X-Git-Url: https://git.sesse.net/?p=stockfish;a=blobdiff_plain;f=src%2Fmovepick.cpp;h=4b8cf747a0d04e020a28ac2b688aa1dd84d65f02;hp=95172b944c13705182f6c1a7842deece827448e5;hb=d40e7ee20903257cb0126f1945d63257ded022c3;hpb=55604f156b2293e870984c6bb57c1954ad5a9517 diff --git a/src/movepick.cpp b/src/movepick.cpp index 95172b94..4b8cf747 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) 2008-2014 Marco Costalba, Joona Kiiski, Tord Romstad + Copyright (C) 2008-2015 Marco Costalba, Joona Kiiski, Tord Romstad + Copyright (C) 2015-2018 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 @@ -21,372 +21,239 @@ #include #include "movepick.h" -#include "thread.h" namespace { enum Stages { - 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 + 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, which is guaranteed (and also needed) to be stable - void insertion_sort(ExtMove* begin, ExtMove* end) - { - ExtMove 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; - } + // Helper filter used with select_move() + const auto Any = [](){ return true; }; + + // 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 values from remaining - // ones so as to sort the two sets separately, with the second sort delayed. - inline bool has_positive_value(const ExtMove& ms) { return ms.value > 0; } - - // Picks the best move in the range (begin, end) and moves it to the front. - // It's faster than sorting all the moves in advance when there are few - // moves e.g. possible captures. - inline ExtMove* pick_best(ExtMove* begin, ExtMove* 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 /// moves to return (in the quiescence search, for instance, we only want to -/// search captures, promotions and some checks) and how important good move +/// search captures, promotions, and some checks) and how important good move /// ordering is at the current node. -MovePicker::MovePicker(const Position& p, Move ttm, Depth d, const HistoryStats& h, - Move* cm, Move* fm, Search::Stack* s) : pos(p), history(h), depth(d) { +/// 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), contHistory(ch), + refutations{{killers[0], 0}, {killers[1], 0}, {cm, 0}}, depth(d){ assert(d > DEPTH_ZERO); - cur = end = moves; - endBadCaptures = moves + MAX_MOVES - 1; - countermoves = cm; - followupmoves = fm; - ss = s; - - if (pos.checkers()) - stage = EVASION; - - else - stage = MAIN_SEARCH; - - ttMove = (ttm && pos.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 HistoryStats& h, - Square s) : pos(p), history(h), cur(moves), end(moves) { +/// MovePicker constructor for quiescence search +MovePicker::MovePicker(const Position& p, Move ttm, Depth d, const ButterflyHistory* mh, + const CapturePieceToHistory* cph, Square rs) + : pos(p), mainHistory(mh), captureHistory(cph), recaptureSquare(rs), depth(d) { assert(d <= DEPTH_ZERO); - if (pos.checkers()) - stage = EVASION; - - else if (d > DEPTH_QS_NO_CHECKS) - stage = QSEARCH_0; - - else if (d > DEPTH_QS_RECAPTURES) - { - stage = QSEARCH_1; - - // 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.capture_or_promotion(ttm)) - ttm = MOVE_NONE; - } - else - { - stage = RECAPTURE; - recaptureSquare = s; - ttm = MOVE_NONE; - } - - ttMove = (ttm && pos.pseudo_legal(ttm) ? ttm : MOVE_NONE); - end += (ttMove != MOVE_NONE); + 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); } -MovePicker::MovePicker(const Position& p, Move ttm, const HistoryStats& h, PieceType pt) - : pos(p), history(h), cur(moves), end(moves) { +/// MovePicker constructor for ProbCut: we generate captures with SEE higher +/// 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()); - stage = PROBCUT; - - // In ProbCut we generate only captures that are better than the parent's - // captured piece. - captureThreshold = PieceValue[MG][pt]; - ttMove = (ttm && pos.pseudo_legal(ttm) ? ttm : MOVE_NONE); - - if (ttMove && (!pos.capture(ttMove) || pos.see(ttMove) <= captureThreshold)) - ttMove = MOVE_NONE; - - end += (ttMove != MOVE_NONE); + stage = PROBCUT_TT; + ttMove = ttm + && pos.pseudo_legal(ttm) + && pos.capture(ttm) + && pos.see_ge(ttm, threshold) ? ttm : MOVE_NONE; + stage += (ttMove == MOVE_NONE); } - -/// score() assign a numerical value to each move in a move list. The moves with -/// highest values 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 the - // badCaptures[] array, but instead of doing it now we delay until the move - // has been picked up in pick_move_from_list(). This way we save some SEE - // calls in case we get a cutoff. - Move m; - - for (ExtMove* it = moves; it != end; ++it) - { - m = it->move; - it->value = PieceValue[MG][pos.piece_on(to_sq(m))] - - Value(type_of(pos.moved_piece(m))); - - if (type_of(m) == ENPASSANT) - it->value += PieceValue[MG][PAWN]; - - else if (type_of(m) == PROMOTION) - it->value += PieceValue[MG][promotion_type(m)] - PieceValue[MG][PAWN]; - } +/// 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 = PieceValue[MG][pos.piece_on(to_sq(m))] + + (*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)] + + (*contHistory[0])[pos.moved_piece(m)][to_sq(m)] + + (*contHistory[1])[pos.moved_piece(m)][to_sq(m)] + + (*contHistory[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)] - (1 << 28); + } } -template<> -void MovePicker::score() { +/// MovePicker::select_move() returns the next move satisfying a predicate function. +/// It never returns the TT move. +template +Move MovePicker::select_move(Pred filter) { - Move m; - - for (ExtMove* it = moves; it != end; ++it) + while (cur < endMoves) { - m = it->move; - it->value = history[pos.moved_piece(m)][to_sq(m)]; - } -} + if (T == BEST_SCORE) + std::swap(*cur, *std::max_element(cur, endMoves)); -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 value. - Move m; - Value see; + move = *cur++; - for (ExtMove* it = moves; it != end; ++it) - { - m = it->move; - if ((see = pos.see_sign(m)) < VALUE_ZERO) - it->value = see - HistoryStats::Max; // At the bottom - - else if (pos.capture(m)) - it->value = PieceValue[MG][pos.piece_on(to_sq(m))] - - Value(type_of(pos.moved_piece(m))) + HistoryStats::Max; - else - it->value = history[pos.moved_piece(m)][to_sq(m)]; + if (move != ttMove && filter()) + return move; } + return move = MOVE_NONE; } - -/// generate_next_stage() generates, scores and sorts the next bunch of moves, -/// when there are no more moves to try for the current stage. - -void MovePicker::generate_next_stage() { - - cur = moves; - - switch (++stage) { - - case CAPTURES_S1: case CAPTURES_S3: case CAPTURES_S4: case CAPTURES_S5: case CAPTURES_S6: - end = generate(pos, moves); +/// 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) { + +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: + endBadCaptures = cur = moves; + endMoves = generate(pos, cur); score(); - return; - - case KILLERS_S1: - cur = killers; - end = cur + 2; - - killers[0].move = ss->killers[0]; - killers[1].move = ss->killers[1]; - killers[2].move = killers[3].move = MOVE_NONE; - killers[4].move = killers[5].move = MOVE_NONE; - - // Please note that following code is racy and could yield to rare (less - // than 1 out of a million) duplicated entries in SMP case. This is harmless. - - // Be sure countermoves are different from killers - for (int i = 0; i < 2; ++i) - if ( countermoves[i] != (cur+0)->move - && countermoves[i] != (cur+1)->move) - (end++)->move = countermoves[i]; - - // Be sure followupmoves are different from killers and countermoves - for (int i = 0; i < 2; ++i) - if ( followupmoves[i] != (cur+0)->move - && followupmoves[i] != (cur+1)->move - && followupmoves[i] != (cur+2)->move - && followupmoves[i] != (cur+3)->move) - (end++)->move = followupmoves[i]; - return; - - case QUIETS_1_S1: - endQuiets = end = generate(pos, moves); + ++stage; + goto top; + + case GOOD_CAPTURE: + if (select_move([&](){ 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_move([&](){ return move != MOVE_NONE + && !pos.capture(move) + && pos.pseudo_legal(move); })) + return move; + ++stage; + /* fallthrough */ + + case QUIET_INIT: + cur = endBadCaptures; + endMoves = generate(pos, cur); score(); - end = std::partition(cur, end, has_positive_value); - 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: - stage = STOP; - /* Fall through */ - - case STOP: - end = cur + 1; // Avoid another next_phase() call - return; - - default: - assert(false); - } -} - + partial_insertion_sort(cur, endMoves, -4000 * depth / ONE_PLY); + ++stage; + /* fallthrough */ + + case QUIET: + if ( !skipQuiets + && select_move([&](){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_move(Any); + + case EVASION_INIT: + cur = moves; + endMoves = generate(pos, cur); + score(); + ++stage; + /* fallthrough */ + + case EVASION: + return select_move(Any); + + case PROBCUT: + return select_move([&](){ return pos.see_ge(move, threshold); }); + + case QCAPTURE: + if (select_move([&](){ 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; -/// 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. It picks the move with the biggest value from a list of generated moves -/// taking care not to return the ttMove if it has already been searched. -template<> -Move MovePicker::next_move() { + ++stage; + /* fallthrough */ - Move move; + case QCHECK_INIT: + cur = moves; + endMoves = generate(pos, cur); + ++stage; + /* fallthrough */ - while (true) - { - while (cur == end) - generate_next_stage(); - - switch (stage) { - - 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) - { - if (pos.see_sign(move) >= VALUE_ZERO) - 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 - && move != ttMove - && pos.pseudo_legal(move) - && !pos.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 - && move != killers[3].move - && move != killers[4].move - && move != killers[5].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: - return MOVE_NONE; - - default: - assert(false); - } + case QCHECK: + return select_move(Any); } -} - -/// 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(); } + assert(false); + return MOVE_NONE; // Silence warning +}