/*
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) 2004-2023 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
along with this program. If not, see <http://www.gnu.org/licenses/>.
*/
+#include "movepick.h"
+
+#include <algorithm>
#include <cassert>
+#include <iterator>
+#include <utility>
-#include "movepick.h"
+#include "bitboard.h"
+#include "position.h"
-namespace {
+namespace Stockfish {
- enum Stages {
- MAIN_SEARCH, CAPTURES_INIT, GOOD_CAPTURES, KILLER0, KILLER1, COUNTERMOVE, QUIET_INIT, QUIET, BAD_CAPTURES,
- EVASION, EVASIONS_INIT, ALL_EVASIONS,
- PROBCUT, PROBCUT_CAPTURES_INIT, PROBCUT_CAPTURES,
- QSEARCH, QCAPTURES_INIT, QCAPTURES, QCHECKS, QSEARCH_RECAPTURES, QRECAPTURES
- };
+namespace {
- // 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) {
+enum Stages {
+ // generate main search moves
+ MAIN_TT,
+ CAPTURE_INIT,
+ GOOD_CAPTURE,
+ REFUTATION,
+ QUIET_INIT,
+ QUIET,
+ BAD_CAPTURE,
+
+ // generate evasion moves
+ EVASION_TT,
+ EVASION_INIT,
+ EVASION,
+
+ // generate probcut moves
+ PROBCUT_TT,
+ PROBCUT_INIT,
+ PROBCUT,
+
+ // generate qsearch moves
+ QSEARCH_TT,
+ QCAPTURE_INIT,
+ QCAPTURE,
+ QCHECK_INIT,
+ QCHECK
+};
+
+// Sort 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) {
for (ExtMove *sortedEnd = begin, *p = begin + 1; p < end; ++p)
if (p->value >= limit)
{
ExtMove tmp = *p, *q;
- *p = *++sortedEnd;
+ *p = *++sortedEnd;
for (q = sortedEnd; q != begin && *(q - 1) < tmp; --q)
*q = *(q - 1);
*q = tmp;
}
- }
+}
+
+} // namespace
+
+
+// Constructors of the MovePicker class. As arguments, we pass information
+// to help it 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 how important a good
+// move ordering is at the current node.
+
+// MovePicker constructor for the main search
+MovePicker::MovePicker(const Position& p,
+ Move ttm,
+ Depth d,
+ const ButterflyHistory* mh,
+ const CapturePieceToHistory* cph,
+ const PieceToHistory** ch,
+ const PawnHistory* ph,
+ Move cm,
+ const Move* killers) :
+ pos(p),
+ mainHistory(mh),
+ captureHistory(cph),
+ continuationHistory(ch),
+ pawnHistory(ph),
+ 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));
+}
- // 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) {
+// Constructor for quiescence search
+MovePicker::MovePicker(const Position& p,
+ Move ttm,
+ Depth d,
+ const ButterflyHistory* mh,
+ const CapturePieceToHistory* cph,
+ const PieceToHistory** ch,
+ const PawnHistory* ph) :
+ pos(p),
+ mainHistory(mh),
+ captureHistory(cph),
+ continuationHistory(ch),
+ pawnHistory(ph),
+ ttMove(ttm),
+ depth(d) {
+ assert(d <= 0);
+
+ stage = (pos.checkers() ? EVASION_TT : QSEARCH_TT) + !(ttm && pos.pseudo_legal(ttm));
+}
+
+// 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),
+ ttMove(ttm),
+ threshold(th) {
+ assert(!pos.checkers());
+
+ stage = PROBCUT_TT
+ + !(ttm && pos.capture_stage(ttm) && pos.pseudo_legal(ttm) && pos.see_ge(ttm, threshold));
+}
- std::swap(*begin, *std::max_element(begin, end));
- return *begin;
- }
+// 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 history tables.
+template<GenType Type>
+void MovePicker::score() {
-} // namespace
+ static_assert(Type == CAPTURES || Type == QUIETS || Type == EVASIONS, "Wrong type");
+
+ [[maybe_unused]] Bitboard threatenedByPawn, threatenedByMinor, threatenedByRook,
+ threatenedPieces;
+ 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;
+
+ // 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[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)
+ {
+ Piece pc = pos.moved_piece(m);
+ PieceType pt = type_of(pos.moved_piece(m));
+ Square from = from_sq(m);
+ Square to = to_sq(m);
+
+ // histories
+ m.value = 2 * (*mainHistory)[pos.side_to_move()][from_to(m)];
+ m.value += 2 * (*pawnHistory)[pawn_structure(pos)][pc][to];
+ m.value += 2 * (*continuationHistory[0])[pc][to];
+ m.value += (*continuationHistory[1])[pc][to];
+ m.value += (*continuationHistory[2])[pc][to] / 4;
+ m.value += (*continuationHistory[3])[pc][to];
+ m.value += (*continuationHistory[5])[pc][to];
+
+ // bonus for checks
+ m.value += bool(pos.check_squares(pt) & to) * 16384;
+
+ // bonus for escaping from capture
+ m.value += threatenedPieces & from ? (pt == QUEEN && !(to & threatenedByRook) ? 50000
+ : pt == ROOK && !(to & threatenedByMinor) ? 25000
+ : !(to & threatenedByPawn) ? 15000
+ : 0)
+ : 0;
+
+ // malus for putting piece en prise
+ m.value -= !(threatenedPieces & from)
+ ? (pt == QUEEN ? bool(to & threatenedByRook) * 50000
+ + bool(to & threatenedByMinor) * 10000
+ + bool(to & threatenedByPawn) * 20000
+ : pt == ROOK ? bool(to & threatenedByMinor) * 25000
+ + bool(to & threatenedByPawn) * 10000
+ : pt != PAWN ? bool(to & threatenedByPawn) * 15000
+ : 0)
+ : 0;
+ }
+ else // Type == EVASIONS
+ {
+ if (pos.capture_stage(m))
+ m.value = PieceValue[pos.piece_on(to_sq(m))] - Value(type_of(pos.moved_piece(m)))
+ + (1 << 28);
+ else
+ m.value = (*mainHistory)[pos.side_to_move()][from_to(m)]
+ + (*continuationHistory[0])[pos.moved_piece(m)][to_sq(m)]
+ + (*pawnHistory)[pawn_structure(pos)][pos.moved_piece(m)][to_sq(m)];
+ }
+}
-/// Constructors of the MovePicker class. As arguments we pass information
-/// 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 how important good move
-/// ordering is at the current node.
+// 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) {
-/// 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), countermove(cm),
- killers{killers_p[0], killers_p[1]}, depth(d){
+ while (cur < endMoves)
+ {
+ if constexpr (T == Best)
+ std::swap(*cur, *std::max_element(cur, endMoves));
- assert(d > DEPTH_ZERO);
+ if (*cur != ttMove && filter())
+ return *cur++;
- stage = pos.checkers() ? EVASION : MAIN_SEARCH;
- ttMove = ttm && pos.pseudo_legal(ttm) ? ttm : MOVE_NONE;
- stage += (ttMove == MOVE_NONE);
+ cur++;
+ }
+ return MOVE_NONE;
}
-/// MovePicker constructor for quiescence search
-MovePicker::MovePicker(const Position& p, Move ttm, Depth d, const ButterflyHistory* mh, const CapturePieceToHistory* cph, Square s)
- : pos(p), mainHistory(mh), captureHistory(cph), depth(d) {
+// 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, picking the move with the highest score from a list of generated moves.
+Move MovePicker::next_move(bool skipQuiets) {
- assert(d <= DEPTH_ZERO);
+top:
+ switch (stage)
+ {
+
+ case MAIN_TT :
+ case EVASION_TT :
+ case QSEARCH_TT :
+ case PROBCUT_TT :
+ ++stage;
+ return ttMove;
+
+ case CAPTURE_INIT :
+ case PROBCUT_INIT :
+ case QCAPTURE_INIT :
+ 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<Next>([&]() {
+ // Move losing capture to endBadCaptures to be tried later
+ return pos.see_ge(*cur, Value(-cur->value)) ? 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].move == refutations[2].move
+ || refutations[1].move == refutations[2].move)
+ --endMoves;
+
+ ++stage;
+ [[fallthrough]];
+
+ case REFUTATION :
+ if (select<Next>([&]() {
+ return *cur != MOVE_NONE && !pos.capture_stage(*cur) && pos.pseudo_legal(*cur);
+ }))
+ return *(cur - 1);
+ ++stage;
+ [[fallthrough]];
+
+ case QUIET_INIT :
+ if (!skipQuiets)
+ {
+ cur = endBadCaptures;
+ endMoves = generate<QUIETS>(pos, cur);
- if (pos.checkers())
- stage = EVASION;
+ score<QUIETS>();
+ partial_insertion_sort(cur, endMoves, -1960 - 3130 * depth);
+ }
- else if (d > DEPTH_QS_RECAPTURES)
- stage = QSEARCH;
+ ++stage;
+ [[fallthrough]];
- else
- {
- stage = QSEARCH_RECAPTURES;
- recaptureSquare = s;
- return;
- }
+ case QUIET :
+ if (!skipQuiets && select<Next>([&]() {
+ return *cur != refutations[0].move && *cur != refutations[1].move
+ && *cur != refutations[2].move;
+ }))
+ return *(cur - 1);
- ttMove = ttm && pos.pseudo_legal(ttm) ? ttm : MOVE_NONE;
- stage += (ttMove == MOVE_NONE);
-}
+ // Prepare the pointers to loop over the bad captures
+ cur = moves;
+ endMoves = endBadCaptures;
-/// MovePicker constructor for ProbCut: we generate captures with SEE higher
-/// 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;
+ [[fallthrough]];
- assert(!pos.checkers());
+ case BAD_CAPTURE :
+ return select<Next>([]() { return true; });
- stage = PROBCUT;
- ttMove = ttm
- && pos.pseudo_legal(ttm)
- && pos.capture(ttm)
- && pos.see_ge(ttm, threshold) ? ttm : MOVE_NONE;
+ case EVASION_INIT :
+ cur = moves;
+ endMoves = generate<EVASIONS>(pos, cur);
- stage += (ttMove == MOVE_NONE);
-}
+ score<EVASIONS>();
+ ++stage;
+ [[fallthrough]];
-/// 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 are ordered using the histories.
-template<GenType Type>
-void MovePicker::score() {
+ case EVASION :
+ return select<Best>([]() { return true; });
- 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)))];
-
- 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)];
-
- else // Type == EVASIONS
- {
- if (pos.capture(m))
- 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);
- }
-}
+ case PROBCUT :
+ return select<Next>([&]() { return pos.see_ge(*cur, threshold); });
-/// 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.
+ case QCAPTURE :
+ if (select<Next>([]() { return true; }))
+ return *(cur - 1);
-Move MovePicker::next_move(bool skipQuiets) {
+ // 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]];
- Move move;
-
- switch (stage) {
-
- case MAIN_SEARCH: case EVASION: case QSEARCH: case PROBCUT:
- ++stage;
- return ttMove;
-
- case CAPTURES_INIT:
- case PROBCUT_CAPTURES_INIT:
- case QCAPTURES_INIT:
- case QSEARCH_RECAPTURES:
- endBadCaptures = cur = moves;
- endMoves = generate<CAPTURES>(pos, cur);
- score<CAPTURES>();
- ++stage;
-
- // Rebranch at the top of the switch via a recursive call
- return next_move(skipQuiets);
-
- case GOOD_CAPTURES:
- while (cur < endMoves)
- {
- move = pick_best(cur++, endMoves);
- if (move != ttMove)
- {
- if (pos.see_ge(move, Value(-55 * (cur-1)->value / 1024)))
- return move;
-
- // Losing capture, move it to the beginning of the array
- *endBadCaptures++ = move;
- }
- }
- ++stage;
- /* fallthrough */
-
- case KILLER0:
- case KILLER1:
- do
- {
- move = killers[++stage - KILLER1];
- if ( move != MOVE_NONE
- && move != ttMove
- && pos.pseudo_legal(move)
- && !pos.capture(move))
- return move;
- } while (stage <= KILLER1);
- /* fallthrough */
-
- case COUNTERMOVE:
- ++stage;
- move = countermove;
- if ( move != MOVE_NONE
- && move != ttMove
- && move != killers[0]
- && move != killers[1]
- && pos.pseudo_legal(move)
- && !pos.capture(move))
- return move;
- /* fallthrough */
-
- case QUIET_INIT:
- cur = endBadCaptures;
- endMoves = generate<QUIETS>(pos, cur);
- score<QUIETS>();
- partial_insertion_sort(cur, endMoves, -4000 * depth / ONE_PLY);
- ++stage;
- /* fallthrough */
-
- case QUIET:
- if (!skipQuiets)
- while (cur < endMoves)
- {
- move = *cur++;
-
- if ( move != ttMove
- && move != killers[0]
- && move != killers[1]
- && move != countermove)
- return move;
- }
- ++stage;
- cur = moves; // Point to beginning of bad captures
- /* fallthrough */
-
- case BAD_CAPTURES:
- if (cur < endBadCaptures)
- return *cur++;
- break;
-
- case EVASIONS_INIT:
- cur = moves;
- endMoves = generate<EVASIONS>(pos, cur);
- score<EVASIONS>();
- ++stage;
- /* fallthrough */
-
- case ALL_EVASIONS:
- while (cur < endMoves)
- {
- move = pick_best(cur++, endMoves);
- if (move != ttMove)
- return move;
- }
- break;
-
- case PROBCUT_CAPTURES:
- while (cur < endMoves)
- {
- move = pick_best(cur++, endMoves);
- if ( move != ttMove
- && pos.see_ge(move, threshold))
- return move;
- }
- break;
-
- case QCAPTURES:
- while (cur < endMoves)
- {
- move = pick_best(cur++, endMoves);
- if (move != ttMove)
- return move;
- }
- if (depth <= DEPTH_QS_NO_CHECKS)
- break;
- cur = moves;
- endMoves = generate<QUIET_CHECKS>(pos, cur);
- ++stage;
- /* fallthrough */
-
- case QCHECKS:
- while (cur < endMoves)
- {
- move = cur++->move;
- if (move != ttMove)
- return move;
- }
- break;
-
- case QRECAPTURES:
- while (cur < endMoves)
- {
- move = *cur++;
- if (to_sq(move) == recaptureSquare)
- return move;
- }
- break;
-
- default:
- assert(false);
- }
-
- return MOVE_NONE;
+ case QCHECK_INIT :
+ cur = moves;
+ endMoves = generate<QUIET_CHECKS>(pos, cur);
+
+ ++stage;
+ [[fallthrough]];
+
+ case QCHECK :
+ return select<Next>([]() { return true; });
+ }
+
+ assert(false);
+ return MOVE_NONE; // Silence warning
}
+
+} // namespace Stockfish
projects / stockfish / blobdiff