/*
Stockfish, a UCI chess playing engine derived from Glaurung 2.1
Copyright (C) 2004-2008 Tord Romstad (Glaurung author)
- Copyright (C) 2008-2009 Marco Costalba
+ 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
along with this program. If not, see <http://www.gnu.org/licenses/>.
*/
-
-////
-//// Includes
-////
-
-#include <algorithm>
#include <cassert>
-#include "history.h"
-#include "evaluate.h"
-#include "movegen.h"
#include "movepick.h"
-#include "search.h"
-#include "value.h"
-
-
-////
-//// Local definitions
-////
+#include "thread.h"
namespace {
- /// Variables
-
- MovePicker::MovegenPhase PhaseTable[32];
- int MainSearchPhaseIndex;
- int EvasionsPhaseIndex;
- int QsearchWithChecksPhaseIndex;
- int QsearchWithoutChecksPhaseIndex;
+ 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
+ };
+
+ // 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;
+ }
+ }
+ // 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& move) { return move.value > 0; }
-////
-//// Functions
-////
+ // 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
-/// 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) : pos(p), H(h) {
- ttMove = ttm;
- if (ss)
- {
- mateKiller = (ss->mateKiller == ttm)? MOVE_NONE : ss->mateKiller;
- killer1 = ss->killers[0];
- killer2 = ss->killers[1];
- } else
- mateKiller = killer1 = killer2 = MOVE_NONE;
-
- movesPicked = numOfMoves = numOfBadCaptures = 0;
- checkKillers = checkLegal = finished = false;
-
- if (p.is_check())
- phaseIndex = EvasionsPhaseIndex;
- else if (d > Depth(0))
- phaseIndex = MainSearchPhaseIndex;
- else if (d == Depth(0))
- phaseIndex = QsearchWithChecksPhaseIndex;
- else
- phaseIndex = QsearchWithoutChecksPhaseIndex;
+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) {
- Color us = pos.side_to_move();
+ assert(d > DEPTH_ZERO);
- dc = p.discovered_check_candidates(us);
- pinned = p.pinned_pieces(us);
+ cur = end = moves;
+ endBadCaptures = moves + MAX_MOVES - 1;
+ countermoves = cm;
+ followupmoves = fm;
+ ss = s;
- finished = false;
+ if (pos.checkers())
+ stage = EVASION;
+
+ else
+ stage = MAIN_SEARCH;
+
+ ttMove = (ttm && pos.pseudo_legal(ttm) ? ttm : MOVE_NONE);
+ end += (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::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() {
+ if (pos.checkers())
+ stage = EVASION;
- Move move;
+ else if (d > DEPTH_QS_NO_CHECKS)
+ stage = QSEARCH_0;
- while (true)
- {
- // 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;
- }
+ else if (d > DEPTH_QS_RECAPTURES)
+ stage = QSEARCH_1;
- // 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();
- std::sort(moves, moves + numOfMoves);
- movesPicked = 0;
- checkLegal = true;
- break;
-
- case PH_KILLERS:
- movesPicked = numOfMoves = 0;
- checkLegal = false;
- if (killer1 != MOVE_NONE && move_is_legal(pos, killer1, pinned) && !pos.move_is_capture(killer1))
- moves[numOfMoves++].move = killer1;
- if (killer2 != MOVE_NONE && move_is_legal(pos, killer2, pinned) && !pos.move_is_capture(killer2) )
- moves[numOfMoves++].move = killer2;
- break;
-
- case PH_NONCAPTURES:
- checkKillers = (numOfMoves != 0); // previous phase is PH_KILLERS
- numOfMoves = generate_noncaptures(pos, moves);
- score_noncaptures();
- std::sort(moves, moves + numOfMoves);
- movesPicked = 0;
- checkLegal = true;
- break;
-
- case PH_BAD_CAPTURES:
- // Bad captures SEE value is already calculated by score_captures()
- // so just sort them to get SEE move ordering.
- std::sort(badCaptures, badCaptures + numOfBadCaptures);
- movesPicked = 0;
- break;
-
- case PH_EVASIONS:
- assert(pos.is_check());
- numOfMoves = generate_evasions(pos, moves, pinned);
- score_evasions();
- std::sort(moves, moves + numOfMoves);
- movesPicked = 0;
- break;
-
- case PH_QCAPTURES:
- numOfMoves = generate_captures(pos, moves);
- score_qcaptures();
- std::sort(moves, moves + numOfMoves);
- movesPicked = 0;
- break;
-
- case PH_QCHECKS:
- // Perhaps we should order moves move here? FIXME
- numOfMoves = generate_non_capture_checks(pos, moves, dc);
- movesPicked = 0;
- break;
-
- case PH_STOP:
- return MOVE_NONE;
-
- default:
- assert(false);
- return MOVE_NONE;
- }
+ else
+ {
+ stage = RECAPTURE;
+ recaptureSquare = s;
+ ttm = MOVE_NONE;
}
+
+ ttMove = (ttm && pos.pseudo_legal(ttm) ? ttm : MOVE_NONE);
+ end += (ttMove != MOVE_NONE);
}
+MovePicker::MovePicker(const Position& p, Move ttm, const HistoryStats& h, PieceType pt)
+ : pos(p), history(h), cur(moves), end(moves) {
-/// 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.
+ assert(!pos.checkers());
-Move MovePicker::get_next_move(Lock &lock) {
+ stage = PROBCUT;
- lock_grab(&lock);
- if (finished)
- {
- lock_release(&lock);
- return MOVE_NONE;
- }
- Move m = get_next_move();
- if (m == MOVE_NONE)
- finished = true;
+ // 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);
- lock_release(&lock);
- return m;
-}
+ if (ttMove && (!pos.capture(ttMove) || pos.see(ttMove) <= captureThreshold))
+ ttMove = MOVE_NONE;
+ end += (ttMove != MOVE_NONE);
+}
-/// 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().
-void MovePicker::score_captures() {
+/// 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<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 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;
- int seeValue;
- for (int i = 0; i < numOfMoves; i++)
+ for (ExtMove* it = moves; it != end; ++it)
{
- m = moves[i].move;
- seeValue = pos.see(m);
- if (seeValue >= 0)
- {
- if (move_is_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)));
- }
- else
- {
- // Losing capture, move it to the badCaptures[] array
- assert(numOfBadCaptures < 63);
- moves[i].score = seeValue;
- badCaptures[numOfBadCaptures++] = moves[i];
- moves[i--] = moves[--numOfMoves];
- }
- }
-}
-
-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.
- Piece piece;
- Square from, to;
- int hs;
-
- for (int i = 0; i < numOfMoves; i++)
- {
- from = move_from(moves[i].move);
- to = move_to(moves[i].move);
- piece = pos.piece_on(from);
- hs = H.move_ordering_score(piece, to);
+ m = it->move;
+ it->value = PieceValue[MG][pos.piece_on(to_sq(m))]
+ - Value(type_of(pos.moved_piece(m)));
- // Ensure history is always preferred to pst
- if (hs > 0)
- hs += 1000;
+ if (type_of(m) == ENPASSANT)
+ it->value += PieceValue[MG][PAWN];
- // pst based scoring
- moves[i].score = hs + pos.pst_delta<Position::MidGame>(piece, from, to);
+ else if (type_of(m) == PROMOTION)
+ it->value += PieceValue[MG][promotion_type(m)] - PieceValue[MG][PAWN];
}
}
-void MovePicker::score_evasions() {
+template<>
+void MovePicker::score<QUIETS>() {
+
+ Move m;
- for (int i = 0; i < numOfMoves; i++)
+ for (ExtMove* it = moves; it != end; ++it)
{
- 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)), move_to(m));
+ m = it->move;
+ it->value = history[pos.moved_piece(m)][to_sq(m)];
}
}
-void MovePicker::score_qcaptures() {
+template<>
+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, then bad-captures and quiet
+ // moves with a negative SEE. This last group is ordered by the SEE value.
+ Move m;
+ Value see;
- // Use MVV/LVA ordering
- for (int i = 0; i < numOfMoves; i++)
+ for (ExtMove* it = moves; it != end; ++it)
{
- Move m = moves[i].move;
- if (move_is_promotion(m))
- moves[i].score = QueenValueMidgame;
+ 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
- moves[i].score = int(pos.midgame_value_of_piece_on(move_to(m)))
- -int(pos.type_of_piece_on(move_from(m)));
+ it->value = history[pos.moved_piece(m)][to_sq(m)];
}
}
-/// 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.
+/// 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<CAPTURES>(pos, moves);
+ score<CAPTURES>();
+ 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<QUIETS>(pos, moves);
+ score<QUIETS>();
+ 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<EVASIONS>(pos, moves);
+ if (end > moves + 1)
+ score<EVASIONS>();
+ return;
+
+ case QUIET_CHECKS_S3:
+ end = generate<QUIET_CHECKS>(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;
-Move MovePicker::pick_move_from_list() {
+ default:
+ assert(false);
+ }
+}
- assert(movesPicked >= 0);
- assert(!pos.is_check() || PhaseTable[phaseIndex] == PH_EVASIONS || PhaseTable[phaseIndex] == PH_STOP);
- assert( pos.is_check() || PhaseTable[phaseIndex] != PH_EVASIONS);
- switch (PhaseTable[phaseIndex]) {
+/// 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<false>() {
+
+ Move move;
+
+ 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 PH_GOOD_CAPTURES:
- case PH_KILLERS:
- case PH_NONCAPTURES:
- while (movesPicked < numOfMoves)
- {
- Move move = moves[movesPicked++].move;
+ case QUIETS_1_S1: case QUIETS_2_S1:
+ move = (cur++)->move;
if ( move != ttMove
- && move != mateKiller
- && (!checkKillers || (move != killer1 && move != killer2))
- && (!checkLegal || pos.pl_move_is_legal(move, pinned)))
+ && 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;
+ break;
- case PH_EVASIONS:
- if (movesPicked < numOfMoves)
- return moves[movesPicked++].move;
+ case BAD_CAPTURES_S1:
+ return (cur--)->move;
- break;
+ case EVASIONS_S2: case CAPTURES_S3: case CAPTURES_S4:
+ move = pick_best(cur++, end)->move;
+ if (move != ttMove)
+ return move;
+ break;
- case PH_BAD_CAPTURES:
- while (movesPicked < numOfBadCaptures)
- {
- Move move = badCaptures[movesPicked++].move;
- if ( move != ttMove
- && move != mateKiller
- && pos.pl_move_is_legal(move, pinned))
+ 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 PH_QCAPTURES:
- case PH_QCHECKS:
- while (movesPicked < numOfMoves)
- {
- Move move = moves[movesPicked++].move;
- // Maybe postpone the legality check until after futility pruning?
- if ( move != ttMove
- && pos.pl_move_is_legal(move, pinned))
+ break;
+
+ case QUIET_CHECKS_S3:
+ move = (cur++)->move;
+ if (move != ttMove)
return move;
- }
- break;
+ break;
- default:
- break;
+ case STOP:
+ return MOVE_NONE;
+
+ default:
+ assert(false);
+ }
}
- return MOVE_NONE;
}
-/// MovePicker::init_phase_table() initializes the PhaseTable[],
-/// MainSearchPhaseIndex, EvasionPhaseIndex, QsearchWithChecksPhaseIndex
-/// and QsearchWithoutChecksPhaseIndex. 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;
- PhaseTable[i++] = PH_KILLERS;
- 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_TT_MOVE;
- PhaseTable[i++] = PH_QCAPTURES;
- PhaseTable[i++] = PH_QCHECKS;
- PhaseTable[i++] = PH_STOP;
-
- // Quiescence search without checks
- QsearchWithoutChecksPhaseIndex = i - 1;
- PhaseTable[i++] = PH_TT_MOVE;
- PhaseTable[i++] = PH_QCAPTURES;
- PhaseTable[i++] = PH_STOP;
-}
+/// 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<true>() { return ss->splitPoint->movePicker->next_move<false>(); }
projects / stockfish / blobdiff