/*
Stockfish, a UCI chess playing engine derived from Glaurung 2.1
Copyright (C) 2004-2008 Tord Romstad (Glaurung author)
- Copyright (C) 2008-2012 Marco Costalba, Joona Kiiski, Tord Romstad
+ Copyright (C) 2008-2015 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/>.
*/
-#include <algorithm>
#include <cassert>
-#include "movegen.h"
#include "movepick.h"
+#include "thread.h"
namespace {
- enum Sequencer {
+ enum Stages {
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,
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; }
+ // Our insertion sort, which is guaranteed to be stable, as it should be
+ void insertion_sort(ExtMove* begin, ExtMove* end)
+ {
+ ExtMove tmp, *p, *q;
+
+ for (p = begin + 1; p < end; ++p)
+ {
+ tmp = *p;
+ for (q = p; q != begin && *(q-1) < tmp; --q)
+ *q = *(q-1);
+ *q = tmp;
+ }
+ }
- // 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)
+ // 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.
+ inline Move pick_best(ExtMove* begin, ExtMove* end)
{
- std::swap(*firstMove, *std::max_element(firstMove, lastMove));
- return firstMove;
+ std::swap(*begin, *std::max_element(begin, end));
+ return *begin;
}
-}
+
+} // namespace
/// Constructors of the MovePicker class. As arguments we pass information
-/// to help it to return the presumably good moves first, to decide which
+/// 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.
+/// search captures, promotions and some checks) and how important good move
+/// ordering is at the current node.
-MovePicker::MovePicker(const Position& p, Move ttm, Depth d, const History& h,
- Search::Stack* ss, Value beta) : pos(p), H(h), depth(d) {
+MovePicker::MovePicker(const Position& p, Move ttm, Depth d, const HistoryStats& h,
+ Move* cm, Move* fm, Search::Stack* s) : pos(p), history(h), depth(d) {
assert(d > DEPTH_ZERO);
- captureThreshold = 0;
- curMove = lastMove = moves;
- lastBadCapture = moves + MAX_MOVES - 1;
+ endBadCaptures = moves + MAX_MOVES - 1;
+ countermoves = cm;
+ followupmoves = fm;
+ ss = s;
- if (p.in_check())
- phase = EVASION;
+ if (pos.checkers())
+ stage = EVASION;
else
- {
- phase = MAIN_SEARCH;
-
- killers[0].move = ss->killers[0];
- killers[1].move = ss->killers[1];
+ stage = MAIN_SEARCH;
- // 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;
-
- // 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);
+ ttMove = (ttm && pos.pseudo_legal(ttm) ? ttm : MOVE_NONE);
+ endMoves += (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::MovePicker(const Position& p, Move ttm, Depth d, const HistoryStats& h,
+ Square s) : pos(p), history(h) {
assert(d <= DEPTH_ZERO);
- if (p.in_check())
- phase = EVASION;
+ if (pos.checkers())
+ stage = EVASION;
else if (d > DEPTH_QS_NO_CHECKS)
- phase = QSEARCH_0;
+ stage = QSEARCH_0;
else if (d > DEPTH_QS_RECAPTURES)
- {
- phase = QSEARCH_1;
+ stage = 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;
+ stage = RECAPTURE;
+ recaptureSquare = s;
ttm = MOVE_NONE;
}
- ttMove = (ttm && pos.is_pseudo_legal(ttm) ? ttm : MOVE_NONE);
- lastMove += (ttMove != MOVE_NONE);
+ ttMove = (ttm && pos.pseudo_legal(ttm) ? ttm : MOVE_NONE);
+ endMoves += (ttMove != MOVE_NONE);
}
-MovePicker::MovePicker(const Position& p, Move ttm, const History& h, PieceType pt)
- : pos(p), H(h), curMove(moves), lastMove(moves) {
+MovePicker::MovePicker(const Position& p, Move ttm, const HistoryStats& h, PieceType pt)
+ : pos(p), history(h) {
- assert(!pos.in_check());
+ assert(!pos.checkers());
- phase = PROBCUT;
+ stage = PROBCUT;
- // 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);
+ // In ProbCut we generate only captures that are better than the parent's
+ // captured piece.
+ captureThreshold = PieceValue[MG][pt];
+ ttMove = (ttm && pos.pseudo_legal(ttm) ? ttm : MOVE_NONE);
- if (ttMove && (!pos.is_capture(ttMove) || pos.see(ttMove) <= captureThreshold))
+ if (ttMove && (!pos.capture(ttMove) || pos.see(ttMove) <= captureThreshold))
ttMove = MOVE_NONE;
- lastMove += (ttMove != MOVE_NONE);
+ endMoves += (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 next_move().
-
-void MovePicker::score_captures() {
+/// score() assign a numerical value to each move in a move list. The moves with
+/// highest values will be picked first.
+template<>
+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
// 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;
-
- for (MoveStack* cur = moves; cur != lastMove; cur++)
- {
- 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_type(m)];
- }
+ // In main search we want to push captures with negative SEE values to the
+ // badCaptures[] array, but instead of doing it now we delay until the move
+ // has been picked up in pick_move_from_list(). This way we save some SEE
+ // calls in case we get a cutoff.
+ for (auto& m : *this)
+ if (type_of(m) == ENPASSANT)
+ m.value = PieceValue[MG][PAWN] - Value(PAWN);
+
+ else if (type_of(m) == PROMOTION)
+ m.value = PieceValue[MG][pos.piece_on(to_sq(m))] - Value(PAWN)
+ + PieceValue[MG][promotion_type(m)] - PieceValue[MG][PAWN];
+ else
+ m.value = PieceValue[MG][pos.piece_on(to_sq(m))]
+ - Value(type_of(pos.moved_piece(m)));
}
-void MovePicker::score_noncaptures() {
-
- Move m;
-
- for (MoveStack* cur = moves; cur != lastMove; cur++)
- {
- m = cur->move;
- cur->score = H.value(pos.piece_moved(m), to_sq(m));
- }
+template<>
+void MovePicker::score<QUIETS>() {
+ for (auto& m : *this)
+ m.value = history[pos.moved_piece(m)][to_sq(m)];
}
-void MovePicker::score_evasions() {
+template<>
+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;
+ // moves with a negative SEE. This last group is ordered by the SEE value.
+ Value see;
- if (lastMove < moves + 2)
- return;
+ for (auto& m : *this)
+ if ((see = pos.see_sign(m)) < VALUE_ZERO)
+ m.value = see - HistoryStats::Max; // At the bottom
- for (MoveStack* cur = moves; cur != lastMove; cur++)
- {
- 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 if (pos.capture(m))
+ m.value = PieceValue[MG][pos.piece_on(to_sq(m))]
+ - Value(type_of(pos.moved_piece(m))) + HistoryStats::Max;
else
- cur->score = H.value(pos.piece_moved(m), to_sq(m));
- }
+ m.value = history[pos.moved_piece(m)][to_sq(m)];
}
-/// MovePicker::generate_next() generates, scores and sorts the next bunch of moves,
-/// when there are no more moves to try for the current phase.
+/// generate_next_stage() generates, scores and sorts the next bunch of moves,
+/// when there are no more moves to try for the current stage.
-void MovePicker::generate_next() {
+void MovePicker::generate_next_stage() {
- curMove = moves;
+ cur = moves;
- switch (++phase) {
+ switch (++stage) {
case CAPTURES_S1: case CAPTURES_S3: case CAPTURES_S4: case CAPTURES_S5: case CAPTURES_S6:
- lastMove = generate<MV_CAPTURE>(pos, moves);
- score_captures();
- return;
+ endMoves = generate<CAPTURES>(pos, moves);
+ score<CAPTURES>();
+ break;
case KILLERS_S1:
- curMove = killers;
- lastMove = curMove + 2;
- return;
+ cur = killers;
+ endMoves = cur + 6;
+ killers[0] = ss->killers[0];
+ killers[1] = ss->killers[1];
+ killers[2] = countermoves[0];
+ killers[3] = countermoves[1];
+ killers[4] = followupmoves[0];
+ killers[5] = followupmoves[1];
+ break;
case QUIETS_1_S1:
- lastQuiet = lastMove = generate<MV_QUIET>(pos, moves);
- score_noncaptures();
- lastMove = std::partition(curMove, lastMove, has_positive_score);
- sort<MoveStack>(curMove, lastMove);
- return;
+ endQuiets = endMoves = generate<QUIETS>(pos, moves);
+ score<QUIETS>();
+ endMoves = std::partition(cur, endMoves, [](const ExtMove& m) { return m.value > VALUE_ZERO; });
+ insertion_sort(cur, endMoves);
+ break;
case QUIETS_2_S1:
- curMove = lastMove;
- lastMove = lastQuiet;
+ cur = endMoves;
+ endMoves = endQuiets;
if (depth >= 3 * ONE_PLY)
- sort<MoveStack>(curMove, lastMove);
- return;
+ insertion_sort(cur, endMoves);
+ break;
case BAD_CAPTURES_S1:
// Just pick them in reverse order to get MVV/LVA ordering
- curMove = moves + MAX_MOVES - 1;
- lastMove = lastBadCapture;
- return;
+ cur = moves + MAX_MOVES - 1;
+ endMoves = endBadCaptures;
+ break;
case EVASIONS_S2:
- lastMove = generate<MV_EVASION>(pos, moves);
- score_evasions();
- return;
+ endMoves = generate<EVASIONS>(pos, moves);
+ if (endMoves - moves > 1)
+ score<EVASIONS>();
+ break;
case QUIET_CHECKS_S3:
- lastMove = generate<MV_QUIET_CHECK>(pos, moves);
- return;
+ endMoves = generate<QUIET_CHECKS>(pos, moves);
+ break;
case EVASION: case QSEARCH_0: case QSEARCH_1: case PROBCUT: case RECAPTURE:
- phase = STOP;
+ stage = STOP;
+ /* Fall through */
+
case STOP:
- lastMove = curMove + 1; // Avoid another next_phase() call
- return;
+ endMoves = cur + 1; // Avoid another next_phase() call
+ break;
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() {
+/// 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.
+template<>
+Move MovePicker::next_move<false>() {
Move move;
while (true)
{
- while (curMove == lastMove)
- generate_next();
+ while (cur == endMoves)
+ generate_next_stage();
- switch (phase) {
+ switch (stage) {
case MAIN_SEARCH: case EVASION: case QSEARCH_0: case QSEARCH_1: case PROBCUT:
- curMove++;
+ ++cur;
return ttMove;
case CAPTURES_S1:
- move = pick_best(curMove++, lastMove)->move;
+ move = pick_best(cur++, endMoves);
if (move != ttMove)
{
- assert(captureThreshold <= 0); // Otherwise we cannot use see_sign()
-
- if (pos.see_sign(move) >= captureThreshold)
+ if (pos.see_sign(move) >= VALUE_ZERO)
return move;
// Losing capture, move it to the tail of the array
- (lastBadCapture--)->move = move;
+ *endBadCaptures-- = move;
}
break;
case KILLERS_S1:
- move = (curMove++)->move;
- if ( move != MOVE_NONE
- && pos.is_pseudo_legal(move)
- && move != ttMove
- && !pos.is_capture(move))
+ move = *cur++;
+ if ( move != MOVE_NONE
+ && move != ttMove
+ && pos.pseudo_legal(move)
+ && !pos.capture(move))
+ {
+ for (int i = 0; i < cur - 1 - killers; i++) // Skip duplicated
+ if (move == killers[i])
+ goto skip;
return move;
+ }
+ skip:
break;
case QUIETS_1_S1: case QUIETS_2_S1:
- move = (curMove++)->move;
+ move = *cur++;
if ( move != ttMove
- && move != killers[0].move
- && move != killers[1].move)
+ && move != killers[0]
+ && move != killers[1]
+ && move != killers[2]
+ && move != killers[3]
+ && move != killers[4]
+ && move != killers[5])
return move;
break;
case BAD_CAPTURES_S1:
- return (curMove--)->move;
+ return *cur--;
case EVASIONS_S2: case CAPTURES_S3: case CAPTURES_S4:
- move = pick_best(curMove++, lastMove)->move;
+ move = pick_best(cur++, endMoves);
if (move != ttMove)
return move;
break;
case CAPTURES_S5:
- move = pick_best(curMove++, lastMove)->move;
+ move = pick_best(cur++, endMoves);
if (move != ttMove && pos.see(move) > captureThreshold)
return move;
break;
case CAPTURES_S6:
- move = pick_best(curMove++, lastMove)->move;
+ move = pick_best(cur++, endMoves);
if (to_sq(move) == recaptureSquare)
return move;
break;
case QUIET_CHECKS_S3:
- move = (curMove++)->move;
+ move = *cur++;
if (move != ttMove)
return move;
break;
}
}
}
+
+
+/// 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 must be lock protected by the caller.
+template<>
+Move MovePicker::next_move<true>() { return ss->splitPoint->movePicker->next_move<false>(); }
projects / stockfish / blobdiff