/*
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) 2008-2012 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
-
- 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_GOOD_CAPTURES, PH_NULL_MOVE, 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 Sequencer {
+ 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
+ };
+
+ // Unary predicate used by std::partition to split positive scores from remaining
+ // ones so to sort separately the two sets, and with the second sort delayed.
+ inline bool has_positive_score(const MoveStack& move) { return move.score > 0; }
+
+ // Picks and moves to the front the best move in the range [firstMove, lastMove),
+ // it is faster than sorting all the moves in advance when moves are few, as
+ // normally are the possible captures.
+ inline MoveStack* pick_best(MoveStack* firstMove, MoveStack* lastMove)
+ {
+ std::swap(*firstMove, *std::max_element(firstMove, lastMove));
+ return firstMove;
+ }
}
-////
-//// Functions
-////
-
-
-/// Constructor for the MovePicker class. Apart from the position for which
-/// it is asked to pick legal moves, MovePicker also wants some information
+/// 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] = ttm;
- if (ss)
- {
- ttMoves[1] = (ss->mateKiller == ttm)? MOVE_NONE : ss->mateKiller;
- killers[0] = ss->killers[0];
- killers[1] = ss->killers[1];
- } else
- ttMoves[1] = killers[0] = killers[1] = MOVE_NONE;
-
- numOfBadCaptures = 0;
- finished = false;
-
- 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;
+MovePicker::MovePicker(const Position& p, Move ttm, Depth d, const History& h,
+ Search::Stack* s, Value beta) : pos(p), H(h), depth(d) {
+
+ assert(d > DEPTH_ZERO);
+
+ captureThreshold = 0;
+ curMove = lastMove = moves;
+ lastBadCapture = moves + MAX_MOVES - 1;
+ ss = s;
+
+ if (p.in_check())
+ phase = EVASION;
+
else
- phasePtr = QsearchWithoutChecksPhaseTable;
+ {
+ phase = MAIN_SEARCH;
- phasePtr--;
- go_next_phase();
-}
+ killers[0].move = ss->killers[0];
+ killers[1].move = ss->killers[1];
+ // Consider sligtly negative captures as good if at low depth and far from beta
+ if (ss && ss->eval < beta - PawnValueMg && d < 3 * ONE_PLY)
+ captureThreshold = -PawnValueMg;
-/// 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.
+ // Consider negative captures as good if still enough to reach beta
+ else if (ss && ss->eval > beta)
+ captureThreshold = beta - ss->eval;
+ }
-void MovePicker::go_next_phase() {
+ ttMove = (ttm && pos.is_pseudo_legal(ttm) ? ttm : MOVE_NONE);
+ lastMove += (ttMove != MOVE_NONE);
+}
- curMove = moves;
- phase = *(++phasePtr);
- switch (phase) {
+MovePicker::MovePicker(const Position& p, Move ttm, Depth d, const History& h,
+ Square sq) : pos(p), H(h), curMove(moves), lastMove(moves) {
- case PH_NULL_MOVE:
- case PH_TT_MOVES:
- movesPicked = 0;
- return;
+ assert(d <= DEPTH_ZERO);
- case PH_GOOD_CAPTURES:
- lastMove = generate_captures(pos, moves);
- score_captures();
- std::sort(moves, lastMove);
- return;
+ if (p.in_check())
+ phase = EVASION;
- case PH_KILLERS:
- movesPicked = 0;
- return;
+ else if (d > DEPTH_QS_NO_CHECKS)
+ phase = QSEARCH_0;
- case PH_NONCAPTURES:
- lastMove = generate_noncaptures(pos, moves);
- score_noncaptures();
- std::sort(moves, lastMove);
- return;
+ else if (d > DEPTH_QS_RECAPTURES)
+ {
+ phase = QSEARCH_1;
- 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;
+ // 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 && !pos.is_capture_or_promotion(ttm))
+ ttm = MOVE_NONE;
+ }
+ else
+ {
+ phase = RECAPTURE;
+ recaptureSquare = sq;
+ ttm = MOVE_NONE;
+ }
- case PH_EVASIONS:
- assert(pos.is_check());
- lastMove = generate_evasions(pos, moves, pinned);
- score_evasions();
- std::sort(moves, lastMove);
- return;
+ ttMove = (ttm && pos.is_pseudo_legal(ttm) ? ttm : MOVE_NONE);
+ lastMove += (ttMove != MOVE_NONE);
+}
- case PH_QCAPTURES:
- lastMove = generate_captures(pos, moves);
- score_captures();
- std::sort(moves, lastMove);
- return;
+MovePicker::MovePicker(const Position& p, Move ttm, const History& h, PieceType pt)
+ : pos(p), H(h), curMove(moves), lastMove(moves) {
- case PH_QCHECKS:
- // Perhaps we should order moves move here? FIXME
- lastMove = generate_non_capture_checks(pos, moves, dc);
- return;
+ assert(!pos.in_check());
- case PH_STOP:
- return;
+ phase = PROBCUT;
- default:
- assert(false);
- return;
- }
+ // In ProbCut we generate only captures better than parent's captured piece
+ captureThreshold = PieceValue[Mg][pt];
+ ttMove = (ttm && pos.is_pseudo_legal(ttm) ? ttm : MOVE_NONE);
+
+ if (ttMove && (!pos.is_capture(ttMove) || pos.see(ttMove) <= captureThreshold))
+ ttMove = MOVE_NONE;
+
+ lastMove += (ttMove != MOVE_NONE);
}
/// 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().
+/// picked first by next_move().
void MovePicker::score_captures() {
// Winning and equal captures in the main search are ordered by MVV/LVA.
// 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)));
+ cur->score = PieceValue[Mg][pos.piece_on(to_sq(m))]
+ - type_of(pos.piece_moved(m));
+
+ if (type_of(m) == PROMOTION)
+ cur->score += PieceValue[Mg][promotion_type(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.
- Piece piece;
- Square from, to;
- int hs;
+
+ Move m;
for (MoveStack* cur = moves; cur != lastMove; cur++)
{
- from = move_from(cur->move);
- to = move_to(cur->move);
- 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);
+ m = cur->move;
+ cur->score = H.value(pos.piece_moved(m), to_sq(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, then bad-captures and quiet
+ // moves with a negative SEE. This last group is ordered by the SEE score.
+ Move m;
+ int seeScore;
+
+ if (lastMove < moves + 2)
+ return;
for (MoveStack* cur = moves; cur != lastMove; cur++)
{
- Move m = cur->move;
- if (m == ttMoves[0])
- cur->score = 2*HistoryMax;
- else if (!pos.square_is_empty(move_to(m)))
- {
- int seeScore = pos.see(m);
- cur->score = (seeScore >= 0)? seeScore + HistoryMax : seeScore;
- } else
- cur->score = H.move_ordering_score(pos.piece_on(move_from(m)), move_to(m));
+ 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.is_capture(m))
+ cur->score = PieceValue[Mg][pos.piece_on(to_sq(m))]
+ - type_of(pos.piece_moved(m)) + History::MaxValue;
+ else
+ cur->score = H.value(pos.piece_moved(m), to_sq(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 that has already been serched previously.
-Move MovePicker::get_next_move() {
+/// MovePicker::generate_next() generates, scores and sorts the next bunch of moves,
+/// when there are no more moves to try for the current phase.
+
+void MovePicker::generate_next() {
+
+ curMove = moves;
+
+ switch (++phase) {
+
+ case CAPTURES_S1: case CAPTURES_S3: case CAPTURES_S4: case CAPTURES_S5: case CAPTURES_S6:
+ lastMove = generate<CAPTURES>(pos, moves);
+ score_captures();
+ return;
- assert(!pos.is_check() || *phasePtr == PH_EVASIONS || *phasePtr == PH_STOP);
- assert( pos.is_check() || *phasePtr != PH_EVASIONS);
+ case KILLERS_S1:
+ curMove = killers;
+ lastMove = curMove + 2;
+ return;
+
+ case QUIETS_1_S1:
+ lastQuiet = lastMove = generate<QUIETS>(pos, moves);
+ score_noncaptures();
+ lastMove = std::partition(curMove, lastMove, has_positive_score);
+ sort<MoveStack>(curMove, lastMove);
+ return;
+
+ case QUIETS_2_S1:
+ curMove = lastMove;
+ lastMove = lastQuiet;
+ if (depth >= 3 * ONE_PLY)
+ sort<MoveStack>(curMove, lastMove);
+ return;
+
+ case BAD_CAPTURES_S1:
+ // Just pick them in reverse order to get MVV/LVA ordering
+ curMove = moves + MAX_MOVES - 1;
+ lastMove = lastBadCapture;
+ return;
+
+ case EVASIONS_S2:
+ lastMove = generate<EVASIONS>(pos, moves);
+ score_evasions();
+ return;
+
+ case QUIET_CHECKS_S3:
+ lastMove = generate<QUIET_CHECKS>(pos, moves);
+ return;
+
+ case EVASION: case QSEARCH_0: case QSEARCH_1: case PROBCUT: case RECAPTURE:
+ phase = STOP;
+ case STOP:
+ lastMove = curMove + 1; // Avoid another next_phase() call
+ return;
+
+ default:
+ assert(false);
+ }
+}
+
+
+/// 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 biggest score from a list
+/// of generated moves taking care not to return the tt move if has already been
+/// searched previously.
+template<>
+Move MovePicker::next_move<false>() {
+
+ Move move;
while (true)
{
+ while (curMove == lastMove)
+ generate_next();
+
switch (phase) {
- case PH_NULL_MOVE:
- go_next_phase();
- return MOVE_NULL;
+ case MAIN_SEARCH: case EVASION: case QSEARCH_0: case QSEARCH_1: case PROBCUT:
+ curMove++;
+ return ttMove;
- case PH_TT_MOVES:
- while (movesPicked < 2)
+ case CAPTURES_S1:
+ move = pick_best(curMove++, lastMove)->move;
+ if (move != ttMove)
{
- Move move = ttMoves[movesPicked++];
- if ( move != MOVE_NONE
- && move_is_legal(pos, move, pinned))
+ assert(captureThreshold <= 0); // Otherwise we cannot use see_sign()
+
+ if (pos.see_sign(move) >= captureThreshold)
return move;
+
+ // Losing capture, move it to the tail of the array
+ (lastBadCapture--)->move = move;
}
break;
- case PH_GOOD_CAPTURES:
- while (curMove != lastMove)
- {
- Move move = (curMove++)->move;
- if ( move != ttMoves[0]
- && move != ttMoves[1]
- && 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;
- }
- }
+ case KILLERS_S1:
+ move = (curMove++)->move;
+ if ( move != MOVE_NONE
+ && pos.is_pseudo_legal(move)
+ && move != ttMove
+ && !pos.is_capture(move))
+ return move;
break;
- case PH_KILLERS:
- while (movesPicked < 2)
- {
- Move move = killers[movesPicked++];
- if ( move != MOVE_NONE
- && move != ttMoves[0]
- && move != ttMoves[1]
- && move_is_legal(pos, move, pinned)
- && !pos.move_is_capture(move))
- return move;
- }
+ case QUIETS_1_S1: case QUIETS_2_S1:
+ move = (curMove++)->move;
+ if ( move != ttMove
+ && move != killers[0].move
+ && move != killers[1].move)
+ return move;
break;
- case PH_NONCAPTURES:
- while (curMove != lastMove)
- {
- Move move = (curMove++)->move;
- if ( move != ttMoves[0]
- && move != ttMoves[1]
- && move != killers[0]
- && move != killers[1]
- && pos.pl_move_is_legal(move, pinned))
- return move;
- }
+ case BAD_CAPTURES_S1:
+ return (curMove--)->move;
+
+ case EVASIONS_S2: case CAPTURES_S3: case CAPTURES_S4:
+ move = pick_best(curMove++, lastMove)->move;
+ if (move != ttMove)
+ return move;
break;
- case PH_EVASIONS:
- case PH_BAD_CAPTURES:
- if (curMove != lastMove)
- return (curMove++)->move;
+ case CAPTURES_S5:
+ move = pick_best(curMove++, lastMove)->move;
+ if (move != ttMove && pos.see(move) > captureThreshold)
+ return move;
+ break;
+
+ case CAPTURES_S6:
+ move = pick_best(curMove++, lastMove)->move;
+ if (to_sq(move) == recaptureSquare)
+ return move;
break;
- case PH_QCAPTURES:
- case PH_QCHECKS:
- while (curMove != lastMove)
- {
- Move move = (curMove++)->move;
- // Maybe postpone the legality check until after futility pruning?
- if ( move != ttMoves[0]
- && pos.pl_move_is_legal(move, pinned))
- return move;
- }
+ case QUIET_CHECKS_S3:
+ move = (curMove++)->move;
+ if (move != ttMove)
+ return move;
break;
- case PH_STOP:
+ case STOP:
return MOVE_NONE;
default:
assert(false);
- break;
}
- go_next_phase();
}
- 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.
-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;
-
- lock_release(&lock);
- return m;
-}
+/// 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 should be lock protected by the caller.
+template<>
+Move MovePicker::next_move<true>() { return ss->sp->mp->next_move<false>(); }
projects / stockfish / blobdiff