Key psq[PIECE_NB][SQUARE_NB];
Key enpassant[FILE_NB];
Key castling[CASTLING_RIGHT_NB];
- Key side;
+ Key side, noPawns;
}
namespace {
/// 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);
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 e = std::min(st->rule50, st->pliesFromNull);
+
+ if (e < 4)
+ return false;
+
+ StateInfo* stp = st->previous->previous;
+
+ do {
stp = stp->previous->previous;
if (stp->key == st->key)
return true; // Draw at first repetition
- }
+
+ } while ((e -= 2) >= 4);
return false;
}