X-Git-Url: https://git.sesse.net/?p=stockfish;a=blobdiff_plain;f=src%2Fmovepick.cpp;h=37775faa33aa666e8b0bea1b4eb9e9d23cee2690;hp=77c42efac8026716cd14237ddbe966a5d1bd0785;hb=df31398bb91b0e43661176e2f1681617ee64f1ad;hpb=e0c47a6cebbea453a1e74ca8ce1f5f8219b9b3f8
diff --git a/src/movepick.cpp b/src/movepick.cpp
index 77c42efa..37775faa 100644
--- a/src/movepick.cpp
+++ b/src/movepick.cpp
@@ -1,7 +1,7 @@
/*
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
@@ -18,211 +18,131 @@
along with this program. If not, see .
*/
-
-////
-//// Includes
-////
-
#include
#include
-#include "history.h"
-#include "evaluate.h"
#include "movegen.h"
#include "movepick.h"
-#include "search.h"
-#include "value.h"
-
-
-////
-//// Local definitions
-////
namespace {
- /// Variables
-
- CACHE_LINE_ALIGNMENT
- int MainSearchPhaseIndex;
- int EvasionsPhaseIndex;
- int QsearchWithChecksPhaseIndex;
- int QsearchWithoutChecksPhaseIndex;
- uint8_t PhaseTable[32];
+ 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) : 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;
+MovePicker::MovePicker(const Position& p, Move ttm, Depth d, const History& h,
+ Search::Stack* ss, Value beta) : pos(p), H(h), depth(d) {
+
+ assert(d > DEPTH_ZERO);
+
+ captureThreshold = 0;
+ curMove = lastMove = moves;
+ lastBadCapture = moves + MAX_MOVES - 1;
+
+ if (p.in_check())
+ phase = EVASION;
+
else
- phaseIndex = QsearchWithoutChecksPhaseIndex;
+ {
+ phase = MAIN_SEARCH;
- Color us = pos.side_to_move();
+ killers[0].move = ss->killers[0];
+ killers[1].move = ss->killers[1];
- dc = p.discovered_check_candidates(us);
- pinned = p.pinned_pieces(us);
+ // Consider sligtly negative captures as good if at low depth and far from beta
+ if (ss && ss->eval < beta - PawnValueMidgame && d < 3 * ONE_PLY)
+ captureThreshold = -PawnValueMidgame;
- finished = false;
+ // Consider negative captures as good if still enough to reach beta
+ else if (ss && ss->eval > beta)
+ captureThreshold = beta - ss->eval;
+ }
+
+ ttMove = (ttm && pos.is_pseudo_legal(ttm) ? ttm : MOVE_NONE);
+ lastMove += (ttMove != MOVE_NONE);
}
+MovePicker::MovePicker(const Position& p, Move ttm, Depth d, const History& h,
+ Square sq) : pos(p), H(h), curMove(moves), lastMove(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 (p.in_check())
+ phase = EVASION;
- Move move;
+ else if (d > DEPTH_QS_NO_CHECKS)
+ phase = QSEARCH_0;
- while (true)
+ else if (d > DEPTH_QS_RECAPTURES)
{
- // 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)
- {
- 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;
- break;
-
- case PH_KILLERS:
- movesPicked = numOfMoves = 0;
- 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
- checkLegal = true;
- numOfMoves = generate_noncaptures(pos, moves);
- score_noncaptures();
- std::sort(moves, moves + numOfMoves);
- movesPicked = 0;
- break;
-
- case PH_BAD_CAPTURES:
- // Bad captures SEE value is already calculated 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_captures();
- 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;
- }
+ phase = QSEARCH_1;
+
+ // 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;
+ }
+
+ ttMove = (ttm && pos.is_pseudo_legal(ttm) ? ttm : MOVE_NONE);
+ lastMove += (ttMove != MOVE_NONE);
}
+MovePicker::MovePicker(const Position& p, Move ttm, const History& h, PieceType pt)
+ : pos(p), H(h), curMove(moves), lastMove(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.in_check());
-Move MovePicker::get_next_move(Lock &lock) {
+ phase = 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 better than parent's captured piece
+ captureThreshold = PieceValueMidgame[pt];
+ ttMove = (ttm && pos.is_pseudo_legal(ttm) ? ttm : MOVE_NONE);
- lock_release(&lock);
- return m;
+ if (ttMove && (!pos.is_capture(ttMove) || pos.see(ttMove) <= captureThreshold))
+ ttMove = MOVE_NONE;
+
+ lastMove += (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().
+/// 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 next_move().
void MovePicker::score_captures() {
// Winning and equal captures in the main search are ordered by MVV/LVA.
@@ -240,169 +160,199 @@ void MovePicker::score_captures() {
// some SEE calls in case we get a cutoff (idea from Pablo Vazquez).
Move m;
- // Use MVV/LVA ordering
- for (int i = 0; i < numOfMoves; i++)
+ for (MoveStack* cur = moves; cur != lastMove; cur++)
{
- m = moves[i].move;
- 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)));
+ m = cur->move;
+ cur->score = PieceValueMidgame[pos.piece_on(to_sq(m))]
+ - type_of(pos.piece_moved(m));
+
+ if (is_promotion(m))
+ cur->score += PieceValueMidgame[promotion_piece_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;
-
- 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);
- // Ensure history is always preferred to pst
- if (hs > 0)
- hs += 1000;
+ Move m;
+ Square from;
- // pst based scoring
- moves[i].score = hs + pos.pst_delta(piece, from, to);
+ for (MoveStack* cur = moves; cur != lastMove; cur++)
+ {
+ m = cur->move;
+ from = from_sq(m);
+ cur->score = H.value(pos.piece_on(from), 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;
- for (int i = 0; i < numOfMoves; i++)
+ if (lastMove < moves + 2)
+ return;
+
+ for (MoveStack* cur = moves; cur != lastMove; cur++)
{
- 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 = 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 = PieceValueMidgame[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::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.
+/// MovePicker::generate_next() generates, scores and sorts the next bunch of moves,
+/// when there are no more moves to try for the current phase.
-Move MovePicker::pick_move_from_list() {
+void MovePicker::generate_next() {
- assert(movesPicked >= 0);
- assert(!pos.is_check() || PhaseTable[phaseIndex] == PH_EVASIONS || PhaseTable[phaseIndex] == PH_STOP);
- assert( pos.is_check() || PhaseTable[phaseIndex] != PH_EVASIONS);
+ curMove = moves;
- switch (PhaseTable[phaseIndex]) {
+ switch (++phase) {
- case PH_GOOD_CAPTURES:
- while (movesPicked < numOfMoves)
- {
- Move move = moves[movesPicked++].move;
- if ( move != ttMove
- && move != mateKiller
- && pos.pl_move_is_legal(move, pinned))
+ case CAPTURES_S1: case CAPTURES_S3: case CAPTURES_S4: case CAPTURES_S5: case CAPTURES_S6:
+ lastMove = generate(pos, moves);
+ score_captures();
+ return;
+
+ case KILLERS_S1:
+ curMove = killers;
+ lastMove = curMove + 2;
+ return;
+
+ case QUIETS_1_S1:
+ lastQuiet = lastMove = generate(pos, moves);
+ score_noncaptures();
+ lastMove = std::partition(curMove, lastMove, has_positive_score);
+ sort(curMove, lastMove);
+ return;
+
+ case QUIETS_2_S1:
+ curMove = lastMove;
+ lastMove = lastQuiet;
+ if (depth >= 3 * ONE_PLY)
+ sort(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(pos, moves);
+ score_evasions();
+ return;
+
+ case QUIET_CHECKS_S3:
+ lastMove = generate(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. Note that this function is not thread safe so should be
+/// lock protected by caller when accessed through a shared MovePicker object.
+
+Move MovePicker::next_move() {
+
+ Move move;
+
+ while (true)
+ {
+ while (curMove == lastMove)
+ generate_next();
+
+ switch (phase) {
+
+ case MAIN_SEARCH: case EVASION: case QSEARCH_0: case QSEARCH_1: case PROBCUT:
+ curMove++;
+ return ttMove;
+
+ case CAPTURES_S1:
+ move = pick_best(curMove++, lastMove)->move;
+ if (move != ttMove)
{
- // Check for a non negative SEE now
- int seeValue = pos.see_sign(move);
- if (seeValue >= 0)
+ assert(captureThreshold <= 0); // Otherwise we cannot use see_sign()
+
+ if (pos.see_sign(move) >= captureThreshold)
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;
+ // Losing capture, move it to the tail of the array
+ (lastBadCapture--)->move = move;
}
- }
- break;
- case PH_KILLERS:
- case PH_NONCAPTURES:
- while (movesPicked < numOfMoves)
- {
- Move move = moves[movesPicked++].move;
- if ( move != ttMove
- && move != mateKiller
- && (!checkKillers || (move != killer1 && move != killer2))
- && (!checkLegal || pos.pl_move_is_legal(move, pinned)))
+ break;
+
+ 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_EVASIONS:
- if (movesPicked < numOfMoves)
- return moves[movesPicked++].move;
- break;
-
- case PH_BAD_CAPTURES:
- if (movesPicked < numOfBadCaptures)
- return badCaptures[movesPicked++].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?
+ break;
+
+ case QUIETS_1_S1: case QUIETS_2_S1:
+ move = (curMove++)->move;
if ( move != ttMove
- && pos.pl_move_is_legal(move, pinned))
+ && move != killers[0].move
+ && move != killers[1].move)
return move;
- }
- break;
+ break;
- default:
- break;
- }
- return MOVE_NONE;
-}
+ 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 CAPTURES_S5:
+ move = pick_best(curMove++, lastMove)->move;
+ if (move != ttMove && pos.see(move) > captureThreshold)
+ return move;
+ break;
-/// 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;
+ case CAPTURES_S6:
+ move = pick_best(curMove++, lastMove)->move;
+ if (to_sq(move) == recaptureSquare)
+ return move;
+ break;
+
+ case QUIET_CHECKS_S3:
+ move = (curMove++)->move;
+ if (move != ttMove)
+ return move;
+ break;
+
+ case STOP:
+ return MOVE_NONE;
+
+ default:
+ assert(false);
+ }
+ }
}