/*
- Glaurung, a UCI chess playing engine.
- Copyright (C) 2004-2008 Tord Romstad
+ Stockfish, a UCI chess playing engine derived from Glaurung 2.1
+ Copyright (C) 2004-2008 Tord Romstad (Glaurung author)
+ Copyright (C) 2008 Marco Costalba
- Glaurung is free software: you can redistribute it and/or modify
+ 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.
-
- Glaurung is distributed in the hope that it will be useful,
+
+
+ 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
GNU General Public License for more details.
-
+
You should have received a copy of the GNU General Public License
along with this program. If not, see <http://www.gnu.org/licenses/>.
*/
#include <cassert>
#include "history.h"
+#include "evaluate.h"
#include "movegen.h"
#include "movepick.h"
#include "search.h"
/// Variables
- MovePicker::MovegenPhase PhaseTable[32];
+ MovePicker::MovegenPhase PhaseTable[32];
int MainSearchPhaseIndex;
int EvasionsPhaseIndex;
int QsearchWithChecksPhaseIndex;
+ int QsearchNoCapturesPhaseIndex;
int QsearchWithoutChecksPhaseIndex;
+ int NoMovesPhaseIndex;
}
/// search captures, promotions and some checks) and about how important good
/// move ordering is at the current node.
-MovePicker::MovePicker(Position &p, bool pvnode, Move ttm, Move mk,
- Move k1, Move k2, Depth dpth) {
- pos = &p;
- pvNode = pvnode;
+MovePicker::MovePicker(const Position& p, bool pv, Move ttm,
+ const SearchStack& ss, Depth d, EvalInfo* ei) : pos(p) {
+ pvNode = pv;
ttMove = ttm;
- mateKiller = (mk == ttm)? MOVE_NONE : mk;
- killer1 = k1;
- killer2 = k2;
- depth = dpth;
+ mateKiller = (ss.mateKiller == ttm)? MOVE_NONE : ss.mateKiller;
+ killer1 = ss.killers[0];
+ killer2 = ss.killers[1];
+ 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;
+
+ // With EvalInfo we are able to know how many captures are possible before
+ // generating them. So avoid generating in case we know are zero.
+ Color us = pos.side_to_move();
+ Color them = opposite_color(us);
+ bool noCaptures = ei
+ && (ei->attackedBy[us][0] & pos.pieces_of_color(them)) == 0
+ && !ei->mi->specialized_eval_exists()
+ && (pos.ep_square() == SQ_NONE)
+ && !pos.has_pawn_on_7th(us);
+
+ if (p.is_check())
+ phaseIndex = EvasionsPhaseIndex;
+ else if (depth > Depth(0))
+ phaseIndex = MainSearchPhaseIndex;
+ else if (depth == Depth(0))
+ phaseIndex = (noCaptures ? QsearchNoCapturesPhaseIndex : QsearchWithChecksPhaseIndex);
else
- phaseIndex = QsearchWithoutChecksPhaseIndex;
+ phaseIndex = (noCaptures ? NoMovesPhaseIndex : QsearchWithoutChecksPhaseIndex);
+ dc = p.discovered_check_candidates(us);
pinned = p.pinned_pieces(p.side_to_move());
finished = false;
/// are no more moves left of the types we are interested in.
Move MovePicker::get_next_move() {
+
Move move;
- while(true) {
+ while (true)
+ {
// If we already have a list of generated moves, pick the best move from
- // the list, and return it:
- move = this->pick_move_from_list();
- if(move != MOVE_NONE) {
- assert(move_is_ok(move));
- return move;
+ // the list, and return it.
+ move = pick_move_from_list();
+ if (move != MOVE_NONE)
+ {
+ assert(move_is_ok(move));
+ return move;
}
- // Next phase:
+ // Next phase
phaseIndex++;
- switch(PhaseTable[phaseIndex]) {
+ switch (PhaseTable[phaseIndex]) {
case PH_TT_MOVE:
- if(ttMove != MOVE_NONE) {
- assert(move_is_ok(ttMove));
- Move m = generate_move_if_legal(*pos, ttMove, pinned);
- if(m != MOVE_NONE) {
- assert(m == ttMove);
- return m;
+ if (ttMove != MOVE_NONE)
+ {
+ assert(move_is_ok(ttMove));
+ if (move_is_legal(pos, ttMove, pinned))
+ return ttMove;
}
- }
- break;
+ break;
case PH_MATE_KILLER:
- if(mateKiller != MOVE_NONE) {
- assert(move_is_ok(mateKiller));
- Move m = generate_move_if_legal(*pos, mateKiller, pinned);
- if(m != MOVE_NONE) {
- assert(m == mateKiller);
- return m;
- }
- }
- break;
+ if (mateKiller != MOVE_NONE)
+ {
+ assert(move_is_ok(mateKiller));
+ if (move_is_legal(pos, mateKiller, pinned))
+ return mateKiller;
+ }
+ break;
case PH_GOOD_CAPTURES:
- // pinned = pos->pinned_pieces(pos->side_to_move());
- numOfMoves = generate_captures(*pos, moves);
- this->score_captures();
- movesPicked = 0;
- break;
+ numOfMoves = generate_captures(pos, moves);
+ score_captures();
+ movesPicked = 0;
+ break;
case PH_BAD_CAPTURES:
- badCapturesPicked = 0;
- break;
+ badCapturesPicked = 0;
+ break;
case PH_NONCAPTURES:
- numOfMoves = generate_noncaptures(*pos, moves);
- this->score_noncaptures();
- movesPicked = 0;
- break;
+ numOfMoves = generate_noncaptures(pos, moves);
+ score_noncaptures();
+ movesPicked = 0;
+ break;
case PH_EVASIONS:
- assert(pos->is_check());
- // pinned = pos->pinned_pieces(pos->side_to_move());
- numOfMoves = generate_evasions(*pos, moves);
- this->score_evasions();
- movesPicked = 0;
- break;
+ assert(pos.is_check());
+ numOfMoves = generate_evasions(pos, moves);
+ score_evasions();
+ movesPicked = 0;
+ break;
case PH_QCAPTURES:
- // pinned = pos->pinned_pieces(pos->side_to_move());
- numOfMoves = generate_captures(*pos, moves);
- this->score_qcaptures();
- movesPicked = 0;
- break;
+ numOfMoves = generate_captures(pos, moves);
+ score_qcaptures();
+ movesPicked = 0;
+ break;
case PH_QCHECKS:
- numOfMoves = generate_checks(*pos, moves, dc);
- movesPicked = 0;
- break;
+ numOfMoves = generate_checks(pos, moves, dc);
+ movesPicked = 0;
+ break;
case PH_STOP:
- return MOVE_NONE;
+ return MOVE_NONE;
default:
- assert(false);
- return MOVE_NONE;
+ assert(false);
+ return MOVE_NONE;
}
}
-
- assert(false);
-
- return MOVE_NONE;
}
/// prevent multiple threads from picking the same move at a split point.
Move MovePicker::get_next_move(Lock &lock) {
- Move m;
lock_grab(&lock);
- if(finished) {
- lock_release(&lock);
- return MOVE_NONE;
+ if (finished)
+ {
+ lock_release(&lock);
+ return MOVE_NONE;
}
- m = this->get_next_move();
- if(m == MOVE_NONE)
- finished = true;
+ Move m = get_next_move();
+ if (m == MOVE_NONE)
+ finished = true;
+
lock_release(&lock);
-
return m;
}
-
-/// MovePicker::number_of_moves() simply returns the numOfMoves member
-/// variable. It is intended to be used in positions where the side to move
-/// is in check, for detecting checkmates or situations where there is only
-/// a single reply to check.
-
-int MovePicker::number_of_moves() const {
- return numOfMoves;
-}
-
/// 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
-/// MovePicker::pick_move_from_list().
+/// 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.
// 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
+ // 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.
- for(int i = 0; i < numOfMoves; i++) {
- int seeValue = pos->see(moves[i].move);
- if(seeValue >= 0) {
- if(move_promotion(moves[i].move))
- moves[i].score = QueenValueMidgame;
- else
- moves[i].score =
- int(pos->midgame_value_of_piece_on(move_to(moves[i].move))) -
- int(pos->type_of_piece_on(move_from(moves[i].move)));
- }
- else
- moves[i].score = seeValue;
-
+ // While scoring captures it moves all captures with negative SEE values
+ // to the badCaptures[] array.
+ Move m;
+ int seeValue;
+
+ for (int i = 0; i < numOfMoves; i++)
+ {
+ m = moves[i].move;
+ seeValue = pos.see(m);
+ if (seeValue >= 0)
+ {
+ 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)));
+ }
+ else
+ {
+ // Losing capture, move it to the badCaptures[] array
+ assert(numOfBadCaptures < 63);
+ moves[i].score = seeValue;
+ badCaptures[numOfBadCaptures++] = moves[i];
+ moves[i--] = moves[--numOfMoves];
+ }
}
}
void MovePicker::score_noncaptures() {
- for(int i = 0; i < numOfMoves; i++) {
- Move m = moves[i].move;
- if(m == killer1)
- moves[i].score = HistoryMax + 2;
- else if(m == killer2)
- moves[i].score = HistoryMax + 1;
- else
- moves[i].score = H.move_ordering_score(pos->piece_on(move_from(m)), 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;
+ int hs;
+
+ for (int i = 0; i < numOfMoves; i++)
+ {
+ m = moves[i].move;
+
+ 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);
+
+ // Ensure history is always preferred to pst
+ if (hs > 0)
+ hs += 1000;
+
+ // pst based scoring
+ moves[i].score = hs + pos.mg_pst_delta(m);
}
}
void MovePicker::score_evasions() {
- for(int i = 0; i < numOfMoves; i++) {
- 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)), m);
+
+ for (int i = 0; i < numOfMoves; i++)
+ {
+ 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)), m);
}
}
void MovePicker::score_qcaptures() {
- // 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->midgame_value_of_piece_on(move_to(m))) / 64;
+
+ // 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)));
+ }
+}
+
+
+/// find_best_index() loops across the moves and returns index of
+/// the highest scored one. There is also a second version that
+/// lowers the priority of moves that attack the same square,
+/// so that if the best move that attack a square fails the next
+/// move picked attacks a different square if any, not the same one.
+
+int MovePicker::find_best_index() {
+
+ assert(movesPicked < numOfMoves);
+
+ int bestIndex = movesPicked, bestScore = moves[movesPicked].score;
+
+ for (int i = movesPicked + 1; i < numOfMoves; i++)
+ if (moves[i].score > bestScore)
+ {
+ bestIndex = i;
+ bestScore = moves[i].score;
+ }
+ return bestIndex;
+}
+
+int MovePicker::find_best_index(Bitboard* squares, int values[]) {
+
+ assert(movesPicked < numOfMoves);
+
+ int hs;
+ Move m;
+ Square to;
+ int bestScore = -10000000, bestIndex = -1;
+
+ for (int i = movesPicked; i < numOfMoves; i++)
+ {
+ m = moves[i].move;
+ to = move_to(m);
+
+ if (!bit_is_set(*squares, to))
+ {
+ // Init at first use
+ set_bit(squares, to);
+ values[to] = 0;
+ }
+
+ hs = moves[i].score - values[to];
+ if (hs > bestScore)
+ {
+ bestIndex = i;
+ bestScore = hs;
+ }
+ }
+
+ if (bestIndex != -1)
+ {
+ // Raise value of the picked square, so next attack
+ // to the same square will get low priority.
+ to = move_to(moves[bestIndex].move);
+ values[to] += 0xB00;
}
+ return bestIndex;
}
/// 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 bestScore = -10000000;
+
int bestIndex;
Move move;
- switch(PhaseTable[phaseIndex]) {
+ switch (PhaseTable[phaseIndex]) {
case PH_GOOD_CAPTURES:
- assert(!pos->is_check());
- assert(movesPicked >= 0);
- while(movesPicked < numOfMoves) {
- bestScore = -10000000;
- bestIndex = -1;
- for(int i = movesPicked; i < numOfMoves; i++) {
- if(moves[i].score < 0) {
- // Losing capture, move it to the badCaptures[] array
- assert(numOfBadCaptures < 63);
- badCaptures[numOfBadCaptures++] = moves[i];
- moves[i--] = moves[--numOfMoves];
- }
- else if(moves[i].score > bestScore) {
- bestIndex = i;
- bestScore = moves[i].score;
- }
+ assert(!pos.is_check());
+ assert(movesPicked >= 0);
+
+ while (movesPicked < numOfMoves)
+ {
+ bestIndex = find_best_index();
+ move = moves[bestIndex].move;
+ moves[bestIndex] = moves[movesPicked++];
+ if ( move != ttMove
+ && move != mateKiller
+ && pos.pl_move_is_legal(move, pinned))
+ return move;
}
- if(bestIndex != -1) { // Found a good capture
- move = moves[bestIndex].move;\r
- moves[bestIndex] = moves[movesPicked++];
- if(move != ttMove && move != mateKiller &&
- pos->move_is_legal(move, pinned))
- return move;
- }
- }
- break;
+ break;
case PH_NONCAPTURES:
- assert(!pos->is_check());
- assert(movesPicked >= 0);
- while(movesPicked < numOfMoves) {
- bestScore = -10000000;
-
- // 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.
- if(pvNode || movesPicked < 12) {
- bestIndex = -1;
- for(int i = movesPicked; i < numOfMoves; i++)
- if(moves[i].score > bestScore) {
- bestIndex = i;
- bestScore = moves[i].score;
- }
- }
- else
- bestIndex = movesPicked;
-
- if(bestIndex != -1) {
- move = moves[bestIndex].move;\r
- moves[bestIndex] = moves[movesPicked++];
- if(move != ttMove && move != mateKiller &&
- pos->move_is_legal(move, pinned))
- return move;
+ 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;
+ move = moves[bestIndex].move;
+ moves[bestIndex] = moves[movesPicked++];
+ if ( move != ttMove
+ && move != mateKiller
+ && pos.pl_move_is_legal(move, pinned))
+ return move;
}
- }
- break;
+ break;
case PH_EVASIONS:
- assert(pos->is_check());
- assert(movesPicked >= 0);
- while(movesPicked < numOfMoves) {
- bestScore = -10000000;
- bestIndex = -1;
- for(int i = movesPicked; i < numOfMoves; i++)
- if(moves[i].score > bestScore) {
- bestIndex = i;
- bestScore = moves[i].score;
- }
-
- if(bestIndex != -1) {
- move = moves[bestIndex].move;\r
- moves[bestIndex] = moves[movesPicked++];
- return move;
- }
+ assert(pos.is_check());
+ assert(movesPicked >= 0);
+
+ while (movesPicked < numOfMoves)
+ {
+ bestIndex = find_best_index();
+ 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->move_is_legal(move, pinned))
- return move;
- }
- break;
+ 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;
case PH_QCAPTURES:
- assert(!pos->is_check());
- assert(movesPicked >= 0);
- while(movesPicked < numOfMoves) {
- bestScore = -10000000;
- if(movesPicked < 4) {
- bestIndex = -1;
- for(int i = movesPicked; i < numOfMoves; i++)
- if(moves[i].score > bestScore) {
- bestIndex = i;
- bestScore = moves[i].score;
- }
+ assert(!pos.is_check());
+ assert(movesPicked >= 0);
+ while (movesPicked < numOfMoves)
+ {
+ bestIndex = (movesPicked < 4 ? find_best_index() : movesPicked);
+ 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;
}
- else
- bestIndex = movesPicked;
-
- if(bestIndex != -1) {
- move = moves[bestIndex].move;\r
- 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->move_is_legal(move, pinned))
- return move;
- }
- }
- break;
+ 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) {
- move = moves[movesPicked++].move;
- // Remember to change the line below if we decide to hash the qsearch!
- if(/* move != ttMove && */ pos->move_is_legal(move, pinned))
- return move;
- }
- break;
+ assert(!pos.is_check());
+ assert(movesPicked >= 0);
+ // Perhaps we should do something better than just picking the first
+ // move here? FIXME
+ while (movesPicked < numOfMoves)
+ {
+ 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))
+ return move;
+ }
+ break;
default:
- break;
+ break;
}
-
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.
+/// QsearchNoCapturesPhaseIndex, QsearchWithoutChecksPhaseIndex and
+/// NoMovesPhaseIndex 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
PhaseTable[i++] = PH_QCHECKS;
PhaseTable[i++] = PH_STOP;
+ // Quiescence search with checks only and no captures
+ QsearchNoCapturesPhaseIndex = i - 1;
+ PhaseTable[i++] = PH_QCHECKS;
+ PhaseTable[i++] = PH_STOP;
+
// Quiescence search without checks
QsearchWithoutChecksPhaseIndex = i - 1;
PhaseTable[i++] = PH_QCAPTURES;
PhaseTable[i++] = PH_STOP;
+
+ // Do not generate any move
+ NoMovesPhaseIndex = i - 1;
+ PhaseTable[i++] = PH_STOP;
}
projects / stockfish / blobdiff