/*
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) 2004-2022 The Stockfish developers (see AUTHORS file)
Stockfish is free software: you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
#include <cassert>
+#include "bitboard.h"
#include "movepick.h"
+namespace Stockfish {
+
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){
-
- assert(d > DEPTH_ZERO);
-
- stage = pos.checkers() ? EVASION_TT : MAIN_TT;
- ttMove = ttm && pos.pseudo_legal(ttm) ? ttm : MOVE_NONE;
- stage += (ttMove == MOVE_NONE);
+ const CapturePieceToHistory* cph,
+ const PieceToHistory** ch,
+ Move cm,
+ const Move* killers)
+ : pos(p), mainHistory(mh), captureHistory(cph), continuationHistory(ch),
+ ttMove(ttm), refutations{{killers[0], 0}, {killers[1], 0}, {cm, 0}}, depth(d)
+{
+ assert(d > 0);
+
+ stage = (pos.checkers() ? EVASION_TT : MAIN_TT) +
+ !(ttm && pos.pseudo_legal(ttm));
+ threatenedPieces = 0;
}
/// 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) {
-
- 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;
- stage += (ttMove == MOVE_NONE);
+ const CapturePieceToHistory* cph,
+ const PieceToHistory** ch,
+ Square rs)
+ : pos(p), mainHistory(mh), captureHistory(cph), continuationHistory(ch), ttMove(ttm), recaptureSquare(rs), depth(d)
+{
+ assert(d <= 0);
+
+ stage = (pos.checkers() ? EVASION_TT : QSEARCH_TT) +
+ !( ttm
+ && pos.pseudo_legal(ttm));
}
-/// 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) {
-
+ : pos(p), captureHistory(cph), ttMove(ttm), threshold(th)
+{
assert(!pos.checkers());
- stage = PROBCUT_TT;
- ttMove = ttm
- && pos.pseudo_legal(ttm)
- && pos.capture(ttm)
- && pos.see_ge(ttm, threshold) ? ttm : MOVE_NONE;
- stage += (ttMove == MOVE_NONE);
+ stage = PROBCUT_TT + !(ttm && pos.capture(ttm)
+ && pos.pseudo_legal(ttm)
+ && pos.see_ge(ttm, threshold));
}
/// MovePicker::score() assigns a numerical value to each move in a list, used
/// for sorting. Captures are ordered by Most Valuable Victim (MVV), preferring
-/// captures with a good history. Quiets moves are ordered using the histories.
+/// captures with a good history. Quiets moves are ordered using the history tables.
template<GenType Type>
void MovePicker::score() {
static_assert(Type == CAPTURES || Type == QUIETS || Type == EVASIONS, "Wrong type");
- 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)))];
+ [[maybe_unused]] Bitboard threatenedByPawn, threatenedByMinor, threatenedByRook;
+ if constexpr (Type == QUIETS)
+ {
+ Color us = pos.side_to_move();
+
+ threatenedByPawn = pos.attacks_by<PAWN>(~us);
+ threatenedByMinor = pos.attacks_by<KNIGHT>(~us) | pos.attacks_by<BISHOP>(~us) | threatenedByPawn;
+ threatenedByRook = pos.attacks_by<ROOK>(~us) | threatenedByMinor;
- 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)];
+ // Pieces threatened by pieces of lesser material value
+ threatenedPieces = (pos.pieces(us, QUEEN) & threatenedByRook)
+ | (pos.pieces(us, ROOK) & threatenedByMinor)
+ | (pos.pieces(us, KNIGHT, BISHOP) & threatenedByPawn);
+ }
+ for (auto& m : *this)
+ if constexpr (Type == CAPTURES)
+ m.value = (7 * int(PieceValue[MG][pos.piece_on(to_sq(m))])
+ + (*captureHistory)[pos.moved_piece(m)][to_sq(m)][type_of(pos.piece_on(to_sq(m)))]) / 16;
+
+ else if constexpr (Type == QUIETS)
+ m.value = 2 * (*mainHistory)[pos.side_to_move()][from_to(m)]
+ + 2 * (*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)]
+ + (threatenedPieces & from_sq(m) ?
+ (type_of(pos.moved_piece(m)) == QUEEN && !(to_sq(m) & threatenedByRook) ? 50000
+ : type_of(pos.moved_piece(m)) == ROOK && !(to_sq(m) & threatenedByMinor) ? 25000
+ : !(to_sq(m) & threatenedByPawn) ? 15000
+ : 0)
+ : 0)
+ + bool(pos.check_squares(type_of(pos.moved_piece(m))) & to_sq(m)) * 16384;
else // Type == EVASIONS
{
if (pos.capture(m))
m.value = PieceValue[MG][pos.piece_on(to_sq(m))]
- - Value(type_of(pos.moved_piece(m)));
+ - Value(type_of(pos.moved_piece(m)))
+ + (1 << 28);
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)];
}
}
-/// 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>();
+ partial_insertion_sort(cur, endMoves, std::numeric_limits<int>::min());
++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<Next>([&](){
+ return pos.see_ge(*cur, Value(-cur->value)) ?
+ // 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 REFUTATION:
+ if (select<Next>([&](){ return *cur != MOVE_NONE
+ && !pos.capture(*cur)
+ && pos.pseudo_legal(*cur); }))
+ return *(cur - 1);
++stage;
- /* fallthrough */
+ [[fallthrough]];
- case KILLER0:
- case KILLER1:
- case COUNTERMOVE:
- while (stage <= COUNTERMOVE)
+ case QUIET_INIT:
+ if (!skipQuiets)
{
- move = refutations[ stage++ - KILLER0];
- if ( move != MOVE_NONE
- && move != ttMove
- && pos.pseudo_legal(move)
- && !pos.capture(move))
- return move;
+ cur = endBadCaptures;
+ endMoves = generate<QUIETS>(pos, cur);
+
+ score<QUIETS>();
+ partial_insertion_sort(cur, endMoves, -3000 * depth);
}
- /* fallthrough */
- case QUIET_INIT:
- cur = endBadCaptures;
- endMoves = generate<QUIETS>(pos, cur);
- score<QUIETS>();
- partial_insertion_sort(cur, endMoves, -4000 * depth / ONE_PLY);
++stage;
- /* fallthrough */
+ [[fallthrough]];
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 */
+ [[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 */
+ [[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<Next>([&](){ 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<Next>([&](){ 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)
return MOVE_NONE;
++stage;
- /* fallthrough */
+ [[fallthrough]];
case QCHECK_INIT:
cur = moves;
endMoves = generate<QUIET_CHECKS>(pos, cur);
+
++stage;
- /* fallthrough */
+ [[fallthrough]];
case QCHECK:
- return select_move<NEXT>(Any);
+ return select<Next>([](){ return true; });
}
assert(false);
return MOVE_NONE; // Silence warning
}
+
+} // namespace Stockfish