/*
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) 2008-2010 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
-////
-
namespace {
- /// Variables
-
- MovePicker::MovegenPhase PhaseTable[32];
- int MainSearchPhaseIndex;
- int EvasionsPhaseIndex;
- int QsearchWithChecksPhaseIndex;
- int QsearchWithoutChecksPhaseIndex;
-
+ enum MovegenPhase {
+ PH_TT_MOVES, // Transposition table move and mate killer
+ PH_GOOD_CAPTURES, // Queen promotions and captures with SEE values >= 0
+ PH_KILLERS, // Killer moves from the current ply
+ PH_NONCAPTURES, // Non-captures and underpromotions
+ PH_BAD_CAPTURES, // Queen promotions and captures with SEE values < 0
+ PH_EVASIONS, // Check evasions
+ PH_QCAPTURES, // Captures in quiescence search
+ PH_QCHECKS, // Non-capture checks in quiescence search
+ PH_STOP
+ };
+
+ CACHE_LINE_ALIGNMENT
+ const uint8_t MainSearchPhaseTable[] = { PH_TT_MOVES, PH_GOOD_CAPTURES, PH_KILLERS, PH_NONCAPTURES, PH_BAD_CAPTURES, PH_STOP};
+ const uint8_t EvasionsPhaseTable[] = { PH_TT_MOVES, PH_EVASIONS, PH_STOP};
+ const uint8_t QsearchWithChecksPhaseTable[] = { PH_TT_MOVES, PH_QCAPTURES, PH_QCHECKS, PH_STOP};
+ const uint8_t QsearchWithoutChecksPhaseTable[] = { PH_TT_MOVES, PH_QCAPTURES, PH_STOP};
}
-////
-//// Functions
-////
-
-
-/// Constructor for the MovePicker class. Apart from the position for which
+/// 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, 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;
+MovePicker::MovePicker(const Position& p, Move ttm, Depth d, const History& h,
+ SearchStack* ss, Value beta) : pos(p), H(h) {
+ int searchTT = ttm;
+ ttMoves[0].move = ttm;
+ badCaptureThreshold = 0;
+ badCaptures = moves + MOVES_MAX;
- movesPicked = numOfMoves = numOfBadCaptures = 0;
- checkKillers = checkLegal = finished = false;
+ assert(d > DEPTH_ZERO);
+
+ pinned = p.pinned_pieces(pos.side_to_move());
if (p.is_check())
- phaseIndex = EvasionsPhaseIndex;
- else if (d > Depth(0))
- phaseIndex = MainSearchPhaseIndex;
- else if (d == Depth(0))
- phaseIndex = QsearchWithChecksPhaseIndex;
+ {
+ ttMoves[1].move = killers[0].move = killers[1].move = MOVE_NONE;
+ phasePtr = EvasionsPhaseTable;
+ }
else
- phaseIndex = QsearchWithoutChecksPhaseIndex;
+ {
+ ttMoves[1].move = (ss->mateKiller == ttm) ? MOVE_NONE : ss->mateKiller;
+ searchTT |= ttMoves[1].move;
+ killers[0].move = ss->killers[0];
+ killers[1].move = ss->killers[1];
- Color us = pos.side_to_move();
+ // Consider sligtly negative captures as good if at low
+ // depth and far from beta.
+ if (ss && ss->eval < beta - PawnValueMidgame && d < 3 * ONE_PLY)
+ badCaptureThreshold = -PawnValueMidgame;
- dc = p.discovered_check_candidates(us);
- pinned = p.pinned_pieces(us);
+ phasePtr = MainSearchPhaseTable;
+ }
- finished = false;
+ phasePtr += int(!searchTT) - 1;
+ go_next_phase();
}
+MovePicker::MovePicker(const Position& p, Move ttm, Depth d, const History& h)
+ : pos(p), H(h) {
+ int searchTT = ttm;
+ ttMoves[0].move = ttm;
+ ttMoves[1].move = MOVE_NONE;
-/// 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() {
+ assert(d <= DEPTH_ZERO);
- Move move;
+ pinned = p.pinned_pieces(pos.side_to_move());
- while (true)
+ if (p.is_check())
+ phasePtr = EvasionsPhaseTable;
+ else if (d >= DEPTH_QS_CHECKS)
+ phasePtr = QsearchWithChecksPhaseTable;
+ else
{
- // 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;
- }
+ phasePtr = QsearchWithoutChecksPhaseTable;
+
+ // 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 != MOVE_NONE && !pos.move_is_capture_or_promotion(ttm))
+ searchTT = ttMoves[0].move = MOVE_NONE;
}
+
+ phasePtr += int(!searchTT) - 1;
+ go_next_phase();
}
-/// 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.
+/// 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_TT_MOVES:
+ curMove = ttMoves;
+ lastMove = curMove + 2;
+ return;
+
+ case PH_GOOD_CAPTURES:
+ lastMove = generate<MV_CAPTURE>(pos, moves);
+ score_captures();
+ return;
+
+ case PH_KILLERS:
+ curMove = killers;
+ lastMove = curMove + 2;
+ return;
+
+ case PH_NONCAPTURES:
+ lastMove = generate<MV_NON_CAPTURE>(pos, moves);
+ score_noncaptures();
+ sort_moves(moves, lastMove, &lastGoodNonCapture);
+ return;
+
+ case PH_BAD_CAPTURES:
+ // Bad captures SEE value is already calculated so just pick
+ // them in order to get SEE move ordering.
+ curMove = badCaptures;
+ lastMove = moves + MOVES_MAX;
+ return;
+
+ case PH_EVASIONS:
+ assert(pos.is_check());
+ lastMove = generate<MV_EVASION>(pos, moves);
+ score_evasions();
+ return;
+
+ case PH_QCAPTURES:
+ lastMove = generate<MV_CAPTURE>(pos, moves);
+ score_captures();
+ return;
-Move MovePicker::get_next_move(Lock &lock) {
+ case PH_QCHECKS:
+ lastMove = generate<MV_NON_CAPTURE_CHECK>(pos, moves);
+ return;
- lock_grab(&lock);
- if (finished)
- {
- lock_release(&lock);
- return MOVE_NONE;
- }
- Move m = get_next_move();
- if (m == MOVE_NONE)
- finished = true;
+ case PH_STOP:
+ lastMove = curMove + 1; // Avoids another go_next_phase() call
+ return;
- lock_release(&lock);
- return m;
+ default:
+ assert(false);
+ return;
+ }
}
-/// 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 get_next_move().
void MovePicker::score_captures() {
// Winning and equal captures in the main search are ordered by MVV/LVA.
Move m;
// Use MVV/LVA ordering
- for (int i = 0; i < numOfMoves; i++)
+ for (MoveStack* cur = moves; cur != lastMove; cur++)
{
- m = moves[i].move;
+ m = cur->move;
if (move_is_promotion(m))
- moves[i].score = QueenValueMidgame;
+ cur->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)));
+ cur->score = pos.midgame_value_of_piece_on(move_to(m))
+ - pos.type_of_piece_on(move_from(m));
}
}
// 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 (int i = 0; i < numOfMoves; i++)
+ for (MoveStack* cur = moves; cur != lastMove; cur++)
{
- from = move_from(moves[i].move);
- to = move_to(moves[i].move);
+ 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
- moves[i].score = hs + pos.pst_delta<Position::MidGame>(piece, from, to);
+ cur->score = H.value(piece, to) + H.gain(piece, to);
}
}
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, and at the end bad-captures and non-captures with a
+ // negative SEE. This last group is ordered by the SEE score.
+ Move m;
+ int seeScore;
+
+ // Skip if we don't have at least two moves to order
+ if (lastMove < moves + 2)
+ return;
- for (int i = 0; i < numOfMoves; i++)
+ 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.move_is_capture(m))
+ cur->score = pos.midgame_value_of_piece_on(move_to(m))
+ - pos.type_of_piece_on(move_from(m)) + History::MaxValue;
+ else
+ cur->score = H.value(pos.piece_on(move_from(m)), move_to(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 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.
-/// 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.
-
-Move MovePicker::pick_move_from_list() {
-
- assert(movesPicked >= 0);
- assert(!pos.is_check() || PhaseTable[phaseIndex] == PH_EVASIONS || PhaseTable[phaseIndex] == PH_STOP);
- assert( pos.is_check() || PhaseTable[phaseIndex] != PH_EVASIONS);
+Move MovePicker::get_next_move() {
- switch (PhaseTable[phaseIndex]) {
+ Move move;
- case PH_GOOD_CAPTURES:
- while (movesPicked < numOfMoves)
+ while (true)
+ {
+ while (curMove != lastMove)
{
- Move move = moves[movesPicked++].move;
- if ( move != ttMove
- && move != mateKiller
- && pos.pl_move_is_legal(move, pinned))
- {
- // Check for a non negative SEE now
- int seeValue = pos.see_sign(move);
- if (seeValue >= 0)
+ switch (phase) {
+
+ case PH_TT_MOVES:
+ move = (curMove++)->move;
+ if ( move != MOVE_NONE
+ && move_is_legal(pos, move, pinned))
+ return move;
+ break;
+
+ case PH_GOOD_CAPTURES:
+ move = pick_best(curMove++, lastMove).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 >= badCaptureThreshold)
+ return move;
+
+ // Losing capture, move it to the tail of the array, note
+ // that move has now been already checked for legality.
+ (--badCaptures)->move = move;
+ badCaptures->score = seeValue;
+ }
+ break;
+
+ case PH_KILLERS:
+ move = (curMove++)->move;
+ if ( move != MOVE_NONE
+ && move_is_legal(pos, move, pinned)
+ && move != ttMoves[0].move
+ && move != ttMoves[1].move
+ && !pos.move_is_capture(move))
return move;
+ break;
- // 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;
- 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)))
- return move;
- }
- break;
+ case PH_NONCAPTURES:
- case PH_EVASIONS:
- if (movesPicked < numOfMoves)
- return moves[movesPicked++].move;
- break;
+ // Sort negative scored moves only when we get there
+ if (curMove == lastGoodNonCapture)
+ insertion_sort<MoveStack>(lastGoodNonCapture, lastMove);
- case PH_BAD_CAPTURES:
- if (movesPicked < numOfBadCaptures)
- return badCaptures[movesPicked++].move;
- break;
+ 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;
+ break;
- case PH_QCAPTURES:
- case PH_QCHECKS:
- while (movesPicked < numOfMoves)
- {
- Move move = moves[movesPicked++].move;
- // Maybe postpone the legality check until after futility pruning?
- if ( move != ttMove
- && pos.pl_move_is_legal(move, pinned))
+ case PH_BAD_CAPTURES:
+ move = pick_best(curMove++, lastMove).move;
return move;
- }
- break;
- default:
- break;
- }
- return MOVE_NONE;
-}
+ case PH_EVASIONS:
+ case PH_QCAPTURES:
+ move = pick_best(curMove++, lastMove).move;
+ if ( move != ttMoves[0].move
+ && pos.pl_move_is_legal(move, pinned))
+ return move;
+ break;
+ case PH_QCHECKS:
+ move = (curMove++)->move;
+ if ( move != ttMoves[0].move
+ && pos.pl_move_is_legal(move, pinned))
+ return move;
+ break;
+
+ case PH_STOP:
+ return MOVE_NONE;
-/// 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;
+ default:
+ assert(false);
+ break;
+ }
+ }
+ go_next_phase();
+ }
}
projects / stockfish / blobdiff