/*
Stockfish, a UCI chess playing engine derived from Glaurung 2.1
Copyright (C) 2004-2008 Tord Romstad (Glaurung author)
- Copyright (C) 2008-2010 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
#include <cassert>
-#include "movegen.h"
#include "movepick.h"
-#include "search.h"
-#include "types.h"
+#include "thread.h"
namespace {
- enum MovegenPhase {
- PH_TT_MOVE, // Transposition table move
- PH_GOOD_CAPTURES, // Queen promotions and captures with SEE values >= captureThreshold (captureThreshold <= 0)
- PH_GOOD_PROBCUT, // Queen promotions and captures with SEE values > captureThreshold (captureThreshold >= 0)
- PH_KILLERS, // Killer moves from the current ply
- PH_NONCAPTURES_1, // Non-captures and underpromotions with positive score
- PH_NONCAPTURES_2, // Non-captures and underpromotions with non-positive score
- PH_BAD_CAPTURES, // Queen promotions and captures with SEE values < captureThreshold (captureThreshold <= 0)
- PH_EVASIONS, // Check evasions
- PH_QCAPTURES, // Captures in quiescence search
- PH_QRECAPTURES, // Recaptures in quiescence search
- PH_QCHECKS, // Non-capture checks in quiescence search
- PH_STOP
+ 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
};
- CACHE_LINE_ALIGNMENT
- const uint8_t MainSearchTable[] = { PH_TT_MOVE, PH_GOOD_CAPTURES, PH_KILLERS, PH_NONCAPTURES_1, PH_NONCAPTURES_2, PH_BAD_CAPTURES, PH_STOP };
- const uint8_t EvasionTable[] = { PH_TT_MOVE, PH_EVASIONS, PH_STOP };
- const uint8_t QsearchWithChecksTable[] = { PH_TT_MOVE, PH_QCAPTURES, PH_QCHECKS, PH_STOP };
- const uint8_t QsearchWithoutChecksTable[] = { PH_TT_MOVE, PH_QCAPTURES, PH_STOP };
- const uint8_t QsearchRecapturesTable[] = { PH_TT_MOVE, PH_QRECAPTURES, PH_STOP };
- const uint8_t ProbCutTable[] = { PH_TT_MOVE, PH_GOOD_PROBCUT, PH_STOP };
-}
-
-/// Constructors for 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 about how important good
-/// move ordering is at the current node.
-
-MovePicker::MovePicker(const Position& p, Move ttm, Depth d, const History& h,
- SearchStack* ss, Value beta) : pos(p), H(h), depth(d) {
- captureThreshold = 0;
- badCaptures = moves + MAX_MOVES;
-
- assert(d > DEPTH_ZERO);
-
- if (p.in_check())
+ // Our insertion sort, which is guaranteed (and also needed) to be stable
+ void insertion_sort(ExtMove* begin, ExtMove* end)
{
- killers[0].move = killers[1].move = MOVE_NONE;
- phasePtr = EvasionTable;
+ 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;
+ }
}
- else
- {
- killers[0].move = ss->killers[0];
- killers[1].move = ss->killers[1];
-
- // Consider sligtly negative captures as good if at low
- // depth and far from beta.
- if (ss && ss->eval < beta - PawnValueMidgame && d < 3 * ONE_PLY)
- captureThreshold = -PawnValueMidgame;
- phasePtr = MainSearchTable;
- }
+ // 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& move) { return move.value > 0; }
- ttMove = (ttm && pos.move_is_pl(ttm) ? ttm : MOVE_NONE);
- phasePtr += int(ttMove == MOVE_NONE) - 1;
- go_next_phase();
-}
-
-MovePicker::MovePicker(const Position& p, Move ttm, Depth d, const History& h, Square recaptureSq)
- : pos(p), H(h) {
-
- assert(d <= DEPTH_ZERO);
-
- if (p.in_check())
- phasePtr = EvasionTable;
- else if (d >= DEPTH_QS_CHECKS)
- phasePtr = QsearchWithChecksTable;
- else if (d >= DEPTH_QS_RECAPTURES)
- {
- phasePtr = QsearchWithoutChecksTable;
-
- // 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 != MOVE_NONE && !pos.move_is_capture_or_promotion(ttm))
- ttm = MOVE_NONE;
- }
- else
+ // 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)
{
- phasePtr = QsearchRecapturesTable;
- recaptureSquare = recaptureSq;
- ttm = MOVE_NONE;
+ std::swap(*begin, *std::max_element(begin, end));
+ return begin;
}
+} // namespace
- ttMove = (ttm && pos.move_is_pl(ttm) ? ttm : MOVE_NONE);
- phasePtr += int(ttMove == MOVE_NONE) - 1;
- go_next_phase();
-}
-
-MovePicker::MovePicker(const Position& p, Move ttm, const History& h, int parentCapture)
- : pos(p), H(h) {
- assert (!pos.in_check());
+/// 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.
- // In ProbCut we consider only captures better than parent's move
- captureThreshold = parentCapture;
- phasePtr = ProbCutTable;
+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) {
- if ( ttm != MOVE_NONE
- && (!pos.move_is_capture(ttm) || pos.see(ttm) <= captureThreshold))
- ttm = MOVE_NONE;
+ assert(d > DEPTH_ZERO);
- ttMove = (ttm && pos.move_is_pl(ttm) ? ttm : MOVE_NONE);
- phasePtr += int(ttMove == MOVE_NONE) - 1;
- go_next_phase();
-}
+ cur = end = moves;
+ endBadCaptures = moves + MAX_MOVES - 1;
+ countermoves = cm;
+ followupmoves = fm;
+ ss = s;
+ if (pos.checkers())
+ stage = EVASION;
-/// MovePicker::go_next_phase() generates, scores and sorts the next bunch
-/// of moves when there are no more moves to try for the current phase.
+ else
+ stage = MAIN_SEARCH;
-void MovePicker::go_next_phase() {
+ ttMove = (ttm && pos.pseudo_legal(ttm) ? ttm : MOVE_NONE);
+ end += (ttMove != MOVE_NONE);
+}
- curMove = moves;
- phase = *(++phasePtr);
- switch (phase) {
+MovePicker::MovePicker(const Position& p, Move ttm, Depth d, const HistoryStats& h,
+ Square s) : pos(p), history(h), cur(moves), end(moves) {
- case PH_TT_MOVE:
- lastMove = curMove + 1;
- return;
+ assert(d <= DEPTH_ZERO);
- case PH_GOOD_CAPTURES:
- case PH_GOOD_PROBCUT:
- lastMove = generate<MV_CAPTURE>(pos, moves);
- score_captures();
- return;
+ if (pos.checkers())
+ stage = EVASION;
- case PH_KILLERS:
- curMove = killers;
- lastMove = curMove + 2;
- return;
+ else if (d > DEPTH_QS_NO_CHECKS)
+ stage = QSEARCH_0;
- case PH_NONCAPTURES_1:
- lastNonCapture = lastMove = generate<MV_NON_CAPTURE>(pos, moves);
- score_noncaptures();
- sort_moves(moves, lastNonCapture, &lastMove);
- return;
+ else if (d > DEPTH_QS_RECAPTURES)
+ stage = QSEARCH_1;
- case PH_NONCAPTURES_2:
- curMove = lastMove;
- lastMove = lastNonCapture;
- if (depth >= 3 * ONE_PLY)
- insertion_sort<MoveStack>(curMove, lastMove);
- return;
+ else
+ {
+ stage = RECAPTURE;
+ recaptureSquare = s;
+ ttm = MOVE_NONE;
+ }
- case PH_BAD_CAPTURES:
- // Bad captures SEE value is already calculated so just pick
- // them in order to get SEE move ordering.
- curMove = badCaptures;
- lastMove = moves + MAX_MOVES;
- return;
+ ttMove = (ttm && pos.pseudo_legal(ttm) ? ttm : MOVE_NONE);
+ end += (ttMove != MOVE_NONE);
+}
- case PH_EVASIONS:
- assert(pos.in_check());
- lastMove = generate<MV_EVASION>(pos, moves);
- score_evasions();
- return;
+MovePicker::MovePicker(const Position& p, Move ttm, const HistoryStats& h, PieceType pt)
+ : pos(p), history(h), cur(moves), end(moves) {
- case PH_QCAPTURES:
- lastMove = generate<MV_CAPTURE>(pos, moves);
- score_captures();
- return;
+ assert(!pos.checkers());
- case PH_QRECAPTURES:
- lastMove = generate<MV_CAPTURE>(pos, moves);
- return;
+ stage = PROBCUT;
- case PH_QCHECKS:
- lastMove = generate<MV_NON_CAPTURE_CHECK>(pos, moves);
- return;
+ // 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);
- case PH_STOP:
- lastMove = curMove + 1; // Avoid another go_next_phase() call
- return;
+ if (ttMove && (!pos.capture(ttMove) || pos.see(ttMove) <= captureThreshold))
+ ttMove = MOVE_NONE;
- default:
- assert(false);
- return;
- }
+ end += (ttMove != MOVE_NONE);
}
-/// MovePicker::score_captures(), MovePicker::score_noncaptures() and
-/// MovePicker::score_evasions() assign a numerical move ordering score
-/// to each move in a move list. The moves with highest scores will be
-/// picked first by get_next_move().
-
-void MovePicker::score_captures() {
+/// 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
// 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;
- // Use MVV/LVA ordering
- for (MoveStack* cur = moves; cur != lastMove; cur++)
+ for (ExtMove* it = moves; it != end; ++it)
{
- m = cur->move;
- cur->score = pos.midgame_value_of_piece_on(move_to(m))
- - pos.type_of_piece_on(move_from(m));
+ m = it->move;
+ it->value = PieceValue[MG][pos.piece_on(to_sq(m))]
+ - Value(type_of(pos.moved_piece(m)));
- if (move_is_promotion(m))
- cur->score += QueenValueMidgame;
+ 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];
}
}
-void MovePicker::score_noncaptures() {
+template<>
+void MovePicker::score<QUIETS>() {
Move m;
- Square from;
- for (MoveStack* cur = moves; cur != lastMove; cur++)
+ for (ExtMove* it = moves; it != end; ++it)
{
- m = cur->move;
- from = move_from(m);
- cur->score = H.value(pos.piece_on(from), move_to(m));
+ m = it->move;
+ it->value = history[pos.moved_piece(m)][to_sq(m)];
}
}
-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, and at the end bad-captures and non-captures with a
- // negative SEE. This last group is ordered by the SEE score.
+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;
- int seeScore;
-
- // Skip if we don't have at least two moves to order
- if (lastMove < moves + 2)
- return;
+ Value see;
- for (MoveStack* cur = moves; cur != lastMove; cur++)
+ for (ExtMove* it = moves; it != end; ++it)
{
- m = cur->move;
- if ((seeScore = pos.see_sign(m)) < 0)
- cur->score = seeScore - History::MaxValue; // Be sure we are at the bottom
- else if (pos.move_is_capture(m))
- cur->score = pos.midgame_value_of_piece_on(move_to(m))
- - pos.type_of_piece_on(move_from(m)) + History::MaxValue;
+ 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
- cur->score = H.value(pos.piece_on(move_from(m)), move_to(m));
+ it->value = history[pos.moved_piece(m)][to_sq(m)];
}
}
-/// MovePicker::get_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 score from a list
-/// of generated moves taking care not to return the tt move if has already been
-/// searched previously. Note that this function is not thread safe so should be
-/// lock protected by caller when accessed through a shared MovePicker object.
-Move MovePicker::get_next_move() {
+/// 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);
+ }
+}
+
+
+/// 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 move;
while (true)
{
- while (curMove == lastMove)
- go_next_phase();
+ while (cur == end)
+ generate_next_stage();
- switch (phase) {
+ switch (stage) {
- case PH_TT_MOVE:
- curMove++;
+ case MAIN_SEARCH: case EVASION: case QSEARCH_0: case QSEARCH_1: case PROBCUT:
+ ++cur;
return ttMove;
- break;
- case PH_GOOD_CAPTURES:
- move = pick_best(curMove++, lastMove).move;
+ case CAPTURES_S1:
+ move = pick_best(cur++, end)->move;
if (move != ttMove)
{
- assert(captureThreshold <= 0); // Otherwise we must use see instead of see_sign
-
- // Check for a non negative SEE now
- int seeValue = pos.see_sign(move);
- if (seeValue >= captureThreshold)
+ if (pos.see_sign(move) >= VALUE_ZERO)
return move;
- // Losing capture, move it to the tail of the array, note
- // that move has now been already checked for pseudo legality.
- (--badCaptures)->move = move;
- badCaptures->score = seeValue;
+ // Losing capture, move it to the tail of the array
+ (endBadCaptures--)->move = move;
}
break;
- case PH_GOOD_PROBCUT:
- move = pick_best(curMove++, lastMove).move;
- if ( move != ttMove
- && pos.see(move) > captureThreshold)
- return move;
- break;
-
- case PH_KILLERS:
- move = (curMove++)->move;
- if ( move != MOVE_NONE
- && pos.move_is_pl(move)
- && move != ttMove
- && !pos.move_is_capture(move))
+ case KILLERS_S1:
+ move = (cur++)->move;
+ if ( move != MOVE_NONE
+ && move != ttMove
+ && pos.pseudo_legal(move)
+ && !pos.capture(move))
return move;
break;
- case PH_NONCAPTURES_1:
- case PH_NONCAPTURES_2:
- move = (curMove++)->move;
+ case QUIETS_1_S1: case QUIETS_2_S1:
+ move = (cur++)->move;
if ( move != ttMove
&& move != killers[0].move
- && move != killers[1].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 PH_BAD_CAPTURES:
- move = pick_best(curMove++, lastMove).move;
- return move;
+ case BAD_CAPTURES_S1:
+ return (cur--)->move;
- case PH_EVASIONS:
- case PH_QCAPTURES:
- move = pick_best(curMove++, lastMove).move;
+ case EVASIONS_S2: case CAPTURES_S3: case CAPTURES_S4:
+ move = pick_best(cur++, end)->move;
if (move != ttMove)
return move;
break;
- case PH_QRECAPTURES:
- move = (curMove++)->move;
- if (move_to(move) == recaptureSquare)
+ case CAPTURES_S5:
+ move = pick_best(cur++, end)->move;
+ if (move != ttMove && pos.see(move) > captureThreshold)
+ return move;
+ break;
+
+ case CAPTURES_S6:
+ move = pick_best(cur++, end)->move;
+ if (to_sq(move) == recaptureSquare)
return move;
break;
- case PH_QCHECKS:
- move = (curMove++)->move;
+ case QUIET_CHECKS_S3:
+ move = (cur++)->move;
if (move != ttMove)
return move;
break;
- case PH_STOP:
+ case STOP:
return MOVE_NONE;
default:
assert(false);
- break;
}
}
}
+
+
+/// 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>(); }
projects / stockfish / blobdiff