X-Git-Url: https://git.sesse.net/?p=stockfish;a=blobdiff_plain;f=src%2Fmovepick.cpp;h=4971b304ba0c12f550151564ba0fe5c038c5c61c;hp=61e5527f42c61d638132201f0b2f2efd18bc999a;hb=4c95edddbf1aaec22c343adaca4796df0137e4c3;hpb=8647fbd6ed11c60282e84e4b486a7e8258c88483 diff --git a/src/movepick.cpp b/src/movepick.cpp index 61e5527f..4971b304 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) 2015-2016 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 @@ -20,345 +20,318 @@ #include -#include "movegen.h" #include "movepick.h" -#include "search.h" -#include "types.h" +#include "thread.h" namespace { - enum MovegenPhase { - PH_TT_MOVE, // Transposition table move - PH_GOOD_CAPTURES, // Queen promotions and captures with SEE values >= captureThreshold (captureThreshold <= 0) - PH_GOOD_PROBCUT, // Queen promotions and captures with SEE values > captureThreshold (captureThreshold >= 0) - PH_KILLERS, // Killer moves from the current ply - PH_NONCAPTURES_1, // Non-captures and underpromotions with positive score - PH_NONCAPTURES_2, // Non-captures and underpromotions with non-positive score - PH_BAD_CAPTURES, // Queen promotions and captures with SEE values < captureThreshold (captureThreshold <= 0) - PH_EVASIONS, // Check evasions - PH_QCAPTURES, // Captures in quiescence search - PH_QCHECKS, // Non-capture checks in quiescence search - PH_STOP + enum Stages { + MAIN_SEARCH, GOOD_CAPTURES, KILLERS, QUIET, BAD_CAPTURES, + EVASION, ALL_EVASIONS, + QSEARCH_WITH_CHECKS, QCAPTURES_1, CHECKS, + QSEARCH_WITHOUT_CHECKS, QCAPTURES_2, + PROBCUT, PROBCUT_CAPTURES, + RECAPTURE, RECAPTURES, + STOP }; - CACHE_LINE_ALIGNMENT - const uint8_t MainSearchTable[] = { PH_TT_MOVE, PH_GOOD_CAPTURES, PH_KILLERS, PH_NONCAPTURES_1, PH_NONCAPTURES_2, PH_BAD_CAPTURES, PH_STOP }; - const uint8_t EvasionTable[] = { PH_TT_MOVE, PH_EVASIONS, PH_STOP }; - const uint8_t QsearchWithChecksTable[] = { PH_TT_MOVE, PH_QCAPTURES, PH_QCHECKS, PH_STOP }; - const uint8_t QsearchWithoutChecksTable[] = { PH_TT_MOVE, PH_QCAPTURES, PH_STOP }; - const uint8_t ProbCutTable[] = { PH_TT_MOVE, PH_GOOD_PROBCUT, PH_STOP }; -} + // Our insertion sort, which is guaranteed to be stable, as it should be + 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; + } + } -/// Constructors for 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. + // pick_best() finds 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., the possible captures. + Move pick_best(ExtMove* begin, ExtMove* end) + { + std::swap(*begin, *std::max_element(begin, end)); + return *begin; + } -MovePicker::MovePicker(const Position& p, Move ttm, Depth d, const History& h, - SearchStack* ss, Value beta) : pos(p), H(h), depth(d) { - captureThreshold = 0; - badCaptures = moves + MAX_MOVES; +} // namespace - assert(d > DEPTH_ZERO); - if (p.in_check()) - { - killers[0].move = killers[1].move = MOVE_NONE; - phasePtr = EvasionTable; - } - else - { - killers[0].move = ss->killers[0]; - killers[1].move = ss->killers[1]; +/// 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. - // Consider sligtly negative captures as good if at low - // depth and far from beta. - if (ss && ss->eval < beta - PawnValueMidgame && d < 3 * ONE_PLY) - captureThreshold = -PawnValueMidgame; +MovePicker::MovePicker(const Position& p, Move ttm, Depth d, Search::Stack* s) + : pos(p), ss(s), depth(d) { - phasePtr = MainSearchTable; - } + assert(d > DEPTH_ZERO); + + Square prevSq = to_sq((ss-1)->currentMove); + countermove = pos.this_thread()->counterMoves[pos.piece_on(prevSq)][prevSq]; - ttMove = (ttm && pos.move_is_pl(ttm) ? ttm : MOVE_NONE); - phasePtr += int(ttMove == MOVE_NONE) - 1; - go_next_phase(); + stage = pos.checkers() ? EVASION : MAIN_SEARCH; + ttMove = ttm && pos.pseudo_legal(ttm) ? ttm : MOVE_NONE; + endMoves += (ttMove != MOVE_NONE); } -MovePicker::MovePicker(const Position& p, Move ttm, Depth d, const History& h) - : pos(p), H(h) { +MovePicker::MovePicker(const Position& p, Move ttm, Depth d, Square s) + : pos(p) { assert(d <= DEPTH_ZERO); - if (p.in_check()) - phasePtr = EvasionTable; - else if (d >= DEPTH_QS_CHECKS) - phasePtr = QsearchWithChecksTable; + if (pos.checkers()) + stage = EVASION; + + else if (d > DEPTH_QS_NO_CHECKS) + stage = QSEARCH_WITH_CHECKS; + + else if (d > DEPTH_QS_RECAPTURES) + stage = QSEARCH_WITHOUT_CHECKS; + else { - phasePtr = QsearchWithoutChecksTable; - - // 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(ttm) && !move_is_promotion(ttm)) - ttm = MOVE_NONE; + stage = RECAPTURE; + recaptureSquare = s; + ttm = MOVE_NONE; } - ttMove = (ttm && pos.move_is_pl(ttm) ? ttm : MOVE_NONE); - phasePtr += int(ttMove == MOVE_NONE) - 1; - go_next_phase(); + ttMove = ttm && pos.pseudo_legal(ttm) ? ttm : MOVE_NONE; + endMoves += (ttMove != MOVE_NONE); } -MovePicker::MovePicker(const Position& p, Move ttm, const History& h, int parentCapture) - : pos(p), H(h) { +MovePicker::MovePicker(const Position& p, Move ttm, Value th) + : pos(p), threshold(th) { - assert (!pos.in_check()); + assert(!pos.checkers()); - // In ProbCut we consider only captures better than parent's move - captureThreshold = parentCapture; - phasePtr = ProbCutTable; + stage = PROBCUT; - if ( ttm != MOVE_NONE - && (!pos.move_is_capture(ttm) || pos.see(ttm) <= captureThreshold)) - ttm = MOVE_NONE; + // In ProbCut we generate captures with SEE higher than the given threshold + ttMove = ttm + && pos.pseudo_legal(ttm) + && pos.capture(ttm) + && pos.see(ttm) > threshold ? ttm : MOVE_NONE; - ttMove = (ttm && pos.move_is_pl(ttm) ? ttm : MOVE_NONE); - phasePtr += int(ttMove == MOVE_NONE) - 1; - go_next_phase(); + endMoves += (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_MOVE: - lastMove = curMove + 1; - return; - - case PH_GOOD_CAPTURES: - case PH_GOOD_PROBCUT: - lastMove = generate(pos, moves); - score_captures(); - return; - - case PH_KILLERS: - curMove = killers; - lastMove = curMove + 2; - return; - - case PH_NONCAPTURES_1: - lastNonCapture = lastMove = generate(pos, moves); - score_noncaptures(); - sort_moves(moves, lastNonCapture, &lastMove); - return; - - case PH_NONCAPTURES_2: - curMove = lastMove; - lastMove = lastNonCapture; - if (depth >= 3 * ONE_PLY) - insertion_sort(curMove, lastMove); - 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.in_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; - } +/// score() assigns 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, preferring + // captures near our home rank. Surprisingly, this appears to perform slightly + // better than SEE-based move ordering: exchanging big pieces before capturing + // a hanging piece probably helps to reduce the subtree size. + // In the 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, saving some SEE calls in case we get a cutoff. + for (auto& m : *this) + m.value = PieceValue[MG][pos.piece_on(to_sq(m))] + - Value(200 * relative_rank(pos.side_to_move(), to_sq(m))); } +template<> +void MovePicker::score() { -/// 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++) - { - 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)); - } -} + const HistoryStats& history = pos.this_thread()->history; + const FromToStats& fromTo = pos.this_thread()->fromTo; -void MovePicker::score_noncaptures() { + const CounterMoveStats* cm = (ss-1)->counterMoves; + const CounterMoveStats* fm = (ss-2)->counterMoves; + const CounterMoveStats* f2 = (ss-4)->counterMoves; - Move m; - Square from; + Color c = pos.side_to_move(); - 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)); - } + for (auto& m : *this) + m.value = history[pos.moved_piece(m)][to_sq(m)] + + (cm ? (*cm)[pos.moved_piece(m)][to_sq(m)] : VALUE_ZERO) + + (fm ? (*fm)[pos.moved_piece(m)][to_sq(m)] : VALUE_ZERO) + + (f2 ? (*f2)[pos.moved_piece(m)][to_sq(m)] : VALUE_ZERO) + + fromTo.get(c, m); } -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; +template<> +void MovePicker::score() { + // Try winning and equal captures ordered by MVV/LVA, then non-captures ordered + // by history value, then bad captures and quiet moves with a negative SEE ordered + // by SEE value. + const HistoryStats& history = pos.this_thread()->history; + const FromToStats& fromTo = pos.this_thread()->fromTo; + Color c = pos.side_to_move(); + Value see; + + for (auto& m : *this) + if ((see = pos.see_sign(m)) < VALUE_ZERO) + m.value = see - HistoryStats::Max; // At the bottom + + else if (pos.capture(m)) + m.value = PieceValue[MG][pos.piece_on(to_sq(m))] + - Value(type_of(pos.moved_piece(m))) + HistoryStats::Max; + else + m.value = history[pos.moved_piece(m)][to_sq(m)] + fromTo.get(c, m); +} - // Skip if we don't have at least two moves to order - if (lastMove < moves + 2) - return; - 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)); +/// 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() { + + assert(stage != STOP); + + cur = moves; + + switch (++stage) { + + case GOOD_CAPTURES: case QCAPTURES_1: case QCAPTURES_2: + case PROBCUT_CAPTURES: case RECAPTURES: + endMoves = generate(pos, moves); + score(); + break; + + case KILLERS: + killers[0] = ss->killers[0]; + killers[1] = ss->killers[1]; + killers[2] = countermove; + cur = killers; + endMoves = cur + 2 + (countermove != killers[0] && countermove != killers[1]); + break; + + case QUIET: + endMoves = generate(pos, moves); + score(); + if (depth < 3 * ONE_PLY) + { + ExtMove* goodQuiet = std::partition(cur, endMoves, [](const ExtMove& m) + { return m.value > VALUE_ZERO; }); + insertion_sort(cur, goodQuiet); + } else + insertion_sort(cur, endMoves); + break; + + case BAD_CAPTURES: + // Just pick them in reverse order to get correct ordering + cur = moves + MAX_MOVES - 1; + endMoves = endBadCaptures; + break; + + case ALL_EVASIONS: + endMoves = generate(pos, moves); + if (endMoves - moves > 1) + score(); + break; + + case CHECKS: + endMoves = generate(pos, moves); + break; + + case EVASION: case QSEARCH_WITH_CHECKS: case QSEARCH_WITHOUT_CHECKS: + case PROBCUT: case RECAPTURE: case STOP: + stage = STOP; + break; + + default: + assert(false); } } -/// MovePicker::get_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 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. +int MovePicker::see_sign() const +{ + return stage == GOOD_CAPTURES ? 1 + : stage == BAD_CAPTURES ? -1 : 0; +} + +/// 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. -Move MovePicker::get_next_move() { +Move MovePicker::next_move() { Move move; while (true) { - while (curMove == lastMove) - go_next_phase(); + while (cur == endMoves && stage != STOP) + generate_next_stage(); - switch (phase) { + switch (stage) { - case PH_TT_MOVE: - curMove++; + case MAIN_SEARCH: case EVASION: case QSEARCH_WITH_CHECKS: + case QSEARCH_WITHOUT_CHECKS: case PROBCUT: + ++cur; return ttMove; - break; - case PH_GOOD_CAPTURES: - move = pick_best(curMove++, lastMove).move; + case GOOD_CAPTURES: + move = pick_best(cur++, endMoves); if (move != ttMove) { - assert(captureThreshold <= 0); // Otherwise we must use see instead of see_sign - - // Check for a non negative SEE now - int seeValue = pos.see_sign(move); - if (seeValue >= captureThreshold) + if (pos.see_sign(move) >= VALUE_ZERO) return move; - // Losing capture, move it to the tail of the array, note - // that move has now been already checked for pseudo legality. - (--badCaptures)->move = move; - badCaptures->score = seeValue; + // Losing capture, move it to the tail of the array + *endBadCaptures-- = move; } break; - case PH_GOOD_PROBCUT: - move = pick_best(curMove++, lastMove).move; - if ( move != ttMove - && pos.see(move) > captureThreshold) + case KILLERS: + move = *cur++; + if ( move != MOVE_NONE + && move != ttMove + && pos.pseudo_legal(move) + && !pos.capture(move)) return move; break; - case PH_KILLERS: - move = (curMove++)->move; - if ( move != MOVE_NONE - && pos.move_is_pl(move) - && move != ttMove - && !pos.move_is_capture(move)) + case QUIET: + move = *cur++; + if ( move != ttMove + && move != killers[0] + && move != killers[1] + && move != killers[2]) return move; break; - case PH_NONCAPTURES_1: - case PH_NONCAPTURES_2: - move = (curMove++)->move; - if ( move != ttMove - && move != killers[0].move - && move != killers[1].move) + case BAD_CAPTURES: + return *cur--; + + case ALL_EVASIONS: case QCAPTURES_1: case QCAPTURES_2: + move = pick_best(cur++, endMoves); + if (move != ttMove) return move; break; - case PH_BAD_CAPTURES: - move = pick_best(curMove++, lastMove).move; - return move; + case PROBCUT_CAPTURES: + move = pick_best(cur++, endMoves); + if (move != ttMove && pos.see(move) > threshold) + return move; + break; - case PH_EVASIONS: - case PH_QCAPTURES: - move = pick_best(curMove++, lastMove).move; - if (move != ttMove) + case RECAPTURES: + move = pick_best(cur++, endMoves); + if (to_sq(move) == recaptureSquare) return move; break; - case PH_QCHECKS: - move = (curMove++)->move; + case CHECKS: + move = *cur++; if (move != ttMove) return move; break; - case PH_STOP: + case STOP: return MOVE_NONE; default: assert(false); - break; } } }