/*
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) 2008-2015 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 <algorithm>
#include <cassert>
-#include "history.h"
-#include "movegen.h"
#include "movepick.h"
-#include "search.h"
-#include "value.h"
-
-
-////
-//// Local definitions
-////
namespace {
- CACHE_LINE_ALIGNMENT
- const MovegenPhaseT MainSearchPhaseTable[] = { PH_NULL_MOVE, PH_TT_MOVES, PH_GOOD_CAPTURES, PH_KILLERS, PH_NONCAPTURES, PH_BAD_CAPTURES, PH_STOP};
- const MovegenPhaseT MainSearchNoNullPhaseTable[] = { PH_TT_MOVES, PH_GOOD_CAPTURES, PH_KILLERS, PH_NONCAPTURES, PH_BAD_CAPTURES, PH_STOP};
- const MovegenPhaseT LowSearchPhaseTable[] = { PH_TT_MOVES, PH_NULL_MOVE, PH_GOOD_CAPTURES, PH_KILLERS, PH_NONCAPTURES, PH_BAD_CAPTURES, PH_STOP};
- const MovegenPhaseT EvasionsPhaseTable[] = { PH_EVASIONS, PH_STOP};
- const MovegenPhaseT QsearchWithChecksPhaseTable[] = { PH_TT_MOVES, PH_QCAPTURES, PH_QCHECKS, PH_STOP};
- const MovegenPhaseT QsearchWithoutChecksPhaseTable[] = { PH_TT_MOVES, PH_QCAPTURES, PH_STOP};
-}
+ enum Stages {
+ MAIN_SEARCH, CAPTURES_INIT, GOOD_CAPTURES, KILLER0, KILLER1, COUNTERMOVE, QUIET_INIT, QUIET, BAD_CAPTURES,
+ EVASION, EVASIONS_INIT, ALL_EVASIONS,
+ PROBCUT, PROBCUT_CAPTURES_INIT, PROBCUT_CAPTURES,
+ QSEARCH, QCAPTURES_INIT, QCAPTURES, QCHECKS
+ };
+
+ // 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;
+ }
+ }
+ // 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) {
-////
-//// Functions
-////
+ 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.
-
-MovePicker::MovePicker(const Position& p, Move ttm, Depth d,
- const History& h, SearchStack* ss, bool useNullMove) : pos(p), H(h) {
- ttMoves[0].move = ttm;
- if (ss)
- {
- ttMoves[1].move = (ss->mateKiller == ttm)? MOVE_NONE : ss->mateKiller;
- killers[0].move = ss->killers[0];
- killers[1].move = ss->killers[1];
- } else
- ttMoves[1].move = killers[0].move = killers[1].move = MOVE_NONE;
-
- finished = false;
- numOfBadCaptures = 0;
-
- Color us = pos.side_to_move();
-
- dc = p.discovered_check_candidates(us);
- pinned = p.pinned_pieces(us);
-
- if (p.is_check())
- phasePtr = EvasionsPhaseTable;
- else if (d >= Depth(3 * OnePly))
- phasePtr = useNullMove ? MainSearchPhaseTable : MainSearchNoNullPhaseTable;
- else if (d > Depth(0))
- phasePtr = useNullMove ? LowSearchPhaseTable : MainSearchNoNullPhaseTable;
- else if (d == Depth(0))
- phasePtr = QsearchWithChecksPhaseTable;
- else
- phasePtr = QsearchWithoutChecksPhaseTable;
-
- phasePtr--;
- go_next_phase();
-}
+/// 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_p)
+ : pos(p), mainHistory(mh), captureHistory(cph), contHistory(ch), countermove(cm),
+ killers{killers_p[0], killers_p[1]}, depth(d){
-/// 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_NULL_MOVE:
- return;
-
- case PH_TT_MOVES:
- curMove = ttMoves;
- lastMove = curMove + 2;
- return;
-
- case PH_GOOD_CAPTURES:
- lastMove = generate_captures(pos, moves);
- score_captures();
- std::sort(moves, lastMove);
- return;
-
- case PH_KILLERS:
- curMove = killers;
- lastMove = curMove + 2;
- return;
-
- case PH_NONCAPTURES:
- lastMove = generate_noncaptures(pos, moves);
- score_noncaptures();
- std::sort(moves, lastMove);
- return;
-
- case PH_BAD_CAPTURES:
- // Bad captures SEE value is already calculated so just sort them
- // to get SEE move ordering.
- curMove = badCaptures;
- lastMove = badCaptures + numOfBadCaptures;
- std::sort(badCaptures, lastMove);
- return;
-
- case PH_EVASIONS:
- assert(pos.is_check());
- lastMove = generate_evasions(pos, moves, pinned);
- score_evasions();
- std::sort(moves, lastMove);
- return;
-
- case PH_QCAPTURES:
- lastMove = generate_captures(pos, moves);
- score_captures();
- std::sort(moves, lastMove);
- return;
-
- case PH_QCHECKS:
- // Perhaps we should order moves move here? FIXME
- lastMove = generate_non_capture_checks(pos, moves, dc);
- return;
-
- case PH_STOP:
- return;
+ assert(d > DEPTH_ZERO);
- default:
- assert(false);
- return;
- }
+ stage = pos.checkers() ? EVASION : MAIN_SEARCH;
+ ttMove = ttm && pos.pseudo_legal(ttm) ? ttm : MOVE_NONE;
+ stage += (ttMove == MOVE_NONE);
}
+/// MovePicker constructor for quiescence search
+MovePicker::MovePicker(const Position& p, Move ttm, Depth d, const ButterflyHistory* mh, const CapturePieceToHistory* cph, Square s)
+ : pos(p), mainHistory(mh), captureHistory(cph), recaptureSquare(s), depth(d) {
-/// 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 = int(pos.midgame_value_of_piece_on(move_to(m)))
- -int(pos.type_of_piece_on(move_from(m)));
- }
+ assert(d <= DEPTH_ZERO);
+
+ stage = pos.checkers() ? EVASION : QSEARCH;
+ ttMove = ttm
+ && pos.pseudo_legal(ttm)
+ && (depth > DEPTH_QS_RECAPTURES || to_sq(ttm) == recaptureSquare) ? 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;
- Piece piece;
- Square from, to;
- int hs;
-
- for (MoveStack* cur = moves; cur != lastMove; cur++)
- {
- m = cur->move;
- from = move_from(m);
- to = move_to(m);
- piece = pos.piece_on(from);
- hs = H.move_ordering_score(piece, to);
-
- // Ensure history is always preferred to pst
- if (hs > 0)
- hs += 1000;
-
- // pst based scoring
- cur->score = hs + pos.pst_delta<Position::MidGame>(piece, from, to);
- }
+/// 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) {
+
+ assert(!pos.checkers());
+
+ stage = PROBCUT;
+ ttMove = ttm
+ && pos.pseudo_legal(ttm)
+ && pos.capture(ttm)
+ && pos.see_ge(ttm, threshold) ? ttm : MOVE_NONE;
+ stage += (ttMove == MOVE_NONE);
}
-void MovePicker::score_evasions() {
+/// 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 are ordered using the histories.
+template<GenType Type>
+void MovePicker::score() {
- Move m;
+ static_assert(Type == CAPTURES || Type == QUIETS || Type == EVASIONS, "Wrong type");
- for (MoveStack* cur = moves; cur != lastMove; cur++)
- {
- m = cur->move;
- if (m == ttMoves[0].move)
- cur->score = 2 * HistoryMax;
- else if (!pos.square_is_empty(move_to(m)))
+ 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)))];
+
+ 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)];
+
+ else // Type == EVASIONS
{
- int seeScore = pos.see(m);
- cur->score = seeScore + (seeScore >= 0 ? HistoryMax : 0);
- } else
- cur->score = H.move_ordering_score(pos.piece_on(move_from(m)), move_to(m));
- }
+ 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);
+ }
}
-/// 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 that has already been serched previously.
+/// 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(bool skipQuiets) {
- assert(!pos.is_check() || *phasePtr == PH_EVASIONS || *phasePtr == PH_STOP);
- assert( pos.is_check() || *phasePtr != PH_EVASIONS);
+ Move move;
- while (true)
- {
- switch (phase) {
+ switch (stage) {
- case PH_NULL_MOVE:
- go_next_phase();
- return MOVE_NULL;
+ case MAIN_SEARCH: case EVASION: case QSEARCH: case PROBCUT:
+ ++stage;
+ return ttMove;
- case PH_TT_MOVES:
- while (curMove != lastMove)
- {
- Move move = (curMove++)->move;
- if ( move != MOVE_NONE
- && move_is_legal(pos, move, pinned))
- return move;
- }
- break;
+ case CAPTURES_INIT:
+ case PROBCUT_CAPTURES_INIT:
+ case QCAPTURES_INIT:
+ endBadCaptures = cur = moves;
+ endMoves = generate<CAPTURES>(pos, cur);
+ score<CAPTURES>();
+ ++stage;
- case PH_GOOD_CAPTURES:
- while (curMove != lastMove)
- {
- Move move = (curMove++)->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 >= 0)
- return move;
-
- // Losing capture, move it to the badCaptures[] array, note
- // that move has now been already checked for legality.
- assert(numOfBadCaptures < 63);
- badCaptures[numOfBadCaptures].move = move;
- badCaptures[numOfBadCaptures++].score = seeValue;
- }
- }
- break;
+ // Rebranch at the top of the switch via a recursive call
+ return next_move(skipQuiets);
- case PH_KILLERS:
- while (curMove != lastMove)
+ case GOOD_CAPTURES:
+ while (cur < endMoves)
+ {
+ move = pick_best(cur++, endMoves);
+ if (move != ttMove)
{
- Move move = (curMove++)->move;
- if ( move != MOVE_NONE
- && move != ttMoves[0].move
- && move != ttMoves[1].move
- && move_is_legal(pos, move, pinned)
- && !pos.move_is_capture(move))
+ if (pos.see_ge(move, Value(-55 * (cur-1)->value / 1024)))
return move;
- }
- break;
- case PH_NONCAPTURES:
- while (curMove != lastMove)
- {
- Move 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;
+ // Losing capture, move it to the beginning of the array
+ *endBadCaptures++ = move;
}
- break;
-
- case PH_EVASIONS:
- case PH_BAD_CAPTURES:
- if (curMove != lastMove)
- return (curMove++)->move;
- break;
+ }
+ ++stage;
+ /* fallthrough */
- case PH_QCAPTURES:
- case PH_QCHECKS:
- while (curMove != lastMove)
+ case KILLER0:
+ case KILLER1:
+ do
+ {
+ move = killers[++stage - KILLER1];
+ if ( move != MOVE_NONE
+ && move != ttMove
+ && pos.pseudo_legal(move)
+ && !pos.capture(move))
+ return move;
+ } while (stage <= KILLER1);
+ /* fallthrough */
+
+ case COUNTERMOVE:
+ ++stage;
+ move = countermove;
+ if ( move != MOVE_NONE
+ && move != ttMove
+ && move != killers[0]
+ && move != killers[1]
+ && pos.pseudo_legal(move)
+ && !pos.capture(move))
+ return move;
+ /* 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)
+ while (cur < endMoves)
{
- Move move = (curMove++)->move;
- // Maybe postpone the legality check until after futility pruning?
- if ( move != ttMoves[0].move
- && pos.pl_move_is_legal(move, pinned))
+ move = *cur++;
+ if ( move != ttMove
+ && move != killers[0]
+ && move != killers[1]
+ && move != countermove)
return move;
}
- break;
-
- case PH_STOP:
- return MOVE_NONE;
+ ++stage;
+ cur = moves; // Point to beginning of bad captures
+ /* fallthrough */
+
+ case BAD_CAPTURES:
+ if (cur < endBadCaptures)
+ return *cur++;
+ break;
+
+ case EVASIONS_INIT:
+ cur = moves;
+ endMoves = generate<EVASIONS>(pos, cur);
+ score<EVASIONS>();
+ ++stage;
+ /* fallthrough */
+
+ case ALL_EVASIONS:
+ while (cur < endMoves)
+ {
+ move = pick_best(cur++, endMoves);
+ if (move != ttMove)
+ return move;
+ }
+ break;
- default:
- assert(false);
- break;
+ case PROBCUT_CAPTURES:
+ while (cur < endMoves)
+ {
+ move = pick_best(cur++, endMoves);
+ if ( move != ttMove
+ && pos.see_ge(move, threshold))
+ return move;
}
- go_next_phase();
- }
-}
+ break;
-/// 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.
+ case QCAPTURES:
+ while (cur < endMoves)
+ {
+ move = pick_best(cur++, endMoves);
+ if ( move != ttMove
+ && (depth > DEPTH_QS_RECAPTURES || to_sq(move) == recaptureSquare))
+ return move;
+ }
+ if (depth <= DEPTH_QS_NO_CHECKS)
+ break;
+ cur = moves;
+ endMoves = generate<QUIET_CHECKS>(pos, cur);
+ ++stage;
+ /* fallthrough */
-Move MovePicker::get_next_move(Lock &lock) {
+ case QCHECKS:
+ while (cur < endMoves)
+ {
+ move = *cur++;
+ if (move != ttMove)
+ return move;
+ }
+ break;
- lock_grab(&lock);
- if (finished)
- {
- lock_release(&lock);
- return MOVE_NONE;
- }
- Move m = get_next_move();
- if (m == MOVE_NONE)
- finished = true;
+ default:
+ assert(false);
+ }
- lock_release(&lock);
- return m;
+ return MOVE_NONE;
}
projects / stockfish / blobdiff