/*
- Glaurung, a UCI chess playing engine.
- Copyright (C) 2004-2008 Tord Romstad
+ Stockfish, a UCI chess playing engine derived from Glaurung 2.1
+ Copyright (C) 2004-2008 Tord Romstad (Glaurung author)
+ Copyright (C) 2008-2015 Marco Costalba, Joona Kiiski, Tord Romstad
+ Copyright (C) 2015-2020 Marco Costalba, Joona Kiiski, Gary Linscott, Tord Romstad
- Glaurung is free software: you can redistribute it and/or modify
+ 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.
-
- Glaurung is distributed in the hope that it will be useful,
+
+ 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
GNU General Public License for more details.
-
+
You should have received a copy of the GNU General Public License
along with this program. If not, see <http://www.gnu.org/licenses/>.
*/
-
-////
-//// Includes
-////
-
#include <cassert>
-#include "history.h"
-#include "movegen.h"
#include "movepick.h"
-#include "search.h"
-#include "value.h"
+namespace {
-////
-//// Local definitions
-////
+ 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
+ };
+
+ // 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 {
+} // namespace
- /// Variables
- MovePicker::MovegenPhase PhaseTable[32];
- int MainSearchPhaseIndex;
- int EvasionsPhaseIndex;
- int QsearchWithChecksPhaseIndex;
- int QsearchWithoutChecksPhaseIndex;
+/// 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.
-}
+/// 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), continuationHistory(ch),
+ refutations{{killers[0], 0}, {killers[1], 0}, {cm, 0}}, depth(d) {
+ assert(d > 0);
+ stage = pos.checkers() ? EVASION_TT : MAIN_TT;
+ ttMove = ttm && pos.pseudo_legal(ttm) ? ttm : MOVE_NONE;
+ stage += (ttMove == MOVE_NONE);
+}
-////
-//// Functions
-////
+/// MovePicker constructor for quiescence search
+MovePicker::MovePicker(const Position& p, Move ttm, Depth d, const ButterflyHistory* mh,
+ const CapturePieceToHistory* cph, const PieceToHistory** ch, Square rs)
+ : pos(p), mainHistory(mh), captureHistory(cph), continuationHistory(ch), recaptureSquare(rs), depth(d) {
+ assert(d <= 0);
-/// 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(Position &p, bool pvnode, Move ttm, Move mk,
- Move k1, Move k2, Depth dpth) {
- pos = &p;
- pvNode = pvnode;
- ttMove = ttm;
- mateKiller = (mk == ttm)? MOVE_NONE : mk;
- killer1 = k1;
- killer2 = k2;
- depth = dpth;
- movesPicked = 0;
- numOfMoves = 0;
- numOfBadCaptures = 0;
- dc = p.discovered_check_candidates(p.side_to_move());
-
- if(p.is_check())
- phaseIndex = EvasionsPhaseIndex;
- else if(depth > Depth(0))
- phaseIndex = MainSearchPhaseIndex;
- else if(depth == Depth(0))
- phaseIndex = QsearchWithChecksPhaseIndex;
- else
- phaseIndex = QsearchWithoutChecksPhaseIndex;
-
- pinned = p.pinned_pieces(p.side_to_move());
-
- finished = false;
+ stage = pos.checkers() ? EVASION_TT : QSEARCH_TT;
+ ttMove = ttm
+ && (depth > DEPTH_QS_RECAPTURES || to_sq(ttm) == recaptureSquare)
+ && pos.pseudo_legal(ttm) ? ttm : MOVE_NONE;
+ stage += (ttMove == MOVE_NONE);
}
+/// 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) {
-/// 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.
-
-Move MovePicker::get_next_move() {
- Move move;
-
- while(true) {
- // If we already have a list of generated moves, pick the best move from
- // the list, and return it:
- move = this->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));
- Move m = generate_move_if_legal(*pos, ttMove, pinned);
- if(m != MOVE_NONE) {
- assert(m == ttMove);
- return m;
- }
- }
- break;
-
- case PH_MATE_KILLER:
- if(mateKiller != MOVE_NONE) {
- assert(move_is_ok(mateKiller));
- Move m = generate_move_if_legal(*pos, mateKiller, pinned);
- if(m != MOVE_NONE) {
- assert(m == mateKiller);
- return m;
- }
+ assert(!pos.checkers());
+
+ stage = PROBCUT_TT;
+ ttMove = ttm
+ && pos.capture(ttm)
+ && pos.pseudo_legal(ttm)
+ && pos.see_ge(ttm, threshold) ? ttm : MOVE_NONE;
+ stage += (ttMove == MOVE_NONE);
+}
+
+/// 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<GenType Type>
+void MovePicker::score() {
+
+ static_assert(Type == CAPTURES || Type == QUIETS || Type == EVASIONS, "Wrong type");
+
+ for (auto& m : *this)
+ if (Type == CAPTURES)
+ m.value = int(PieceValue[MG][pos.piece_on(to_sq(m))]) * 6
+ + (*captureHistory)[pos.moved_piece(m)][to_sq(m)][type_of(pos.piece_on(to_sq(m)))];
+
+ else if (Type == QUIETS)
+ m.value = (*mainHistory)[pos.side_to_move()][from_to(m)]
+ + 2 * (*continuationHistory[0])[pos.moved_piece(m)][to_sq(m)]
+ + 2 * (*continuationHistory[1])[pos.moved_piece(m)][to_sq(m)]
+ + 2 * (*continuationHistory[3])[pos.moved_piece(m)][to_sq(m)]
+ + (*continuationHistory[5])[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)]
+ + (*continuationHistory[0])[pos.moved_piece(m)][to_sq(m)]
+ - (1 << 28);
}
- break;
-
- case PH_GOOD_CAPTURES:
- // pinned = pos->pinned_pieces(pos->side_to_move());
- numOfMoves = generate_captures(*pos, moves);
- this->score_captures();
- movesPicked = 0;
- break;
-
- case PH_BAD_CAPTURES:
- badCapturesPicked = 0;
- break;
-
- case PH_NONCAPTURES:
- numOfMoves = generate_noncaptures(*pos, moves);
- this->score_noncaptures();
- movesPicked = 0;
- break;
-
- case PH_EVASIONS:
- assert(pos->is_check());
- // pinned = pos->pinned_pieces(pos->side_to_move());
- numOfMoves = generate_evasions(*pos, moves);
- this->score_evasions();
- movesPicked = 0;
- break;
-
- case PH_QCAPTURES:
- // pinned = pos->pinned_pieces(pos->side_to_move());
- numOfMoves = generate_captures(*pos, moves);
- this->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;
- }
- }
+}
- assert(false);
+/// MovePicker::select() returns the next move satisfying a predicate function.
+/// It never returns the TT move.
+template<MovePicker::PickType T, typename Pred>
+Move MovePicker::select(Pred filter) {
+
+ while (cur < endMoves)
+ {
+ if (T == Best)
+ std::swap(*cur, *std::max_element(cur, endMoves));
+
+ if (*cur != ttMove && filter())
+ return *cur++;
+ cur++;
+ }
return MOVE_NONE;
}
+/// 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<CAPTURES>(pos, cur);
+
+ score<CAPTURES>();
+ ++stage;
+ goto top;
+
+ case GOOD_CAPTURE:
+ if (select<Best>([&](){
+ return pos.see_ge(*cur, Value(-55 * cur->value / 1024)) ?
+ // Move losing capture to endBadCaptures to be tried later
+ true : (*endBadCaptures++ = *cur, false); }))
+ return *(cur - 1);
+
+ // Prepare the pointers to loop over the refutations array
+ cur = std::begin(refutations);
+ endMoves = std::end(refutations);
+
+ // 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;
+
+ ++stage;
+ /* fallthrough */
+
+ case REFUTATION:
+ if (select<Next>([&](){ return *cur != MOVE_NONE
+ && !pos.capture(*cur)
+ && pos.pseudo_legal(*cur); }))
+ return *(cur - 1);
+ ++stage;
+ /* fallthrough */
+
+ case QUIET_INIT:
+ if (!skipQuiets)
+ {
+ cur = endBadCaptures;
+ endMoves = generate<QUIETS>(pos, cur);
+
+ score<QUIETS>();
+ partial_insertion_sort(cur, endMoves, -3000 * depth);
+ }
-/// 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.
+ ++stage;
+ /* fallthrough */
-Move MovePicker::get_next_move(Lock &lock) {
- Move m;
+ case QUIET:
+ if ( !skipQuiets
+ && select<Next>([&](){return *cur != refutations[0].move
+ && *cur != refutations[1].move
+ && *cur != refutations[2].move;}))
+ return *(cur - 1);
- lock_grab(&lock);
- if(finished) {
- lock_release(&lock);
- return MOVE_NONE;
- }
- m = this->get_next_move();
- if(m == MOVE_NONE)
- finished = true;
- lock_release(&lock);
-
- return m;
-}
+ // Prepare the pointers to loop over the bad captures
+ cur = moves;
+ endMoves = endBadCaptures;
-
-/// MovePicker::number_of_moves() simply returns the numOfMoves member
-/// variable. It is intended to be used in positions where the side to move
-/// is in check, for detecting checkmates or situations where there is only
-/// a single reply to check.
+ ++stage;
+ /* fallthrough */
-int MovePicker::number_of_moves() const {
- return numOfMoves;
-}
+ case BAD_CAPTURE:
+ return select<Next>([](){ return true; });
+ case EVASION_INIT:
+ cur = moves;
+ endMoves = generate<EVASIONS>(pos, cur);
-/// 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
-/// MovePicker::pick_move_from_list().
-
-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.
- for(int i = 0; i < numOfMoves; i++) {
- int seeValue = pos->see(moves[i].move);
- if(seeValue >= 0) {
- if(move_promotion(moves[i].move))
- moves[i].score = QueenValueMidgame;
- else
- moves[i].score =
- int(pos->midgame_value_of_piece_on(move_to(moves[i].move))) -
- int(pos->type_of_piece_on(move_from(moves[i].move)));
- }
- else
- moves[i].score = seeValue;
-
- }
-}
+ score<EVASIONS>();
+ ++stage;
+ /* fallthrough */
-void MovePicker::score_noncaptures() {
- for(int i = 0; i < numOfMoves; i++) {
- Move m = moves[i].move;
- if(m == killer1)
- moves[i].score = HistoryMax + 2;
- else if(m == killer2)
- moves[i].score = HistoryMax + 1;
- else
- moves[i].score = H.move_ordering_score(pos->piece_on(move_from(m)), m);
- }
-}
+ case EVASION:
+ return select<Best>([](){ return true; });
-void MovePicker::score_evasions() {
- 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);
- }
-}
+ case PROBCUT:
+ return select<Best>([&](){ return pos.see_ge(*cur, threshold); });
-void MovePicker::score_qcaptures() {
- // Use MVV/LVA ordering.
- for(int i = 0; i < numOfMoves; i++) {
- Move m = moves[i].move;
- if(move_promotion(m))
- moves[i].score = QueenValueMidgame;
- else
- moves[i].score =
- int(pos->midgame_value_of_piece_on(move_to(m))) -
- int(pos->midgame_value_of_piece_on(move_to(m))) / 64;
- }
-}
+ case QCAPTURE:
+ if (select<Best>([&](){ return depth > DEPTH_QS_RECAPTURES
+ || to_sq(*cur) == recaptureSquare; }))
+ return *(cur - 1);
+ // If we did not find any move and we do not try checks, we have finished
+ if (depth != DEPTH_QS_CHECKS)
+ return MOVE_NONE;
-/// 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.
-/// While picking captures in the PH_GOOD_CAPTURES phase (i.e. while picking
-/// non-losing captures in the main search), it moves all captures with
-/// negative SEE values to the badCaptures[] array.
-
-Move MovePicker::pick_move_from_list() {
- int bestScore = -10000000;
- int bestIndex;
- Move move;
-
- switch(PhaseTable[phaseIndex]) {
-
- case PH_GOOD_CAPTURES:
- assert(!pos->is_check());
- assert(movesPicked >= 0);
- while(movesPicked < numOfMoves) {
- bestScore = -10000000;
- bestIndex = -1;
- for(int i = movesPicked; i < numOfMoves; i++) {
- if(moves[i].score < 0) {
- // Losing capture, move it to the badCaptures[] array
- assert(numOfBadCaptures < 63);
- badCaptures[numOfBadCaptures++] = moves[i];
- moves[i--] = moves[--numOfMoves];
- }
- else if(moves[i].score > bestScore) {
- bestIndex = i;
- bestScore = moves[i].score;
- }
- }
- if(bestIndex != -1) { // Found a good capture
- move = moves[bestIndex].move;\r
- moves[bestIndex] = moves[movesPicked++];
- if(move != ttMove && move != mateKiller &&
- pos->move_is_legal(move, pinned))
- return move;
- }
- }
- break;
-
- case PH_NONCAPTURES:
- assert(!pos->is_check());
- assert(movesPicked >= 0);
- while(movesPicked < numOfMoves) {
- bestScore = -10000000;
-
- // 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.
- if(pvNode || movesPicked < 12) {
- bestIndex = -1;
- for(int i = movesPicked; i < numOfMoves; i++)
- if(moves[i].score > bestScore) {
- bestIndex = i;
- bestScore = moves[i].score;
- }
- }
- else
- bestIndex = movesPicked;
-
- if(bestIndex != -1) {
- move = moves[bestIndex].move;\r
- moves[bestIndex] = moves[movesPicked++];
- if(move != ttMove && move != mateKiller &&
- pos->move_is_legal(move, pinned))
- return move;
- }
- }
- break;
-
- case PH_EVASIONS:
- assert(pos->is_check());
- assert(movesPicked >= 0);
- while(movesPicked < numOfMoves) {
- bestScore = -10000000;
- bestIndex = -1;
- for(int i = movesPicked; i < numOfMoves; i++)
- if(moves[i].score > bestScore) {
- bestIndex = i;
- bestScore = moves[i].score;
- }
+ ++stage;
+ /* fallthrough */
- if(bestIndex != -1) {
- move = moves[bestIndex].move;\r
- moves[bestIndex] = moves[movesPicked++];
- return move;
- }
- }
- break;
-
- case PH_BAD_CAPTURES:
- assert(!pos->is_check());
- assert(badCapturesPicked >= 0);
- // It's probably a good idea to use SEE move ordering here, instead
- // of just picking the first move. FIXME
- while(badCapturesPicked < numOfBadCaptures) {
- move = badCaptures[badCapturesPicked++].move;
- if(move != ttMove && move != mateKiller &&
- pos->move_is_legal(move, pinned))
- return move;
- }
- break;
-
- case PH_QCAPTURES:
- assert(!pos->is_check());
- assert(movesPicked >= 0);
- while(movesPicked < numOfMoves) {
- bestScore = -10000000;
- if(movesPicked < 4) {
- bestIndex = -1;
- for(int i = movesPicked; i < numOfMoves; i++)
- if(moves[i].score > bestScore) {
- bestIndex = i;
- bestScore = moves[i].score;
- }
- }
- else
- bestIndex = movesPicked;
-
- if(bestIndex != -1) {
- move = moves[bestIndex].move;\r
- 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->move_is_legal(move, pinned))
- return move;
- }
- }
- 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->move_is_legal(move, pinned))
- return move;
- }
- break;
-
- default:
- break;
- }
+ case QCHECK_INIT:
+ cur = moves;
+ endMoves = generate<QUIET_CHECKS>(pos, cur);
- return MOVE_NONE;
-}
+ ++stage;
+ /* fallthrough */
-MovePicker::MovegenPhase MovePicker::current_move_type() const {
- return PhaseTable[phaseIndex];
-}
+ case QCHECK:
+ return select<Next>([](){ return true; });
+ }
-/// MovePicker::init_phase_table() initializes the PhaseTable[],
-/// MainSearchPhaseIndex, EvasionPhaseIndex, QsearchWithChecksPhaseIndex
-/// and QsearchWithoutChecksPhaseIndex 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 without checks
- QsearchWithoutChecksPhaseIndex = i - 1;
- PhaseTable[i++] = PH_QCAPTURES;
- PhaseTable[i++] = PH_STOP;
+ assert(false);
+ return MOVE_NONE; // Silence warning
}
projects / stockfish / blobdiff