X-Git-Url: https://git.sesse.net/?p=stockfish;a=blobdiff_plain;f=src%2Fmovepick.cpp;h=8872e39f3691a8740a8ba1244f8fc3c4664951c5;hp=eb57f78a9cf1eb5b09e3f76926465291d4913477;hb=c9d7e99de682516c560009b550c41da9ae2008b8;hpb=d5b77ad45e210376795c1a2b8ca8d73576cf80dc diff --git a/src/movepick.cpp b/src/movepick.cpp index eb57f78a..8872e39f 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 Marco Costalba + Copyright (C) 2008-2010 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 @@ -18,524 +18,333 @@ along with this program. If not, see . */ - -//// -//// Includes -//// - #include -#include "history.h" -#include "evaluate.h" #include "movegen.h" #include "movepick.h" #include "search.h" -#include "value.h" - - -//// -//// Local definitions -//// +#include "types.h" namespace { - /// Variables - - MovePicker::MovegenPhase PhaseTable[32]; - int MainSearchPhaseIndex; - int EvasionsPhaseIndex; - int QsearchWithChecksPhaseIndex; - int QsearchNoCapturesPhaseIndex; - int QsearchWithoutChecksPhaseIndex; - int NoMovesPhaseIndex; - + 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 + }; + + 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 }; } - -//// -//// Functions -//// - - -/// Constructor for the MovePicker class. Apart from the position for which +/// 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 /// 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, bool pv, Move ttm, - const SearchStack& ss, Depth d, EvalInfo* ei) : pos(p) { - pvNode = pv; - ttMove = ttm; - mateKiller = (ss.mateKiller == ttm)? MOVE_NONE : ss.mateKiller; - killer1 = ss.killers[0]; - killer2 = ss.killers[1]; - depth = d; - movesPicked = 0; - numOfMoves = 0; - numOfBadCaptures = 0; - - // With EvalInfo we are able to know how many captures are possible before - // generating them. So avoid generating in case we know are zero. - Color us = pos.side_to_move(); - Color them = opposite_color(us); - bool noCaptures = ei - && (ei->attackedBy[us][0] & pos.pieces_of_color(them)) == 0 - && !ei->mi->specialized_eval_exists() - && (pos.ep_square() == SQ_NONE) - && !pos.has_pawn_on_7th(us); +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; + + assert(d > DEPTH_ZERO); + + pinned = p.pinned_pieces(pos.side_to_move()); if (p.is_check()) - phaseIndex = EvasionsPhaseIndex; - else if (depth > Depth(0)) - phaseIndex = MainSearchPhaseIndex; - else if (depth == Depth(0)) - phaseIndex = (noCaptures ? QsearchNoCapturesPhaseIndex : QsearchWithChecksPhaseIndex); + { + ttMoves[1].move = killers[0].move = killers[1].move = MOVE_NONE; + phasePtr = EvasionTable; + } else - phaseIndex = (noCaptures ? NoMovesPhaseIndex : QsearchWithoutChecksPhaseIndex); + { + 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]; - dc = p.discovered_check_candidates(us); - pinned = p.pinned_pieces(p.side_to_move()); + // 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; - finished = false; + phasePtr = MainSearchTable; + } + + phasePtr += int(!searchTT) - 1; + go_next_phase(); } +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::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 of the types we are interested in. + assert(d <= DEPTH_ZERO); -Move MovePicker::get_next_move() { + pinned = p.pinned_pieces(pos.side_to_move()); - Move move; - - while (true) + if (p.is_check()) + phasePtr = EvasionTable; + else if (d >= DEPTH_QS_CHECKS) + phasePtr = QsearchWithChecksTable; + else { - // If we already have a list of generated moves, pick the best move from - // the list, and return it. - move = pick_move_from_list(); - if (move != MOVE_NONE) - { - assert(move_is_ok(move)); - return move; - } - - // Next phase - phaseIndex++; - switch (PhaseTable[phaseIndex]) { - - case PH_TT_MOVE: - if (ttMove != MOVE_NONE) - { - assert(move_is_ok(ttMove)); - if (move_is_legal(pos, ttMove, pinned)) - return ttMove; - } - break; - - case PH_MATE_KILLER: - if (mateKiller != MOVE_NONE) - { - assert(move_is_ok(mateKiller)); - if (move_is_legal(pos, mateKiller, pinned)) - return mateKiller; - } - break; - - case PH_GOOD_CAPTURES: - numOfMoves = generate_captures(pos, moves); - score_captures(); - movesPicked = 0; - break; - - case PH_BAD_CAPTURES: - movesPicked = 0; - break; - - case PH_NONCAPTURES: - numOfMoves = generate_noncaptures(pos, moves); - score_noncaptures(); - movesPicked = 0; - break; - - case PH_EVASIONS: - assert(pos.is_check()); - numOfMoves = generate_evasions(pos, moves); - score_evasions(); - movesPicked = 0; - break; - - case PH_QCAPTURES: - numOfMoves = generate_captures(pos, moves); - score_qcaptures(); - movesPicked = 0; - break; - - case PH_QCHECKS: - numOfMoves = generate_checks(pos, moves, dc); - movesPicked = 0; - break; - - case PH_STOP: - return MOVE_NONE; - - default: - assert(false); - return MOVE_NONE; - } + 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_or_promotion(ttm)) + searchTT = ttMoves[0].move = MOVE_NONE; } + + phasePtr += int(!searchTT) - 1; + go_next_phase(); } -/// A variant of get_next_move() which takes a lock as a parameter, used to -/// prevent multiple threads from picking the same move at a split point. +/// 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) { -Move MovePicker::get_next_move(Lock &lock) { + case PH_TT_MOVES: + curMove = ttMoves; + lastMove = curMove + 2; + return; - lock_grab(&lock); - if (finished) - { - lock_release(&lock); - return MOVE_NONE; - } - Move m = get_next_move(); - if (m == MOVE_NONE) - finished = true; + 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; - lock_release(&lock); - return m; + default: + assert(false); + return; + } } -/// MovePicker::score_captures(), MovePicker::score_noncaptures(), -/// MovePicker::score_evasions() and MovePicker::score_qcaptures() assign a -/// numerical move ordering score to each move in a move list. The moves -/// with highest scores will be picked first by pick_move_from_list(). +/// 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 + // 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 + // 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. - // While scoring captures it moves all captures with negative SEE values - // to the badCaptures[] array. + // 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; - int seeValue; - for (int i = 0; i < numOfMoves; i++) + // Use MVV/LVA ordering + for (MoveStack* cur = moves; cur != lastMove; cur++) { - m = moves[i].move; - seeValue = pos.see(m); - if (seeValue >= 0) - { - if (move_promotion(m)) - moves[i].score = QueenValueMidgame; - else - moves[i].score = int(pos.midgame_value_of_piece_on(move_to(m))) - -int(pos.type_of_piece_on(move_from(m))); - } + m = cur->move; + if (move_is_promotion(m)) + cur->score = QueenValueMidgame; else - { - // Losing capture, move it to the badCaptures[] array - assert(numOfBadCaptures < 63); - moves[i].score = seeValue; - badCaptures[numOfBadCaptures++] = moves[i]; - moves[i--] = moves[--numOfMoves]; - } + cur->score = pos.midgame_value_of_piece_on(move_to(m)) + - pos.type_of_piece_on(move_from(m)); } } void MovePicker::score_noncaptures() { - // First score by history, when no history is available then use - // piece/square tables values. This seems to be better then a - // random choice when we don't have an history for any move. + Move m; - int hs; + Square from; - for (int i = 0; i < numOfMoves; i++) + for (MoveStack* cur = moves; cur != lastMove; cur++) { - m = moves[i].move; - - if (m == killer1) - hs = HistoryMax + 2; - else if (m == killer2) - hs = HistoryMax + 1; - else - hs = H.move_ordering_score(pos.piece_on(move_from(m)), m); - - // Ensure history is always preferred to pst - if (hs > 0) - hs += 1000; - - // pst based scoring - moves[i].score = hs + pos.mg_pst_delta(m); + m = cur->move; + from = move_from(m); + cur->score = H.value(pos.piece_on(from), move_to(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; - for (int i = 0; i < numOfMoves; i++) - { - Move m = moves[i].move; - if (m == ttMove) - moves[i].score = 2*HistoryMax; - else if (!pos.square_is_empty(move_to(m))) - { - int seeScore = pos.see(m); - moves[i].score = (seeScore >= 0)? seeScore + HistoryMax : seeScore; - } else - moves[i].score = H.move_ordering_score(pos.piece_on(move_from(m)), m); - } -} - -void MovePicker::score_qcaptures() { + // Skip if we don't have at least two moves to order + if (lastMove < moves + 2) + return; - // Use MVV/LVA ordering - for (int i = 0; i < numOfMoves; i++) + for (MoveStack* cur = moves; cur != lastMove; cur++) { - Move m = moves[i].move; - if (move_promotion(m)) - moves[i].score = QueenValueMidgame; + 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 - moves[i].score = int(pos.midgame_value_of_piece_on(move_to(m))) - -int(pos.type_of_piece_on(move_from(m))); + cur->score = H.value(pos.piece_on(move_from(m)), move_to(m)); } } +/// 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. -/// find_best_index() loops across the moves and returns index of -/// the highest scored one. There is also a second version that -/// lowers the priority of moves that attack the same square, -/// so that if the best move that attack a square fails the next -/// move picked attacks a different square if any, not the same one. - -int MovePicker::find_best_index() { - - assert(movesPicked < numOfMoves); - - int bestIndex = movesPicked, bestScore = moves[movesPicked].score; - - for (int i = movesPicked + 1; i < numOfMoves; i++) - if (moves[i].score > bestScore) - { - bestIndex = i; - bestScore = moves[i].score; - } - return bestIndex; -} - -int MovePicker::find_best_index(Bitboard* squares, int values[]) { - - assert(movesPicked < numOfMoves); - - int hs; - Move m; - Square to; - int bestScore = -10000000, bestIndex = -1; - - for (int i = movesPicked; i < numOfMoves; i++) - { - m = moves[i].move; - to = move_to(m); - - if (!bit_is_set(*squares, to)) - { - // Init at first use - set_bit(squares, to); - values[to] = 0; - } +Move MovePicker::get_next_move() { - hs = moves[i].score - values[to]; - if (hs > bestScore) - { - bestIndex = i; - bestScore = hs; - } - } + Move move; - if (bestIndex != -1) + while (true) { - // Raise value of the picked square, so next attack - // to the same square will get low priority. - to = move_to(moves[bestIndex].move); - values[to] += 0xB00; - } - return bestIndex; -} - - -/// MovePicker::pick_move_from_list() picks the move with the biggest score -/// from a list of generated moves (moves[] or badCaptures[], depending on -/// the current move generation phase). It takes care not to return the -/// transposition table move if that has already been serched previously. - -Move MovePicker::pick_move_from_list() { + while (curMove == lastMove) + go_next_phase(); - int bestIndex; - Move move; + switch (phase) { - switch (PhaseTable[phaseIndex]) { + case PH_TT_MOVES: + move = (curMove++)->move; + if ( move != MOVE_NONE + && pos.move_is_legal(move, pinned)) + return move; + break; - case PH_GOOD_CAPTURES: - assert(!pos.is_check()); - assert(movesPicked >= 0); - - while (movesPicked < numOfMoves) - { - bestIndex = find_best_index(); - move = moves[bestIndex].move; - moves[bestIndex] = moves[movesPicked++]; - if ( move != ttMove - && move != mateKiller + 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: - assert(!pos.is_check()); - assert(movesPicked >= 0); - - while (movesPicked < numOfMoves) - { - // If this is a PV node or we have only picked a few moves, scan - // the entire move list for the best move. If many moves have already - // been searched and it is not a PV node, we are probably failing low - // anyway, so we just pick the first move from the list. - bestIndex = (pvNode || movesPicked < 12) ? find_best_index() : movesPicked; - move = moves[bestIndex].move; - moves[bestIndex] = moves[movesPicked++]; - if ( move != ttMove - && move != mateKiller + 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; + break; - case PH_EVASIONS: - assert(pos.is_check()); - assert(movesPicked >= 0); - - while (movesPicked < numOfMoves) - { - bestIndex = find_best_index(); - move = moves[bestIndex].move; - moves[bestIndex] = moves[movesPicked++]; + case PH_BAD_CAPTURES: + move = pick_best(curMove++, lastMove).move; return move; - } - break; - case PH_BAD_CAPTURES: - assert(!pos.is_check()); - assert(movesPicked >= 0); - // It's probably a good idea to use SEE move ordering here, instead - // of just picking the first move. FIXME - while (movesPicked < numOfBadCaptures) - { - move = badCaptures[movesPicked++].move; - if ( move != ttMove - && move != mateKiller + 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; + break; - case PH_QCAPTURES: - assert(!pos.is_check()); - assert(movesPicked >= 0); - while (movesPicked < numOfMoves) - { - bestIndex = (movesPicked < 4 ? find_best_index() : movesPicked); - move = moves[bestIndex].move; - moves[bestIndex] = moves[movesPicked++]; - // Remember to change the line below if we decide to hash the qsearch! - // Maybe also postpone the legality check until after futility pruning? - if (/* move != ttMove && */ pos.pl_move_is_legal(move, pinned)) + case PH_QCHECKS: + move = (curMove++)->move; + if ( move != ttMoves[0].move + && pos.pl_move_is_legal(move, pinned)) return move; - } - break; + break; - case PH_QCHECKS: - assert(!pos.is_check()); - assert(movesPicked >= 0); - // Perhaps we should do something better than just picking the first - // move here? FIXME - while (movesPicked < numOfMoves) - { - move = moves[movesPicked++].move; - // Remember to change the line below if we decide to hash the qsearch! - if (/* move != ttMove && */ pos.pl_move_is_legal(move, pinned)) - return move; - } - break; + case PH_STOP: + return MOVE_NONE; - default: - break; + default: + assert(false); + break; + } } - return MOVE_NONE; -} - - -/// MovePicker::current_move_type() returns the type of the just -/// picked next move. It can be used in search to further differentiate -/// according to the current move type: capture, non capture, escape, etc. -MovePicker::MovegenPhase MovePicker::current_move_type() const { - - return PhaseTable[phaseIndex]; -} - - -/// MovePicker::init_phase_table() initializes the PhaseTable[], -/// MainSearchPhaseIndex, EvasionPhaseIndex, QsearchWithChecksPhaseIndex -/// QsearchNoCapturesPhaseIndex, QsearchWithoutChecksPhaseIndex and -/// NoMovesPhaseIndex variables. It is only called once during program -/// startup, and never again while the program is running. - -void MovePicker::init_phase_table() { - - int i = 0; - - // Main search - MainSearchPhaseIndex = i - 1; - PhaseTable[i++] = PH_TT_MOVE; - PhaseTable[i++] = PH_MATE_KILLER; - PhaseTable[i++] = PH_GOOD_CAPTURES; - // PH_KILLER_1 and PH_KILLER_2 are not yet used. - // PhaseTable[i++] = PH_KILLER_1; - // PhaseTable[i++] = PH_KILLER_2; - PhaseTable[i++] = PH_NONCAPTURES; - PhaseTable[i++] = PH_BAD_CAPTURES; - PhaseTable[i++] = PH_STOP; - - // Check evasions - EvasionsPhaseIndex = i - 1; - PhaseTable[i++] = PH_EVASIONS; - PhaseTable[i++] = PH_STOP; - - // Quiescence search with checks - QsearchWithChecksPhaseIndex = i - 1; - PhaseTable[i++] = PH_QCAPTURES; - PhaseTable[i++] = PH_QCHECKS; - PhaseTable[i++] = PH_STOP; - - // Quiescence search with checks only and no captures - QsearchNoCapturesPhaseIndex = i - 1; - PhaseTable[i++] = PH_QCHECKS; - PhaseTable[i++] = PH_STOP; - - // Quiescence search without checks - QsearchWithoutChecksPhaseIndex = i - 1; - PhaseTable[i++] = PH_QCAPTURES; - PhaseTable[i++] = PH_STOP; - - // Do not generate any move - NoMovesPhaseIndex = i - 1; - PhaseTable[i++] = PH_STOP; }