/*
Stockfish, a UCI chess playing engine derived from Glaurung 2.1
Copyright (C) 2004-2008 Tord Romstad (Glaurung author)
- Copyright (C) 2008-2014 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
namespace {
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,
- QSEARCH_1, CAPTURES_S4,
- PROBCUT, CAPTURES_S5,
- RECAPTURE, CAPTURES_S6,
+ MAIN_SEARCH, GOOD_CAPTURES, KILLERS, GOOD_QUIETS, BAD_QUIETS, BAD_CAPTURES,
+ EVASION, ALL_EVASIONS,
+ QSEARCH_WITH_CHECKS, QCAPTURES_1, CHECKS,
+ QSEARCH_WITHOUT_CHECKS, QCAPTURES_2,
+ PROBCUT, PROBCUT_CAPTURES,
+ RECAPTURE, RECAPTURES,
STOP
};
- // Our insertion sort, which is guaranteed (and also needed) to be stable
+ // Our insertion sort, which is guaranteed to be stable, as it should be
void insertion_sort(ExtMove* begin, ExtMove* end)
{
ExtMove tmp, *p, *q;
}
}
- // Unary predicate used by std::partition to split positive values from remaining
- // ones so as to sort the two sets separately, with the second sort delayed.
- inline bool has_positive_value(const ExtMove& ms) { return ms.value > 0; }
-
- // Picks 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. possible captures.
- inline ExtMove* pick_best(ExtMove* begin, ExtMove* end)
+ // 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.
+ Move pick_best(ExtMove* begin, ExtMove* end)
{
std::swap(*begin, *std::max_element(begin, end));
- return begin;
+ return *begin;
}
+
} // namespace
/// ordering is at the current node.
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) {
+ const CounterMovesHistoryStats& cmh, Move cm, Search::Stack* s)
+ : pos(p), history(h), counterMovesHistory(cmh), ss(s), countermove(cm), depth(d) {
assert(d > DEPTH_ZERO);
- cur = end = moves;
- endBadCaptures = moves + MAX_MOVES - 1;
- countermoves = cm;
- followupmoves = fm;
- ss = s;
-
- if (pos.checkers())
- stage = EVASION;
-
- else
- stage = MAIN_SEARCH;
-
- ttMove = (ttm && pos.pseudo_legal(ttm) ? ttm : MOVE_NONE);
- end += (ttMove != MOVE_NONE);
+ stage = pos.checkers() ? EVASION : MAIN_SEARCH;
+ ttMove = ttm && pos.pseudo_legal(ttm) ? ttm : MOVE_NONE;
+ endMoves += (ttMove != MOVE_NONE);
}
MovePicker::MovePicker(const Position& p, Move ttm, Depth d, const HistoryStats& h,
- Square s) : pos(p), history(h), cur(moves), end(moves) {
+ const CounterMovesHistoryStats& cmh, Square s)
+ : pos(p), history(h), counterMovesHistory(cmh) {
assert(d <= DEPTH_ZERO);
stage = EVASION;
else if (d > DEPTH_QS_NO_CHECKS)
- stage = QSEARCH_0;
+ stage = QSEARCH_WITH_CHECKS;
else if (d > DEPTH_QS_RECAPTURES)
- {
- stage = QSEARCH_1;
+ stage = QSEARCH_WITHOUT_CHECKS;
- // 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.capture_or_promotion(ttm))
- ttm = MOVE_NONE;
- }
else
{
stage = RECAPTURE;
ttm = MOVE_NONE;
}
- ttMove = (ttm && pos.pseudo_legal(ttm) ? ttm : MOVE_NONE);
- end += (ttMove != MOVE_NONE);
+ ttMove = ttm && pos.pseudo_legal(ttm) ? ttm : MOVE_NONE;
+ endMoves += (ttMove != MOVE_NONE);
}
-MovePicker::MovePicker(const Position& p, Move ttm, const HistoryStats& h, PieceType pt)
- : pos(p), history(h), cur(moves), end(moves) {
+MovePicker::MovePicker(const Position& p, Move ttm, const HistoryStats& h,
+ const CounterMovesHistoryStats& cmh, Value th)
+ : pos(p), history(h), counterMovesHistory(cmh), threshold(th) {
assert(!pos.checkers());
stage = PROBCUT;
- // 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.capture(ttMove) || pos.see(ttMove) <= captureThreshold))
- ttMove = MOVE_NONE;
+ // In ProbCut we generate captures with SEE higher than the given threshold
+ ttMove = ttm
+ && pos.pseudo_legal(ttm)
+ && pos.capture(ttm)
+ && pos.see(ttm) > threshold ? ttm : MOVE_NONE;
- end += (ttMove != MOVE_NONE);
+ endMoves += (ttMove != MOVE_NONE);
}
-/// score() assign a numerical value to each move in a move list. The moves with
+/// score() assigns 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
- // 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
- // big pieces before capturing a hanging piece probably helps to reduce
- // the subtree size.
+ // Winning and equal captures in the main search are ordered by MVV, preferring
+ // captures near our home rank. Surprisingly, this appears to perform slightly
+ // better than SEE based move ordering: 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 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.
- Move m;
-
- for (ExtMove* it = moves; it != end; ++it)
- {
- m = it->move;
- it->value = PieceValue[MG][pos.piece_on(to_sq(m))]
- - Value(type_of(pos.moved_piece(m)));
-
- if (type_of(m) == ENPASSANT)
- it->value += PieceValue[MG][PAWN];
-
- else if (type_of(m) == PROMOTION)
- it->value += PieceValue[MG][promotion_type(m)] - PieceValue[MG][PAWN];
- }
+ // has been picked up, saving some SEE calls in case we get a cutoff.
+ for (auto& m : *this)
+ m.value = PieceValue[MG][pos.piece_on(to_sq(m))]
+ - Value(200 * relative_rank(pos.side_to_move(), to_sq(m)));
}
template<>
void MovePicker::score<QUIETS>() {
- Move m;
+ Square prevSq = to_sq((ss-1)->currentMove);
+ const HistoryStats& cmh = counterMovesHistory[pos.piece_on(prevSq)][prevSq];
- for (ExtMove* it = moves; it != end; ++it)
- {
- m = it->move;
- it->value = history[pos.moved_piece(m)][to_sq(m)];
- }
+ for (auto& m : *this)
+ m.value = history[pos.moved_piece(m)][to_sq(m)]
+ + cmh[pos.moved_piece(m)][to_sq(m)];
}
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 value.
- Move m;
+ // Try winning and equal captures captures ordered by MVV/LVA, then non-captures
+ // ordered by history value, then bad-captures and quiet moves with a negative
+ // SEE ordered by SEE value.
Value see;
- for (ExtMove* it = moves; it != end; ++it)
- {
- m = it->move;
+ for (auto& m : *this)
if ((see = pos.see_sign(m)) < VALUE_ZERO)
- it->value = see - HistoryStats::Max; // At the bottom
+ m.value = see - HistoryStats::Max; // At the bottom
else if (pos.capture(m))
- it->value = PieceValue[MG][pos.piece_on(to_sq(m))]
- - Value(type_of(pos.moved_piece(m))) + HistoryStats::Max;
+ m.value = PieceValue[MG][pos.piece_on(to_sq(m))]
+ - Value(type_of(pos.moved_piece(m))) + HistoryStats::Max;
else
- it->value = history[pos.moved_piece(m)][to_sq(m)];
- }
+ m.value = history[pos.moved_piece(m)][to_sq(m)];
}
void MovePicker::generate_next_stage() {
+ assert(stage != STOP);
+
cur = moves;
switch (++stage) {
- case CAPTURES_S1: case CAPTURES_S3: case CAPTURES_S4: case CAPTURES_S5: case CAPTURES_S6:
- end = generate<CAPTURES>(pos, moves);
+ case GOOD_CAPTURES: case QCAPTURES_1: case QCAPTURES_2:
+ case PROBCUT_CAPTURES: case RECAPTURES:
+ endMoves = generate<CAPTURES>(pos, moves);
score<CAPTURES>();
- return;
+ break;
- case KILLERS_S1:
+ case KILLERS:
+ killers[0] = ss->killers[0];
+ killers[1] = ss->killers[1];
+ killers[2] = countermove;
cur = killers;
- end = cur + 2;
-
- killers[0].move = ss->killers[0];
- killers[1].move = ss->killers[1];
- killers[2].move = killers[3].move = MOVE_NONE;
- killers[4].move = killers[5].move = MOVE_NONE;
-
- // Please note that following code is racy and could yield to rare (less
- // than 1 out of a million) duplicated entries in SMP case. This is harmless.
-
- // Be sure countermoves are different from killers
- for (int i = 0; i < 2; ++i)
- if ( countermoves[i] != (cur+0)->move
- && countermoves[i] != (cur+1)->move)
- (end++)->move = countermoves[i];
-
- // Be sure followupmoves are different from killers and countermoves
- for (int i = 0; i < 2; ++i)
- if ( followupmoves[i] != (cur+0)->move
- && followupmoves[i] != (cur+1)->move
- && followupmoves[i] != (cur+2)->move
- && followupmoves[i] != (cur+3)->move)
- (end++)->move = followupmoves[i];
- return;
-
- case QUIETS_1_S1:
- endQuiets = end = generate<QUIETS>(pos, moves);
+ endMoves = cur + 2 + (countermove != killers[0] && countermove != killers[1]);
+ break;
+
+ case GOOD_QUIETS:
+ endQuiets = endMoves = generate<QUIETS>(pos, moves);
score<QUIETS>();
- end = std::partition(cur, end, has_positive_value);
- insertion_sort(cur, end);
- return;
+ endMoves = std::partition(cur, endMoves, [](const ExtMove& m) { return m.value > VALUE_ZERO; });
+ insertion_sort(cur, endMoves);
+ break;
- case QUIETS_2_S1:
- cur = end;
- end = endQuiets;
+ case BAD_QUIETS:
+ cur = endMoves;
+ endMoves = endQuiets;
if (depth >= 3 * ONE_PLY)
- insertion_sort(cur, end);
- return;
+ insertion_sort(cur, endMoves);
+ break;
- case BAD_CAPTURES_S1:
- // Just pick them in reverse order to get MVV/LVA ordering
+ case BAD_CAPTURES:
+ // Just pick them in reverse order to get correct ordering
cur = moves + MAX_MOVES - 1;
- end = endBadCaptures;
- return;
+ endMoves = endBadCaptures;
+ break;
- case EVASIONS_S2:
- end = generate<EVASIONS>(pos, moves);
- if (end > moves + 1)
+ case ALL_EVASIONS:
+ endMoves = generate<EVASIONS>(pos, moves);
+ if (endMoves - moves > 1)
score<EVASIONS>();
- return;
+ break;
- case QUIET_CHECKS_S3:
- end = generate<QUIET_CHECKS>(pos, moves);
- return;
+ case CHECKS:
+ endMoves = generate<QUIET_CHECKS>(pos, moves);
+ break;
- case EVASION: case QSEARCH_0: case QSEARCH_1: case PROBCUT: case RECAPTURE:
+ case EVASION: case QSEARCH_WITH_CHECKS: case QSEARCH_WITHOUT_CHECKS:
+ case PROBCUT: case RECAPTURE: case STOP:
stage = STOP;
- /* Fall through */
-
- case STOP:
- end = cur + 1; // Avoid another next_phase() call
- return;
+ break;
default:
assert(false);
/// 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 MovePicker::next_move() {
Move move;
while (true)
{
- while (cur == end)
+ while (cur == endMoves && stage != STOP)
generate_next_stage();
switch (stage) {
- case MAIN_SEARCH: case EVASION: case QSEARCH_0: case QSEARCH_1: case PROBCUT:
+ case MAIN_SEARCH: case EVASION: case QSEARCH_WITH_CHECKS:
+ case QSEARCH_WITHOUT_CHECKS: case PROBCUT:
++cur;
return ttMove;
- case CAPTURES_S1:
- move = pick_best(cur++, end)->move;
+ case GOOD_CAPTURES:
+ move = pick_best(cur++, endMoves);
if (move != ttMove)
{
if (pos.see_sign(move) >= VALUE_ZERO)
return move;
// Losing capture, move it to the tail of the array
- (endBadCaptures--)->move = move;
+ *endBadCaptures-- = move;
}
break;
- case KILLERS_S1:
- move = (cur++)->move;
+ case KILLERS:
+ move = *cur++;
if ( move != MOVE_NONE
&& move != ttMove
&& pos.pseudo_legal(move)
return move;
break;
- case QUIETS_1_S1: case QUIETS_2_S1:
- move = (cur++)->move;
+ case GOOD_QUIETS: case BAD_QUIETS:
+ move = *cur++;
if ( move != ttMove
- && move != killers[0].move
- && move != killers[1].move
- && move != killers[2].move
- && move != killers[3].move
- && move != killers[4].move
- && move != killers[5].move)
+ && move != killers[0]
+ && move != killers[1]
+ && move != killers[2])
return move;
break;
- case BAD_CAPTURES_S1:
- return (cur--)->move;
+ case BAD_CAPTURES:
+ return *cur--;
- case EVASIONS_S2: case CAPTURES_S3: case CAPTURES_S4:
- move = pick_best(cur++, end)->move;
+ case ALL_EVASIONS: case QCAPTURES_1: case QCAPTURES_2:
+ move = pick_best(cur++, endMoves);
if (move != ttMove)
return move;
break;
- case CAPTURES_S5:
- move = pick_best(cur++, end)->move;
- if (move != ttMove && pos.see(move) > captureThreshold)
+ case PROBCUT_CAPTURES:
+ move = pick_best(cur++, endMoves);
+ if (move != ttMove && pos.see(move) > threshold)
return move;
break;
- case CAPTURES_S6:
- move = pick_best(cur++, end)->move;
+ case RECAPTURES:
+ move = pick_best(cur++, endMoves);
if (to_sq(move) == recaptureSquare)
return move;
break;
- case QUIET_CHECKS_S3:
- move = (cur++)->move;
+ case CHECKS:
+ 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