reverse order to get MVV/LVA ordering - cur = moves + MAX_MOVES - 1; - end = endBadCaptures; - return; - - case EVASIONS_S2: - end = generate(pos, moves); - if (end > moves + 1) - score(); - return; - - case QUIET_CHECKS_S3: - end = generate(pos, moves); - return; - - case EVASION: case QSEARCH_0: case QSEARCH_1: case PROBCUT: case RECAPTURE: - phase = STOP; - case STOP: - end = cur + 1; // Avoid another next_phase() call - return; - - default: - assert(false); - } -} + case EVASION_INIT: + cur = moves; + endMoves = generate(pos, cur); + score(); + ++stage; + /* fallthrough */ -/// next_move() is the most important method of the MovePicker class. It returns -/// a new pseudo legal move every time is called, until there are no more moves -/// left. It picks the move with the biggest score from a list of generated moves -/// taking care not returning the ttMove if has already been searched previously. -template<> -Move MovePicker::next_move() { + case EVASION: + return select([](){ return true; }); - Move move; + case PROBCUT: + return select([&](){ return pos.see_ge(*cur, threshold); }); - while (true) - { - while (cur == end) - generate_next(); - - switch (phase) { - - case MAIN_SEARCH: case EVASION: case QSEARCH_0: case QSEARCH_1: case PROBCUT: - cur++; - return ttMove; - - case CAPTURES_S1: - move = pick_best(cur++, end)->move; - if (move != ttMove) - { - assert(captureThreshold <= 0); // Otherwise we cannot use see_sign() - - if (pos.see_sign(move) >= captureThreshold) - return move; - - // Losing capture, move it to the tail of the array - (endBadCaptures--)->move = move; - } - break; - - case KILLERS_S1: - move = (cur++)->move; - if ( move != MOVE_NONE - && pos.is_pseudo_legal(move) - && move != ttMove - && !pos.is_capture(move)) - return move; - break; - - case QUIETS_1_S1: case QUIETS_2_S1: - move = (cur++)->move; - if ( move != ttMove - && move != killers[0].move - && move != killers[1].move - && move != killers[2].move) - return move; - break; - - case BAD_CAPTURES_S1: - return (cur--)->move; - - case EVASIONS_S2: case CAPTURES_S3: case CAPTURES_S4: - move = pick_best(cur++, end)->move; - if (move != ttMove) - return move; - break; - - case CAPTURES_S5: - move = pick_best(cur++, end)->move; - if (move != ttMove && pos.see(move) > captureThreshold) - return move; - break; - - case CAPTURES_S6: - move = pick_best(cur++, end)->move; - if (to_sq(move) == recaptureSquare) - return move; - break; - - case QUIET_CHECKS_S3: - move = (cur++)->move; - if (move != ttMove) - return move; - break; - - case STOP: + case QCAPTURE: + if (select([&](){ return depth > DEPTH_QS_RECAPTURES + || to_sq(*cur) == recaptureSquare; })) + return *(cur - 1); + + // If we did not find any move and we do not try checks, we have finished + if (depth != DEPTH_QS_CHECKS) return MOVE_NONE; - default: - assert(false); - } - } -} + ++stage; + /* fallthrough */ + + case QCHECK_INIT: + cur = moves; + endMoves = generate(pos, cur); + ++stage; + /* fallthrough */ -/// Version of next_move() to use at split point nodes where the move is grabbed -/// from the split point's shared MovePicker object. This function is not thread -/// safe so must be lock protected by the caller. -template<> -Move MovePicker::next_move() { return ss->splitPoint->movePicker->next_move(); } + case QCHECK: + return select([](){ return true; }); + } + + assert(false); + return MOVE_NONE; // Silence warning +}