- // Update castle rights
- key ^= zobCastle[castleRights];
- castleRights &= castleRightsMask[to];
- key ^= zobCastle[castleRights];
-
- // Reset rule 50 counter
- rule50 = 0;
-
- // Update checkers BB
- checkersBB = attacks_to(king_square(them), us);
-}
-
-
-/// Position::do_ep_move() is a private method used to make an en passant
-/// capture. It is called from the main Position::do_move function. Because
-/// the captured piece is always a pawn, we don't need to pass an UndoInfo
-/// object in which to store the captured piece.
-
-void Position::do_ep_move(Move m) {
-
- Color us, them;
- Square from, to, capsq;
-
- assert(is_ok());
- assert(move_is_ok(m));
- assert(move_is_ep(m));
-
- us = side_to_move();
- them = opposite_color(us);
- from = move_from(m);
- to = move_to(m);
- capsq = (us == WHITE)? (to - DELTA_N) : (to - DELTA_S);
-
- assert(to == epSquare);
- assert(relative_rank(us, to) == RANK_6);
- assert(piece_on(to) == EMPTY);
- assert(piece_on(from) == pawn_of_color(us));
- assert(piece_on(capsq) == pawn_of_color(them));
-
- // Remove captured piece
- clear_bit(&(byColorBB[them]), capsq);
- clear_bit(&(byTypeBB[PAWN]), capsq);
- clear_bit(&(byTypeBB[0]), capsq); // HACK: byTypeBB[0] == occupied squares
- board[capsq] = EMPTY;
-
- // Remove moving piece from source square
- clear_bit(&(byColorBB[us]), from);
- clear_bit(&(byTypeBB[PAWN]), from);
- clear_bit(&(byTypeBB[0]), from); // HACK: byTypeBB[0] == occupied squares
-
- // Put moving piece on destination square
- set_bit(&(byColorBB[us]), to);
- set_bit(&(byTypeBB[PAWN]), to);
- set_bit(&(byTypeBB[0]), to); // HACK: byTypeBB[0] == occupied squares
- board[to] = board[from];
- board[from] = EMPTY;
-
- // Update material hash key
- materialKey ^= zobMaterial[them][PAWN][pieceCount[them][PAWN]];
+ // Put the piece back at the source square
+ Bitboard move_bb = make_move_bb(to, from);
+ do_move_bb(&(byColorBB[us]), move_bb);
+ do_move_bb(&(byTypeBB[pt]), move_bb);
+ do_move_bb(&(byTypeBB[0]), move_bb); // HACK: byTypeBB[0] == occupied squares