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) 2015-2016 Marco Costalba, Joona Kiiski, Gary Linscott, Tord Romstad
+ Copyright (C) 2015-2017 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
Key psq[PIECE_NB][SQUARE_NB];
Key enpassant[FILE_NB];
Key castling[CASTLING_RIGHT_NB];
- Key side;
+ Key side, noPawns;
}
namespace {
const string PieceToChar(" PNBRQK pnbrqk");
-// min_attacker() is a helper function used by see() to locate the least
+// min_attacker() is a helper function used by see_ge() to locate the least
// valuable attacker for the side to move, remove the attacker we just found
// from the bitboards and scan for new X-ray attacks behind it.
/// operator<<(Position) returns an ASCII representation of the position
-std::ostream& operator<<(std::ostream& os, Position& pos) {
+std::ostream& operator<<(std::ostream& os, const Position& pos) {
os << "\n +---+---+---+---+---+---+---+---+\n";
if ( int(Tablebases::MaxCardinality) >= popcount(pos.pieces())
&& !pos.can_castle(ANY_CASTLING))
{
+ StateInfo st;
+ Position p;
+ p.set(pos.fen(), pos.is_chess960(), &st, pos.this_thread());
Tablebases::ProbeState s1, s2;
- Tablebases::WDLScore wdl = Tablebases::probe_wdl(pos, &s1);
- int dtz = Tablebases::probe_dtz(pos, &s2);
+ Tablebases::WDLScore wdl = Tablebases::probe_wdl(p, &s1);
+ int dtz = Tablebases::probe_dtz(p, &s2);
os << "\nTablebases WDL: " << std::setw(4) << wdl << " (" << s1 << ")"
<< "\nTablebases DTZ: " << std::setw(4) << dtz << " (" << s2 << ")";
}
}
Zobrist::side = rng.rand<Key>();
+ Zobrist::noPawns = rng.rand<Key>();
}
4) En passant target square (in algebraic notation). If there's no en passant
target square, this is "-". If a pawn has just made a 2-square move, this
- is the position "behind" the pawn. This is recorded regardless of whether
- there is a pawn in position to make an en passant capture.
+ is the position "behind" the pawn. This is recorded only if there is a pawn
+ in position to make an en passant capture, and if there really is a pawn
+ that might have advanced two squares.
5) Halfmove clock. This is the number of halfmoves since the last pawn advance
or capture. This is used to determine if a draw can be claimed under the
{
st->epSquare = make_square(File(col - 'a'), Rank(row - '1'));
- if (!(attackers_to(st->epSquare) & pieces(sideToMove, PAWN)))
+ if ( !(attackers_to(st->epSquare) & pieces(sideToMove, PAWN))
+ || !(pieces(~sideToMove, PAWN) & (st->epSquare + pawn_push(~sideToMove))))
st->epSquare = SQ_NONE;
}
else
void Position::set_state(StateInfo* si) const {
- si->key = si->pawnKey = si->materialKey = 0;
+ si->key = si->materialKey = 0;
+ si->pawnKey = Zobrist::noPawns;
si->nonPawnMaterial[WHITE] = si->nonPawnMaterial[BLACK] = VALUE_ZERO;
si->psq = SCORE_ZERO;
si->checkersBB = attackers_to(square<KING>(sideToMove)) & pieces(~sideToMove);
/// Position::set() is an overload to initialize the position object with
-/// the given endgame code string like "KBPKN". It is manily an helper to
+/// the given endgame code string like "KBPKN". It is mainly a helper to
/// get the material key out of an endgame code. Position is not playable,
/// indeed is even not guaranteed to be legal.
&& empty(to - pawn_push(us))))
return false;
}
- else if (!(attacks_from(pc, from) & to))
+ else if (!(attacks_from(type_of(pc), from) & to))
return false;
// Evasions generator already takes care to avoid some kind of illegal moves
return false;
case PROMOTION:
- return attacks_bb(Piece(promotion_type(m)), to, pieces() ^ from) & square<KING>(~sideToMove);
+ return attacks_bb(promotion_type(m), to, pieces() ^ from) & square<KING>(~sideToMove);
// En passant capture with check? We have already handled the case
// of direct checks and ordinary discovered check, so the only case we
// Update pawn hash key and prefetch access to pawnsTable
st->pawnKey ^= Zobrist::psq[pc][from] ^ Zobrist::psq[pc][to];
- prefetch(thisThread->pawnsTable[st->pawnKey]);
+ prefetch2(thisThread->pawnsTable[st->pawnKey]);
// Reset rule 50 draw counter
st->rule50 = 0;
/// Position::is_draw() tests whether the position is drawn by 50-move rule
/// or by repetition. It does not detect stalemates.
-bool Position::is_draw() const {
+bool Position::is_draw(int ply) const {
if (st->rule50 > 99 && (!checkers() || MoveList<LEGAL>(*this).size()))
return true;
- StateInfo* stp = st;
- for (int i = 2, e = std::min(st->rule50, st->pliesFromNull); i <= e; i += 2)
+ int end = std::min(st->rule50, st->pliesFromNull);
+
+ if (end < 4)
+ return false;
+
+ StateInfo* stp = st->previous->previous;
+ int cnt = 0;
+
+ for (int i = 4; i <= end; i += 2)
{
stp = stp->previous->previous;
- if (stp->key == st->key)
- return true; // Draw at first repetition
+ // At root position ply is 1, so return a draw score if a position
+ // repeats once earlier but after or at the root, or repeats twice
+ // strictly before the root.
+ if ( stp->key == st->key
+ && ++cnt + (ply - i > 0) == 2)
+ return true;
}
return false;
projects / stockfish / blobdiff