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Fixed a bug in PV extraction from the transposition table: The

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previous used move_is_legal to verify that the move from the TT
was legal, and the old version of move_is_legal only works when
the side to move is not in check. Fixed this by adding a separate,
slower version of move_is_legal which works even when the side to
move is in check.
This commit is contained in:
Tord Romstad 2009-08-06 18:07:32 +02:00
parent 2fff532f4e
commit ae49677446
3 changed files with 25 additions and 1 deletions
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23
src/movegen.cpp
View file

@ -567,6 +567,29 @@ bool move_is_legal(const Position& pos, const Move m, Bitboard pinned) {
}
/// Another version of move_is_legal(), which takes only a position and a move
/// as input. This function does not require that the side to move is not in
/// check. It is not optimized for speed, and is only used for verifying move
/// legality when building a PV from the transposition table.
bool move_is_legal(const Position& pos, const Move m) {
Bitboard pinned = pos.pinned_pieces(pos.side_to_move());
if (!pos.is_check())
return move_is_legal(pos, m, pinned);
else
{
Position p(pos);
MoveStack moves[64];
int n = generate_evasions(p, moves, pinned);
for (int i = 0; i < n; i++)
if (moves[i].move == m)
return true;
return false;
}
}
namespace {
template<PieceType Piece>

1
src/movegen.h
View file

@ -38,6 +38,7 @@ extern int generate_non_capture_checks(const Position& pos, MoveStack* mlist, Bi
extern int generate_evasions(const Position& pos, MoveStack* mlist, Bitboard pinned);
extern int generate_legal_moves(const Position& pos, MoveStack* mlist);
extern bool move_is_legal(const Position& pos, const Move m, Bitboard pinned);
extern bool move_is_legal(const Position& pos, const Move m);
#endif // !defined(MOVEGEN_H_INCLUDED)

2
src/tt.cpp
View file

@ -207,7 +207,7 @@ void TranspositionTable::extract_pv(const Position& pos, Move pv[]) {
tte && tte->move() != MOVE_NONE && !stop;
tte = retrieve(p.get_key()), ply++)
{
if (!move_is_legal(p, tte->move(), p.pinned_pieces(p.side_to_move())))
if (!move_is_legal(p, tte->move()))
break;
pv[ply] = tte->move();
p.do_move(pv[ply], st[ply]);