/*
Stockfish, a UCI chess playing engine derived from Glaurung 2.1
Copyright (C) 2004-2008 Tord Romstad (Glaurung author)
- Copyright (C) 2008-2009 Marco Costalba
+ Copyright (C) 2008-2010 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
//// Includes
////
-#include <algorithm>
#include <cassert>
#include "history.h"
};
CACHE_LINE_ALIGNMENT
- const uint8_t MainSearchPhaseTable[] = { PH_TT_MOVES, PH_GOOD_CAPTURES, PH_KILLERS, PH_NONCAPTURES, PH_BAD_CAPTURES, PH_STOP};
- const uint8_t EvasionsPhaseTable[] = { PH_EVASIONS, PH_STOP};
- const uint8_t QsearchWithChecksPhaseTable[] = { PH_TT_MOVES, PH_QCAPTURES, PH_QCHECKS, PH_STOP};
- const uint8_t QsearchWithoutChecksPhaseTable[] = { PH_TT_MOVES, PH_QCAPTURES, PH_STOP};
+ const int MainSearchPhaseTable[] = { PH_TT_MOVES, PH_GOOD_CAPTURES, PH_KILLERS, PH_NONCAPTURES, PH_BAD_CAPTURES, PH_STOP};
+ const int EvasionsPhaseTable[] = { PH_TT_MOVES, PH_EVASIONS, PH_STOP};
+ const int QsearchWithChecksPhaseTable[] = { PH_TT_MOVES, PH_QCAPTURES, PH_QCHECKS, PH_STOP};
+ const int QsearchWithoutChecksPhaseTable[] = { PH_TT_MOVES, PH_QCAPTURES, PH_STOP};
}
/// 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) : pos(p), H(h) {
+MovePicker::MovePicker(const Position& p, Move ttm, Depth d, const History& h,
+ SearchStack* ss, Value beta) : pos(p), H(h) {
int searchTT = ttm;
ttMoves[0].move = ttm;
- finished = false;
- lastBadCapture = badCaptures;
+ badCaptureThreshold = 0;
+ badCaptures = moves + MOVES_MAX;
- if (ss)
+ pinned = p.pinned_pieces(pos.side_to_move());
+
+ if (ss && !p.is_check())
{
- ttMoves[1].move = (ss->mateKiller == ttm)? MOVE_NONE : ss->mateKiller;
+ ttMoves[1].move = (ss->mateKiller == ttm) ? MOVE_NONE : ss->mateKiller;
searchTT |= ttMoves[1].move;
killers[0].move = ss->killers[0];
killers[1].move = ss->killers[1];
} else
ttMoves[1].move = killers[0].move = killers[1].move = MOVE_NONE;
- Color us = pos.side_to_move();
-
- dc = p.discovered_check_candidates(us);
- pinned = p.pinned_pieces(us);
-
if (p.is_check())
phasePtr = EvasionsPhaseTable;
- else if (d > Depth(0))
- phasePtr = MainSearchPhaseTable + !searchTT;
- else if (d == Depth(0))
- phasePtr = QsearchWithChecksPhaseTable + !searchTT;
+ else if (d > DEPTH_ZERO)
+ {
+ // Consider sligtly negative captures as good if at low
+ // depth and far from beta.
+ if (ss && ss->eval < beta - PawnValueMidgame && d < 3 * ONE_PLY)
+ badCaptureThreshold = -PawnValueMidgame;
+
+ phasePtr = MainSearchPhaseTable;
+ }
+ else if (d == DEPTH_ZERO)
+ phasePtr = QsearchWithChecksPhaseTable;
else
- phasePtr = QsearchWithoutChecksPhaseTable + !searchTT;
+ {
+ phasePtr = QsearchWithoutChecksPhaseTable;
+
+ // 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))
+ searchTT = ttMoves[0].move = MOVE_NONE;
+ }
- phasePtr--;
+ phasePtr += int(!searchTT) - 1;
go_next_phase();
}
case PH_GOOD_CAPTURES:
lastMove = generate_captures(pos, moves);
score_captures();
- std::sort(moves, lastMove);
return;
case PH_KILLERS:
case PH_NONCAPTURES:
lastMove = generate_noncaptures(pos, moves);
score_noncaptures();
- std::sort(moves, lastMove);
+ sort_moves(moves, lastMove, &lastGoodNonCapture);
return;
case PH_BAD_CAPTURES:
- // Bad captures SEE value is already calculated so just sort them
- // to get SEE move ordering.
+ // Bad captures SEE value is already calculated so just pick
+ // them in order to get SEE move ordering.
curMove = badCaptures;
- lastMove = lastBadCapture;
- std::sort(badCaptures, lastMove);
+ lastMove = moves + MOVES_MAX;
return;
case PH_EVASIONS:
assert(pos.is_check());
- lastMove = generate_evasions(pos, moves, pinned);
+ lastMove = generate_evasions(pos, moves);
score_evasions();
- std::sort(moves, lastMove);
return;
case PH_QCAPTURES:
lastMove = generate_captures(pos, moves);
score_captures();
- std::sort(moves, lastMove);
return;
case PH_QCHECKS:
- // Perhaps we should order moves move here? FIXME
- lastMove = generate_non_capture_checks(pos, moves, dc);
+ lastMove = generate_non_capture_checks(pos, moves);
return;
case PH_STOP:
- lastMove = curMove + 1; // hack to be friendly for get_next_move()
+ lastMove = curMove + 1; // Avoids another go_next_phase() call
return;
default:
if (move_is_promotion(m))
cur->score = QueenValueMidgame;
else
- cur->score = int(pos.midgame_value_of_piece_on(move_to(m)))
- -int(pos.type_of_piece_on(move_from(m)));
+ cur->score = pos.midgame_value_of_piece_on(move_to(m))
+ - pos.type_of_piece_on(move_from(m));
}
}
Move m;
Piece piece;
Square from, to;
- int hs;
for (MoveStack* cur = moves; cur != lastMove; cur++)
{
from = move_from(m);
to = move_to(m);
piece = pos.piece_on(from);
- hs = H.move_ordering_score(piece, to);
-
- // Ensure history is always preferred to pst
- if (hs > 0)
- hs += 1000;
-
- // pst based scoring
- cur->score = hs + pos.pst_delta<Position::MidGame>(piece, from, to);
+ cur->score = H.value(piece, to) + H.gain(piece, to);
}
}
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.
Move m;
+ int seeScore;
+
+ // Skip if we don't have at least two moves to order
+ if (lastMove < moves + 2)
+ return;
for (MoveStack* cur = moves; cur != lastMove; cur++)
{
m = cur->move;
- if (m == ttMoves[0].move)
- cur->score = 2 * HistoryMax;
- else if (!pos.square_is_empty(move_to(m)))
- {
- int seeScore = pos.see(m);
- cur->score = seeScore + (seeScore >= 0 ? HistoryMax : 0);
- } else
- cur->score = H.move_ordering_score(pos.piece_on(move_from(m)), move_to(m));
+ if ((seeScore = pos.see_sign(m)) < 0)
+ cur->score = seeScore - HistoryMax; // Be sure 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)) + HistoryMax;
+ else
+ cur->score = H.value(pos.piece_on(move_from(m)), move_to(m));
}
}
/// 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() {
- assert(!pos.is_check() || *phasePtr == PH_EVASIONS || *phasePtr == PH_STOP);
- assert( pos.is_check() || *phasePtr != PH_EVASIONS);
-
Move move;
while (true)
{
while (curMove != lastMove)
{
- move = (curMove++)->move;
-
switch (phase) {
case PH_TT_MOVES:
+ move = (curMove++)->move;
if ( move != MOVE_NONE
&& move_is_legal(pos, move, pinned))
return move;
break;
case PH_GOOD_CAPTURES:
+ move = pick_best(curMove++, lastMove).move;
if ( move != ttMoves[0].move
&& move != ttMoves[1].move
&& pos.pl_move_is_legal(move, pinned))
{
// Check for a non negative SEE now
int seeValue = pos.see_sign(move);
- if (seeValue >= 0)
+ if (seeValue >= badCaptureThreshold)
return move;
- // Losing capture, move it to the badCaptures[] array, note
+ // Losing capture, move it to the tail of the array, note
// that move has now been already checked for legality.
- assert(int(lastBadCapture - badCaptures) < 63);
- lastBadCapture->move = move;
- lastBadCapture->score = seeValue;
- lastBadCapture++;
+ (--badCaptures)->move = move;
+ badCaptures->score = seeValue;
}
break;
case PH_KILLERS:
+ move = (curMove++)->move;
if ( move != MOVE_NONE
+ && move_is_legal(pos, move, pinned)
&& move != ttMoves[0].move
&& move != ttMoves[1].move
- && move_is_legal(pos, move, pinned)
&& !pos.move_is_capture(move))
return move;
break;
case PH_NONCAPTURES:
+
+ // Sort negative scored moves only when we get there
+ if (curMove == lastGoodNonCapture)
+ insertion_sort(lastGoodNonCapture, lastMove);
+
+ move = (curMove++)->move;
if ( move != ttMoves[0].move
&& move != ttMoves[1].move
&& move != killers[0].move
return move;
break;
- case PH_EVASIONS:
case PH_BAD_CAPTURES:
+ move = pick_best(curMove++, lastMove).move;
return move;
+ case PH_EVASIONS:
case PH_QCAPTURES:
+ move = pick_best(curMove++, lastMove).move;
+ if ( move != ttMoves[0].move
+ && pos.pl_move_is_legal(move, pinned))
+ return move;
+ break;
+
case PH_QCHECKS:
- // Maybe postpone the legality check until after futility pruning?
+ move = (curMove++)->move;
if ( move != ttMoves[0].move
&& pos.pl_move_is_legal(move, pinned))
return move;
}
}
-/// A variant of get_next_move() which takes a lock as a parameter, used to
-/// prevent multiple threads from picking the same move at a split point.
-
-Move MovePicker::get_next_move(Lock &lock) {
-
- lock_grab(&lock);
- if (finished)
- {
- lock_release(&lock);
- return MOVE_NONE;
- }
- Move m = get_next_move();
- if (m == MOVE_NONE)
- finished = true;
-
- lock_release(&lock);
- return m;
-}
projects / stockfish / blobdiff