diff --git a/src/movegen.cpp b/src/movegen.cpp index 14705d30..cbb71688 100644 --- a/src/movegen.cpp +++ b/src/movegen.cpp @@ -756,13 +756,15 @@ namespace { const Bitboard TRank8BB = (Us == WHITE ? Rank8BB : Rank1BB); const Bitboard TRank3BB = (Us == WHITE ? Rank3BB : Rank6BB); const SquareDelta TDELTA_N = (Us == WHITE ? DELTA_N : DELTA_S); + const SquareDelta TDELTA_S = (Us == WHITE ? DELTA_S : DELTA_N); Bitboard b1, b2, b3; - Bitboard empty = pos.empty_squares(); Bitboard pawns = pos.pawns(Us); if (dc & pawns) { + Bitboard empty = pos.empty_squares(); + // Pawn moves which gives discovered check. This is possible only if the // pawn is not on the same file as the enemy king, because we don't // generate captures. @@ -786,10 +788,15 @@ namespace { } // Direct checks. These are possible only for pawns on neighboring files - // of the enemy king. + // and in the two ranks that, after the push, are in front of the enemy king. b1 = pawns & neighboring_files_bb(ksq) & ~dc; + b2 = rank_bb(ksq + 2 * TDELTA_S) | rank_bb(ksq + 3 * TDELTA_S); + b1 &= b2; + if (!b1) + return mlist; // Direct checks, single pawn pushes + Bitboard empty = pos.empty_squares(); b2 = move_pawns(b1) & empty; b3 = b2 & pos.pawn_attacks(Them, ksq); while (b3)