/*
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) 2008-2015 Marco Costalba, Joona Kiiski, Tord Romstad
+ Copyright (C) 2015-2018 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
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"
-
-
-////
-//// Local definitions
-////
namespace {
- /// Variables
-
- MovePicker::MovegenPhase PhaseTable[32];
- int MainSearchPhaseIndex;
- int EvasionsPhaseIndex;
- int QsearchWithChecksPhaseIndex;
- int QsearchWithoutChecksPhaseIndex;
-
-}
-
-
-
-////
-//// Functions
-////
-
-
-/// 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 pvnode, Move ttm, Move mk,
- Move k1, Move k2, Depth d) : pos(p) {
- pvNode = pvnode;
- ttMove = ttm;
- mateKiller = (mk == ttm)? MOVE_NONE : mk;
- killer1 = k1;
- killer2 = k2;
- depth = d;
- 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;
-}
-
+ enum Stages {
+ MAIN_TT, CAPTURE_INIT, GOOD_CAPTURE, KILLER0, KILLER1, COUNTERMOVE, QUIET_INIT, QUIET, BAD_CAPTURE,
+ EVASION_TT, EVASION_INIT, EVASION,
+ PROBCUT_TT, PROBCUT_INIT, PROBCUT,
+ QSEARCH_TT, QCAPTURE_INIT, QCAPTURE, QCHECK_INIT, QCHECK
+ };
-/// 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.
+ // Helper filter used with select_move()
+ const auto Any = [](){ return true; };
-Move MovePicker::get_next_move() {
+ // 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) {
- Move move;
-
- 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;
- }
-
- // Next phase
- phaseIndex++;
- switch (PhaseTable[phaseIndex]) {
-
- case PH_TT_MOVE:
- if (ttMove != MOVE_NONE)
+ for (ExtMove *sortedEnd = begin, *p = begin + 1; p < end; ++p)
+ if (p->value >= limit)
{
- assert(move_is_ok(ttMove));
- if (move_is_legal(pos, ttMove, pinned))
- return ttMove;
+ ExtMove tmp = *p, *q;
+ *p = *++sortedEnd;
+ for (q = sortedEnd; q != begin && *(q - 1) < tmp; --q)
+ *q = *(q - 1);
+ *q = tmp;
}
- 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:
- badCapturesPicked = 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;
- }
}
-}
-
-/// 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.
+} // namespace
-Move MovePicker::get_next_move(Lock &lock) {
- lock_grab(&lock);
- if (finished)
- {
- lock_release(&lock);
- return MOVE_NONE;
- }
- Move m = get_next_move();
- if (m == MOVE_NONE)
- finished = true;
+/// 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.
- lock_release(&lock);
- return m;
-}
+/// 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_p)
+ : pos(p), mainHistory(mh), captureHistory(cph), contHistory(ch),
+ refutations{killers_p[0], killers_p[1], cm}, depth(d){
+ assert(d > DEPTH_ZERO);
-/// 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() {
- // 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. Instead of calculating SEE here to filter out
- // loosing captures, we delay the filtering in pick_move_from_list()
- Move m;
-
- for (int i = 0; i < numOfMoves; i++)
- {
- 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.type_of_piece_on(move_from(m)));
- }
+ stage = pos.checkers() ? EVASION_TT : MAIN_TT;
+ ttMove = ttm && pos.pseudo_legal(ttm) ? ttm : MOVE_NONE;
+ stage += (ttMove == MOVE_NONE);
}
-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;
-
- for (int i = 0; i < numOfMoves; i++)
- {
- m = moves[i].move;
+/// MovePicker constructor for quiescence search
+MovePicker::MovePicker(const Position& p, Move ttm, Depth d, const ButterflyHistory* mh,
+ const CapturePieceToHistory* cph, Square rs)
+ : pos(p), mainHistory(mh), captureHistory(cph), recaptureSquare(rs), depth(d) {
- 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);
+ assert(d <= DEPTH_ZERO);
- // Ensure moves in history are always sorted as first
- if (hs > 0)
- hs += 1000;
-
- moves[i].score = hs + pos.mg_pst_delta(m);
- }
+ stage = pos.checkers() ? EVASION_TT : QSEARCH_TT;
+ ttMove = ttm
+ && pos.pseudo_legal(ttm)
+ && (depth > DEPTH_QS_RECAPTURES || to_sq(ttm) == recaptureSquare) ? ttm : MOVE_NONE;
+ stage += (ttMove == MOVE_NONE);
}
-void MovePicker::score_evasions() {\r
-\r
- Move m;\r
- int hs;\r
-\r
- // Use MVV/LVA ordering\r
- for (int i = 0; i < numOfMoves; i++)\r
- {\r
- m = moves[i].move;\r
-\r
- if (m == ttMove)\r
- hs = 2*HistoryMax;\r
- else if (!pos.square_is_empty(move_to(m)))\r
- hs = int(pos.midgame_value_of_piece_on(move_to(m)))\r
- -int(pos.type_of_piece_on(move_from(m))) + HistoryMax;\r
- else\r
- hs = H.move_ordering_score(pos.piece_on(move_from(m)), m);\r
-\r
- moves[i].score = hs;\r
- }\r
-}
+/// MovePicker constructor for ProbCut: we generate captures with SEE higher
+/// 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) {
-void MovePicker::score_qcaptures() {
+ assert(!pos.checkers());
- // 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.type_of_piece_on(move_from(m)));
- }
+ stage = PROBCUT_TT;
+ ttMove = ttm
+ && pos.pseudo_legal(ttm)
+ && pos.capture(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() {
-/// find_best_index() loops across the moves and returns index of
-/// the highest scored one.
+ static_assert(Type == CAPTURES || Type == QUIETS || Type == EVASIONS, "Wrong type");
-int MovePicker::find_best_index() {
+ for (auto& m : *this)
+ if (Type == CAPTURES)
+ m.value = PieceValue[MG][pos.piece_on(to_sq(m))]
+ + (*captureHistory)[pos.moved_piece(m)][to_sq(m)][type_of(pos.piece_on(to_sq(m)))];
- int bestScore = -10000000, bestIndex = -1;
+ else if (Type == QUIETS)
+ m.value = (*mainHistory)[pos.side_to_move()][from_to(m)]
+ + (*contHistory[0])[pos.moved_piece(m)][to_sq(m)]
+ + (*contHistory[1])[pos.moved_piece(m)][to_sq(m)]
+ + (*contHistory[3])[pos.moved_piece(m)][to_sq(m)];
- for (int i = movesPicked; i < numOfMoves; i++)
- if (moves[i].score > bestScore)
+ else // Type == EVASIONS
{
- bestIndex = i;
- bestScore = moves[i].score;
+ 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)] - (1 << 28);
}
- return bestIndex;
}
+/// MovePicker::select_move() returns the next move satisfying a predicate function
+template<PickType T, typename Pred>
+Move MovePicker::select_move(Pred filter) {
-/// 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 bestIndex;
- Move move;
-
- switch (PhaseTable[phaseIndex]) {
- case PH_GOOD_CAPTURES:
- assert(!pos.is_check());
- assert(movesPicked >= 0);
-
- while (movesPicked < numOfMoves)
- {
- bestIndex = find_best_index();
-
- if (bestIndex != -1) // Found a possibly good capture
- {
- move = moves[bestIndex].move;
- int seeValue = pos.see(move);
- if (seeValue < 0)
- {
- // Losing capture, move it to the badCaptures[] array
- assert(numOfBadCaptures < 63);
- moves[bestIndex].score = seeValue;
- badCaptures[numOfBadCaptures++] = moves[bestIndex];
- moves[bestIndex] = moves[--numOfMoves];
- continue;
- }
- moves[bestIndex] = moves[movesPicked++];
- if ( move != ttMove
- && move != mateKiller
- && pos.pl_move_is_legal(move, pinned))
- 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;
-
- if (bestIndex != -1)
- {
- move = moves[bestIndex].move;
- moves[bestIndex] = moves[movesPicked++];
- if ( move != ttMove
- && move != mateKiller
- && pos.pl_move_is_legal(move, pinned))
- return move;
- }
- }
- break;
-
- case PH_EVASIONS:
- assert(pos.is_check());
- assert(movesPicked >= 0);
+ while (cur < endMoves)
+ {
+ if (T == BEST_SCORE)
+ std::swap(*cur, *std::max_element(cur, endMoves));
- while (movesPicked < numOfMoves)
- {
- bestIndex = find_best_index();
+ move = *cur++;
- if (bestIndex != -1)
- {
- move = moves[bestIndex].move;
- 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.pl_move_is_legal(move, pinned))
- return move;
- }
- break;
+ if (move != ttMove && filter())
+ return move;
+ }
+ return move = MOVE_NONE;
+}
- case PH_QCAPTURES:
- assert(!pos.is_check());
- assert(movesPicked >= 0);
- while (movesPicked < numOfMoves)
- {
- bestIndex = (movesPicked < 4 ? find_best_index() : movesPicked);
-
- if (bestIndex != -1)
- {
- 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))
- 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)
+/// 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. It picks 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:
+ endBadCaptures = cur = moves;
+ endMoves = generate<CAPTURES>(pos, cur);
+ score<CAPTURES>();
+ ++stage;
+ goto top;
+
+ case GOOD_CAPTURE:
+ if (select_move<BEST_SCORE>([&](){ return pos.see_ge(move, Value(-55 * (cur-1)->value / 1024)) ?
+ // Move losing capture to endBadCaptures to be tried later
+ true : (*endBadCaptures++ = move, false); }))
+ return move;
+
+ // If the countermove is the same as a killer, skip it
+ if ( refutations[0] == refutations[2]
+ || refutations[1] == refutations[2])
+ refutations[2] = MOVE_NONE;
+ ++stage;
+ /* fallthrough */
+
+ case KILLER0:
+ case KILLER1:
+ case COUNTERMOVE:
+ while (stage <= COUNTERMOVE)
{
- 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))
+ move = refutations[ stage++ - KILLER0];
+ if ( move != MOVE_NONE
+ && move != ttMove
+ && pos.pseudo_legal(move)
+ && !pos.capture(move))
return move;
}
- break;
-
- default:
- break;
+ /* fallthrough */
+
+ case QUIET_INIT:
+ cur = endBadCaptures;
+ endMoves = generate<QUIETS>(pos, cur);
+ score<QUIETS>();
+ partial_insertion_sort(cur, endMoves, -4000 * depth / ONE_PLY);
+ ++stage;
+ /* fallthrough */
+
+ case QUIET:
+ if ( !skipQuiets
+ && select_move<NEXT>([&](){return move != refutations[0]
+ && move != refutations[1]
+ && move != refutations[2];}))
+ return move;
+
+ // Point to beginning and end of bad captures
+ cur = moves, endMoves = endBadCaptures;
+ ++stage;
+ /* fallthrough */
+
+ case BAD_CAPTURE:
+ return select_move<NEXT>(Any);
+
+ case EVASION_INIT:
+ cur = moves;
+ endMoves = generate<EVASIONS>(pos, cur);
+ score<EVASIONS>();
+ ++stage;
+ /* fallthrough */
+
+ case EVASION:
+ return select_move<BEST_SCORE>(Any);
+
+ case PROBCUT:
+ return select_move<BEST_SCORE>([&](){ return pos.see_ge(move, threshold); });
+
+ case QCAPTURE:
+ if (select_move<BEST_SCORE>([&](){ return depth > DEPTH_QS_RECAPTURES
+ || to_sq(move) == recaptureSquare; }))
+ return move;
+
+ // If we did not find any move and we do not try checks, we have finished
+ if (depth != DEPTH_QS_CHECKS)
+ return MOVE_NONE;
+
+ ++stage;
+ /* fallthrough */
+
+ case QCHECK_INIT:
+ cur = moves;
+ endMoves = generate<QUIET_CHECKS>(pos, cur);
+ ++stage;
+ /* fallthrough */
+
+ case QCHECK:
+ return select_move<NEXT>(Any);
}
- 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
-/// 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