/*
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
+ Copyright (C) 2015-2018 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
the Free Software Foundation, either version 3 of the License, or
(at your option) any later version.
-
Stockfish is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
#include <cassert>
#include "movepick.h"
-#include "thread.h"
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,
- STOP
+ 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
};
- // Our insertion sort, which is guaranteed (and also needed) to be stable
- void insertion_sort(ExtMove* begin, ExtMove* end)
- {
- ExtMove tmp, *p, *q;
-
- for (p = begin + 1; p < end; ++p)
- {
- tmp = *p;
- for (q = p; q != begin && *(q-1) < tmp; --q)
- *q = *(q-1);
- *q = tmp;
- }
+ // 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) {
+
+ for (ExtMove *sortedEnd = begin, *p = begin + 1; p < end; ++p)
+ if (p->value >= limit)
+ {
+ ExtMove tmp = *p, *q;
+ *p = *++sortedEnd;
+ for (q = sortedEnd; q != begin && *(q - 1) < tmp; --q)
+ *q = *(q - 1);
+ *q = tmp;
+ }
}
- // 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)
- {
- std::swap(*begin, *std::max_element(begin, end));
- return begin;
+ // 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;
}
-}
+
+} // namespace
/// 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
+/// 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, Move* fm, Search::Stack* s) : pos(p), history(h), depth(d) {
+/// 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){
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;
+ stage += (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) {
+/// 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), recaptureSquare(s), depth(d) {
assert(d <= DEPTH_ZERO);
- if (pos.checkers())
- stage = EVASION;
-
- else if (d > DEPTH_QS_NO_CHECKS)
- stage = QSEARCH_0;
-
- else if (d > DEPTH_QS_RECAPTURES)
- {
- stage = QSEARCH_1;
-
- // 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;
- recaptureSquare = s;
- ttm = MOVE_NONE;
- }
-
- ttMove = (ttm && pos.pseudo_legal(ttm) ? ttm : MOVE_NONE);
- end += (ttMove != MOVE_NONE);
+ stage = pos.checkers() ? EVASION : QSEARCH;
+ ttMove = ttm
+ && pos.pseudo_legal(ttm)
+ && (depth > DEPTH_QS_RECAPTURES || to_sq(ttm) == recaptureSquare) ? ttm : MOVE_NONE;
+ stage += (ttMove == MOVE_NONE);
}
-MovePicker::MovePicker(const Position& p, Move ttm, const HistoryStats& h, PieceType pt)
- : pos(p), history(h), cur(moves), end(moves) {
+/// 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) {
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;
-
- end += (ttMove != MOVE_NONE);
+ ttMove = ttm
+ && pos.pseudo_legal(ttm)
+ && pos.capture(ttm)
+ && pos.see_ge(ttm, threshold) ? ttm : MOVE_NONE;
+ stage += (ttMove == MOVE_NONE);
}
-
-/// score() assign 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.
- // 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];
- }
-}
-
-template<>
-void MovePicker::score<QUIETS>() {
-
- Move m;
-
- for (ExtMove* it = moves; it != end; ++it)
- {
- m = it->move;
- it->value = history[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;
- Value see;
-
- for (ExtMove* it = moves; it != end; ++it)
- {
- m = it->move;
- if ((see = pos.see_sign(m)) < VALUE_ZERO)
- it->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;
- else
- it->value = history[pos.moved_piece(m)][to_sq(m)];
- }
-}
-
-
-/// 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_stage() {
-
- cur = moves;
-
- switch (++stage) {
-
- case CAPTURES_S1: case CAPTURES_S3: case CAPTURES_S4: case CAPTURES_S5: case CAPTURES_S6:
- end = generate<CAPTURES>(pos, moves);
- score<CAPTURES>();
- return;
-
- case KILLERS_S1:
- 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);
- score<QUIETS>();
- end = std::partition(cur, end, has_positive_value);
- insertion_sort(cur, end);
- return;
-
- case QUIETS_2_S1:
- cur = end;
- end = endQuiets;
- if (depth >= 3 * ONE_PLY)
- insertion_sort(cur, end);
- return;
-
- case BAD_CAPTURES_S1:
- // Just pick them in reverse order to get MVV/LVA ordering
- cur = moves + MAX_MOVES - 1;
- end = endBadCaptures;
- return;
-
- case EVASIONS_S2:
- end = generate<EVASIONS>(pos, moves);
- if (end > moves + 1)
- score<EVASIONS>();
- return;
-
- case QUIET_CHECKS_S3:
- end = generate<QUIET_CHECKS>(pos, moves);
- return;
-
- case EVASION: case QSEARCH_0: case QSEARCH_1: case PROBCUT: case RECAPTURE:
- stage = STOP;
- /* Fall through */
-
- case STOP:
- end = cur + 1; // Avoid another next_phase() call
- return;
-
- default:
- assert(false);
- }
+/// 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() {
+
+ 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);
+ }
}
-
/// 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.
-template<>
-Move MovePicker::next_move<false>() {
+
+Move MovePicker::next_move(bool skipQuiets) {
Move move;
- while (true)
- {
- while (cur == end)
- generate_next_stage();
+ switch (stage) {
- switch (stage) {
+ case MAIN_SEARCH: case EVASION: case QSEARCH: case PROBCUT:
+ ++stage;
+ return ttMove;
- case MAIN_SEARCH: case EVASION: case QSEARCH_0: case QSEARCH_1: case PROBCUT:
- ++cur;
- return ttMove;
+ case CAPTURES_INIT:
+ case PROBCUT_CAPTURES_INIT:
+ case QCAPTURES_INIT:
+ 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 CAPTURES_S1:
- move = pick_best(cur++, end)->move;
+ case GOOD_CAPTURES:
+ while (cur < endMoves)
+ {
+ move = pick_best(cur++, endMoves);
if (move != ttMove)
{
- if (pos.see_sign(move) >= VALUE_ZERO)
+ if (pos.see_ge(move, Value(-55 * (cur-1)->value / 1024)))
return move;
- // Losing capture, move it to the tail of the array
- (endBadCaptures--)->move = move;
+ // Losing capture, move it to the beginning of the array
+ *endBadCaptures++ = move;
}
- break;
-
- case KILLERS_S1:
- move = (cur++)->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;
- break;
-
- case QUIETS_1_S1: case QUIETS_2_S1:
- move = (cur++)->move;
- 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)
- return move;
- break;
-
- case BAD_CAPTURES_S1:
- return (cur--)->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 EVASIONS_S2: case CAPTURES_S3: case CAPTURES_S4:
- move = pick_best(cur++, end)->move;
+ 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;
+ }
+ break;
- case CAPTURES_S5:
- move = pick_best(cur++, end)->move;
- if (move != ttMove && pos.see(move) > captureThreshold)
- 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 CAPTURES_S6:
- move = pick_best(cur++, end)->move;
- if (to_sq(move) == recaptureSquare)
+ case QCAPTURES:
+ while (cur < endMoves)
+ {
+ move = pick_best(cur++, endMoves);
+ if ( move != ttMove
+ && (depth > DEPTH_QS_RECAPTURES || to_sq(move) == recaptureSquare))
return move;
+ }
+ if (depth <= DEPTH_QS_NO_CHECKS)
break;
-
- case QUIET_CHECKS_S3:
- move = (cur++)->move;
+ cur = moves;
+ endMoves = generate<QUIET_CHECKS>(pos, cur);
+ ++stage;
+ /* fallthrough */
+
+ case QCHECKS:
+ while (cur < endMoves)
+ {
+ move = *cur++;
if (move != ttMove)
return move;
- break;
-
- case STOP:
- return MOVE_NONE;
-
- default:
- assert(false);
}
- }
-}
+ break;
+ default:
+ assert(false);
+ }
-/// 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>(); }
+ return MOVE_NONE;
+}
projects / stockfish / blobdiff