/*
Stockfish, a UCI chess playing engine derived from Glaurung 2.1
Copyright (C) 2004-2008 Tord Romstad (Glaurung author)
- Copyright (C) 2008-2013 Marco Costalba, Joona Kiiski, Tord Romstad
+ Copyright (C) 2008-2014 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
EVASION, EVASIONS_S2,
QSEARCH_0, CAPTURES_S3, QUIET_CHECKS_S3,
QSEARCH_1, CAPTURES_S4,
- PROBCUT, CAPTURES_S5,
+ MULTICUT, CAPTURES_S5,
RECAPTURE, CAPTURES_S6,
STOP
};
- // Our insertion sort, guaranteed to be stable, as is needed
+ // Our insertion sort, which is guaranteed (and also needed) to be stable
void insertion_sort(ExtMove* begin, ExtMove* end)
{
ExtMove tmp, *p, *q;
}
// 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.
+ // ones so as to sort the two sets separately, with the second sort delayed.
inline bool has_positive_score(const ExtMove& ms) { return ms.score > 0; }
- // Picks and moves to the front the best move in the range [begin, end),
- // it is faster than sorting all the moves in advance when moves are few, as
- // normally are the possible captures.
+ // 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)
{
std::swap(*begin, *std::max_element(begin, end));
/// 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 HistoryStats& h,
- Move* cm, Search::Stack* s) : pos(p), history(h), depth(d) {
+ Move* cm, Move* fm, Search::Stack* s) : pos(p), history(h), depth(d) {
assert(d > DEPTH_ZERO);
cur = end = moves;
endBadCaptures = moves + MAX_MOVES - 1;
countermoves = cm;
+ followupmoves = fm;
ss = s;
if (p.checkers())
{
stage = QSEARCH_1;
- // Skip TT move if is not a capture or a promotion, this avoids qsearch
+ // 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))
assert(!pos.checkers());
- stage = PROBCUT;
+ stage = MULTICUT;
- // In ProbCut we generate only captures better than parent's captured piece
+ // In MultiCut 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);
}
-/// quiet_moves() returns a pointer to the beginning of moves array. It
-/// is used to access already tried quiet moves when updating history.
-
-const ExtMove* MovePicker::quiet_moves() const {
- return stage == KILLERS_S1 ? killers
- : stage == QUIETS_1_S1 || stage == QUIETS_2_S1 ? moves : NULL;
-}
-
-
/// score() assign a numerical move ordering score to each move in a move list.
/// The moves with highest scores will be picked first.
template<>
// 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).
+ // 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)
}
-/// 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() {
cur = moves;
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->move && countermoves[i] != (cur+1)->move)
+ if ( countermoves[i] != (cur+0)->move
+ && countermoves[i] != (cur+1)->move)
(end++)->move = countermoves[i];
- if (countermoves[1] && countermoves[1] == countermoves[0]) // Due to SMP races
- killers[3].move = MOVE_NONE;
-
+ // 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:
end = generate<QUIET_CHECKS>(pos, moves);
return;
- case EVASION: case QSEARCH_0: case QSEARCH_1: case PROBCUT: case RECAPTURE:
+ case EVASION: case QSEARCH_0: case QSEARCH_1: case MULTICUT: case RECAPTURE:
stage = STOP;
case STOP:
end = cur + 1; // Avoid another next_phase() call
/// next_move() is the most important method of the MovePicker class. It returns
-/// a new pseudo legal move every time is called, until there are no more moves
+/// 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 returning the ttMove if has already been searched previously.
+/// taking care not to return the ttMove if it has already been searched.
template<>
Move MovePicker::next_move<false>() {
while (true)
{
while (cur == end)
- generate_next();
+ 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_0: case QSEARCH_1: case MULTICUT:
++cur;
return ttMove;
&& move != killers[0].move
&& move != killers[1].move
&& move != killers[2].move
- && move != killers[3].move)
+ && move != killers[3].move
+ && move != killers[4].move
+ && move != killers[5].move)
return move;
break;
projects / stockfish / blobdiff