Stockfish, a UCI chess playing engine derived from Glaurung 2.1
Copyright (C) 2004-2008 Tord Romstad (Glaurung author)
Copyright (C) 2008-2015 Marco Costalba, Joona Kiiski, Tord Romstad
- Copyright (C) 2015-2018 Marco Costalba, Joona Kiiski, Gary Linscott, Tord Romstad
+ Copyright (C) 2015-2019 Marco Costalba, Joona Kiiski, Gary Linscott, 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_TT, CAPTURE_INIT, GOOD_CAPTURE, KILLER0, KILLER1, COUNTERMOVE, QUIET_INIT, QUIET, BAD_CAPTURE,
+ MAIN_TT, CAPTURE_INIT, GOOD_CAPTURE, REFUTATION, QUIET_INIT, QUIET, BAD_CAPTURE,
EVASION_TT, EVASION_INIT, EVASION,
PROBCUT_TT, PROBCUT_INIT, PROBCUT,
QSEARCH_TT, QCAPTURE_INIT, QCAPTURE, QCHECK_INIT, QCHECK
};
- // Helper filter used with select_move()
- const auto Any = [](){ return true; };
-
// partial_insertion_sort() sorts moves in descending order up to and including
// a given limit. The order of moves smaller than the limit is left unspecified.
void partial_insertion_sort(ExtMove* begin, ExtMove* end, int limit) {
/// MovePicker constructor for the main search
MovePicker::MovePicker(const Position& p, Move ttm, Depth d, const ButterflyHistory* mh,
- const CapturePieceToHistory* cph, const PieceToHistory** ch, Move cm, Move* killers_p)
- : pos(p), mainHistory(mh), captureHistory(cph), contHistory(ch),
- refutations{killers_p[0], killers_p[1], cm}, depth(d){
+ const CapturePieceToHistory* cph, const PieceToHistory** ch, Move cm, Move* killers)
+ : pos(p), mainHistory(mh), captureHistory(cph), continuationHistory(ch),
+ refutations{{killers[0], 0}, {killers[1], 0}, {cm, 0}}, depth(d) {
assert(d > DEPTH_ZERO);
/// MovePicker constructor for quiescence search
MovePicker::MovePicker(const Position& p, Move ttm, Depth d, const ButterflyHistory* mh,
- const CapturePieceToHistory* cph, Square rs)
- : pos(p), mainHistory(mh), captureHistory(cph), recaptureSquare(rs), depth(d) {
+ const CapturePieceToHistory* cph, const PieceToHistory** ch, Square rs)
+ : pos(p), mainHistory(mh), captureHistory(cph), continuationHistory(ch), recaptureSquare(rs), depth(d) {
assert(d <= DEPTH_ZERO);
stage = pos.checkers() ? EVASION_TT : QSEARCH_TT;
- ttMove = ttm
- && pos.pseudo_legal(ttm)
- && (depth > DEPTH_QS_RECAPTURES || to_sq(ttm) == recaptureSquare) ? ttm : MOVE_NONE;
+ ttMove = ttm
+ && (depth > DEPTH_QS_RECAPTURES || to_sq(ttm) == recaptureSquare)
+ && pos.pseudo_legal(ttm) ? ttm : MOVE_NONE;
stage += (ttMove == MOVE_NONE);
}
-/// MovePicker constructor for ProbCut: we generate captures with SEE higher
+/// MovePicker constructor for ProbCut: we generate captures with SEE greater
/// than or equal to the given threshold.
MovePicker::MovePicker(const Position& p, Move ttm, Value th, const CapturePieceToHistory* cph)
: pos(p), captureHistory(cph), threshold(th) {
stage = PROBCUT_TT;
ttMove = ttm
- && pos.pseudo_legal(ttm)
&& pos.capture(ttm)
+ && pos.pseudo_legal(ttm)
&& pos.see_ge(ttm, threshold) ? ttm : MOVE_NONE;
stage += (ttMove == MOVE_NONE);
}
for (auto& m : *this)
if (Type == CAPTURES)
m.value = PieceValue[MG][pos.piece_on(to_sq(m))]
- + (*captureHistory)[pos.moved_piece(m)][to_sq(m)][type_of(pos.piece_on(to_sq(m)))];
+ + (*captureHistory)[pos.moved_piece(m)][to_sq(m)][type_of(pos.piece_on(to_sq(m)))] / 8;
else if (Type == QUIETS)
m.value = (*mainHistory)[pos.side_to_move()][from_to(m)]
- + (*contHistory[0])[pos.moved_piece(m)][to_sq(m)]
- + (*contHistory[1])[pos.moved_piece(m)][to_sq(m)]
- + (*contHistory[3])[pos.moved_piece(m)][to_sq(m)];
+ + (*continuationHistory[0])[pos.moved_piece(m)][to_sq(m)]
+ + (*continuationHistory[1])[pos.moved_piece(m)][to_sq(m)]
+ + (*continuationHistory[3])[pos.moved_piece(m)][to_sq(m)]
+ + (*continuationHistory[5])[pos.moved_piece(m)][to_sq(m)] / 2;
else // Type == EVASIONS
{
m.value = PieceValue[MG][pos.piece_on(to_sq(m))]
- Value(type_of(pos.moved_piece(m)));
else
- m.value = (*mainHistory)[pos.side_to_move()][from_to(m)] - (1 << 28);
+ m.value = (*mainHistory)[pos.side_to_move()][from_to(m)]
+ + (*continuationHistory[0])[pos.moved_piece(m)][to_sq(m)]
+ - (1 << 28);
}
}
-/// MovePicker::select_move() returns the next move satisfying a predicate function
-template<PickType T, typename Pred>
-Move MovePicker::select_move(Pred filter) {
+/// MovePicker::select() returns the next move satisfying a predicate function.
+/// It never returns the TT move.
+template<MovePicker::PickType T, typename Pred>
+Move MovePicker::select(Pred filter) {
while (cur < endMoves)
{
- if (T == BEST_SCORE)
+ if (T == Best)
std::swap(*cur, *std::max_element(cur, endMoves));
- move = *cur++;
+ if (*cur != ttMove && filter())
+ return *cur++;
- if (move != ttMove && filter())
- return move;
+ cur++;
}
- return move = MOVE_NONE;
+ return MOVE_NONE;
}
/// 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 highest score from a list of generated moves.
+/// returns a new pseudo legal move every time it is called until there are no more
+/// moves left, picking the move with the highest score from a list of generated moves.
Move MovePicker::next_move(bool skipQuiets) {
top:
case CAPTURE_INIT:
case PROBCUT_INIT:
case QCAPTURE_INIT:
- endBadCaptures = cur = moves;
+ cur = endBadCaptures = moves;
endMoves = generate<CAPTURES>(pos, cur);
+
score<CAPTURES>();
++stage;
goto top;
case GOOD_CAPTURE:
- if (select_move<BEST_SCORE>([&](){ return pos.see_ge(move, Value(-55 * (cur-1)->value / 1024)) ?
- // Move losing capture to endBadCaptures to be tried later
- true : (*endBadCaptures++ = move, false); }))
- return move;
+ if (select<Best>([&](){
+ return pos.see_ge(*cur, Value(-55 * cur->value / 1024)) ?
+ // Move losing capture to endBadCaptures to be tried later
+ true : (*endBadCaptures++ = *cur, false); }))
+ return *(cur - 1);
+
+ // Prepare the pointers to loop over the refutations array
+ cur = std::begin(refutations);
+ endMoves = std::end(refutations);
// If the countermove is the same as a killer, skip it
- if ( refutations[0] == refutations[2]
- || refutations[1] == refutations[2])
- refutations[2] = MOVE_NONE;
+ if ( refutations[0].move == refutations[2].move
+ || refutations[1].move == refutations[2].move)
+ --endMoves;
+
++stage;
/* fallthrough */
- case KILLER0:
- case KILLER1:
- case COUNTERMOVE:
- while (stage <= COUNTERMOVE)
- {
- move = refutations[ stage++ - KILLER0];
- if ( move != MOVE_NONE
- && move != ttMove
- && pos.pseudo_legal(move)
- && !pos.capture(move))
- return move;
- }
+ case REFUTATION:
+ if (select<Next>([&](){ return *cur != MOVE_NONE
+ && !pos.capture(*cur)
+ && pos.pseudo_legal(*cur); }))
+ return *(cur - 1);
+ ++stage;
/* fallthrough */
case QUIET_INIT:
cur = endBadCaptures;
endMoves = generate<QUIETS>(pos, cur);
+
score<QUIETS>();
partial_insertion_sort(cur, endMoves, -4000 * depth / ONE_PLY);
++stage;
case QUIET:
if ( !skipQuiets
- && select_move<NEXT>([&](){return move != refutations[0]
- && move != refutations[1]
- && move != refutations[2];}))
- return move;
+ && select<Next>([&](){return *cur != refutations[0].move
+ && *cur != refutations[1].move
+ && *cur != refutations[2].move;}))
+ return *(cur - 1);
+
+ // Prepare the pointers to loop over the bad captures
+ cur = moves;
+ endMoves = endBadCaptures;
- // Point to beginning and end of bad captures
- cur = moves, endMoves = endBadCaptures;
++stage;
/* fallthrough */
case BAD_CAPTURE:
- return select_move<NEXT>(Any);
+ return select<Next>([](){ return true; });
case EVASION_INIT:
cur = moves;
endMoves = generate<EVASIONS>(pos, cur);
+
score<EVASIONS>();
++stage;
/* fallthrough */
case EVASION:
- return select_move<BEST_SCORE>(Any);
+ return select<Best>([](){ return true; });
case PROBCUT:
- return select_move<BEST_SCORE>([&](){ return pos.see_ge(move, threshold); });
+ return select<Best>([&](){ return pos.see_ge(*cur, threshold); });
case QCAPTURE:
- if (select_move<BEST_SCORE>([&](){ return depth > DEPTH_QS_RECAPTURES
- || to_sq(move) == recaptureSquare; }))
- return move;
+ if (select<Best>([&](){ return depth > DEPTH_QS_RECAPTURES
+ || to_sq(*cur) == recaptureSquare; }))
+ return *(cur - 1);
// If we did not find any move and we do not try checks, we have finished
if (depth != DEPTH_QS_CHECKS)
case QCHECK_INIT:
cur = moves;
endMoves = generate<QUIET_CHECKS>(pos, cur);
+
++stage;
/* fallthrough */
case QCHECK:
- return select_move<NEXT>(Any);
+ return select<Next>([](){ return true; });
}
assert(false);
projects / stockfish / blobdiff