X-Git-Url: https://git.sesse.net/?p=stockfish;a=blobdiff_plain;f=src%2Fmovepick.cpp;h=e1042ea6005f0255ccb1f4b21f809e0f0e4a3b84;hp=8872e39f3691a8740a8ba1244f8fc3c4664951c5;hb=2af2c67650c4ac2531e6ab2753830f91c0999876;hpb=c9d7e99de682516c560009b550c41da9ae2008b8 diff --git a/src/movepick.cpp b/src/movepick.cpp index 8872e39f..e1042ea6 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) 2008-2010 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 @@ -20,331 +20,248 @@ #include -#include "movegen.h" #include "movepick.h" -#include "search.h" -#include "types.h" namespace { - enum MovegenPhase { - PH_TT_MOVES, // Transposition table move and mate killer - PH_GOOD_CAPTURES, // Queen promotions and captures with SEE values >= 0 - PH_KILLERS, // Killer moves from the current ply - PH_NONCAPTURES, // Non-captures and underpromotions - PH_BAD_CAPTURES, // Queen promotions and captures with SEE values < 0 - PH_EVASIONS, // Check evasions - PH_QCAPTURES, // Captures in quiescence search - PH_QCHECKS, // Non-capture checks in quiescence search - PH_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 }; - CACHE_LINE_ALIGNMENT - const uint8_t MainSearchTable[] = { PH_TT_MOVES, PH_GOOD_CAPTURES, PH_KILLERS, PH_NONCAPTURES, PH_BAD_CAPTURES, PH_STOP }; - const uint8_t EvasionTable[] = { PH_TT_MOVES, PH_EVASIONS, PH_STOP }; - const uint8_t QsearchWithChecksTable[] = { PH_TT_MOVES, PH_QCAPTURES, PH_QCHECKS, PH_STOP }; - const uint8_t QsearchWithoutChecksTable[] = { PH_TT_MOVES, PH_QCAPTURES, PH_STOP }; -} + // Helper filter used with select() + 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; + } + } +} // namespace -/// Constructor for the MovePicker class. Apart from the position for which -/// it is asked to pick legal moves, MovePicker also wants some information -/// to help it to return the presumably good moves first, to decide which + +/// 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 about how important good -/// move ordering is at the current node. +/// 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 History& h, - SearchStack* ss, Value beta) : pos(p), H(h) { - int searchTT = ttm; - ttMoves[0].move = ttm; - badCaptureThreshold = 0; - badCaptures = moves + MAX_MOVES; +/// 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); - pinned = p.pinned_pieces(pos.side_to_move()); - - if (p.is_check()) - { - ttMoves[1].move = killers[0].move = killers[1].move = MOVE_NONE; - phasePtr = EvasionTable; - } - else - { - ttMoves[1].move = (ss->mateKiller == ttm) ? MOVE_NONE : ss->mateKiller; - searchTT |= ttMoves[1].move; - killers[0].move = ss->killers[0]; - killers[1].move = ss->killers[1]; - - // Consider sligtly negative captures as good if at low - // depth and far from beta. - if (ss && ss->eval < beta - PawnValueMidgame && d < 3 * ONE_PLY) - badCaptureThreshold = -PawnValueMidgame; - - phasePtr = MainSearchTable; - } - - phasePtr += int(!searchTT) - 1; - go_next_phase(); + 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) - : pos(p), H(h) { - int searchTT = ttm; - ttMoves[0].move = ttm; - ttMoves[1].move = MOVE_NONE; +/// 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); - pinned = p.pinned_pieces(pos.side_to_move()); + 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); +} - if (p.is_check()) - phasePtr = EvasionTable; - else if (d >= DEPTH_QS_CHECKS) - phasePtr = QsearchWithChecksTable; - else - { - phasePtr = QsearchWithoutChecksTable; +/// 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) { - // 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 != MOVE_NONE && !pos.move_is_capture_or_promotion(ttm)) - searchTT = ttMoves[0].move = MOVE_NONE; - } + assert(!pos.checkers()); - phasePtr += int(!searchTT) - 1; - go_next_phase(); + stage = PROBCUT_TT; + ttMove = ttm + && pos.pseudo_legal(ttm) + && pos.capture(ttm) + && pos.see_ge(ttm, threshold) ? ttm : MOVE_NONE; + stage += (ttMove == MOVE_NONE); } - -/// MovePicker::go_next_phase() generates, scores and sorts the next bunch -/// of moves when there are no more moves to try for the current phase. - -void MovePicker::go_next_phase() { - - curMove = moves; - phase = *(++phasePtr); - switch (phase) { - - case PH_TT_MOVES: - curMove = ttMoves; - lastMove = curMove + 2; - return; - - case PH_GOOD_CAPTURES: - lastMove = generate(pos, moves); - score_captures(); - return; - - case PH_KILLERS: - curMove = killers; - lastMove = curMove + 2; - return; - - case PH_NONCAPTURES: - lastMove = generate(pos, moves); - score_noncaptures(); - sort_moves(moves, lastMove, &lastGoodNonCapture); - return; - - case PH_BAD_CAPTURES: - // Bad captures SEE value is already calculated so just pick - // them in order to get SEE move ordering. - curMove = badCaptures; - lastMove = moves + MAX_MOVES; - return; - - case PH_EVASIONS: - assert(pos.is_check()); - lastMove = generate(pos, moves); - score_evasions(); - return; - - case PH_QCAPTURES: - lastMove = generate(pos, moves); - score_captures(); - return; - - case PH_QCHECKS: - lastMove = generate(pos, moves); - return; - - case PH_STOP: - lastMove = curMove + 1; // Avoid another go_next_phase() call - return; - - default: - assert(false); - return; - } +/// 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)))] / 16; + + 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); + } } +/// MovePicker::select() returns the next move satisfying a predicate function. +/// It never returns the TT move. +template +Move MovePicker::select(Pred filter) { -/// MovePicker::score_captures(), MovePicker::score_noncaptures() and -/// MovePicker::score_evasions() assign a numerical move ordering score -/// to each move in a move list. The moves with highest scores will be -/// picked first by get_next_move(). - -void MovePicker::score_captures() { - // 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; - - // Use MVV/LVA ordering - for (MoveStack* cur = moves; cur != lastMove; cur++) + while (cur < endMoves) { - m = cur->move; - if (move_is_promotion(m)) - cur->score = QueenValueMidgame; - else - cur->score = pos.midgame_value_of_piece_on(move_to(m)) - - pos.type_of_piece_on(move_from(m)); + if (T == Best) + std::swap(*cur, *std::max_element(cur, endMoves)); + + move = *cur++; + + if (move != ttMove && filter()) + return move; } + return move = MOVE_NONE; } -void MovePicker::score_noncaptures() { +/// 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: + cur = endBadCaptures = moves; + endMoves = generate(pos, cur); + + score(); + ++stage; + goto top; + + case GOOD_CAPTURE: + if (select([&](){ + 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; - Move m; - Square from; + // Prepare the pointers to loop over the refutations array + cur = std::begin(refutations); + endMoves = std::end(refutations); - for (MoveStack* cur = moves; cur != lastMove; cur++) - { - m = cur->move; - from = move_from(m); - cur->score = H.value(pos.piece_on(from), move_to(m)); - } -} + // 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; -void MovePicker::score_evasions() { - // Try good captures ordered by MVV/LVA, then non-captures if - // destination square is not under attack, ordered by history - // value, and at the end bad-captures and non-captures with a - // negative SEE. This last group is ordered by the SEE score. - Move m; - int seeScore; + ++stage; + /* fallthrough */ - // Skip if we don't have at least two moves to order - if (lastMove < moves + 2) - return; + case REFUTATION: + if (select([&](){ 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(); + partial_insertion_sort(cur, endMoves, -4000 * depth / ONE_PLY); + ++stage; + /* fallthrough */ + + case QUIET: + if ( !skipQuiets + && select([&](){return move != refutations[0] + && move != refutations[1] + && move != refutations[2];})) + return move; - for (MoveStack* cur = moves; cur != lastMove; cur++) - { - m = cur->move; - if ((seeScore = pos.see_sign(m)) < 0) - cur->score = seeScore - History::MaxValue; // Be sure we are at the bottom - else if (pos.move_is_capture(m)) - cur->score = pos.midgame_value_of_piece_on(move_to(m)) - - pos.type_of_piece_on(move_from(m)) + History::MaxValue; - else - cur->score = H.value(pos.piece_on(move_from(m)), move_to(m)); - } -} + // Prepare the pointers to loop over the bad captures + cur = moves; + endMoves = endBadCaptures; -/// MovePicker::get_next_move() is the most important method of the MovePicker -/// class. It returns a new legal move every time it 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 to return the tt move if has already been -/// searched previously. Note that this function is not thread safe so should be -/// lock protected by caller when accessed through a shared MovePicker object. + ++stage; + /* fallthrough */ -Move MovePicker::get_next_move() { + case BAD_CAPTURE: + return select(Any); - Move move; + case EVASION_INIT: + cur = moves; + endMoves = generate(pos, cur); - while (true) - { - while (curMove == lastMove) - go_next_phase(); - - switch (phase) { - - case PH_TT_MOVES: - move = (curMove++)->move; - if ( move != MOVE_NONE - && pos.move_is_legal(move, pinned)) - return move; - break; - - case PH_GOOD_CAPTURES: - move = pick_best(curMove++, lastMove).move; - if ( move != ttMoves[0].move - && move != ttMoves[1].move - && pos.pl_move_is_legal(move, pinned)) - { - // Check for a non negative SEE now - int seeValue = pos.see_sign(move); - if (seeValue >= badCaptureThreshold) - return move; - - // Losing capture, move it to the tail of the array, note - // that move has now been already checked for legality. - (--badCaptures)->move = move; - badCaptures->score = seeValue; - } - break; - - case PH_KILLERS: - move = (curMove++)->move; - if ( move != MOVE_NONE - && pos.move_is_legal(move, pinned) - && move != ttMoves[0].move - && move != ttMoves[1].move - && !pos.move_is_capture(move)) - return move; - break; - - case PH_NONCAPTURES: - // Sort negative scored moves only when we get there - if (curMove == lastGoodNonCapture) - insertion_sort(lastGoodNonCapture, lastMove); - - move = (curMove++)->move; - if ( move != ttMoves[0].move - && move != ttMoves[1].move - && move != killers[0].move - && move != killers[1].move - && pos.pl_move_is_legal(move, pinned)) - return move; - break; - - case PH_BAD_CAPTURES: - move = pick_best(curMove++, lastMove).move; + score(); + ++stage; + /* fallthrough */ + + case EVASION: + return select(Any); + + case PROBCUT: + return select([&](){ return pos.see_ge(move, threshold); }); + + case QCAPTURE: + if (select([&](){ return depth > DEPTH_QS_RECAPTURES + || to_sq(move) == recaptureSquare; })) return move; - case PH_EVASIONS: - case PH_QCAPTURES: - move = pick_best(curMove++, lastMove).move; - if ( move != ttMoves[0].move - && pos.pl_move_is_legal(move, pinned)) - return move; - break; - - case PH_QCHECKS: - move = (curMove++)->move; - if ( move != ttMoves[0].move - && pos.pl_move_is_legal(move, pinned)) - return move; - break; - - case PH_STOP: + // 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); - break; - } + ++stage; + /* fallthrough */ + + case QCHECK_INIT: + cur = moves; + endMoves = generate(pos, cur); + + ++stage; + /* fallthrough */ + + case QCHECK: + return select(Any); } + + assert(false); + return MOVE_NONE; // Silence warning }