X-Git-Url: https://git.sesse.net/?p=stockfish;a=blobdiff_plain;f=src%2Fmovepick.cpp;h=84f26dbf7835c08a2794313aad91560d4e6f3991;hp=06ea5e25d2da257d57a1668e0ed3d2c10aa6384d;hb=8a7876d48d4360d14d918c1ff444b5d6eb0382de;hpb=d9c7cad6302ddeff9f8a32a3fe66359c556a868e diff --git a/src/movepick.cpp b/src/movepick.cpp index 06ea5e25..84f26dbf 100644 --- a/src/movepick.cpp +++ b/src/movepick.cpp @@ -1,7 +1,7 @@ /* 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) 2008-2014 Marco Costalba, Joona Kiiski, 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 @@ -35,7 +35,7 @@ namespace { STOP }; - // Our insertion sort, guaranteed to be stable, as is needed + // Our insertion sort, which is guaranteed (and also needed) to be stable void insertion_sort(ExtMove* begin, ExtMove* end) { ExtMove tmp, *p, *q; @@ -49,38 +49,39 @@ namespace { } } - // 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 ExtMove& ms) { return ms.score > 0; } + // 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 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. + // 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 +/// 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 HistoryStats& h, - Move* cm, Search::Stack* s) : pos(p), history(h), depth(d) { + Move* cm, Move* fm, Search::Stack* s) : pos(p), history(h), depth(d) { assert(d > DEPTH_ZERO); cur = end = moves; endBadCaptures = moves + MAX_MOVES - 1; countermoves = cm; + followupmoves = fm; ss = s; - if (p.checkers()) + if (pos.checkers()) stage = EVASION; else @@ -91,11 +92,11 @@ MovePicker::MovePicker(const Position& p, Move ttm, Depth d, const HistoryStats& } MovePicker::MovePicker(const Position& p, Move ttm, Depth d, const HistoryStats& h, - Square sq) : pos(p), history(h), cur(moves), end(moves) { + Square s) : pos(p), history(h), cur(moves), end(moves) { assert(d <= DEPTH_ZERO); - if (p.checkers()) + if (pos.checkers()) stage = EVASION; else if (d > DEPTH_QS_NO_CHECKS) @@ -105,7 +106,7 @@ MovePicker::MovePicker(const Position& p, Move ttm, Depth d, const HistoryStats& { stage = QSEARCH_1; - // Skip TT move if is not a capture or a promotion, this avoids qsearch + // 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)) @@ -114,7 +115,7 @@ MovePicker::MovePicker(const Position& p, Move ttm, Depth d, const HistoryStats& else { stage = RECAPTURE; - recaptureSquare = sq; + recaptureSquare = s; ttm = MOVE_NONE; } @@ -129,7 +130,8 @@ MovePicker::MovePicker(const Position& p, Move ttm, const HistoryStats& h, Piece stage = PROBCUT; - // In ProbCut we generate only captures better than parent's captured piece + // 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); @@ -140,17 +142,8 @@ MovePicker::MovePicker(const Position& p, Move ttm, const HistoryStats& h, Piece } -/// stage_moves() returns a pointer to the beginning of moves array. It -/// is used to access already tried quiet moves when updating history. - -const ExtMove* MovePicker::stage_moves() const { - assert(stage == KILLERS_S1 || stage == QUIETS_1_S1 || stage == QUIETS_2_S1); - return stage == KILLERS_S1 ? killers : moves; -} - - -/// score() assign a numerical move ordering score to each move in a move list. -/// The moves with highest scores will be picked first. +/// 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. @@ -162,23 +155,23 @@ void MovePicker::score() { // 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). + // 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->score = PieceValue[MG][pos.piece_on(to_sq(m))] - - type_of(pos.moved_piece(m)); + it->value = PieceValue[MG][pos.piece_on(to_sq(m))] + - Value(type_of(pos.moved_piece(m))); - if (type_of(m) == PROMOTION) - it->score += PieceValue[MG][promotion_type(m)] - PieceValue[MG][PAWN]; + if (type_of(m) == ENPASSANT) + it->value += PieceValue[MG][PAWN]; - else if (type_of(m) == ENPASSANT) - it->score += PieceValue[MG][PAWN]; + else if (type_of(m) == PROMOTION) + it->value += PieceValue[MG][promotion_type(m)] - PieceValue[MG][PAWN]; } } @@ -190,7 +183,7 @@ void MovePicker::score() { for (ExtMove* it = moves; it != end; ++it) { m = it->move; - it->score = history[pos.moved_piece(m)][to_sq(m)]; + it->value = history[pos.moved_piece(m)][to_sq(m)]; } } @@ -198,29 +191,29 @@ 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. + // moves with a negative SEE. This last group is ordered by the SEE value. Move m; - int seeScore; + Value see; for (ExtMove* it = moves; it != end; ++it) { m = it->move; - if ((seeScore = pos.see_sign(m)) < 0) - it->score = seeScore - HistoryStats::Max; // At the bottom + if ((see = pos.see_sign(m)) < VALUE_ZERO) + it->value = see - HistoryStats::Max; // At the bottom else if (pos.capture(m)) - it->score = PieceValue[MG][pos.piece_on(to_sq(m))] - - type_of(pos.moved_piece(m)) + HistoryStats::Max; + it->value = PieceValue[MG][pos.piece_on(to_sq(m))] + - Value(type_of(pos.moved_piece(m))) + HistoryStats::Max; else - it->score = history[pos.moved_piece(m)][to_sq(m)]; + it->value = history[pos.moved_piece(m)][to_sq(m)]; } } -/// generate_next() generates, scores and sorts the next bunch of moves, when -/// there are no more moves to try for the current phase. +/// 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() { +void MovePicker::generate_next_stage() { cur = moves; @@ -238,21 +231,30 @@ void MovePicker::generate_next() { 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->move && countermoves[i] != (cur+1)->move) + if ( countermoves[i] != (cur+0)->move + && countermoves[i] != (cur+1)->move) (end++)->move = countermoves[i]; - if (countermoves[1] && countermoves[1] == countermoves[0]) // Due to SMP races - killers[3].move = MOVE_NONE; - + // 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); score(); - end = std::partition(cur, end, has_positive_score); + end = std::partition(cur, end, has_positive_value); insertion_sort(cur, end); return; @@ -281,6 +283,8 @@ void MovePicker::generate_next() { 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; @@ -292,9 +296,9 @@ void MovePicker::generate_next() { /// 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. +/// 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() { @@ -303,7 +307,7 @@ Move MovePicker::next_move() { while (true) { while (cur == end) - generate_next(); + generate_next_stage(); switch (stage) { @@ -315,7 +319,7 @@ Move MovePicker::next_move() { move = pick_best(cur++, end)->move; if (move != ttMove) { - if (pos.see_sign(move) >= 0) + if (pos.see_sign(move) >= VALUE_ZERO) return move; // Losing capture, move it to the tail of the array @@ -326,8 +330,8 @@ Move MovePicker::next_move() { case KILLERS_S1: move = (cur++)->move; if ( move != MOVE_NONE - && pos.pseudo_legal(move) && move != ttMove + && pos.pseudo_legal(move) && !pos.capture(move)) return move; break; @@ -338,7 +342,9 @@ Move MovePicker::next_move() { && move != killers[0].move && move != killers[1].move && move != killers[2].move - && move != killers[3].move) + && move != killers[3].move + && move != killers[4].move + && move != killers[5].move) return move; break;